major rewrite of fs_download, hopefully fixing 1641

12 files changed, 1663 insertions, 1134 deletions

diff --git a/src/fs/Makefile.am b/src/fs/Makefile.am
index c0a0420b7..2f67ce36a 100644
--- a/src/fs/Makefile.am
+++ b/src/fs/Makefile.am
@@ -23,6 +23,7 @@ libgnunetfs_la_SOURCES = \
   fs_getopt.c \
   fs_list_indexed.c \
   fs_publish.c \
+  fs_misc.c \
   fs_namespace.c \
   fs_search.c \
   fs_tree.c fs_tree.h \
diff --git a/src/fs/fs.c b/src/fs/fs.c
index c8ce4d651..d748e89ab 100644
--- a/src/fs/fs.c
+++ b/src/fs/fs.c
@@ -1639,49 +1639,102 @@ GNUNET_FS_unindex_sync_ (struct GNUNET_FS_UnindexContext *uc)
 
 
 /**
- * Serialize an active or pending download request.
+ * Serialize a download request.
  * 
- * @param cls the 'struct GNUNET_BIO_WriteHandle*'
- * @param key unused, can be NULL
- * @param value the 'struct DownloadRequest'
+ * @param wh the 'struct GNUNET_BIO_WriteHandle*'
+ * @param dr the 'struct DownloadRequest'
  * @return GNUNET_YES on success, GNUNET_NO on error
  */
 static int
-write_download_request (void *cls,
-                        const GNUNET_HashCode *key,
-                        void *value)
-{
-  struct GNUNET_BIO_WriteHandle *wh = cls;
-  struct DownloadRequest *dr = value;
+write_download_request (struct GNUNET_BIO_WriteHandle *wh,
+                        struct DownloadRequest *dr)
+{ 
+  unsigned int i;
   
   if ( (GNUNET_OK !=
-        GNUNET_BIO_write (wh, &dr->chk, sizeof (struct ContentHashKey))) ||
+        GNUNET_BIO_write_int32 (wh, dr->state)) ||
        (GNUNET_OK !=
         GNUNET_BIO_write_int64 (wh, dr->offset)) ||
        (GNUNET_OK !=
-        GNUNET_BIO_write_int32 (wh, dr->depth)) )    
+        GNUNET_BIO_write_int32 (wh, dr->num_children)) ||
+       (GNUNET_OK !=
+        GNUNET_BIO_write_int32 (wh, dr->depth)) ) 
     return GNUNET_NO;    
+  if ( (dr->state == BRS_CHK_SET) &&
+       (GNUNET_OK !=
+        GNUNET_BIO_write (wh, &dr->chk, sizeof (struct ContentHashKey))) )
+    return GNUNET_NO;
+  for (i=0;i<dr->num_children;i++)
+    if (GNUNET_NO == 
+        write_download_request (wh, dr->children[i]))
+      return GNUNET_NO;
   return GNUNET_YES;
 }
 
 
 /**
- * Count active download requests.
+ * Read a download request tree.
  * 
- * @param cls the 'uint32_t*' counter
- * @param key unused, can be NULL
- * @param value the 'struct DownloadRequest'
- * @return GNUNET_YES (continue iteration)
+ * @param rh stream to read from
+ * @return value the 'struct DownloadRequest', NULL on error
  */
-static int
-count_download_requests (void *cls,
-                        const GNUNET_HashCode *key,
-                        void *value)
-{
-  uint32_t *counter = cls;
-  
-  (*counter)++;
-  return GNUNET_YES;
+static struct DownloadRequest *
+read_download_request (struct GNUNET_BIO_ReadHandle *rh)
+{ 
+  struct DownloadRequest *dr;
+  unsigned int i;
+
+  dr = GNUNET_malloc (sizeof (struct DownloadRequest));
+
+  if ( (GNUNET_OK !=
+        GNUNET_BIO_read_int32 (rh, &dr->state)) ||
+       (GNUNET_OK !=
+        GNUNET_BIO_read_int64 (rh, &dr->offset)) ||
+       (GNUNET_OK !=
+        GNUNET_BIO_read_int32 (rh, &dr->num_children)) ||
+       (dr->num_children > CHK_PER_INODE) ||
+       (GNUNET_OK !=
+        GNUNET_BIO_read_int32 (rh, &dr->depth)) ||
+       ( (dr->depth == 0) && (dr->num_children > 0) ) ||
+       ( (dr->depth > 0) && (dr->num_children == 0) ) )
+    {
+      GNUNET_break (0);
+      dr->num_children = 0;
+      goto cleanup;        
+    }
+  if (dr->num_children > 0)
+    dr->children = GNUNET_malloc (dr->num_children *
+                                  sizeof (struct ContentHashKey));
+  switch (dr->state)
+    {
+    case BRS_INIT:
+    case BRS_RECONSTRUCT_DOWN:
+    case BRS_RECONSTRUCT_META_UP:
+    case BRS_RECONSTRUCT_UP:    
+      break;
+    case BRS_CHK_SET:
+      if (GNUNET_OK !=
+          GNUNET_BIO_read (rh, "chk", &dr->chk, sizeof (struct ContentHashKey))) 
+        goto cleanup;  
+      break;
+    case BRS_DOWNLOAD_DOWN:
+    case BRS_DOWNLOAD_UP:
+    case BRS_ERROR:
+      break;
+    default:
+      GNUNET_break (0);
+      goto cleanup;
+    }
+  for (i=0;i<dr->num_children;i++)
+    {
+      if (NULL == (dr->children[i] = read_download_request (rh)))
+        goto cleanup;
+      dr->children[i]->parent = dr;
+    }
+  return dr;
+ cleanup:
+  GNUNET_FS_free_download_request_ (dr);
+  return NULL;
 }
 
 
@@ -1739,7 +1792,6 @@ GNUNET_FS_download_sync_ (struct GNUNET_FS_DownloadContext *dc)
   char *uris;
   char *fn;
   char *dir;
-  uint32_t num_pending;
 
   if (NULL == dc->serialization)    
     {
@@ -1780,14 +1832,6 @@ GNUNET_FS_download_sync_ (struct GNUNET_FS_DownloadContext *dc)
   GNUNET_assert ( (GNUNET_YES == GNUNET_FS_uri_test_chk (dc->uri)) ||
                   (GNUNET_YES == GNUNET_FS_uri_test_loc (dc->uri)) );
   uris = GNUNET_FS_uri_to_string (dc->uri);
-  num_pending = 0;
-  if (dc->emsg == NULL)
-    (void) GNUNET_CONTAINER_multihashmap_iterate (dc->active,
-                                                  &count_download_requests,
-                                                  &num_pending);    
-  GNUNET_assert ( (dc->length == dc->completed) ||
-                  (dc->emsg != NULL) ||
-                  (num_pending > 0) );
   if ( (GNUNET_OK !=
         GNUNET_BIO_write_string (wh, uris)) ||
        (GNUNET_OK !=
@@ -1813,22 +1857,20 @@ GNUNET_FS_download_sync_ (struct GNUNET_FS_DownloadContext *dc)
        (GNUNET_OK !=
         GNUNET_BIO_write_int32 (wh, (uint32_t) dc->options)) ||
        (GNUNET_OK !=
-        GNUNET_BIO_write_int32 (wh, (uint32_t) dc->has_finished)) ||
-       (GNUNET_OK !=
-        GNUNET_BIO_write_int32 (wh, num_pending)) ||
-       (GNUNET_OK !=
-        GNUNET_BIO_write_int32 (wh, dc->start_task != GNUNET_SCHEDULER_NO_TASK)) )
+        GNUNET_BIO_write_int32 (wh, (uint32_t) dc->has_finished)) )
     {
       GNUNET_break (0);           
       goto cleanup; 
     }
-  if (GNUNET_SYSERR ==
-      GNUNET_CONTAINER_multihashmap_iterate (dc->active,
-                                             &write_download_request,
-                                             wh))
+  if (NULL == dc->emsg)
     {
-      GNUNET_break (0);
-      goto cleanup;
+      GNUNET_assert (dc->top_request != NULL);
+      if (GNUNET_YES !=
+          write_download_request (wh, dc->top_request))
+        {
+          GNUNET_break (0);
+          goto cleanup;
+        }
     }
   GNUNET_free_non_null (uris);
   uris = NULL;
@@ -2348,7 +2390,7 @@ signal_download_resume (struct GNUNET_FS_DownloadContext *dc)
       signal_download_resume (dcc);
       dcc = dcc->next;
     }
-  if (dc->pending != NULL)
+  if (dc->pending_head != NULL)
     GNUNET_FS_download_start_downloading_ (dc);
 }
 
@@ -2537,7 +2579,7 @@ static void
 free_download_context (struct GNUNET_FS_DownloadContext *dc)
 {
   struct GNUNET_FS_DownloadContext *dcc;
-  struct DownloadRequest *dr;
+
   if (dc->meta != NULL)
     GNUNET_CONTAINER_meta_data_destroy (dc->meta);
   if (dc->uri != NULL)
@@ -2552,11 +2594,7 @@ free_download_context (struct GNUNET_FS_DownloadContext *dc)
                                    dcc);
       free_download_context (dcc);
     }
-  while (NULL != (dr = dc->pending))
-    {
-      dc->pending = dr->next;
-      GNUNET_free (dr);
-    }
+  GNUNET_FS_free_download_request_ (dc->top_request);
   GNUNET_free (dc);
 }
 
@@ -2584,8 +2622,6 @@ deserialize_download (struct GNUNET_FS_Handle *h,
   char *dn;
   uint32_t options;
   uint32_t status;
-  uint32_t num_pending;
-  int32_t  start_pending;
 
   uris = NULL;
   emsg = NULL;
@@ -2622,51 +2658,27 @@ deserialize_download (struct GNUNET_FS_Handle *h,
        (GNUNET_OK !=
         GNUNET_BIO_read_int32 (rh, &options)) ||
        (GNUNET_OK !=
-        GNUNET_BIO_read_int32 (rh, &status)) ||
-       (GNUNET_OK !=
-        GNUNET_BIO_read_int32 (rh, &num_pending)) ||
-       (GNUNET_OK !=
-        GNUNET_BIO_read_int32 (rh, &start_pending)) )
+        GNUNET_BIO_read_int32 (rh, &status)) )
     {
       GNUNET_break (0);
       goto cleanup;          
     }
   dc->options = (enum GNUNET_FS_DownloadOptions) options;
-  dc->active = GNUNET_CONTAINER_multihashmap_create (16);
+  dc->active = GNUNET_CONTAINER_multihashmap_create (1 + 2 * (dc->length / DBLOCK_SIZE));
   dc->has_finished = (int) status;
   dc->treedepth = GNUNET_FS_compute_depth (GNUNET_FS_uri_chk_get_file_size (dc->uri));
   if (GNUNET_FS_uri_test_loc (dc->uri))
     GNUNET_assert (GNUNET_OK ==
                    GNUNET_FS_uri_loc_get_peer_identity (dc->uri,
                                                         &dc->target));
-  if ( (dc->length > dc->completed) &&
-       (num_pending == 0) )
-    {
-      GNUNET_break (0);           
-      goto cleanup;    
-    }
-  while (0 < num_pending--)
+  if (dc->emsg == NULL)
     {
-      dr = GNUNET_malloc (sizeof (struct DownloadRequest));
-      if ( (GNUNET_OK !=
-            GNUNET_BIO_read (rh, "chk", &dr->chk, sizeof (struct ContentHashKey))) ||
-           (GNUNET_OK !=
-            GNUNET_BIO_read_int64 (rh, &dr->offset)) ||
-           (GNUNET_OK !=
-            GNUNET_BIO_read_int32 (rh, &dr->depth)) )
+      dc->top_request = read_download_request (rh);
+      if (dc->top_request == NULL)
         {
           GNUNET_break (0);
-          goto cleanup;    
+          goto cleanup;
         }
-      dr->is_pending = GNUNET_YES;
-      dr->next = dc->pending;
-      dc->pending = dr;
-      GNUNET_CONTAINER_multihashmap_put (dc->active,
-                                         &dr->chk.query,
-                                         dr,
-                                         GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
-
-      dr = NULL;
     }
   dn = get_download_sync_filename (dc, dc->serialization, ".dir");
   if (dn != NULL)
@@ -2697,13 +2709,11 @@ deserialize_download (struct GNUNET_FS_Handle *h,
       signal_download_resume (dc);  
     }
   GNUNET_free (uris);
-  if (start_pending)
-    dc->start_task 
-      = GNUNET_SCHEDULER_add_now (&GNUNET_FS_download_start_task_, dc);
+  dc->task 
+    = GNUNET_SCHEDULER_add_now (&GNUNET_FS_download_start_task_, dc);
   return;
  cleanup:
   GNUNET_free_non_null (uris);
-  GNUNET_free_non_null (dr);
   GNUNET_free_non_null (emsg);
   free_download_context (dc);
 }
diff --git a/src/fs/fs.h b/src/fs/fs.h
index 0ba1d08a1..a9aa7ef74 100644
--- a/src/fs/fs.h
+++ b/src/fs/fs.h
@@ -925,6 +925,7 @@ GNUNET_FS_download_start_task_ (void *cls,
                                 const struct GNUNET_SCHEDULER_TaskContext *tc);
 
 
+
 /**
  * Fill in all of the generic fields for 
  * an unindex event and call the callback.
@@ -1612,7 +1613,7 @@ struct GNUNET_FS_SearchContext
    * when the search is being stopped (if not
    * GNUNET_SCHEDULER_NO_TASK).  Used for the task that adds some
    * artificial delay when trying to reconnect to the FS service.
-o   */
+   */
   GNUNET_SCHEDULER_TaskIdentifier task;
 
   /**
@@ -1645,37 +1646,131 @@ o   */
 
 
 /**
+ * FSM for possible states a block can go through.  The typical
+ * order of progression is linear through the states, alternatives
+ * are documented in the comments.
+ */
+enum BlockRequestState
+  {
+    /**
+     * Initial state, block has only been allocated (since it is
+     * relevant to the overall download request).
+     */
+    BRS_INIT = 0,
+
+    /**
+     * We've checked the block on the path down the tree, and the
+     * content on disk did match the desired CHK, but not all
+     * the way down, so at the bottom some blocks will still
+     * need to be reconstructed).
+     */
+    BRS_RECONSTRUCT_DOWN = 1,
+
+    /**
+     * We've calculated the CHK bottom-up based on the meta data.
+     * This may work, but if it did we have to write the meta data to
+     * disk at the end (and we still need to check against the
+     * CHK set on top).
+     */
+    BRS_RECONSTRUCT_META_UP = 2,
+
+    /**
+     * We've calculated the CHK bottom-up based on what we have on
+     * disk, which may not be what the desired CHK is.  If the
+     * reconstructed CHKs match whatever comes from above, we're
+     * done with the respective subtree.
+     */
+    BRS_RECONSTRUCT_UP = 3,
+
+    /**
+     * We've determined the real, desired CHK for this block 
+     * (full tree reconstruction failed), request is now pending.
+     * If the CHK that bubbled up through reconstruction did match
+     * the top-level request, the state machine for the subtree
+     * would have moved to BRS_DOWNLOAD_UP.
+     */
+    BRS_CHK_SET = 4,
+
+    /**
+     * We've successfully downloaded this block, but the children
+     * still need to be either downloaded or verified (download
+     * request propagates down).  If the download fails, the
+     * state machine for this block may move to 
+     * BRS_DOWNLOAD_ERROR instead.
+     */
+    BRS_DOWNLOAD_DOWN = 5,
+
+    /**
+     * This block and all of its children have been downloaded
+     * successfully (full completion propagates up).
+     */
+    BRS_DOWNLOAD_UP = 6,
+
+    /**
+     * We got a block back that matched the query but did not hash to
+     * the key (malicious publisher or hash collision); this block
+     * can never be downloaded (error propagates up).
+     */
+    BRS_ERROR = 7
+    
+  };
+
+
+/**
  * Information about an active download request.
  */ 
 struct DownloadRequest
 {
   /**
-   * While pending, we keep all download requests in a linked list.
+   * While pending, we keep all download requests in a doubly-linked list.
    */
   struct DownloadRequest *next;
 
   /**
-   * CHK for the request.
+   * While pending, we keep all download requests in a doubly-linked list.
    */
-  struct ContentHashKey chk;
+  struct DownloadRequest *prev;
+
+  /**
+   * Parent in the CHK-tree.
+   */
+  struct DownloadRequest *parent;
+
+  /**
+   * Array (!) of child-requests, or NULL for the bottom of the tree.
+   */
+  struct DownloadRequest **children;
 
   /**
-   * Offset of the corresponding block.
+   * CHK for the request for this block (set during reconstruction
+   * to what we have on disk, later to what we want to have).
+   */
+  struct ContentHashKey chk;  
+
+  /**
+   * Offset of the corresponding block.  Specifically, first (!) byte of
+   * the first DBLOCK in the subtree induced by block represented by
+   * this request.
    */
   uint64_t offset;
 
   /**
-   * Depth of the corresponding block in the tree.
+   * Number of entries in 'children' array.
+   */
+  unsigned int num_children;
+
+  /**
+   * Depth of the corresponding block in the tree.  0==DBLOCKs.
    */
   unsigned int depth;
 
   /**
-   * Set if this request is currently in the linked list of pending
-   * requests.  Needed in case we get a response for a request that we
-   * have not yet send (i.e. due to two blocks with identical
-   * content); in this case, we would need to remove the block from
-   * the pending list (and need a fast way to check if the block is on
-   * it).
+   * State in the FSM.
+   */
+  enum BlockRequestState state;
+
+  /**
+   * GNUNET_YES if this entry is in the pending list.
    */
   int is_pending;
 
