improving datastore API

8 files changed, 454 insertions, 119 deletions

diff --git a/src/datastore/datastore.h b/src/datastore/datastore.h
index 9165c8af8..92a2889d8 100644
--- a/src/datastore/datastore.h
+++ b/src/datastore/datastore.h
@@ -33,10 +33,10 @@
  * Message from datastore service informing client about
  * the current size of the datastore.
  */
-struct SizeMessage
+struct ReserveMessage
 {
   /**
-   * Type is GNUNET_MESSAGE_TYPE_DATASTORE_SIZE.
+   * Type is GNUNET_MESSAGE_TYPE_DATASTORE_RESERVE.
    */
   struct GNUNET_MessageHeader header;
 
@@ -46,9 +46,55 @@ struct SizeMessage
   uint32_t reserved GNUNET_PACKED;
 
   /**
-   * Size of the datastore in bytes.
+   * Number of bytes to reserve.
    */
   uint64_t size GNUNET_PACKED;
+
+  /**
+   * Number of items to reserve.
+   */
+  uint64_t items GNUNET_PACKED;
+};
+
+
+/**
+ * Message from datastore service informing client about
+ * the success or failure of a requested operation.
+ * This header is optionally followed by a variable-size,
+ * 0-terminated error message.
+ */
+struct StatusMessage
+{
+  /**
+   * Type is GNUNET_MESSAGE_TYPE_DATASTORE_STATUS.
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Status code.
+   */
+  int32_t status GNUNET_PACKED;
+
+};
+
+
+/**
+ * Message from datastore client informing service that
+ * the remainder of the reserved bytes can now be released
+ * for other requests.
+ */
+struct ReleaseReserveMessage
+{
+  /**
+   * Type is GNUNET_MESSAGE_TYPE_DATASTORE_RELEASE_RESERVE.
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Reservation id.
+   */
+  int32_t rid GNUNET_PACKED;
+
 };
 
 
@@ -80,6 +126,35 @@ struct GetMessage
 
 
 /**
+ * Message to the datastore service requesting an update
+ * to the priority or expiration for some content.
+ */
+struct UpdateMessage
+{
+  /**
+   * Type is GNUNET_MESSAGE_TYPE_DATASTORE_UPDATE.
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Desired priority increase.
+   */
+  int32_t priority GNUNET_PACKED;
+
+  /**
+   * Desired new expiration time.
+   */
+  struct GNUNET_TIME_AbsoluteNBO expiration;
+
+  /**
+   * Unique ID for the content.
+   */
+  uint64_t uid;
+
+};
+
+
+/**
  * Message transmitting content from or to the datastore
  * service.
  */
@@ -94,9 +169,9 @@ struct DataMessage
   struct GNUNET_MessageHeader header;
 
   /**
-   * Always zero.
+   * Reservation ID to use; use zero for none.
    */
-  uint32_t reserved GNUNET_PACKED;
+  uint32_t rid GNUNET_PACKED;
 
   /**
    * Number of bytes in the item (NBO).
@@ -117,6 +192,11 @@ struct DataMessage
    * Desired anonymity level (NBO), zero for remove.
    */
   uint32_t anonymity GNUNET_PACKED;
+
+  /**
+   * Unique ID for the content (can be used for UPDATE).
+   */
+  uint64_t uid;
   
   /**
    * Expiration time (NBO); zero for remove.
diff --git a/src/datastore/datastore_api.c b/src/datastore/datastore_api.c
index 95ae25f03..960d7d34e 100644
--- a/src/datastore/datastore_api.c
+++ b/src/datastore/datastore_api.c
@@ -26,7 +26,6 @@
  * TODO:
  * 1) clarify API (wrt. efficient UPDATE of priority/expiration after GET)
  * 2) implement INIT
- * 3) implement SIZE handling (=> API impact?)
  * 4) implement DROP
  * 5) implement PUT
  * 6) implement GET
@@ -93,17 +92,6 @@ struct GNUNET_DATASTORE_Handle
    */
   void *response_proc_cls;
 
-  /**
-   * Current size of the datastore (cached).
-   */ 
-  unsigned long long size;
-
-  /**
-   * Set to GNUNET_YES if we have received the size
-   * from the datastore.
-   */
-  int ready;
-
 };
 
 
@@ -129,7 +117,6 @@ struct GNUNET_DATASTORE_Handle *GNUNET_DATASTORE_connect (struct
     return NULL; /* oops */
   h = GNUNET_malloc (sizeof(struct GNUNET_DATASTORE_Handle));
   h->client = c;
-  /* FIXME: send 'join' request */
   return h;
 }
 
@@ -154,19 +141,6 @@ void GNUNET_DATASTORE_disconnect (struct GNUNET_DATASTORE_Handle *h,
 
 
 /**
- * Get the current on-disk size of the datastore.
- * @param h handle to the datastore
- * @return size estimate, -1 if datastore is not available (yet)
- */
-unsigned long long GNUNET_DATASTORE_size (struct GNUNET_DATASTORE_Handle *h)
-{
-  if (GNUNET_YES != h->ready)
-    return (unsigned long long) -1LL;
-  return h->size;
-}
-
-
-/**
  * Store an item in the datastore.  If the item is already present,
  * the priorities are summed up and the higher expiration time and
  * lower anonymity level is used.
@@ -179,17 +153,89 @@ unsigned long long GNUNET_DATASTORE_size (struct GNUNET_DATASTORE_Handle *h)
  * @param priority priority of the content
  * @param anonymity anonymity-level for the content
  * @param expiration expiration time for the content
+ * @param cont continuation to call when done
+ * @param cont_cls closure for cont
  */
 void
 GNUNET_DATASTORE_put (struct GNUNET_DATASTORE_Handle *h,
+                      int rid,
                       const GNUNET_HashCode * key,
                       uint32_t size,
                       const void *data,
                       uint32_t type,
                       uint32_t priority,
                       uint32_t anonymity,
-                      struct GNUNET_TIME_Absolute expiration)
+                      struct GNUNET_TIME_Absolute expiration,
+                      GNUNET_DATASTORE_ContinuationWithStatus cont,
+                      void *cont_cls)
+{
+  cont (cont_cls, GNUNET_SYSERR, "not implemented");
+}
+
+
+/**
+ * Reserve space in the datastore.  This function should be used
+ * to avoid "out of space" failures during a longer sequence of "put"
+ * operations (for example, when a file is being inserted).
+ *
+ * @param h handle to the datastore
+ * @param amount how much space (in bytes) should be reserved (for content only)
+ * @param entries how many entries will be created (to calculate per-entry overhead)
+ * @param cont continuation to call when done; "success" will be set to
+ *             a positive reservation value if space could be reserved.
+ * @param cont_cls closure for cont
+ */
+void
+GNUNET_DATASTORE_reserve (struct GNUNET_DATASTORE_Handle *h,
+                          uint64_t amount,
+                          uint64_t entries,
+                          GNUNET_DATASTORE_ContinuationWithStatus cont,
+                          void *cont_cls)
 {
+  cont (cont_cls, GNUNET_SYSERR, "not implemented");
+}
+
+
+/**
+ * Signal that all of the data for which a