@@ -1683,9 +1778,12 @@ struct DownloadRequest
 
 
 /**
- * Closure for 'reconstruct_cont' and 'reconstruct_cb'.
+ * (recursively) free download request structure
+ *
+ * @param dr request to free
  */
-struct ReconstructContext;
+void
+GNUNET_FS_free_download_request_ (struct DownloadRequest *dr);
 
 
 /**
@@ -1732,11 +1830,6 @@ struct GNUNET_FS_DownloadContext
   struct GNUNET_FS_DownloadContext *child_tail;
 
   /**
-   * State for block reconstruction.
-   */
-  struct ReconstructContext *rcc;
-
-  /**
    * Previous download belonging to the same parent.
    */
   struct GNUNET_FS_DownloadContext *prev;
@@ -1752,8 +1845,7 @@ struct GNUNET_FS_DownloadContext
   void *client_info;
 
   /**
-   * URI that identifies the file that
-   * we are downloading.
+   * URI that identifies the file that we are downloading.
    */
   struct GNUNET_FS_Uri *uri;
 
@@ -1787,16 +1879,9 @@ struct GNUNET_FS_DownloadContext
   char *temp_filename;
 
   /**
-   * Map of active requests (those waiting
-   * for a response).  The key is the hash
-   * of the encryped block (aka query).
-   */
-  struct GNUNET_CONTAINER_MultiHashMap *active;
-
-  /**
-   * Linked list of pending requests.
+   * Our entry in the job queue.
    */
-  struct DownloadRequest *pending;
+  struct GNUNET_FS_QueueEntry *job_queue;
 
   /**
    * Non-NULL if we are currently having a request for
@@ -1805,38 +1890,52 @@ struct GNUNET_FS_DownloadContext
   struct GNUNET_CLIENT_TransmitHandle *th;
 
   /**
-   * Our entry in the job queue.
+   * Tree encoder used for the reconstruction.
    */
-  struct GNUNET_FS_QueueEntry *job_queue;
+  struct GNUNET_FS_TreeEncoder *te;
 
   /**
-   * Identity of the peer having the content, or all-zeros
-   * if we don't know of such a peer.
+   * File handle for reading data from an existing file
+   * (to pass to tree encoder).
    */
-  struct GNUNET_PeerIdentity target;
+  struct GNUNET_DISK_FileHandle *rfh;
 
   /**
-   * ID of a task that is using this struct
-   * and that must be cancelled when the download
-   * is being stopped (if not GNUNET_SCHEDULER_NO_TASK).
-   * Used for the task that adds some artificial
-   * delay when trying to reconnect to the FS
-   * service.
+   * Map of active requests (those waiting for a response).  The key
+   * is the hash of the encryped block (aka query).
    */
-  GNUNET_SCHEDULER_TaskIdentifier task;
+  struct GNUNET_CONTAINER_MultiHashMap *active;
 
   /**
-   * Task used to start the download.
+   * Head of linked list of pending requests.
    */
-  GNUNET_SCHEDULER_TaskIdentifier start_task;
+  struct DownloadRequest *pending_head;
 
   /**
-   * What was the size of the file on disk that we're downloading
-   * before we started?  Used to detect if there is a point in
-   * checking an existing block on disk for matching the desired
-   * content.  0 if the file did not exist already.
+   * Head of linked list of pending requests.
    */
-  uint64_t old_file_size;
+  struct DownloadRequest *pending_tail;
+
+  /**
+   * Top-level download request.
+   */
+  struct DownloadRequest *top_request;
+
+  /**
+   * Identity of the peer having the content, or all-zeros
+   * if we don't know of such a peer.
+   */
+  struct GNUNET_PeerIdentity target;
+
+  /**
+   * ID of a task that is using this struct and that must be cancelled
+   * when the download is being stopped (if not
+   * GNUNET_SCHEDULER_NO_TASK).  Used for the task that adds some
+   * artificial delay when trying to reconnect to the FS service or
+   * the task processing incrementally the data on disk, or the
+   * task requesting blocks, etc.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier task;
 
   /**
    * What is the first offset that we're interested
@@ -1857,6 +1956,14 @@ struct GNUNET_FS_DownloadContext
   uint64_t completed;
 
   /**
+   * What was the size of the file on disk that we're downloading
+   * before we started?  Used to detect if there is a point in
+   * checking an existing block on disk for matching the desired
+   * content.  0 if the file did not exist already.
+   */
+  uint64_t old_file_size;
+
+  /**
    * Time download was started.
    */
   struct GNUNET_TIME_Absolute start_time;
@@ -1883,17 +1990,6 @@ struct GNUNET_FS_DownloadContext
    */
   int has_finished;
 
-  /**
-   * Have we tried (and failed) to find matching full
-   * data from the meta data yet?
-   */
-  int tried_full_data;
-
-  /**
-   * Have we tried to reconstruct an IBLOCK from disk
-   * and failed (and should hence not try again?)
-   */
-  int reconstruct_failed;
 };
 
 
diff --git a/src/fs/fs_download.c b/src/fs/fs_download.c
index d7f1de283..8d2e1b7a4 100644
--- a/src/fs/fs_download.c
+++ b/src/fs/fs_download.c
@@ -1,6 +1,6 @@
 /*
      This file is part of GNUnet.
-     (C) 2001, 2002, 2003, 2004, 2005, 2006, 2008, 2009, 2010 Christian Grothoff (and other contributing authors)
+     (C) 2001-2011 Christian Grothoff (and other contributing authors)
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
@@ -61,8 +61,7 @@ is_recursive_download (struct GNUNET_FS_DownloadContext *dc)
  * 
  * @param fsize overall file size
  * @param off offset of the block in the file
- * @param depth depth of the block in the tree
- * @param treedepth maximum depth of the tree
+ * @param depth depth of the block in the tree, 0 for DBLOCK
  * @return off for DBLOCKS (depth == treedepth),
  *         otherwise an offset past the end
  *         of the file that does not overlap
@@ -71,23 +70,22 @@ is_recursive_download (struct GNUNET_FS_DownloadContext *dc)
 static uint64_t
 compute_disk_offset (uint64_t fsize,
                      uint64_t off,
-                     unsigned int depth,
-                     unsigned int treedepth)
+                     unsigned int depth)
 {
   unsigned int i;
   uint64_t lsize; /* what is the size of all IBlocks for depth "i"? */
   uint64_t loff; /* where do IBlocks for depth "i" start? */
   unsigned int ioff; /* which IBlock corresponds to "off" at depth "i"? */
   
-  if (depth == treedepth)
+  if (depth == 0)
     return off;
   /* first IBlocks start at the end of file, rounded up
      to full DBLOCK_SIZE */
   loff = ((fsize + DBLOCK_SIZE - 1) / DBLOCK_SIZE) * DBLOCK_SIZE;
-  lsize = ( (fsize + DBLOCK_SIZE-1) / DBLOCK_SIZE) * sizeof (struct ContentHashKey);
+  lsize = ( (fsize + DBLOCK_SIZE - 1) / DBLOCK_SIZE) * sizeof (struct ContentHashKey);
   GNUNET_assert (0 == (off % DBLOCK_SIZE));
   ioff = (off / DBLOCK_SIZE);
-  for (i=treedepth-1;i>depth;i--)
+  for (i=1;i<depth;i++)
     {
       loff += lsize;
       lsize = (lsize + CHK_PER_INODE - 1) / CHK_PER_INODE;
@@ -100,35 +98,32 @@ compute_disk_offset (uint64_t fsize,
 
 
 /**
- * Given a file of the specified treedepth and a block at the given
- * offset and depth, calculate the offset for the CHK at the given
- * index.
+ * Given a block at the given offset and depth, calculate the offset
+ * for the CHK at the given index.
  *
  * @param offset the offset of the first
  *        DBLOCK in the subtree of the 
  *        identified IBLOCK
- * @param depth the depth of the IBLOCK in the tree
- * @param treedepth overall depth of the tree
+ * @param depth the depth of the IBLOCK in the tree, 0 for DBLOCK
  * @param k which CHK in the IBLOCK are we 
  *        talking about
  * @return offset if k=0, otherwise an appropriately
- *         larger value (i.e., if depth = treedepth-1,
- *         the returned value should be offset+DBLOCK_SIZE)
+ *         larger value (i.e., if depth = 1,
+ *         the returned value should be offset+k*DBLOCK_SIZE)
  */
 static uint64_t
 compute_dblock_offset (uint64_t offset,
                        unsigned int depth,
-                       unsigned int treedepth,
                        unsigned int k)
 {
   unsigned int i;
   uint64_t lsize; /* what is the size of the sum of all DBlocks 
                      that a CHK at depth i corresponds to? */
 
-  if (depth == treedepth)
+  if (depth == 0)
     return offset;
   lsize = DBLOCK_SIZE;
-  for (i=treedepth-1;i>depth;i--)
+  for (i=1;i<depth;i++)
     lsize *= CHK_PER_INODE;
   return offset + k * lsize;
 }
@@ -177,6 +172,7 @@ GNUNET_FS_download_make_status_ (struct GNUNET_FS_ProgressInfo *pi,
                                                         pi);
 }
 
+
 /**
  * We're ready to transmit a search request to the
  * file-sharing service.  Do it.  If there is 
@@ -255,20 +251,18 @@ process_result_with_request (void *cls,
  * 
  * @param dc download in question
  * @param chk request this relates to
- * @param sm request details
+ * @param dr request details
  * @param block plaintext data matching request
  * @param len number of bytes in block
- * @param depth depth of the block
  * @param do_store should we still store the block on disk?
  * @return GNUNET_OK on success
  */
 static int
 encrypt_existing_match (struct GNUNET_FS_DownloadContext *dc,
                         const struct ContentHashKey *chk,
-                        struct DownloadRequest *sm,
+                        struct DownloadRequest *dr,
                         const char * block,                    
                         size_t len,
-                        int depth,
                         int do_store)
 {
   struct ProcessResultClosure prc;
@@ -302,613 +296,19 @@ encrypt_existing_match (struct GNUNET_FS_DownloadContext *dc,
   prc.dc = dc;
   prc.data = enc;
   prc.size = len;
-  prc.type = (dc->treedepth == depth) 
+  prc.type = (0 == dr->depth) 
     ? GNUNET_BLOCK_TYPE_FS_DBLOCK 
     : GNUNET_BLOCK_TYPE_FS_IBLOCK;
   prc.query = chk->query;
   prc.do_store = do_store;
   process_result_with_request (&prc,
                                &chk->key,
-                               sm);
+                               dr);
   return GNUNET_OK;
 }
 
 
 /**
- * Closure for match_full_data.
- */
-struct MatchDataContext 
-{
-  /**
-   * CHK we are looking for.
-   */
-  const struct ContentHashKey *chk;
-
-  /**
-   * Download we're processing.
-   */
-  struct GNUNET_FS_DownloadContext *dc;
-
-  /**
-   * Request details.
-   */
-  struct DownloadRequest *sm;
-
-  /**
-   * Overall offset in the file.
-   */
-  uint64_t offset;
-
-  /**
-   * Desired length of the block.
-   */
-  size_t len;
-
-  /**
-   * Flag set to GNUNET_YES on success.
-   */
-  int done;
-};
-
-/**
- * Type of a function that libextractor calls for each
- * meta data item found.
- *
- * @param cls closure (user-defined)
- * @param plugin_name name of the plugin that produced this value;
- *        special values can be used (i.e. '&lt;zlib&gt;' for zlib being
- *        used in the main libextractor library and yielding
- *        meta data).
- * @param type libextractor-type describing the meta data
- * @param format basic format information about data 
- * @param data_mime_type mime-type of data (not of the original file);
- *        can be NULL (if mime-type is not known)
- * @param data actual meta-data found
- * @param data_len number of bytes in data
- * @return 0 to continue extracting, 1 to abort
- */ 
-static int
-match_full_data (void *cls,
-                 const char *plugin_name,
-                 enum EXTRACTOR_MetaType type,
-                 enum EXTRACTOR_MetaFormat format,
-                 const char *data_mime_type,
-                 const char *data,
-                 size_t data_len)
-{
-  struct MatchDataContext *mdc = cls;
-  GNUNET_HashCode key;
-
-  if (type == EXTRACTOR_METATYPE_GNUNET_FULL_DATA) 
-    {
-      if ( (mdc->offset > data_len) ||
-           (mdc->offset + mdc->len > data_len) )
-        return 1;
-      GNUNET_CRYPTO_hash (&data[mdc->offset],
-                          mdc->len,
-                          &key);
-      if (0 != memcmp (&key,
-                       &mdc->chk->key,
-                       sizeof (GNUNET_HashCode)))
-        {
-          GNUNET_break_op (0);
-          return 1;
-        }
-      /* match found! */
-      if (GNUNET_OK !=
-          encrypt_existing_match (mdc->dc,
-                                  mdc->chk,
-                                  mdc->sm,
-                                  &data[mdc->offset],
-                                  mdc->len,
-                                  0,
-                                  GNUNET_YES))
-        {
-          GNUNET_break_op (0);
-          return 1;
-        }
-      mdc->done = GNUNET_YES;
-      return 1;
-    }
-  return 0;
-}
-
-
-
-/**
- * Closure for 'reconstruct_cont' and 'reconstruct_cb'.
- */
-struct ReconstructContext
-{
-  /**
-   * File handle open for the reconstruction.
-   */
-  struct GNUNET_DISK_FileHandle *fh;
-
-  /**
-   * the download context.
-   */
-  struct GNUNET_FS_DownloadContext *dc;
-
-  /**
-   * Tree encoder used for the reconstruction.
-   */
-  struct GNUNET_FS_TreeEncoder *te;
-
-  /**
-   * CHK of block we are trying to reconstruct.
-   */
-  struct ContentHashKey chk;
-
-  /**
-   * Request that was generated.
-   */
-  struct DownloadRequest *sm;
-
-  /**
-   * Helper task.
-   */
-  GNUNET_SCHEDULER_TaskIdentifier task;
-
-  /**
-   * Offset of block we are trying to reconstruct.
-   */
-  uint64_t offset;
-
-  /**
-   * Depth of block we are trying to reconstruct.
-   */
-  unsigned int depth;
-
-};
-
-
-/**
- * Continuation after a possible attempt to reconstruct
- * the current IBlock from the existing file.
- *
- * @param cls the 'struct ReconstructContext'
- * @param tc scheduler context
- */
-static void
-reconstruct_cont (void *cls,
-                  const struct GNUNET_SCHEDULER_TaskContext *tc)
-{
-  struct ReconstructContext *rcc = cls;
-
-  if (rcc->te != NULL)
-    {
-      GNUNET_FS_tree_encoder_finish (rcc->te, NULL, NULL);
-    }
-  rcc->dc->reconstruct_failed = GNUNET_YES;
-  rcc->dc->rcc = NULL;
-  if (rcc->fh != NULL)
-    GNUNET_break (GNUNET_OK == GNUNET_DISK_file_close (rcc->fh));
-  if ( (rcc->dc->th == NULL) &&
-       (rcc->dc->client != NULL) )
-    {
-#if DEBUG_DOWNLOAD
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "Asking for transmission to FS service\n");
-#endif
-      rcc->dc->th = GNUNET_CLIENT_notify_transmit_ready (rcc->dc->client,
-                                                         sizeof (struct SearchMessage),
-                                                         GNUNET_CONSTANTS_SERVICE_TIMEOUT,
-                                                         GNUNET_NO,
-                                                         &transmit_download_request,
-                                                         rcc->dc);
-    }
-  else
-    {
-#if DEBUG_DOWNLOAD
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "Transmission request not issued (%p %p)\n",
-                  rcc->dc->th, 
-                  rcc->dc->client);
-#endif
-    }
-  GNUNET_free (rcc);
-}
-
-
-static void
-get_next_block (void *cls,
-                const struct GNUNET_SCHEDULER_TaskContext *tc)
-{
-  struct ReconstructContext *rcc = cls;  
-
-  rcc->task = GNUNET_SCHEDULER_NO_TASK;
-  GNUNET_FS_tree_encoder_next (rcc->te);
-}
-
-
-/**
- * Function called asking for the current (encoded)
- * block to be processed.  After processing the
- * client should either call "GNUNET_FS_tree_encode_next"
- * or (on error) "GNUNET_FS_tree_encode_finish".
- *
- * This function checks if the content on disk matches
- * the expected content based on the URI.
- * 
- * @param cls closure
- * @param query the query for the block (key for lookup in the datastore)
- * @param offset offset of the block
- * @param depth depth
- * @param type type of the block (IBLOCK or DBLOCK)
- * @param block the (encrypted) block
- * @param block_size size of block (in bytes)
- */
-static void 
-reconstruct_cb (void *cls,
-                const GNUNET_HashCode *query,
-                uint64_t offset,
-                unsigned int depth,
-                enum GNUNET_BLOCK_Type type,
-                const void *block,
-                uint16_t block_size)
-{
-  struct ReconstructContext *rcc = cls;
-  struct ProcessResultClosure prc;
-  struct GNUNET_FS_TreeEncoder *te;
-  uint64_t off;
-  uint64_t boff;
-  uint64_t roff;
-  unsigned int i;
-
-  roff = offset / DBLOCK_SIZE;
-  for (i=rcc->dc->treedepth;i>depth;i--)
-    roff /= CHK_PER_INODE;
-  boff = roff * DBLOCK_SIZE;
-  for (i=rcc->dc->treedepth;i>depth;i--)
-    boff *= CHK_PER_INODE;
-  /* convert reading offset into IBLOCKs on-disk offset */
-  off = compute_disk_offset (GNUNET_FS_uri_chk_get_file_size (rcc->dc->uri),
-                             boff,
-                             depth,
-                             rcc->dc->treedepth);
-  if ( (off == rcc->offset) &&
-       (depth == rcc->depth) &&
-       (0 == memcmp (query,
-                     &rcc->chk.query,
-                     sizeof (GNUNET_HashCode))) )
-    {
-      /* already got it! */
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  _("Block reconstruction at offset %llu and depth %u successful\n"),
-                  (unsigned long long) offset,
-                  depth);
-      prc.dc = rcc->dc;
-      prc.data = block;
-      prc.size = block_size;
-      prc.type = type;
-      prc.query = rcc->chk.query;
-      prc.do_store = GNUNET_NO;
-      process_result_with_request (&prc,
-                                   &rcc->chk.key,
-                                   rcc->sm);
-      te = rcc->te;
-      rcc->te = NULL;
-      GNUNET_FS_tree_encoder_finish (te, NULL, NULL);
-      GNUNET_free (rcc);
-      return;     
-    }
-  rcc->task = GNUNET_SCHEDULER_add_now (&get_next_block,
-                                        rcc);
-}
-
-
-/**
- * Function called by the tree encoder to obtain
- * a block of plaintext data (for the lowest level
- * of the tree).
- *
- * @param cls our 'struct ReconstructContext'
- * @param offset identifies which block to get
- * @param max (maximum) number of bytes to get; returning
- *        fewer will also cause errors
- * @param buf where to copy the plaintext buffer
- * @param emsg location to store an error message (on error)
- * @return number of bytes copied to buf, 0 on error
- */
-static size_t
-fh_reader (void *cls,
-           uint64_t offset,
-           size_t max, 
-           void *buf,
-           char **emsg)
-{
-  struct ReconstructContext *rcc = cls;
-  struct GNUNET_DISK_FileHandle *fh = rcc->fh;
-  ssize_t ret;
-
-  *emsg = NULL;
-  if (offset !=
-      GNUNET_DISK_file_seek (fh,
-                             offset,
-                             GNUNET_DISK_SEEK_SET))
-    {
-      *emsg = GNUNET_strdup (strerror (errno));
-      return 0;
-    }
-  ret = GNUNET_DISK_file_read (fh, buf, max);
-  if (ret < 0)
-    {
-      *emsg = GNUNET_strdup (strerror (errno));
-      return 0;
-    }
-  return ret;
-}
-
-
-/**
- * Schedule the download of the specified block in the tree.
- *
- * @param dc overall download this block belongs to
- * @param chk content-hash-key of the block
- * @param offset offset of the block in the file
- *         (for IBlocks, the offset is the lowest
- *          offset of any DBlock in the subtree under
- *          the IBlock)
- * @param depth depth of the block, 0 is the root of the tree
- */
-static void
-schedule_block_download (struct GNUNET_FS_DownloadContext *dc,
-                         const struct ContentHashKey *chk,
-                         uint64_t offset,
-                         unsigned int depth)
-{
-  struct DownloadRequest *sm;
-  uint64_t total;
-  uint64_t off;
-  size_t len;
-  char block[DBLOCK_SIZE];
-  GNUNET_HashCode key;
-  struct MatchDataContext mdc;
-  struct GNUNET_DISK_FileHandle *fh;
-  struct ReconstructContext *rcc;
-
-  total = GNUNET_FS_uri_chk_get_file_size (dc->uri);
-  len = GNUNET_FS_tree_calculate_block_size (total,
-                                             dc->treedepth,
-                                             offset,
-                                             depth);
-  off = compute_disk_offset (total,
-                             offset,
-                             depth,
-                             dc->treedepth);
-  sm = GNUNET_malloc (sizeof (struct DownloadRequest));
-  sm->chk = *chk;
-  sm->offset = offset;
-  sm->depth = depth;
-  sm->is_pending = GNUNET_YES;
-  sm->next = dc->pending;
-  dc->pending = sm;
-  GNUNET_CONTAINER_multihashmap_put (dc->active,
-                                     &chk->query,
-                                     sm,
-                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
-  if ( (dc->tried_full_data == GNUNET_NO) &&
-       (depth == 0) )
-    {      
-      mdc.dc = dc;
-      mdc.sm = sm;
-      mdc.chk = chk;
-      mdc.offset = offset;
-      mdc.len = len;
-      mdc.done = GNUNET_NO;
-      GNUNET_CONTAINER_meta_data_iterate (dc->meta,
-                                          &match_full_data,
-                                          &mdc);
-      if (mdc.done == GNUNET_YES)
-        return;
-      dc->tried_full_data = GNUNET_YES; 
-    }
-#if DEBUG_DOWNLOAD
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "Scheduling download at offset %llu and depth %u for `%s'\n",
-              (unsigned long long) offset,
-              depth,
-              GNUNET_h2s (&chk->query));
-#endif
-  fh = NULL;
-  if ( ( (dc->old_file_size > off) ||
-         ( (depth < dc->treedepth) &&
-           (dc->reconstruct_failed == GNUNET_NO) ) ) &&
-       (dc->filename != NULL) )    
-    fh = GNUNET_DISK_file_open (dc->filename,
-                                GNUNET_DISK_OPEN_READ,
-                                GNUNET_DISK_PERM_NONE);    
-  if ( (fh != NULL) &&
-       (dc->old_file_size > off) &&
-       (off  == 
-        GNUNET_DISK_file_seek (fh,
-                               off,
-                               GNUNET_DISK_SEEK_SET) ) &&
-       (len == 
-        GNUNET_DISK_file_read (fh,
-                               block,
-                               len)) )
-    {
-      GNUNET_CRYPTO_hash (block, len, &key);
-      if ( (0 == memcmp (&key,
-                         &chk->key,
-                         sizeof (GNUNET_HashCode))) &&
-           (GNUNET_OK ==
-            encrypt_existing_match (dc,
-                                    chk,
-                                    sm,
-                                    block,
-                                    len,
-                                    depth,
-                                    GNUNET_NO)) )
-        {
-          GNUNET_break (GNUNET_OK == GNUNET_DISK_file_close (fh));
-          return;
-        }
-    }
-  rcc = GNUNET_malloc (sizeof (struct ReconstructContext));
-  rcc->fh = fh;
-  rcc->dc = dc;
-  rcc->sm = sm;
-  rcc->chk = *chk;
-  rcc->offset = off;
-  rcc->depth = depth;
-  dc->rcc = rcc;
-  if ( (depth < dc->treedepth) &&
-       (dc->reconstruct_failed == GNUNET_NO) &&
-       (fh != NULL) )
-    {
-      rcc->te = GNUNET_FS_tree_encoder_create (dc->h,
-                                               dc->old_file_size,
-                                               rcc,
-                                               fh_reader,
-                                               &reconstruct_cb,
-                                               NULL,
-                                               &reconstruct_cont);
-      GNUNET_FS_tree_encoder_next (rcc->te);
-      return;
-    }
-  reconstruct_cont (rcc, NULL);
-}
-
-
-/**
- * Suggest a filename based on given metadata.
- * 
- * @param md given meta data
- * @return NULL if meta data is useless for suggesting a filename
- */
-char *
-GNUNET_FS_meta_data_suggest_filename (const struct GNUNET_CONTAINER_MetaData *md)
-{
-  static const char *mimeMap[][2] = {
-    {"application/bz2", ".bz2"},
-    {"application/gnunet-directory", ".gnd"},
-    {"application/java", ".class"},
-    {"application/msword", ".doc"},
-    {"application/ogg", ".ogg"},
-    {"application/pdf", ".pdf"},
-    {"application/pgp-keys", ".key"},
-    {"application/pgp-signature", ".pgp"},
-    {"application/postscript", ".ps"},
-    {"application/rar", ".rar"},
-    {"application/rtf", ".rtf"},
-    {"application/xml", ".xml"},
-    {"application/x-debian-package", ".deb"},
-    {"application/x-dvi", ".dvi"},
-    {"applixation/x-flac", ".flac"},
-    {"applixation/x-gzip", ".gz"},
-    {"application/x-java-archive", ".jar"},
-    {"application/x-java-vm", ".class"},
-    {"application/x-python-code", ".pyc"},
-    {"application/x-redhat-package-manager", ".rpm"},
-    {"application/x-rpm", ".rpm"},
-    {"application/x-tar", ".tar"},
-    {"application/x-tex-pk", ".pk"},
-    {"application/x-texinfo", ".texinfo"},
-    {"application/x-xcf", ".xcf"},
-    {"application/x-xfig", ".xfig"},
-    {"application/zip", ".zip"},
-    
-    {"audio/midi", ".midi"},
-    {"audio/mpeg", ".mp3"},
-    {"audio/real", ".rm"},
-    {"audio/x-wav", ".wav"},
-    
-    {"image/gif", ".gif"},
-    {"image/jpeg", ".jpg"},
-    {"image/pcx", ".pcx"},
-    {"image/png", ".png"},
-    {"image/tiff", ".tiff"},
-    {"image/x-ms-bmp", ".bmp"},
-    {"image/x-xpixmap", ".xpm"},
-    
-    {"text/css", ".css"},
-    {"text/html", ".html"},
-    {"text/plain", ".txt"},
-    {"text/rtf", ".rtf"},
-    {"text/x-c++hdr", ".h++"},
-    {"text/x-c++src", ".c++"},
-    {"text/x-chdr", ".h"},
-    {"text/x-csrc", ".c"},
-    {"text/x-java", ".java"},
-    {"text/x-moc", ".moc"},
-    {"text/x-pascal", ".pas"},
-    {"text/x-perl", ".pl"},
-    {"text/x-python", ".py"},
-    {"text/x-tex", ".tex"},
-    
-    {"video/avi", ".avi"},
-    {"video/mpeg", ".mpeg"},
-    {"video/quicktime", ".qt"},
-    {"video/real", ".rm"},
-    {"video/x-msvideo", ".avi"},
-    {NULL, NULL},
-  };
-  char *ret;
-  unsigned int i;
-  char *mime;
-  char *base;
-  const char *ext;
-
-  ret = GNUNET_CONTAINER_meta_data_get_by_type (md,
-                                                EXTRACTOR_METATYPE_GNUNET_ORIGINAL_FILENAME);
-  if (ret != NULL)
-    return ret;  
-  ext = NULL;
-  mime = GNUNET_CONTAINER_meta_data_get_by_type (md,
-                                                 EXTRACTOR_METATYPE_MIMETYPE);
-  if (mime != NULL)
-    {
-      i = 0;
-      while ( (mimeMap[i][0] != NULL) && 
-              (0 != strcmp (mime, mimeMap[i][0])))
-        i++;
-      if (mimeMap[i][1] == NULL)
-        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG | 
-                    GNUNET_ERROR_TYPE_BULK,
-                    _("Did not find mime type `%s' in extension list.\n"),
-                    mime);
-      else
-        ext = mimeMap[i][1];
-      GNUNET_free (mime);
-    }
-  base = GNUNET_CONTAINER_meta_data_get_first_by_types (md,
-                                                        EXTRACTOR_METATYPE_TITLE,
-                                                        EXTRACTOR_METATYPE_BOOK_TITLE,
-                                                        EXTRACTOR_METATYPE_ORIGINAL_TITLE,
-                                                        EXTRACTOR_METATYPE_PACKAGE_NAME,
-                                                        EXTRACTOR_METATYPE_URL,
-                                                        EXTRACTOR_METATYPE_URI, 
-                                                        EXTRACTOR_METATYPE_DESCRIPTION,
-                                                        EXTRACTOR_METATYPE_ISRC,
-                                                        EXTRACTOR_METATYPE_JOURNAL_NAME,
-                                                        EXTRACTOR_METATYPE_AUTHOR_NAME,
-                                                        EXTRACTOR_METATYPE_SUBJECT,
-                                                        EXTRACTOR_METATYPE_ALBUM,
-                                                        EXTRACTOR_METATYPE_ARTIST,
-                                                        EXTRACTOR_METATYPE_KEYWORDS,
-                                                        EXTRACTOR_METATYPE_COMMENT,
-                                                        EXTRACTOR_METATYPE_UNKNOWN,
-                                                        -1);
-  if ( (base == NULL) &&
-       (ext == NULL) )
-    return NULL;
-  if (base == NULL)
-    return GNUNET_strdup (ext);
-  if (ext == NULL)
-    return base;
-  GNUNET_asprintf (&ret,
-                   "%s%s",
-                   base,
-                   ext);
-  GNUNET_free (base);
-  return ret;
-}
-
-
-/**
  * We've lost our connection with the FS service.
  * Re-establish it and re-transmit all of our
  * pending requests.
@@ -1006,9 +406,14 @@ full_recursive_download (struct GNUNET_FS_DownloadContext *dc)
 
 
 /**
- * Check if all child-downloads have completed and
- * if so, signal completion (and possibly recurse to
- * parent).
+ * Check if all child-downloads have completed (or trigger them if
+ * necessary) and once we're completely done, signal completion (and
+ * possibly recurse to parent).  This function MUST be called when the
+ * download of a file itself is done or when the download of a file is
+ * done and then later a direct child download has completed (and
+ * hence this download may complete itself).
+ *
+ * @param dc download to check for completion of children
  */
 static void
 check_completed (struct GNUNET_FS_DownloadContext *dc)
@@ -1016,6 +421,11 @@ check_completed (struct GNUNET_FS_DownloadContext *dc)
   struct GNUNET_FS_ProgressInfo pi;
   struct GNUNET_FS_DownloadContext *pos;
 
+  /* first, check if we need to download children */
+  if ( (dc->child_head == NULL) &&
+       (is_recursive_download (dc)) )
+    full_recursive_download (dc);  
+  /* then, check if children are done already */
   pos = dc->child_head;
   while (pos != NULL)
     {
@@ -1027,16 +437,416 @@ check_completed (struct GNUNET_FS_DownloadContext *dc)
         return; /* not transitively done yet */
       pos = pos->next;
     }
+  /* All of our children are done, so mark this download done */
   dc->has_finished = GNUNET_YES;
   GNUNET_FS_download_sync_ (dc);
+
   /* signal completion */
   pi.status = GNUNET_FS_STATUS_DOWNLOAD_COMPLETED;
   GNUNET_FS_download_make_status_ (&pi, dc);
+
+  /* let parent know */
   if (dc->parent != NULL)
     check_completed (dc->parent);  
 }
 
 
+/**
+ * We got a block of plaintext data (from the meta data).
+ * Try it for upward reconstruction of the data.  On success,
+ * the top-level block will move to state BRS_DOWNLOAD_UP.
+ *
+ * @param dr one of our request entries
+ * @param data plaintext data, starting from the beginning of the file
+ * @param data_len number of bytes in data
+ */ 
+static void
+try_match_block (struct GNUNET_FS_DownloadContext *dc,
+                 struct DownloadRequest *dr,
+                 const char *data,
+                 size_t data_len)
+{
+  struct GNUNET_FS_ProgressInfo pi;
+  unsigned int i;
+  char enc[DBLOCK_SIZE];
+  struct ContentHashKey chks[CHK_PER_INODE];
+  struct ContentHashKey chk;
+  struct GNUNET_CRYPTO_AesSessionKey sk;
+  struct GNUNET_CRYPTO_AesInitializationVector iv;
+  size_t dlen;
+  struct DownloadRequest *drc;
+  struct GNUNET_DISK_FileHandle *fh;
+  int complete;
+  const char *fn;
+  
+  if (BRS_DOWNLOAD_UP == dr->state)
+    return;
+  if (dr->depth > 0)
+    {
+      complete = GNUNET_YES;
+      for (i=0;i<dr->num_children;i++)
+        {
+          drc = dr->children[i];
+          try_match_block (dc,
+                           drc,
+                           data, data_len);
+          if (drc->state != BRS_RECONSTRUCT_META_UP)
+            complete = GNUNET_NO;
+        }
+      if (GNUNET_YES != complete)
+        return;
+      data = (const char*) chks;
+      dlen = dr->num_children * sizeof (struct ContentHashKey);
+    }
+  else
+    {
+      if (dr->offset > data_len) 
+        return; /* oops */
+      dlen = GNUNET_MIN (data_len - dr->offset,
+                         DBLOCK_SIZE);
+    }
+  GNUNET_CRYPTO_hash (&data[dr->offset],
+                      dlen,
+                      &chk.key);
+  GNUNET_CRYPTO_hash_to_aes_key (&chk.key, &sk, &iv);
+  if (-1 == GNUNET_CRYPTO_aes_encrypt (data, dlen,
+                                       &sk,
+                                       &iv,
+                                       enc))
+    {
+      GNUNET_break (0);
+      return;
+    }
+  GNUNET_CRYPTO_hash (enc, dlen, &chk.query);
+  switch (dr->state)
+    {
+    case BRS_INIT:
+      dr->chk = chk;
+      dr->state = BRS_RECONSTRUCT_META_UP;
+      break;
+    case BRS_CHK_SET:
+      if (0 != memcmp (&chk,
+                       &dr->chk,
+                       sizeof (struct ContentHashKey)))
+        {
+          /* other peer provided bogus meta data */
+          GNUNET_break_op (0);
+          break;
+        }
+      /* write block to disk */
+      fn = dc->filename != NULL 
+        ? dc->filename 
+        : dc->temp_filename;
+      fh = GNUNET_DISK_file_open (fn,
+                                  GNUNET_DISK_OPEN_READWRITE | 
+                                  GNUNET_DISK_OPEN_CREATE | 
+                                  GNUNET_DISK_OPEN_TRUNCATE,
+                                  GNUNET_DISK_PERM_USER_READ |
+                                  GNUNET_DISK_PERM_USER_WRITE |
+                                  GNUNET_DISK_PERM_GROUP_READ |
+                                  GNUNET_DISK_PERM_OTHER_READ);     
+      if (fh == NULL)
+        {
+          GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+                                    "open",
+                                    fn);
+          GNUNET_asprintf (&dc->emsg,
+                           _("Failed to open file `%s' for writing"),
+                           fn);
+          GNUNET_DISK_file_close (fh);
+          dr->state = BRS_ERROR;
+          pi.status = GNUNET_FS_STATUS_DOWNLOAD_ERROR;
+          pi.value.download.specifics.error.message = dc->emsg;
+          GNUNET_FS_download_make_status_ (&pi, dc); 
+          return;
+        }
+      if (data_len != 
+          GNUNET_DISK_file_write (fh,
+                                  data,
+                                  data_len))
+        {
+          GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+                                    "write",
+                                    fn);              
+          GNUNET_asprintf (&dc->emsg,
+                           _("Failed to open file `%s' for writing"),
+                           fn);
+          GNUNET_DISK_file_close (fh);
+          dr->state = BRS_ERROR;
+          pi.status = GNUNET_FS_STATUS_DOWNLOAD_ERROR;
+          pi.value.download.specifics.error.message = dc->emsg;
+          GNUNET_FS_download_make_status_ (&pi, dc);      
+          return;
+        }
+      GNUNET_DISK_file_close (fh);
+      /* signal success */      
+      dr->state = BRS_DOWNLOAD_UP;
+      dc->completed = dc->length;
+      GNUNET_FS_download_sync_ (dc);
+      pi.status = GNUNET_FS_STATUS_DOWNLOAD_PROGRESS;
+      pi.value.download.specifics.progress.data = data;
+      pi.value.download.specifics.progress.offset = 0;
+      pi.value.download.specifics.progress.data_len = dlen;
+      pi.value.download.specifics.progress.depth = 0;
+      GNUNET_FS_download_make_status_ (&pi, dc);
+      check_completed (dc);      
+      break;
+    default:
+      /* how did we get here? */
+      GNUNET_break (0);
+      break;
+    }
+}
+
+
+/**
+ * Type of a function that libextractor calls for each
+ * meta data item found.  If we find full data meta data,
+ * call 'try_match_block' on it.
+ *
+ * @param cls our 'struct GNUNET_FS_DownloadContext*'
+ * @param plugin_name name of the plugin that produced this value;
+ *        special values can be used (i.e. '&lt;zlib&gt;' for zlib being
+ *        used in the main libextractor library and yielding
+ *        meta data).
+ * @param type libextractor-type describing the meta data
+ * @param format basic format information about data 
+ * @param data_mime_type mime-type of data (not of the original file);
+ *        can be NULL (if mime-type is not known)
+ * @param data actual meta-data found
+ * @param data_len number of bytes in data
+ * @return 0 to continue extracting, 1 to abort
+ */ 
+static int
+match_full_data (void *cls,
+                 const char *plugin_name,
+                 enum EXTRACTOR_MetaType type,
+                 enum EXTRACTOR_MetaFormat format,
+                 const char *data_mime_type,
+                 const char *data,
+                 size_t data_len)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+
+  if (type != EXTRACTOR_METATYPE_GNUNET_FULL_DATA) 
+    return 0;
+  if (GNUNET_FS_uri_chk_get_file_size (dc->uri) != data_len)
+    {
+      GNUNET_break_op (0);
+      return 1; /* bogus meta data */
+    }
+  try_match_block (dc,
+                   dc->top_request,
+                   data,
+                   data_len);
+  return 1;
+}
+
+
+/**
+ * Set the state of the given download request to
+ * BRS_DOWNLOAD_UP and propagate it up the tree.
+ *
+ * @param dr download request that is done
+ */
+static void
+propagate_up (struct DownloadRequest *dr)
+{
+  unsigned int i;
+
+  do
+    {
+      dr->state = BRS_DOWNLOAD_UP;
+      dr = dr->parent;
+      if (dr == NULL)
+        break;
+      for (i=0;i<dr->num_children;i++)
+        if (dr->children[i]->state != BRS_DOWNLOAD_UP)
+          break;
+    }
+  while (i == dr->num_children);
+}
+
+
+/**
+ * Try top-down reconstruction.  Before, the given request node
+ * must have the state BRS_CHK_SET.  Afterwards, more nodes may
+ * have that state or advanced to BRS_DOWNLOAD_DOWN or even
+ * BRS_DOWNLOAD_UP.  It is also possible to get BRS_ERROR on the
+ * top level.
+ *
+ * @param dc overall download this block belongs to
+ * @param dr block to reconstruct
+ */
+static void
+try_top_down_reconstruction (struct GNUNET_FS_DownloadContext *dc,
+                             struct DownloadRequest *dr)
+{
+  uint64_t off;
+  char block[DBLOCK_SIZE];
+  GNUNET_HashCode key;
+  uint64_t total;
+  size_t len;
+  unsigned int i;
+  unsigned int chk_off;
+  struct DownloadRequest *drc;
+  uint64_t child_block_size;
+  const struct ContentHashKey *chks;
+  int up_done;
+  
+  GNUNET_assert (dc->rfh != NULL);
+  GNUNET_assert (dr->state == BRS_CHK_SET);
+  total = GNUNET_FS_uri_chk_get_file_size (dc->uri);
+  GNUNET_assert (dr->depth < dc->treedepth);
+  len = GNUNET_FS_tree_calculate_block_size (total,
+                                             dr->offset,
+                                             dr->depth);
+  GNUNET_assert (len <= DBLOCK_SIZE);
+  off = compute_disk_offset (total,
+                             dr->offset,
+                             dr->depth);
+  if (dc->old_file_size < off + len) 
+    return; /* failure */
+  if (off  != 
+      GNUNET_DISK_file_seek (dc->rfh,
+                             off,
+                             GNUNET_DISK_SEEK_SET) ) 
+    {
+      GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
+                                "seek",
+                                dc->filename);
+      return; /* failure */
+    }
+  if (len != 
+      GNUNET_DISK_file_read (dc->rfh,
+                             block,
+                             len)) 
+    {
+      GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
+                                "read",
+                                dc->filename);
+      return; /* failure */
+    }
+  GNUNET_CRYPTO_hash (block, len, &key);
+  if (0 != memcmp (&key,
+                   &dr->chk.key,
+                   sizeof (GNUNET_HashCode)))
+    return; /* mismatch */
+  if (GNUNET_OK !=
+      encrypt_existing_match (dc,
+                              chk,
+                              dr,
+                              block,
+                              len,
+                              GNUNET_NO))
+    {
+      /* hash matches but encrypted block does not, really bad */
+      dr->state = BRS_ERROR;
+      /* propagate up */
+      while (dr->parent != NULL)
+        {
+          dr = dr->parent;
+          dr->state = BRS_ERROR;
+        }
+      return;
+    }
+  /* block matches */
+  dr->state = BRS_DOWNLOAD_DOWN;
+
+  /* set CHKs for children */
+  up_done = GNUNET_YES;
+  chks = (const struct ContentHashKey*) block;
+  for (i=0;i<dr->num_children;i++)
+    {
+      drc = dr->children[i];
+      GNUNET_assert (drc->offset >= dr->offset);
+      child_block_size = GNUNET_FS_tree_compute_tree_size (drc->depth);
+      GNUNET_assert (0 == (drc->offset - dr->offset) % child_block_size);
+      chk_off = (drc->offset - dr->offset) / child_block_size;
+      GNUNET_assert (drc->state == BRS_INIT);
+      drc->state = BRS_CHK_SET;
+      drc->chk = chks[chk_off];
+      try_top_down_reconstruction (dc, drc);
+      if (drc->state != BRS_DOWNLOAD_UP)
+        up_done = GNUNET_NO; /* children not all done */
+    } 
+  if (up_done == GNUNET_YES)
+    propagate_up (dr); /* children all done (or no children...) */
+}
+
+
+/**
+ * Schedule the download of the specified block in the tree.
+ *
+ * @param dc overall download this block belongs to
+ * @param chk content-hash-key of the block
+ * @param offset offset of the block in the file
+ *         (for IBlocks, the offset is the lowest
+ *          offset of any DBlock in the subtree under
+ *          the IBlock)
+ * @param depth depth of the block, 0 is the root of the tree
+ */
+static void
+schedule_block_download (struct GNUNET_FS_DownloadContext *dc,
+                         struct DownloadRequest *dr)
+{
+  unsigned int i;
+
+  switch (dr->state)
+    {
+    case BRS_INIT:
+      GNUNET_assert (0);
+      break;
+    case BRS_RECONSTRUCT_DOWN:
+      GNUNET_assert (0);
+      break;
+    case BRS_RECONSTRUCT_META_UP:
+      GNUNET_assert (0);
+      break;
+    case BRS_RECONSTRUCT_UP:
+      GNUNET_assert (0);
+      break;
+    case BRS_CHK_SET:
+      /* normal case, start download */
+      break;
+    case BRS_DOWNLOAD_DOWN:
+      for (i=0;i<dr->num_children;i++)
+        schedule_block_download (dc, dr->children[i]);
+      return;
+    case BRS_DOWNLOAD_UP:
+      /* We're done! */
+      return;
+    case BRS_ERROR:
+      GNUNET_break (0);
+      return;
+    }
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Scheduling download at offset %llu and depth %u for `%s'\n",
+              (unsigned long long) dr->offset,
+              dr->depth,
+              GNUNET_h2s (&dr->chk.query));
+#endif
+  GNUNET_CONTAINER_DLL_insert (dc->pending_head,
+                               dc->pending_tail,
+                               dr);
+  dr->is_pending = GNUNET_YES;
+  GNUNET_CONTAINER_multihashmap_put (dc->active,
+                                     &dr->chk.query,
+                                     dr,
+                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
+  if (dc->client == NULL)
+    return; /* download not active */
+  if (NULL == dc->th)
+    dc->th = GNUNET_CLIENT_notify_transmit_ready (dc->client,
+                                                  sizeof (struct SearchMessage),
+                                                  GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+                                                  GNUNET_NO,
+                                                  &transmit_download_request,
+                                                  dc);
+}
+
+
 #define GNUNET_FS_URI_CHK_PREFIX GNUNET_FS_URI_PREFIX GNUNET_FS_URI_CHK_INFIX
 
 /**
@@ -1178,7 +988,7 @@ trigger_recursive_download (void *cls,
     {
       if (full_name == NULL)
         {
-          temp_name = GNUNET_DISK_mktemp ("gnunet-directory-download-tmp");
+          temp_name = GNUNET_DISK_mktemp ("gnunet-download-trd");
           real_name = temp_name;
         }
       else
@@ -1226,20 +1036,21 @@ trigger_recursive_download (void *cls,
 
 
 /**
- * Free entries in the map.
+ * (recursively) free download request structure
  *
- * @param cls unused (NULL)
- * @param key unused
- * @param entry entry of type "struct DownloadRequest" which is freed
- * @return GNUNET_OK
+ * @param dr request to free
  */
-static int
-free_entry (void *cls,
-            const GNUNET_HashCode *key,
-            void *entry)
+void
+GNUNET_FS_free_download_request_ (struct DownloadRequest *dr)
 {
-  GNUNET_free (entry);
-  return GNUNET_OK;
+  unsigned int i;
+
+  if (dr == NULL)
+    return;
+  for (i=0;i<dr->num_children;i++)
+    GNUNET_FS_free_download_request_ (dr->children[i]);
+  GNUNET_free_non_null (dr->children);
+  GNUNET_free (dr);
 }
 
 
@@ -1254,15 +1065,14 @@ free_entry (void *cls,
  */
 static int
 process_result_with_request (void *cls,
-                             const GNUNET_HashCode * key,
+                             const GNUNET_HashCode *key,
                              void *value)
 {
   struct ProcessResultClosure *prc = cls;
-  struct DownloadRequest *sm = value;
-  struct DownloadRequest *ppos;
-  struct DownloadRequest *pprev;
-  struct GNUNET_DISK_FileHandle *fh;
+  struct DownloadRequest *dr = value;
   struct GNUNET_FS_DownloadContext *dc = prc->dc;
+  struct DownloadRequest *drc;
+  struct GNUNET_DISK_FileHandle *fh = NULL;
   struct GNUNET_CRYPTO_AesSessionKey skey;
   struct GNUNET_CRYPTO_AesInitializationVector iv;
   char pt[prc->size];
@@ -1273,43 +1083,53 @@ process_result_with_request (void *cls,
   int i;
   struct ContentHashKey *chk;
 
-  fh = NULL;
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Received block `%s' matching pending request at depth %u and offset %llu/%llu\n",
+              GNUNET_h2s (key),
+              dr->depth,
+              (unsigned long long) dr->offset,
+              (unsigned long long) GNUNET_ntohll (dc->uri->data.chk.file_length));
+              
+#endif
   bs = GNUNET_FS_tree_calculate_block_size (GNUNET_ntohll (dc->uri->data.chk.file_length),
-                                            dc->treedepth,
-                                            sm->offset,
-                                            sm->depth);
+                                            dr->offset,
+                                            dr->depth);
   if (prc->size != bs)
     {
-#if DEBUG_DOWNLOAD
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "Internal error or bogus download URI (expected %u bytes, got %u)\n",
-                  bs,
-                  prc->size);
-#endif
-      dc->emsg = GNUNET_strdup ("Internal error or bogus download URI");
+      GNUNET_asprintf (&dc->emsg,
+                       _("Internal error or bogus download URI (expected %u bytes at depth %u and offset %llu/%llu, got %u bytes)\n"),
+                       bs,
+                       dr->depth,
+                       (unsigned long long) dr->offset,
+                       (unsigned long long) GNUNET_ntohll (dc->uri->data.chk.file_length),
+                       prc->size);
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                  "%s", 
+                  dc->emsg);
+      while (dr->parent != NULL)
+        {
+          dr->state = BRS_ERROR;
+          dr = dr->parent;
+        }
+      dr->state = BRS_ERROR;
       goto signal_error;
     }
+
   GNUNET_assert (GNUNET_YES ==
                  GNUNET_CONTAINER_multihashmap_remove (dc->active,
                                                        &prc->query,
-                                                       sm));
-  /* if this request is on the pending list, remove it! */
-  pprev = NULL;
-  ppos = dc->pending;
-  while (ppos != NULL)
+                                                       dr));
+  if (GNUNET_YES == dr->is_pending)
     {
-      if (ppos == sm)
-        {
-          if (pprev == NULL)
-            dc->pending = ppos->next;
-          else
-            pprev->next = ppos->next;
-          break;
-        }
-      pprev = ppos;
-      ppos = ppos->next;
+      GNUNET_CONTAINER_DLL_remove (dc->pending_head,
+                                   dc->pending_tail,
+                                   dr);
+      dr->is_pending = GNUNET_NO;
     }
-  GNUNET_CRYPTO_hash_to_aes_key (&sm->chk.key, &skey, &iv);
+
+
+  GNUNET_CRYPTO_hash_to_aes_key (&dr->chk.key, &skey, &iv);
   if (-1 == GNUNET_CRYPTO_aes_decrypt (prc->data,
                                        prc->size,
                                        &skey,
@@ -1317,18 +1137,17 @@ process_result_with_request (void *cls,
                                        pt))
     {
       GNUNET_break (0);
-      dc->emsg = GNUNET_strdup ("internal error decrypting content");
+      dc->emsg = GNUNET_strdup (_("internal error decrypting content"));
       goto signal_error;
     }
   off = compute_disk_offset (GNUNET_ntohll (dc->uri->data.chk.file_length),
-                             sm->offset,
-                             sm->depth,
-                             dc->treedepth);
+                             dr->offset,
+                             dr->depth);
   /* save to disk */
   if ( ( GNUNET_YES == prc->do_store) &&
        ( (dc->filename != NULL) ||
          (is_recursive_download (dc)) ) &&
-       ( (sm->depth == dc->treedepth) ||
+       ( (dr->depth == dc->treedepth) ||
          (0 == (dc->options & GNUNET_FS_DOWNLOAD_NO_TEMPORARIES)) ) )
     {
       fh = GNUNET_DISK_file_open (dc->filename != NULL 
@@ -1339,23 +1158,15 @@ process_result_with_request (void *cls,
                                   GNUNET_DISK_PERM_USER_READ |
                                   GNUNET_DISK_PERM_USER_WRITE |
                                   GNUNET_DISK_PERM_GROUP_READ |
-                                  GNUNET_DISK_PERM_OTHER_READ);
-    }
-  if ( (NULL == fh) &&
-       (GNUNET_YES == prc->do_store) &&
-       ( (dc->filename != NULL) ||
-         (is_recursive_download (dc)) ) &&
-       ( (sm->depth == dc->treedepth) ||
-         (0 == (dc->options & GNUNET_FS_DOWNLOAD_NO_TEMPORARIES)) ) )
-    {
-      GNUNET_asprintf (&dc->emsg,
-                       _("Download failed: could not open file `%s': %s\n"),
-                       dc->filename,
-                       STRERROR (errno));
-      goto signal_error;
-    }
-  if (fh != NULL)
-    {
+                                  GNUNET_DISK_PERM_OTHER_READ);    
+      if (NULL == fh)
+        {
+          GNUNET_asprintf (&dc->emsg,
+                           _("Download failed: could not open file `%s': %s\n"),
+                           dc->filename,
+                           STRERROR (errno));
+          goto signal_error;
+        }      
 #if DEBUG_DOWNLOAD
       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                   "Saving decrypted block to disk at offset %llu\n",
@@ -1389,22 +1200,24 @@ process_result_with_request (void *cls,
       GNUNET_break (GNUNET_OK == GNUNET_DISK_file_close (fh));
       fh = NULL;
     }
-  if (sm->depth == dc->treedepth) 
+
+  if (dr->depth == 0) 
     {
+      /* DBLOCK, update progress and try recursion if applicable */
       app = prc->size;
-      if (sm->offset < dc->offset)
+      if (dr->offset < dc->offset)
         {
           /* starting offset begins in the middle of pt,
              do not count first bytes as progress */
-          GNUNET_assert (app > (dc->offset - sm->offset));
-          app -= (dc->offset - sm->offset);       
+          GNUNET_assert (app > (dc->offset - dr->offset));
+          app -= (dc->offset - dr->offset);       
         }
-      if (sm->offset + prc->size > dc->offset + dc->length)
+      if (dr->offset + prc->size > dc->offset + dc->length)
         {
           /* end of block is after relevant range,
              do not count last bytes as progress */
-          GNUNET_assert (app > (sm->offset + prc->size) - (dc->offset + dc->length));
-          app -= (sm->offset + prc->size) - (dc->offset + dc->length);
+          GNUNET_assert (app > (dr->offset + prc->size) - (dc->offset + dc->length));
+          app -= (dr->offset + prc->size) - (dc->offset + dc->length);
         }
       dc->completed += app;
 
@@ -1419,15 +1232,18 @@ process_result_with_request (void *cls,
                                            dc);         
             
     }
+  dr->state = BRS_DOWNLOAD_DOWN;
   pi.status = GNUNET_FS_STATUS_DOWNLOAD_PROGRESS;
   pi.value.download.specifics.progress.data = pt;
-  pi.value.download.specifics.progress.offset = sm->offset;
+  pi.value.download.specifics.progress.offset = dr->offset;
   pi.value.download.specifics.progress.data_len = prc->size;
-  pi.value.download.specifics.progress.depth = sm->depth;
+  pi.value.download.specifics.progress.depth = dr->depth;
   GNUNET_FS_download_make_status_ (&pi, dc);
   GNUNET_assert (dc->completed <= dc->length);
+
   if (dc->completed == dc->length)
     {
+      /* download completed, signal */
 #if DEBUG_DOWNLOAD
       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                   "Download completed, truncating file to desired length %llu\n",
@@ -1447,46 +1263,64 @@ process_result_with_request (void *cls,
           GNUNET_FS_dequeue_ (dc->job_queue);
           dc->job_queue = NULL;
         }
-      if (is_recursive_download (dc))
-        full_recursive_download (dc);
-      if (dc->child_head == NULL)
-        {
-          /* signal completion */
-          pi.status = GNUNET_FS_STATUS_DOWNLOAD_COMPLETED;
-          GNUNET_FS_download_make_status_ (&pi, dc);
-          if (dc->parent != NULL)
-            check_completed (dc->parent);
-        }
-      GNUNET_assert (sm->depth == dc->treedepth);
+      GNUNET_assert (dr->depth == 0);
+      check_completed (dc);
     }
-  if (sm->depth == dc->treedepth) 
+  if (dr->depth == 0) 
     {
+      propagate_up (dr);
+      /* bottom of the tree, no child downloads possible, just sync */
       GNUNET_FS_download_sync_ (dc);
-      GNUNET_free (sm);      
       return GNUNET_YES;
     }
+
 #if DEBUG_DOWNLOAD
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "Triggering downloads of children (this block was at depth %u and offset %llu)\n",
-              sm->depth,
-              (unsigned long long) sm->offset);
+              dr->depth,
+              (unsigned long long) dr->offset);
 #endif
   GNUNET_assert (0 == (prc->size % sizeof(struct ContentHashKey)));
   chk = (struct ContentHashKey*) pt;
   for (i=(prc->size / sizeof(struct ContentHashKey))-1;i>=0;i--)
     {
-      off = compute_dblock_offset (sm->offset,
-                                   sm->depth,
-                                   dc->treedepth,
+      off = compute_dblock_offset (dr->offset,
+                                   dr->depth,
                                    i);
-      if ( (off + DBLOCK_SIZE >= dc->offset) &&
-           (off < dc->offset + dc->length) ) 
-        schedule_block_download (dc,
-                                 &chk[i],
-                                 off,
-                                 sm->depth + 1);
-    }
-  GNUNET_free (sm);
+      drc = dr->children[i];
+      switch (drc->state)
+        {
+        case BRS_INIT:
+          drc->chk = chk[i];
+          drc->state = BRS_CHK_SET;
+          schedule_block_download (dc, drc);
+          break;
+        case BRS_RECONSTRUCT_DOWN:
+          GNUNET_assert (0);
+          break;
+        case BRS_RECONSTRUCT_META_UP:
+          GNUNET_assert (0);
+          break;
+        case BRS_RECONSTRUCT_UP:
+          GNUNET_assert (0);
+          break;
+        case BRS_CHK_SET:
+          GNUNET_assert (0);
+          break;
+        case BRS_DOWNLOAD_DOWN:
+          GNUNET_assert (0);
+          break;
+        case BRS_DOWNLOAD_UP:
+          GNUNET_assert (0);
+          break;
+        case BRS_ERROR:
+          GNUNET_assert (0);
+          break;
+        default:
+          GNUNET_assert (0);
+          break;
+        }
+    }
   GNUNET_FS_download_sync_ (dc);
   return GNUNET_YES;
 
@@ -1503,12 +1337,13 @@ process_result_with_request (void *cls,
       dc->th = NULL;
     }
   GNUNET_CLIENT_disconnect (dc->client, GNUNET_NO);
-  GNUNET_CONTAINER_multihashmap_iterate (dc->active,
-                                         &free_entry,
-                                         NULL);
-  dc->pending = NULL;
   dc->client = NULL;
-  GNUNET_free (sm);
+  GNUNET_FS_free_download_request_ (dc->top_request);
+  dc->top_request = NULL;
+  GNUNET_CONTAINER_multihashmap_destroy (dc->active);
+  dc->active = NULL;
+  dc->pending_head = NULL;
+  dc->pending_tail = NULL;
   GNUNET_FS_download_sync_ (dc);
   return GNUNET_NO;
 }
@@ -1608,6 +1443,7 @@ transmit_download_request (void *cls,
   struct GNUNET_FS_DownloadContext *dc = cls;
   size_t msize;
   struct SearchMessage *sm;
+  struct DownloadRequest *dr;
 
   dc->th = NULL;
   if (NULL == buf)
@@ -1622,13 +1458,13 @@ transmit_download_request (void *cls,
   GNUNET_assert (size >= sizeof (struct SearchMessage));
   msize = 0;
   sm = buf;
-  while ( (dc->pending != NULL) &&
+  while ( (NULL != (dr = dc->pending_head)) &&
           (size >= msize + sizeof (struct SearchMessage)) )
     {
 #if DEBUG_DOWNLOAD
       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                   "Transmitting download request for `%s' to `%s'-service\n",
-                  GNUNET_h2s (&dc->pending->chk.query),
+                  GNUNET_h2s (&dr->chk.query),
                   "FS");
 #endif
       memset (sm, 0, sizeof (struct SearchMessage));
@@ -1638,25 +1474,30 @@ transmit_download_request (void *cls,
         sm->options = htonl (1);
       else
         sm->options = htonl (0);      
-      if (dc->pending->depth == dc->treedepth)
+      if (dr->depth == 0)
         sm->type = htonl (GNUNET_BLOCK_TYPE_FS_DBLOCK);
       else
         sm->type = htonl (GNUNET_BLOCK_TYPE_FS_IBLOCK);
       sm->anonymity_level = htonl (dc->anonymity);
       sm->target = dc->target.hashPubKey;
-      sm->query = dc->pending->chk.query;
-      dc->pending->is_pending = GNUNET_NO;
-      dc->pending = dc->pending->next;
+      sm->query = dr->chk.query;
+      GNUNET_CONTAINER_DLL_remove (dc->pending_head,
+                                   dc->pending_tail,
+                                   dr);
+      dr->is_pending = GNUNET_NO;
       msize += sizeof (struct SearchMessage);
       sm++;
     }
-  if (dc->pending != NULL)
-    dc->th = GNUNET_CLIENT_notify_transmit_ready (dc->client,
-                                                  sizeof (struct SearchMessage),
-                                                  GNUNET_CONSTANTS_SERVICE_TIMEOUT,
-                                                  GNUNET_NO,
-                                                  &transmit_download_request,
-                                                  dc); 
+  if (dc->pending_head != NULL)
+    {
+      dc->th = GNUNET_CLIENT_notify_transmit_ready (dc->client,
+                                                    sizeof (struct SearchMessage),
+                                                    GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+                                                    GNUNET_NO,
+                                                    &transmit_download_request,
+                                                    dc); 
+      GNUNET_assert (dc->th != NULL);
+    }
   return msize;
 }
 
@@ -1686,12 +1527,16 @@ do_reconnect (void *cls,
       return;
     }
   dc->client = client;
-  dc->th = GNUNET_CLIENT_notify_transmit_ready (client,
-                                                sizeof (struct SearchMessage),
-                                                GNUNET_CONSTANTS_SERVICE_TIMEOUT,
-                                                GNUNET_NO,
-                                                &transmit_download_request,
-                                                dc);  
+  if (dc->pending_head != NULL)
+    {
+      dc->th = GNUNET_CLIENT_notify_transmit_ready (client,
+                                                    sizeof (struct SearchMessage),
+                                                    GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+                                                    GNUNET_NO,
+                                                    &transmit_download_request,
+                                                    dc);
+      GNUNET_assert (dc->th != NULL);
+    }
   GNUNET_CLIENT_receive (client,
                          &receive_results,
                          dc,
@@ -1700,7 +1545,7 @@ do_reconnect (void *cls,
 
 
 /**
- * Add entries that are not yet pending back to the pending list.
+ * Add entries to the pending list.
  *
  * @param cls our download context
  * @param key unused
@@ -1715,12 +1560,10 @@ retry_entry (void *cls,
   struct GNUNET_FS_DownloadContext *dc = cls;
   struct DownloadRequest *dr = entry;
 
-  if (! dr->is_pending)
-    {
-      dr->next = dc->pending;
-      dr->is_pending = GNUNET_YES;
-      dc->pending = entry;
-    }
+  GNUNET_CONTAINER_DLL_insert (dc->pending_head,
+                               dc->pending_tail,
+                               dr);
+  dr->is_pending = GNUNET_YES;
   return GNUNET_OK;
 }
 
@@ -1747,6 +1590,9 @@ try_reconnect (struct GNUNET_FS_DownloadContext *dc)
           GNUNET_CLIENT_notify_transmit_ready_cancel (dc->th);
           dc->th = NULL;
         }
+      /* full reset of the pending list */
+      dc->pending_head = NULL;
+      dc->pending_tail = NULL;
       GNUNET_CONTAINER_multihashmap_iterate (dc->active,
                                              &retry_entry,
                                              dc);
@@ -1764,7 +1610,6 @@ try_reconnect (struct GNUNET_FS_DownloadContext *dc)
 }
 
 
-
 /**
  * We're allowed to ask the FS service for our blocks.  Start the download.
  *
@@ -1799,13 +1644,16 @@ activate_fs_download (void *cls,
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "Asking for transmission to FS service\n");
 #endif
-  dc->th = GNUNET_CLIENT_notify_transmit_ready (dc->client,
-                                                sizeof (struct SearchMessage),
-                                                GNUNET_CONSTANTS_SERVICE_TIMEOUT,
-                                                GNUNET_NO,
-                                                &transmit_download_request,
-                                                dc);    
-  GNUNET_assert (dc->th != NULL);
+  if (dc->pending_head != NULL)
+    {
+      dc->th = GNUNET_CLIENT_notify_transmit_ready (dc->client,
+                                                    sizeof (struct SearchMessage),
+                                                    GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+                                                    GNUNET_NO,
+                                                    &transmit_download_request,
+                                                    dc);    
+      GNUNET_assert (dc->th != NULL);
+    }
 }
 
 
@@ -1840,6 +1688,271 @@ deactivate_fs_download (void *cls)
 
 
 /**
+ * (recursively) Create a download request structure.
+ *
+ * @param parent parent of the current entry
+ * @param depth depth of the current entry, 0 are the DBLOCKs,
+ *              top level block is 'dc->treedepth - 1'
+ * @param dr_offset offset in the original file this block maps to
+ *              (as in, offset of the first byte of the first DBLOCK 
+ *               in the subtree rooted in the returned download request tree)
+ * @param file_start_offset desired starting offset for the download
+ *             in the original file; requesting tree should not contain
+ *             DBLOCKs prior to the file_start_offset
+ * @param file_length desired number of bytes the user wanted to access
+ *        (from file_start_offset).  Resulting tree should not contain
+ *        DBLOCKs after file_start_offset + file_length.
+ * @return download request tree for the given range of DBLOCKs at
+ *         the specified depth
+ */
+static struct DownloadRequest *
+create_download_request (struct DownloadRequest *parent,
+                         unsigned int depth,
+                         uint64_t dr_offset,
+                         uint64_t file_start_offset,
+                         uint64_t desired_length)
+{
+  struct DownloadRequest *dr;
+  unsigned int i;
+  unsigned int head_skip;
+  uint64_t child_block_size;
+  
+  dr = GNUNET_malloc (sizeof (struct DownloadRequest));
+  dr->parent = parent;
+  dr->depth = depth;
+  dr->offset = dr_offset;
+  if (depth > 0)
+    {
+      child_block_size = GNUNET_FS_tree_compute_tree_size (depth - 1);
+      
+      /* calculate how many blocks at this level are not interesting
+         from the start (rounded down), either because of the requested
+         file offset or because this IBlock is further along */
+      if (dr_offset < file_start_offset)
+        head_skip = file_start_offset / child_block_size;       
+      else
+        head_skip = dr_offset / child_block_size;       
+
+      /* calculate index of last block at this level that is interesting (rounded up) */
+      dr->num_children = file_start_offset + desired_length / child_block_size;
+      if (dr->num_children * child_block_size < file_start_offset + desired_length)
+        dr->num_children++; /* round up */
+
+      /* now we can get the total number of children for this block */
+      dr->num_children -= head_skip;
+      if (dr->num_children > CHK_PER_INODE)
+        dr->num_children = CHK_PER_INODE; /* cap at max */
+
+      /* why else would we have gotten here to begin with? (that'd be a bad logic error) */
+      GNUNET_assert (dr->num_children > 0); 
+
+      dr->children = GNUNET_malloc (dr->num_children * 
+                                    sizeof (struct DownloadRequest *));
+      for (i=0;i<dr->num_children;i++)
+        dr->children[i] = create_download_request (dr,
+                                                   depth - 1,
+                                                   dr_offset + i * child_block_size,
+                                                   file_start_offset,
+                                                   desired_length);      
+    }
+  return dr;
+}
+
+
+/**
+ * Continuation after a possible attempt to reconstruct
+ * the current IBlock from the existing file.
+ *
+ * @param cls the 'struct ReconstructContext'
+ * @param tc scheduler context
+ */
+static void
+reconstruct_cont (void *cls,
+                  const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+
+  /* clean up state from tree encoder */
+  if (dc->te != NULL)
+    {
+      GNUNET_FS_tree_encoder_finish (dc->te, NULL, NULL);
+      dc->te = NULL;
+    }
+  if (dc->task != GNUNET_SCHEDULER_NO_TASK)
+    {
+      GNUNET_SCHEDULER_cancel (dc->task);
+      dc->task = GNUNET_SCHEDULER_NO_TASK;
+    }
+  if (dc->rfh != NULL)
+    {
+      GNUNET_break (GNUNET_OK == GNUNET_DISK_file_close (dc->rfh));
+      dc->rfh = NULL;
+    }
+  /* start "normal" download */
+  schedule_block_download (dc, 
+                           dc->top_request);
+}
+
+
+/**
+ * Task requesting the next block from the tree encoder.
+ *
+ * @param tc task context
+ */
+static void
+get_next_block (void *cls,
+                const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+
+  dc->task = GNUNET_SCHEDULER_NO_TASK;
+  GNUNET_FS_tree_encoder_next (dc->te);
+}
+
+
+
+/**
+ * Function called asking for the current (encoded)
+ * block to be processed.  After processing the
+ * client should either call "GNUNET_FS_tree_encode_next"
+ * or (on error) "GNUNET_FS_tree_encode_finish".
+ *
+ * This function checks if the content on disk matches
+ * the expected content based on the URI.
+ * 
+ * @param cls closure
+ * @param chk content hash key for the block
+ * @param offset offset of the block
+ * @param depth depth of the block, 0 for DBLOCK
+ * @param type type of the block (IBLOCK or DBLOCK)
+ * @param block the (encrypted) block
+ * @param block_size size of block (in bytes)
+ */
+static void 
+reconstruct_cb (void *cls,
+                const struct ContentHashKey *chk,
+                uint64_t offset,
+                unsigned int depth,
+                enum GNUNET_BLOCK_Type type,
+                const void *block,
+                uint16_t block_size)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+  struct GNUNET_FS_ProgressInfo pi;
+  struct DownloadRequest *dr;
+  uint64_t blen;
+  unsigned int chld;
+
+  /* find corresponding request entry */
+  dr = dc->top_request;
+  while (dr->depth > depth)
+    {
+      blen = GNUNET_FS_tree_compute_tree_size (dr->depth);
+      chld = (offset - dr->offset) / blen;
+      GNUNET_assert (chld < dr->num_children);
+      dr = dr->children[chld];
+    }
+  switch (dr->state)
+    {
+    case BRS_INIT:
+      break;
+    case BRS_RECONSTRUCT_DOWN:
+      break;
+    case BRS_RECONSTRUCT_META_UP:
+      break;
+    case BRS_RECONSTRUCT_UP:
+      break;
+    case BRS_CHK_SET:
+      if (0 == memcmp (chk,
+                       &dr->chk,
+                       sizeof (struct ContentHashKey)))
+        {
+          /* block matches, hence tree below matches; 
+             this request is done! */
+          dr->state = BRS_DOWNLOAD_UP;
+          /* calculate how many bytes of payload this block
+             corresponds to */
+          blen = GNUNET_FS_tree_compute_tree_size (dr->depth);
+          /* how many of those bytes are in the requested range? */
+          blen = GNUNET_MIN (blen,
+                             dc->length + dc->offset - dr->offset);
+          /* signal progress */
+          dc->completed += blen;
+          pi.status = GNUNET_FS_STATUS_DOWNLOAD_PROGRESS;
+          pi.value.download.specifics.progress.data = NULL;
+          pi.value.download.specifics.progress.offset = offset;
+          pi.value.download.specifics.progress.data_len = 0;
+          pi.value.download.specifics.progress.depth = 0;
+          GNUNET_FS_download_make_status_ (&pi, dc);             
+        }
+      else
+        {
+        }
+      break; 
+    case BRS_DOWNLOAD_DOWN:
+      break; 
+    case BRS_DOWNLOAD_UP:
+      break;
+    case BRS_ERROR:
+      break;
+    default:
+      GNUNET_assert (0);
+      break;
+    }
+  if ( (dr == dc->top_request) &&
+       (dr->state == BRS_DOWNLOAD_UP) )
+    {
+      check_completed (dc);
+      return;
+    }
+  dc->task = GNUNET_SCHEDULER_add_now (&get_next_block,
+                                       dc);
+}
+
+
+/**
+ * Function called by the tree encoder to obtain a block of plaintext
+ * data (for the lowest level of the tree).
+ *
+ * @param cls our 'struct ReconstructContext'
+ * @param offset identifies which block to get
+ * @param max (maximum) number of bytes to get; returning
+ *        fewer will also cause errors
+ * @param buf where to copy the plaintext buffer
+ * @param emsg location to store an error message (on error)
+ * @return number of bytes copied to buf, 0 on error
+ */
+static size_t
+fh_reader (void *cls,
+           uint64_t offset,
+           size_t max, 
+           void *buf,
+           char **emsg)
+{
+  struct GNUNET_FS_DownloadContext *dc = cls;
+  struct GNUNET_DISK_FileHandle *fh = dc->rfh;
+  ssize_t ret;
+
+  *emsg = NULL;
+  if (offset !=
+      GNUNET_DISK_file_seek (fh,
+                             offset,
+                             GNUNET_DISK_SEEK_SET))
+    {
+      *emsg = GNUNET_strdup (strerror (errno));
+      return 0;
+    }
+  ret = GNUNET_DISK_file_read (fh, buf, max);
+  if (ret < 0)
+    {
+      *emsg = GNUNET_strdup (strerror (errno));
+      return 0;
+    }
+  return ret;
+}
+
+
+/**
  * Task that creates the initial (top-level) download
  * request for the file.
  *
@@ -1854,7 +1967,11 @@ GNUNET_FS_download_start_task_ (void *cls,
   struct GNUNET_FS_ProgressInfo pi;
   struct GNUNET_DISK_FileHandle *fh;
 
-  dc->start_task = GNUNET_SCHEDULER_NO_TASK;
+#if DEBUG_DOWNLOAD
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Start task running...\n");
+#endif
+  dc->task = GNUNET_SCHEDULER_NO_TASK;
   if (dc->length == 0)
     {
       /* no bytes required! */
@@ -1863,33 +1980,128 @@ GNUNET_FS_download_start_task_ (void *cls,
           fh = GNUNET_DISK_file_open (dc->filename != NULL 
                                       ? dc->filename 
                                       : dc->temp_filename, 
-                                      GNUNET_DISK_OPEN_READWRITE | 
-                                      GNUNET_DISK_OPEN_CREATE,
+                                      GNUNET_DISK_OPEN_READWRITE |
+                                      GNUNET_DISK_OPEN_CREATE |
+                                      ( (0 == GNUNET_FS_uri_chk_get_file_size (dc->uri)) 
+                                        ? GNUNET_DISK_OPEN_TRUNCATE : 0),
                                       GNUNET_DISK_PERM_USER_READ |
                                       GNUNET_DISK_PERM_USER_WRITE |
                                       GNUNET_DISK_PERM_GROUP_READ |
                                       GNUNET_DISK_PERM_OTHER_READ);
           GNUNET_DISK_file_close (fh);
         }
-
-      pi.status = GNUNET_FS_STATUS_DOWNLOAD_COMPLETED;
-      GNUNET_FS_download_make_status_ (&pi, dc);
       GNUNET_FS_download_sync_ (dc);
-       if (dc->parent != NULL)
-        check_completed (dc->parent);      
+      check_completed (dc);
       return;
     }
-  schedule_block_download (dc, 
-                           (dc->uri->type == chk) 
-                           ? &dc->uri->data.chk.chk
-                           : &dc->uri->data.loc.fi.chk,
-                           0, 
-                           1 /* 0 == CHK, 1 == top */); 
-  GNUNET_FS_download_sync_ (dc);
+  if (dc->emsg != NULL) 
+    return;
+  if (dc->top_request == NULL)
+    {
+      dc->top_request = create_download_request (NULL, dc->treedepth - 1, 0,
+                                                 dc->offset, dc->length);
+      dc->top_request->state = BRS_CHK_SET;
+      dc->top_request->chk = (dc->uri->type == chk) 
+        ? dc->uri->data.chk.chk
+        : dc->uri->data.loc.fi.chk;
+      /* signal start */
+      GNUNET_FS_download_sync_ (dc);
+      pi.status = GNUNET_FS_STATUS_DOWNLOAD_START;
+      pi.value.download.specifics.start.meta = dc->meta;
+      GNUNET_FS_download_make_status_ (&pi, dc);
+    }
   GNUNET_FS_download_start_downloading_ (dc);
-  pi.status = GNUNET_FS_STATUS_DOWNLOAD_START;
-  pi.value.download.specifics.start.meta = dc->meta;
-  GNUNET_FS_download_make_status_ (&pi, dc);
+  /* attempt reconstruction from disk */
+  if (GNUNET_YES == GNUNET_DISK_file_test (dc->filename))    
+    dc->rfh = GNUNET_DISK_file_open (dc->filename,
+                                     GNUNET_DISK_OPEN_READ,
+                                     GNUNET_DISK_PERM_NONE);    
+  if (dc->top_request->state == BRS_CHK_SET)
+    {
+      if (dc->rfh != NULL)
+        {
+          /* first, try top-down */
+          try_top_down_reconstruction (dc, dc->top_request);
+          switch (dc->top_request->state)
+            {
+            case BRS_CHK_SET:
+              break; /* normal */
+            case BRS_DOWNLOAD_DOWN:
+              break; /* normal, some blocks already down */
+            case BRS_DOWNLOAD_UP:
+              /* already done entirely, party! */
+              dc->completed = dc->length;
+              GNUNET_FS_download_sync_ (dc);
+              pi.status = GNUNET_FS_STATUS_DOWNLOAD_PROGRESS;
+              /* slightly ugly: no data provided to callee; maybe mmap the
+                 file instead? Or is 'data' pure convenience!? */
+              pi.value.download.specifics.progress.data = NULL;
+              pi.value.download.specifics.progress.offset = dc->offset;
+              pi.value.download.specifics.progress.data_len = dc->length;
+              pi.value.download.specifics.progress.depth = 0;
+              GNUNET_FS_download_make_status_ (&pi, dc);
+              if (dc->rfh != NULL)
+                {
+                  /* avoid hanging on to file handle longer than 
+                     necessary */
+                  GNUNET_DISK_file_close (dc->rfh);
+                  dc->rfh = NULL;
+                }
+              check_completed (dc);
+              return;      
+            case BRS_ERROR:
+              GNUNET_asprintf (&dc->emsg,
+                               _("Invalid URI"));
+              GNUNET_FS_download_sync_ (dc);
+              pi.status = GNUNET_FS_STATUS_DOWNLOAD_ERROR;
+              pi.value.download.specifics.error.message = dc->emsg;
+              GNUNET_FS_download_make_status_ (&pi, dc);
+              return;
+            default:
+              GNUNET_assert (0);
+              break;
+            }
+        }
+    }
+  /* attempt reconstruction from meta data */
+  if (GNUNET_FS_uri_chk_get_file_size (dc->uri) <= MAX_INLINE_SIZE)
+    {
+      GNUNET_CONTAINER_meta_data_iterate (dc->meta,
+                                          &match_full_data,
+                                          dc);
+      if (dc->top_request->state == BRS_DOWNLOAD_UP)
+        {
+          if (dc->rfh != NULL)
+            {
+              /* avoid hanging on to file handle longer than 
+                 necessary */
+              GNUNET_DISK_file_close (dc->rfh);
+              dc->rfh = NULL;
+            }
+          return; /* finished, status update was already done for us */
+        }
+    }
+  if (dc->rfh != NULL)
+    {
+      /* finally, try bottom-up */
+      dc->te = GNUNET_FS_tree_encoder_create (dc->h,
+                                              dc->old_file_size,
+                                              dc,
+                                              &fh_reader,
+                                              &reconstruct_cb,
+                                              NULL,
+                                              &reconstruct_cont);     
+      dc->task = GNUNET_SCHEDULER_add_now (&get_next_block,
+                                           dc);
+    }
+  else
+    {
+      /* simple, top-level download */
+        schedule_block_download (dc, 
+                                 dc->top_request);
+    }
+  if (dc->top_request->state == BRS_DOWNLOAD_UP)
+    check_completed (dc);
 }
 
 
@@ -1923,30 +2135,29 @@ GNUNET_FS_download_signal_suspend_ (void *cls)
     GNUNET_CONTAINER_DLL_remove (dc->parent->child_head,
                                  dc->parent->child_tail,
                                  dc);  
-  if (GNUNET_SCHEDULER_NO_TASK != dc->task)
-    GNUNET_SCHEDULER_cancel (dc->task);
-  if (dc->start_task != GNUNET_SCHEDULER_NO_TASK)
+  if (dc->task != GNUNET_SCHEDULER_NO_TASK)
     {
-      GNUNET_SCHEDULER_cancel (dc->start_task);
-      dc->start_task = GNUNET_SCHEDULER_NO_TASK;
+      GNUNET_SCHEDULER_cancel (dc->task);
+      dc->task = GNUNET_SCHEDULER_NO_TASK;
     }
-  else
+  pi.status = GNUNET_FS_STATUS_DOWNLOAD_SUSPEND;
+  GNUNET_FS_download_make_status_ (&pi, dc);
+  if (dc->te != NULL)
     {
-      pi.status = GNUNET_FS_STATUS_DOWNLOAD_SUSPEND;
-      GNUNET_FS_download_make_status_ (&pi, dc);
+      GNUNET_FS_tree_encoder_finish (dc->te, NULL, NULL);       
+      dc->te = NULL;
     }
-  if (dc->rcc != NULL)
+  if (dc->rfh != NULL)
     {
-      if (dc->rcc->task != GNUNET_SCHEDULER_NO_TASK)
-        GNUNET_SCHEDULER_cancel (dc->rcc->task);
-      if (dc->rcc->te != NULL)
-        GNUNET_FS_tree_encoder_finish (dc->rcc->te, NULL, NULL);        
-      dc->rcc = NULL;
+      GNUNET_DISK_file_close (dc->rfh);
+      dc->rfh = NULL;
+    }
+  GNUNET_FS_free_download_request_ (dc->top_request);
+  if (dc->active != NULL)
+    {
+      GNUNET_CONTAINER_multihashmap_destroy (dc->active);
+      dc->active = NULL;
     }
-  GNUNET_CONTAINER_multihashmap_iterate (dc->active,
-                                         &free_entry,
-                                         NULL);
-  GNUNET_CONTAINER_multihashmap_destroy (dc->active);
   GNUNET_free_non_null (dc->filename);
   GNUNET_CONTAINER_meta_data_destroy (dc->meta);
   GNUNET_FS_uri_destroy (dc->uri);
@@ -2067,7 +2278,8 @@ GNUNET_FS_download_start (struct GNUNET_FS_Handle *h,
                                     &GNUNET_FS_download_signal_suspend_,
                                     dc);
     }
-  dc->start_task = GNUNET_SCHEDULER_add_now (&GNUNET_FS_download_start_task_, dc);
+  dc->task = GNUNET_SCHEDULER_add_now (&GNUNET_FS_download_start_task_, 
+                                       dc);
   return dc;
 }
 
@@ -2184,10 +2396,12 @@ GNUNET_FS_download_start_from_search (struct GNUNET_FS_Handle *h,
               "Download tree has depth %u\n",
               dc->treedepth);
 #endif
-  dc->start_task = GNUNET_SCHEDULER_add_now (&GNUNET_FS_download_start_task_, dc);
+  dc->task = GNUNET_SCHEDULER_add_now (&GNUNET_FS_download_start_task_, 
+                                       dc);
   return dc;  
 }
 
+
 /**
  * Start the downloading process (by entering the queue).
  *
@@ -2222,10 +2436,12 @@ GNUNET_FS_download_stop (struct GNUNET_FS_DownloadContext *dc,
 
   if (dc->top != NULL)
     GNUNET_FS_end_top (dc->h, dc->top);
-  if (dc->start_task != GNUNET_SCHEDULER_NO_TASK)
+
+
+  if (dc->task != GNUNET_SCHEDULER_NO_TASK)
     {
-      GNUNET_SCHEDULER_cancel (dc->start_task);
-      dc->start_task = GNUNET_SCHEDULER_NO_TASK;
+      GNUNET_SCHEDULER_cancel (dc->task);
+      dc->task = GNUNET_SCHEDULER_NO_TASK;
     }
   if (dc->search != NULL)
     {
@@ -2237,13 +2453,10 @@ GNUNET_FS_download_stop (struct GNUNET_FS_DownloadContext *dc,
       GNUNET_FS_dequeue_ (dc->job_queue);
       dc->job_queue = NULL;
     }
-  if (dc->rcc != NULL)
+  if (dc->te != NULL)
     {
-      if (dc->rcc->task != GNUNET_SCHEDULER_NO_TASK)
-        GNUNET_SCHEDULER_cancel (dc->rcc->task);
-      if (dc->rcc->te != NULL)
-        GNUNET_FS_tree_encoder_finish (dc->rcc->te, NULL, NULL);
-      dc->rcc = NULL;
+      GNUNET_FS_tree_encoder_finish (dc->te, NULL, NULL);
+      dc->te = NULL;
     }
   have_children = (NULL != dc->child_head) ? GNUNET_YES : GNUNET_NO;
   while (NULL != dc->child_head)
@@ -2268,12 +2481,13 @@ GNUNET_FS_download_stop (struct GNUNET_FS_DownloadContext *dc,
                                 dc->serialization);  
   pi.status = GNUNET_FS_STATUS_DOWNLOAD_STOPPED;
   GNUNET_FS_download_make_status_ (&pi, dc);
-  if (GNUNET_SCHEDULER_NO_TASK != dc->task)
-    GNUNET_SCHEDULER_cancel (dc->task);
-  GNUNET_CONTAINER_multihashmap_iterate (dc->active,
-                                         &free_entry,
-                                         NULL);
-  GNUNET_CONTAINER_multihashmap_destroy (dc->active);
+  GNUNET_FS_free_download_request_ (dc->top_request);
+  dc->top_request = NULL;
+  if (dc->active != NULL)
+    {
+      GNUNET_CONTAINER_multihashmap_destroy (dc->active);
+      dc->active = NULL;
+    }
   if (dc->filename != NULL)
     {
       if ( (dc->completed != dc->length) &&
diff --git a/src/fs/fs_misc.c b/src/fs/fs_misc.c
new file mode 100644
index 000000000..e6c4eeea9
--- /dev/null
+++ b/src/fs/fs_misc.c
@@ -0,0 +1,165 @@
+/*
+     This file is part of GNUnet.
+     (C) 2010, 2011 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet is distributed in the hope that it will be useful, but
+     WITHOUT ANY WARRANTY; without even the implied warranty of
+     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+/**
+ * @file fs/fs_misc.c
+ * @brief misc. functions related to file-sharing in general
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "gnunet_constants.h"
+#include "gnunet_fs_service.h"
+#include "fs.h"
+
+
+/**
+ * Suggest a filename based on given metadata.
+ * 
+ * @param md given meta data
+ * @return NULL if meta data is useless for suggesting a filename
+ */
+char *
+GNUNET_FS_meta_data_suggest_filename (const struct GNUNET_CONTAINER_MetaData *md)
+{
+  static const char *mimeMap[][2] = {
+    {"application/bz2", ".bz2"},
+    {"application/gnunet-directory", ".gnd"},
+    {"application/java", ".class"},
+    {"application/msword", ".doc"},
+    {"application/ogg", ".ogg"},
+    {"application/pdf", ".pdf"},
+    {"application/pgp-keys", ".key"},
+    {"application/pgp-signature", ".pgp"},
+    {"application/postscript", ".ps"},
+    {"application/rar", ".rar"},
+    {"application/rtf", ".rtf"},
+    {"application/xml", ".xml"},
+    {"application/x-debian-package", ".deb"},
+    {"application/x-dvi", ".dvi"},
+    {"applixation/x-flac", ".flac"},
+    {"applixation/x-gzip", ".gz"},
+    {"application/x-java-archive", ".jar"},
+    {"application/x-java-vm", ".class"},
+    {"application/x-python-code", ".pyc"},
+    {"application/x-redhat-package-manager", ".rpm"},
+    {"application/x-rpm", ".rpm"},
+    {"application/x-tar", ".tar"},
+    {"application/x-tex-pk", ".pk"},
+    {"application/x-texinfo", ".texinfo"},
+    {"application/x-xcf", ".xcf"},
+    {"application/x-xfig", ".xfig"},
+    {"application/zip", ".zip"},
+    
+    {"audio/midi", ".midi"},
+    {"audio/mpeg", ".mp3"},
+    {"audio/real", ".rm"},
+    {"audio/x-wav", ".wav"},
+    
+    {"image/gif", ".gif"},
+    {"image/jpeg", ".jpg"},
+    {"image/pcx", ".pcx"},
+    {"image/png", ".png"},
+    {"image/tiff", ".tiff"},
+    {"image/x-ms-bmp", ".bmp"},
+    {"image/x-xpixmap", ".xpm"},
+    
+    {"text/css", ".css"},
+    {"text/html", ".html"},
+    {"text/plain", ".txt"},
+    {"text/rtf", ".rtf"},
+    {"text/x-c++hdr", ".h++"},
+    {"text/x-c++src", ".c++"},
+    {"text/x-chdr", ".h"},
+    {"text/x-csrc", ".c"},
+    {"text/x-java", ".java"},
+    {"text/x-moc", ".moc"},
+    {"text/x-pascal", ".pas"},
+    {"text/x-perl", ".pl"},
+    {"text/x-python", ".py"},
+    {"text/x-tex", ".tex"},
+    
+    {"video/avi", ".avi"},
+    {"video/mpeg", ".mpeg"},
+    {"video/quicktime", ".qt"},
+    {"video/real", ".rm"},
+    {"video/x-msvideo", ".avi"},
+    {NULL, NULL},
+  };
+  char *ret;
+  unsigned int i;
+  char *mime;
+  char *base;
+  const char *ext;
+
+  ret = GNUNET_CONTAINER_meta_data_get_by_type (md,
+                                                EXTRACTOR_METATYPE_GNUNET_ORIGINAL_FILENAME);
+  if (ret != NULL)
+    return ret;  
+  ext = NULL;
+  mime = GNUNET_CONTAINER_meta_data_get_by_type (md,
+                                                 EXTRACTOR_METATYPE_MIMETYPE);
+  if (mime != NULL)
+    {
+      i = 0;
+      while ( (mimeMap[i][0] != NULL) && 
+              (0 != strcmp (mime, mimeMap[i][0])))
+        i++;
+      if (mimeMap[i][1] == NULL)
+        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG | 
+                    GNUNET_ERROR_TYPE_BULK,
+                    _("Did not find mime type `%s' in extension list.\n"),
+                    mime);
+      else
+        ext = mimeMap[i][1];
+      GNUNET_free (mime);
+    }
+  base = GNUNET_CONTAINER_meta_data_get_first_by_types (md,
+                                                        EXTRACTOR_METATYPE_TITLE,
+                                                        EXTRACTOR_METATYPE_BOOK_TITLE,
+                                                        EXTRACTOR_METATYPE_ORIGINAL_TITLE,
+                                                        EXTRACTOR_METATYPE_PACKAGE_NAME,
+                                                        EXTRACTOR_METATYPE_URL,
+                                                        EXTRACTOR_METATYPE_URI, 
+                                                        EXTRACTOR_METATYPE_DESCRIPTION,
+                                                        EXTRACTOR_METATYPE_ISRC,
+                                                        EXTRACTOR_METATYPE_JOURNAL_NAME,
+                                                        EXTRACTOR_METATYPE_AUTHOR_NAME,
+                                                        EXTRACTOR_METATYPE_SUBJECT,
+                                                        EXTRACTOR_METATYPE_ALBUM,
+                                                        EXTRACTOR_METATYPE_ARTIST,
+                                                        EXTRACTOR_METATYPE_KEYWORDS,
+                                                        EXTRACTOR_METATYPE_COMMENT,
+                                                        EXTRACTOR_METATYPE_UNKNOWN,
+                                                        -1);
+  if ( (base == NULL) &&
+       (ext == NULL) )
+    return NULL;
+  if (base == NULL)
+    return GNUNET_strdup (ext);
+  if (ext == NULL)
+    return base;
+  GNUNET_asprintf (&ret,
+                   "%s%s",
+                   base,
+                   ext);
+  GNUNET_free (base);
+  return ret;
+}
+
+/* end of fs_misc.c */
diff --git a/src/fs/fs_publish.c b/src/fs/fs_publish.c
index bc75c2a40..6c933a37d 100644
--- a/src/fs/fs_publish.c
+++ b/src/fs/fs_publish.c
@@ -457,6 +457,7 @@ encode_cont (void *cls,
   struct GNUNET_FS_FileInformation *p;
   struct GNUNET_FS_ProgressInfo pi;
   char *emsg;
+  uint64_t flen;
 
   p = sc->fi_pos;
   GNUNET_FS_tree_encoder_finish (p->te,
@@ -484,13 +485,13 @@ encode_cont (void *cls,
               "Finished with tree encoder\n");
 #endif  
   /* final progress event */
+  flen = GNUNET_FS_uri_chk_get_file_size (p->chk_uri);
   pi.status = GNUNET_FS_STATUS_PUBLISH_PROGRESS;
   pi.value.publish.specifics.progress.data = NULL;
-  pi.value.publish.specifics.progress.offset = GNUNET_FS_uri_chk_get_file_size (p->chk_uri);
+  pi.value.publish.specifics.progress.offset = flen;
   pi.value.publish.specifics.progress.data_len = 0;
-  pi.value.publish.specifics.progress.depth = 0;
-  p->client_info = GNUNET_FS_publish_make_status_ (&pi, sc, p, 
-                                                   GNUNET_FS_uri_chk_get_file_size (p->chk_uri));
+  pi.value.publish.specifics.progress.depth = GNUNET_FS_compute_depth (flen);
+  p->client_info = GNUNET_FS_publish_make_status_ (&pi, sc, p, flen);
 
   /* continue with main */
   sc->upload_task 
@@ -507,18 +508,18 @@ encode_cont (void *cls,
  * or (on error) "GNUNET_FS_tree_encode_finish".
  *
  * @param cls closure
- * @param query the query for the block (key for lookup in the datastore)
+ * @param chk content hash key for the block 
  * @param offset offset of the block in the file
- * @param depth depth of the block in the file
+ * @param depth depth of the block in the file, 0 for DBLOCK
  * @param type type of the block (IBLOCK or DBLOCK)
  * @param block the (encrypted) block
  * @param block_size size of block (in bytes)
  */
 static void 
 block_proc (void *cls,
-            const GNUNET_HashCode *query,
+            const struct ContentHashKey *chk,
             uint64_t offset,
-            unsigned int depth,
+            unsigned int depth, 
             enum GNUNET_BLOCK_Type type,
             const void *block,
             uint16_t block_size)
@@ -556,7 +557,7 @@ block_proc (void *cls,
 #if DEBUG_PUBLISH
       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                   "Indexing block `%s' for offset %llu with index size %u\n",
-                  GNUNET_h2s (query),
+                  GNUNET_h2s (&chk->query),
                   (unsigned long long) offset,
                   sizeof (struct OnDemandBlock));
 #endif
@@ -564,7 +565,7 @@ block_proc (void *cls,
       odb.file_id = p->data.file.file_id;
       GNUNET_DATASTORE_put (sc->dsh,
                             (p->is_directory) ? 0 : sc->rid,
-                            query,
+                            &chk->query,
                             sizeof (struct OnDemandBlock),
                             &odb,
                             GNUNET_BLOCK_TYPE_FS_ONDEMAND,
@@ -580,13 +581,13 @@ block_proc (void *cls,
 #if DEBUG_PUBLISH
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "Publishing block `%s' for offset %llu with size %u\n",
-              GNUNET_h2s (query),
+              GNUNET_h2s (&chk->query),
               (unsigned long long) offset,
               (unsigned int) block_size);
 #endif
   GNUNET_DATASTORE_put (sc->dsh,
                         (p->is_directory) ? 0 : sc->rid,
-                        query,
+                        &chk->query,
                         block_size,
                         block,
                         type,
@@ -608,7 +609,7 @@ block_proc (void *cls,
  * @param offset where are we in the file
  * @param pt_block plaintext of the currently processed block
  * @param pt_size size of pt_block
- * @param depth depth of the block in the tree
+ * @param depth depth of the block in the tree, 0 for DBLOCK
  */
 static void 
 progress_proc (void *cls,
diff --git a/src/fs/fs_tree.c b/src/fs/fs_tree.c
index 05c9c55cd..e22ce8221 100644
--- a/src/fs/fs_tree.c
+++ b/src/fs/fs_tree.c
@@ -1,6 +1,6 @@
 /*
      This file is part of GNUnet.
-     (C) 2009 Christian Grothoff (and other contributing authors)
+     (C) 2009-2011 Christian Grothoff (and other contributing authors)
 
      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
@@ -75,7 +75,7 @@ struct GNUNET_FS_TreeEncoder
    * Set to the URI (upon successful completion)
    */
   struct GNUNET_FS_Uri *uri;
-  
+
   /**
    * Overall file size.
    */
@@ -87,12 +87,12 @@ struct GNUNET_FS_TreeEncoder
   uint64_t publish_offset;
 
   /**
-   * How deep are we?
+   * How deep are we?  Depth 0 is for the DBLOCKs.
    */
   unsigned int current_depth;
 
   /**
-   * How deep is the tree?
+   * How deep is the tree? Always > 0.
    */
   unsigned int chk_tree_depth;
 
@@ -121,7 +121,7 @@ struct GNUNET_FS_TreeEncoder
  * Compute the depth of the CHK tree.
  *
  * @param flen file length for which to compute the depth
- * @return depth of the tree
+ * @return depth of the tree, always > 0.  A depth of 1 means only a DBLOCK.
  */
 unsigned int
 GNUNET_FS_compute_depth (uint64_t flen)
@@ -146,73 +146,53 @@ GNUNET_FS_compute_depth (uint64_t flen)
 
 
 /**
- * Initialize a tree encoder.  This function will call "proc" and
- * "progress" on each block in the tree.  Once all blocks have been
- * processed, "cont" will be scheduled.  The "reader" will be called
- * to obtain the (plaintext) blocks for the file.  Note that this
- * function will not actually call "proc".  The client must
- * call "GNUNET_FS_tree_encoder_next" to trigger encryption (and
- * calling of "proc") for the each block.
+ * Calculate how many bytes of payload a block tree of the given
+ * depth MAY correspond to at most (this function ignores the fact that
+ * some blocks will only be present partially due to the total file
+ * size cutting some blocks off at the end).
  *
- * @param h the global FS context
- * @param size overall size of the file to encode
- * @param cls closure for reader, proc, progress and cont
- * @param reader function to call to read plaintext data
- * @param proc function to call on each encrypted block
- * @param progress function to call with progress information 
- * @param cont function to call when done
+ * @param depth depth of the block.  depth==0 is a DBLOCK.
+ * @return number of bytes of payload a subtree of this depth may correspond to
  */
-struct GNUNET_FS_TreeEncoder *
-GNUNET_FS_tree_encoder_create (struct GNUNET_FS_Handle *h,
-                               uint64_t size,
-                               void *cls,
-                               GNUNET_FS_DataReader reader,
-                               GNUNET_FS_TreeBlockProcessor proc,
-                               GNUNET_FS_TreeProgressCallback progress,
-                               GNUNET_SCHEDULER_Task cont)
+uint64_t
+GNUNET_FS_tree_compute_tree_size (unsigned int depth)
 {
-  struct GNUNET_FS_TreeEncoder *te;
-  
-  te = GNUNET_malloc (sizeof (struct GNUNET_FS_TreeEncoder));  
-  te->h = h;
-  te->size = size;
-  te->cls = cls;
-  te->reader = reader;
-  te->proc = proc;
-  te->progress = progress;
-  te->cont = cont;
-  te->chk_tree_depth = GNUNET_FS_compute_depth (size);
-  te->current_depth = te->chk_tree_depth;
-  te->chk_tree = GNUNET_malloc (te->chk_tree_depth *
-                                CHK_PER_INODE *
-                                sizeof (struct ContentHashKey));
-  return te;
+  uint64_t rsize;
+  unsigned int i;
+
+  rsize = DBLOCK_SIZE;
+  for (i = 0; i<depth; i++)
+    rsize *= CHK_PER_INODE;
+  return rsize;
 }
 
 
 /**
- * Compute the size of the current IBlock.
+ * Compute the size of the current IBLOCK.  The encoder is
+ * triggering the calculation of the size of an IBLOCK at the
+ * *end* (hence end_offset) of its construction.  The IBLOCK
+ * maybe a full or a partial IBLOCK, and this function is to
+ * calculate how long it should be.
  *
- * @param height height of the IBlock in the tree (aka overall
- *               number of tree levels minus depth); 0 == DBlock
- * @param offset current offset in the overall file
+ * @param depth depth of the IBlock in the tree, 0 would be a DBLOCK,
+ *        must be > 0 (this function is for IBLOCKs only!)
+ * @param end_offset current offset in the payload (!) of the overall file, 
+ *        must be > 0 (since this function is called at the 
+ *        end of a block).
  * @return size of the corresponding IBlock
  */
-uint16_t 
-GNUNET_FS_tree_compute_iblock_size (unsigned int height,
-                                    uint64_t offset)
+static uint16_t 
+GNUNET_FS_tree_compute_iblock_size (unsigned int depth,
+                                    uint64_t end_offset)
 {
   unsigned int ret;
-  unsigned int i;
   uint64_t mod;
   uint64_t bds;
 
-  GNUNET_assert (height > 0);
-  bds = DBLOCK_SIZE; /* number of bytes each CHK at level "i"
-                                  corresponds to */
-  for (i=0;i<height;i++)
-    bds *= CHK_PER_INODE;
-  mod = offset % bds;
+  GNUNET_assert (depth > 0);
+  GNUNET_assert (end_offset > 0);
+  bds = GNUNET_FS_tree_compute_tree_size (depth);
+  mod = end_offset % bds;
   if (0 == mod)
     {
       /* we were triggered at the end of a full block */
@@ -232,42 +212,40 @@ GNUNET_FS_tree_compute_iblock_size (unsigned int height,
 
 /**
  * Compute how many bytes of data should be stored in
- * the specified node.
+ * the specified block.
  *
- * @param fsize overall file size
- * @param totaldepth depth of the entire tree
- * @param offset offset of the node
- * @param depth depth of the node
+ * @param fsize overall file size, must be > 0.
+ * @param offset offset in the original data corresponding
+ *         to the beginning of the tree induced by the block;
+ *         must be <= fsize
+ * @param depth depth of the node in the tree, 0 for DBLOCK
  * @return number of bytes stored in this node
  */
 size_t
 GNUNET_FS_tree_calculate_block_size (uint64_t fsize,
-                                     unsigned int totaldepth,
                                      uint64_t offset,
                                      unsigned int depth)
 {
-  unsigned int i;
   size_t ret;
   uint64_t rsize;
   uint64_t epos;
   unsigned int chks;
 
+  GNUNET_assert (fsize > 0);
   GNUNET_assert (offset <= fsize);
-  if (depth == totaldepth)
+  if (depth == 0)
     {
       ret = DBLOCK_SIZE;
-      if (offset + ret > fsize)
+      if ( (offset + ret > fsize) ||
+           (offset + ret < offset) )
         ret = (size_t) (fsize - offset);
       return ret;
     }
-  /* FIXME: this code should be *equivalent* to the
-     GNUNET_FS_tree_compute_iblock_size function above! Remove duplication! */
-  rsize = DBLOCK_SIZE;
-  for (i = totaldepth-1; i > depth; i--)
-    rsize *= CHK_PER_INODE;
+
+  rsize = GNUNET_FS_tree_compute_tree_size (depth - 1);
   epos = offset + rsize * CHK_PER_INODE;
-  GNUNET_assert (epos > offset);
-  if (epos > fsize)
+  if ( (epos < offset) ||
+       (epos > fsize) )
     epos = fsize;
   /* round up when computing #CHKs in our IBlock */
   chks = (epos - offset + rsize - 1) / rsize;
@@ -277,29 +255,71 @@ GNUNET_FS_tree_calculate_block_size (uint64_t fsize,
 
 
 /**
+ * Initialize a tree encoder.  This function will call "proc" and
+ * "progress" on each block in the tree.  Once all blocks have been
+ * processed, "cont" will be scheduled.  The "reader" will be called
+ * to obtain the (plaintext) blocks for the file.  Note that this
+ * function will not actually call "proc".  The client must
+ * call "GNUNET_FS_tree_encoder_next" to trigger encryption (and
+ * calling of "proc") for the each block.
+ *
+ * @param h the global FS context
+ * @param size overall size of the file to encode
+ * @param cls closure for reader, proc, progress and cont
+ * @param reader function to call to read plaintext data
+ * @param proc function to call on each encrypted block
+ * @param progress function to call with progress information 
+ * @param cont function to call when done
+ */
+struct GNUNET_FS_TreeEncoder *
+GNUNET_FS_tree_encoder_create (struct GNUNET_FS_Handle *h,
+                               uint64_t size,
+                               void *cls,
+                               GNUNET_FS_DataReader reader,
+                               GNUNET_FS_TreeBlockProcessor proc,
+                               GNUNET_FS_TreeProgressCallback progress,
+                               GNUNET_SCHEDULER_Task cont)
+{
+  struct GNUNET_FS_TreeEncoder *te;
+  
+  te = GNUNET_malloc (sizeof (struct GNUNET_FS_TreeEncoder));  
+  te->h = h;
+  te->size = size;
+  te->cls = cls;
+  te->reader = reader;
+  te->proc = proc;
+  te->progress = progress;
+  te->cont = cont;
+  te->chk_tree_depth = GNUNET_FS_compute_depth (size);
+  te->chk_tree = GNUNET_malloc (te->chk_tree_depth *
+                                CHK_PER_INODE *
+                                sizeof (struct ContentHashKey));
+  return te;
+}
+
+
+/**
  * Compute the offset of the CHK for the
  * current block in the IBlock above.
  *
- * @param height height of the IBlock in the tree (aka overall
+ * @param depth depth of the IBlock in the tree (aka overall
  *               number of tree levels minus depth); 0 == DBlock
- * @param offset current offset in the overall file
+ * @param end_offset current offset in the overall file, 
+ *               at the *beginning* of the block for DBLOCKs (depth==0),
+ *               otherwise at the *end* of the block (exclusive)
  * @return (array of CHKs') offset in the above IBlock
  */
 static unsigned int
-compute_chk_offset (unsigned int height,
-                    uint64_t offset)
+compute_chk_offset (unsigned int depth,
+                    uint64_t end_offset)
 {
   uint64_t bds;
   unsigned int ret;
-  unsigned int i;
 
-  bds = DBLOCK_SIZE; /* number of bytes each CHK at level "i"
-                                  corresponds to */
-  for (i=0;i<height;i++)
-    bds *= CHK_PER_INODE;
-  if (height > 0)
-    offset--; /* round down since for height > 0 offset is at the END of the block */
-  ret = offset / bds;
+  bds = GNUNET_FS_tree_compute_tree_size (depth);
+  if (depth > 0)
+    end_offset--; /* round down since for depth > 0 offset is at the END of the block */
+  ret = end_offset / bds;
   return ret % CHK_PER_INODE; 
 }
 
@@ -325,8 +345,26 @@ GNUNET_FS_tree_encoder_next (struct GNUNET_FS_TreeEncoder * te)
 
   GNUNET_assert (GNUNET_NO == te->in_next);
   te->in_next = GNUNET_YES;
-  if (te->current_depth == te->chk_tree_depth)
+  if (te->chk_tree_depth == te->current_depth)
+    {
+      off = CHK_PER_INODE * (te->chk_tree_depth - 1);
+#if DEBUG_TREE
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "TE done, reading CHK `%s' from %u\n",
+              GNUNET_h2s (&te->chk_tree[off].query),           
+              off);
+#endif
+      te->uri = GNUNET_malloc (sizeof(struct GNUNET_FS_Uri));
+      te->uri->type = chk;
+      te->uri->data.chk.chk = te->chk_tree[off];
+      te->uri->data.chk.file_length = GNUNET_htonll (te->size);
+      te->in_next = GNUNET_NO;
+      te->cont (te->cls, NULL);
+      return;
+    }
+  if (0 == te->current_depth)
     {
+      /* read DBLOCK */
       pt_size = GNUNET_MIN(DBLOCK_SIZE,
                            te->size - te->publish_offset);
       if (pt_size !=
@@ -346,24 +384,12 @@ GNUNET_FS_tree_encoder_next (struct GNUNET_FS_TreeEncoder * te)
     }
   else
     {
-      pt_size = GNUNET_FS_tree_compute_iblock_size (te->chk_tree_depth - te->current_depth,
+      pt_size = GNUNET_FS_tree_compute_iblock_size (te->current_depth,
                                                     te->publish_offset); 
-      pt_block = &te->chk_tree[te->current_depth *
+      pt_block = &te->chk_tree[(te->current_depth - 1) *
                                CHK_PER_INODE];
     }
-  if (0 == te->current_depth)
-    {
-      te->uri = GNUNET_malloc (sizeof(struct GNUNET_FS_Uri));
-      te->uri->type = chk;
-      te->uri->data.chk.chk = te->chk_tree[0];
-      te->uri->data.chk.file_length = GNUNET_htonll (te->size);
-      GNUNET_SCHEDULER_add_continuation (te->cont,
-                                         te->cls,
-                                         GNUNET_SCHEDULER_REASON_PREREQ_DONE);
-      te->in_next = GNUNET_NO;
-      return;
-    }
-  off = compute_chk_offset (te->chk_tree_depth - te->current_depth,
+  off = compute_chk_offset (te->current_depth,
                             te->publish_offset);
 #if DEBUG_TREE
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
@@ -373,7 +399,7 @@ GNUNET_FS_tree_encoder_next (struct GNUNET_FS_TreeEncoder * te)
               (unsigned int) pt_size,
               (unsigned int) off);
 #endif
-  mychk = &te->chk_tree[(te->current_depth-1)*CHK_PER_INODE+off];
+  mychk = &te->chk_tree[te->current_depth*CHK_PER_INODE+off];
   GNUNET_CRYPTO_hash (pt_block, pt_size, &mychk->key);
   GNUNET_CRYPTO_hash_to_aes_key (&mychk->key, &sk, &iv);
   GNUNET_CRYPTO_aes_encrypt (pt_block,
@@ -384,15 +410,16 @@ GNUNET_FS_tree_encoder_next (struct GNUNET_FS_TreeEncoder * te)
   GNUNET_CRYPTO_hash (enc, pt_size, &mychk->query);
 #if DEBUG_TREE
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "TE calculates query to be `%s'\n",
-              GNUNET_h2s (&mychk->query));
+              "TE calculates query to be `%s', stored at %u\n",
+              GNUNET_h2s (&mychk->query),
+              te->current_depth * CHK_PER_INODE + off);
 #endif
   if (NULL != te->proc)
     te->proc (te->cls,
-              &mychk->query,
+              mychk,
               te->publish_offset,
               te->current_depth,
-              (te->current_depth == te->chk_tree_depth) 
+              (0 == te->current_depth)
               ? GNUNET_BLOCK_TYPE_FS_DBLOCK 
               : GNUNET_BLOCK_TYPE_FS_IBLOCK,
               enc,
@@ -403,20 +430,20 @@ GNUNET_FS_tree_encoder_next (struct GNUNET_FS_TreeEncoder * te)
                   pt_block,
                   pt_size,
                   te->current_depth);
-  if (te->current_depth == te->chk_tree_depth) 
+  if (0 == te->current_depth) 
     { 
       te->publish_offset += pt_size;
       if ( (te->publish_offset == te->size) ||
            (0 == te->publish_offset % (CHK_PER_INODE * DBLOCK_SIZE) ) )
-        te->current_depth--;
+        te->current_depth++;
     }
   else
     {
       if ( (off == CHK_PER_INODE) ||
            (te->publish_offset == te->size) )
-        te->current_depth--;
+        te->current_depth++;
       else
-        te->current_depth = te->chk_tree_depth;
+        te->current_depth = 0;
     }
   te->in_next = GNUNET_NO;
 }
@@ -433,10 +460,11 @@ GNUNET_FS_tree_encoder_next (struct GNUNET_FS_TreeEncoder * te)
  *        prior to completion and prior to an internal error,
  *        both "*uri" and "*emsg" will be set to NULL).
  */
-void GNUNET_FS_tree_encoder_finish (struct GNUNET_FS_TreeEncoder * te,
+void GNUNET_FS_tree_encoder_finish (struct GNUNET_FS_TreeEncoder *te,
                                     struct GNUNET_FS_Uri **uri,
                                     char **emsg)
 {
+  GNUNET_assert (GNUNET_NO == te->in_next);
   if (uri != NULL)
     *uri = te->uri;
   else
diff --git a/src/fs/fs_tree.h b/src/fs/fs_tree.h
index ebeb47e63..5cd4d0afe 100644
--- a/src/fs/fs_tree.h
+++ b/src/fs/fs_tree.h
@@ -21,7 +21,7 @@
 /**
  * @file fs/fs_tree.h
  * @brief Merkle-tree-ish-CHK file encoding for GNUnet
- * @see http://gnunet.org/encoding.php3
+ * @see https://gnunet.org/encoding
  * @author Krista Bennett
  * @author Christian Grothoff
  *
@@ -35,16 +35,46 @@
 #include "fs.h"
 
 /**
- * Compute the depth of the CHK tree.
+ * Compute the depth of the CHK tree.  
  *
  * @param flen file length for which to compute the depth
- * @return depth of the tree
+ * @return depth of the tree, always > 0.  A depth of 1 means only a DBLOCK.
  */
 unsigned int
 GNUNET_FS_compute_depth (uint64_t flen);
 
 
 /**
+ * Calculate how many bytes of payload a block tree of the given
+ * depth MAY correspond to at most (this function ignores the fact that
+ * some blocks will only be present partially due to the total file
+ * size cutting some blocks off at the end).
+ *
+ * @param depth depth of the block.  depth==0 is a DBLOCK.
+ * @return number of bytes of payload a subtree of this depth may correspond to
+ */
+uint64_t
+GNUNET_FS_tree_compute_tree_size (unsigned int depth);
+
+
+/**
+ * Compute how many bytes of data should be stored in
+ * the specified block.
+ *
+ * @param fsize overall file size, must be > 0.
+ * @param offset offset in the original data corresponding
+ *         to the beginning of the tree induced by the block;
+ *         must be < fsize
+ * @param depth depth of the node in the tree, 0 for DBLOCK
+ * @return number of bytes stored in this node
+ */
+size_t
+GNUNET_FS_tree_calculate_block_size (uint64_t fsize,
+                                     uint64_t offset,
+                                     unsigned int depth);
+
+
+/**
  * Context for an ECRS-based file encoder that computes
  * the Merkle-ish-CHK tree.
  */
@@ -58,15 +88,15 @@ struct GNUNET_FS_TreeEncoder;
  * or (on error) "GNUNET_FS_tree_encode_finish".
  *
  * @param cls closure
- * @param query the query for the block (key for lookup in the datastore)
+ * @param chk content hash key for the block
  * @param offset offset of the block
- * @param depth depth of the block
+ * @param depth depth of the block, 0 for DBLOCKs
  * @param type type of the block (IBLOCK or DBLOCK)
  * @param block the (encrypted) block
  * @param block_size size of block (in bytes)
  */
 typedef void (*GNUNET_FS_TreeBlockProcessor)(void *cls,
-                                             const GNUNET_HashCode *query,
+                                             const struct ContentHashKey *chk,
                                              uint64_t offset,
                                              unsigned int depth,
                                              enum GNUNET_BLOCK_Type type,
@@ -82,7 +112,7 @@ typedef void (*GNUNET_FS_TreeBlockProcessor)(void *cls,
  * @param offset where are we in the file
  * @param pt_block plaintext of the currently processed block
  * @param pt_size size of pt_block
- * @param depth depth of the block in the tree
+ * @param depth depth of the block in the tree, 0 for DBLOCKS
  */
 typedef void (*GNUNET_FS_TreeProgressCallback)(void *cls,
                                                uint64_t offset,
@@ -141,41 +171,11 @@ void GNUNET_FS_tree_encoder_next (struct GNUNET_FS_TreeEncoder * te);
  *        prior to completion and prior to an internal error,
  *        both "*uri" and "*emsg" will be set to NULL).
  */
-void GNUNET_FS_tree_encoder_finish (struct GNUNET_FS_TreeEncoder * te,
+void GNUNET_FS_tree_encoder_finish (struct GNUNET_FS_TreeEncoder *te,
                                     struct GNUNET_FS_Uri **uri,
                                     char **emsg);
 
 
-/**
- * Compute the size of the current IBlock.
- *
- * @param height height of the IBlock in the tree (aka overall
- *               number of tree levels minus depth); 0 == DBlock
- * @param offset current offset in the overall file
- * @return size of the corresponding IBlock
- */
-uint16_t 
-GNUNET_FS_tree_compute_iblock_size (unsigned int height,
-                                    uint64_t offset);
-
-
-/**
- * Compute how many bytes of data should be stored in
- * the specified node.
- *
- * @param fsize overall file size
- * @param totaldepth depth of the entire tree
- * @param offset offset of the node
- * @param depth depth of the node
- * @return number of bytes stored in this node
- */
-size_t
-GNUNET_FS_tree_calculate_block_size (uint64_t fsize,
-                                     unsigned int totaldepth,
-                                     uint64_t offset,
-                                     unsigned int depth);
-
-
 #if 0
 /* the functions below will be needed for persistence
    but are not yet implemented -- FIXME... */
@@ -187,7 +187,7 @@ GNUNET_FS_tree_calculate_block_size (uint64_t fsize,
  * @param data set to the resume data
  * @param size set to the size of the resume data
  */
-void GNUNET_FS_tree_encoder_resume_get_data (const struct GNUNET_FS_TreeEncoder * te,
+void GNUNET_FS_tree_encoder_resume_get_data (const struct GNUNET_FS_TreeEncoder *te,
                                              void **data,
                                              size_t *size);
 
@@ -200,7 +200,7 @@ void GNUNET_FS_tree_encoder_resume_get_data (const struct GNUNET_FS_TreeEncoder
  * @param data the resume data
  * @param size the size of the resume data
  */
-void GNUNET_FS_tree_encoder_resume (struct GNUNET_FS_TreeEncoder * te,
+void GNUNET_FS_tree_encoder_resume (struct GNUNET_FS_TreeEncoder *te,
                                     const void *data,
                                     size_t size);
 #endif
diff --git a/src/fs/fs_unindex.c b/src/fs/fs_unindex.c
index aa73bc01d..c4360a82d 100644
--- a/src/fs/fs_unindex.c
+++ b/src/fs/fs_unindex.c
@@ -114,7 +114,7 @@ GNUNET_FS_unindex_make_status_ (struct GNUNET_FS_ProgressInfo *pi,
  * @param offset where are we in the file
  * @param pt_block plaintext of the currently processed block
  * @param pt_size size of pt_block
- * @param depth depth of the block in the tree
+ * @param depth depth of the block in the tree, 0 for DBLOCK
  */
 static void
 unindex_progress (void *cls,
@@ -188,16 +188,16 @@ process_cont (void *cls,
  * or (on error) "GNUNET_FS_tree_encode_finish".
  *
  * @param cls closure
- * @param query the query for the block (key for lookup in the datastore)
+ * @param chk content hash key for the block (key for lookup in the datastore)
  * @param offset offset of the block
- * @param depth depth of the block
+ * @param depth depth of the block, 0 for DBLOCK
  * @param type type of the block (IBLOCK or DBLOCK)
  * @param block the (encrypted) block
  * @param block_size size of block (in bytes)
  */
 static void 
 unindex_process (void *cls,
-                 const GNUNET_HashCode *query,
+                 const struct ContentHashKey *chk,
                  uint64_t offset,
                  unsigned int depth,
                  enum GNUNET_BLOCK_Type type,
@@ -226,7 +226,7 @@ unindex_process (void *cls,
               "Sending REMOVE request to DATASTORE service\n");
 #endif
   GNUNET_DATASTORE_remove (uc->dsh,
-                           query,
+                           &chk->query,
                            size,
                            data,
                            -2, 1,
diff --git a/src/fs/test_fs_download.c b/src/fs/test_fs_download.c
index 0d13b3639..969e83bf9 100644
--- a/src/fs/test_fs_download.c
+++ b/src/fs/test_fs_download.c
@@ -29,7 +29,7 @@
 #include "gnunet_arm_service.h"
 #include "gnunet_fs_service.h"
 
-#define VERBOSE GNUNET_YES
+#define VERBOSE GNUNET_NO
 
 #define START_ARM GNUNET_YES
 
diff --git a/src/fs/test_fs_download_data.conf b/src/fs/test_fs_download_data.conf
index 0bc6cc2b3..a1b202a4d 100644
--- a/src/fs/test_fs_download_data.conf
+++ b/src/fs/test_fs_download_data.conf
@@ -37,7 +37,7 @@ HOSTNAME = localhost
 PORT = 42471
 HOSTNAME = localhost
 ACTIVEMIGRATION = NO
-#DEBUG = YES
+DEBUG = NO
 #PREFIX = valgrind --tool=memcheck --leak-check=yes
 #BINARY = /home/grothoff/bin/gnunet-service-fs
 
diff --git a/src/fs/test_fs_download_persistence.c b/src/fs/test_fs_download_persistence.c
index e00d5255d..0ea7a5524 100644
--- a/src/fs/test_fs_download_persistence.c
+++ b/src/fs/test_fs_download_persistence.c
@@ -78,6 +78,8 @@ static void
 timeout_kill_task (void *cls,
                    const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
+  GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+              "Timeout downloading file\n");
   if (download != NULL)
     {
       GNUNET_FS_download_stop (download, GNUNET_YES);
@@ -134,6 +136,8 @@ static void
 restart_fs_task (void *cls,
                  const struct GNUNET_SCHEDULER_TaskContext *tc)
 {
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Restarting FS.\n");
   GNUNET_FS_stop (fs);
   fs = GNUNET_FS_start (cfg,
                         "test-fs-download-persistence",
@@ -242,18 +246,26 @@ progress_cb (void *cls,
       publish = event->value.publish.pc;
       break;
     case GNUNET_FS_STATUS_DOWNLOAD_SUSPEND:
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Download suspended.\n");
       GNUNET_assert (event->value.download.dc == download);
       download = NULL;
       break;
     case GNUNET_FS_STATUS_DOWNLOAD_RESUME:
       GNUNET_assert (NULL == download);
       download = event->value.download.dc;
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Download resumed.\n");
       break;
     case GNUNET_FS_STATUS_DOWNLOAD_ACTIVE:
       consider_restart (event->status);
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Download active.\n");
       break;
     case GNUNET_FS_STATUS_DOWNLOAD_INACTIVE:
       consider_restart (event->status);
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Download inactive.\n");
       break;
     case GNUNET_FS_STATUS_PUBLISH_START:
       GNUNET_assert (0 == strcmp ("publish-context", event->value.publish.cctx));
@@ -270,6 +282,8 @@ progress_cb (void *cls,
       fs = NULL;
       break;
     case GNUNET_FS_STATUS_DOWNLOAD_START:
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Download started.\n");
       consider_restart (event->status);
       GNUNET_assert (download == NULL);
       download = event->value.download.dc;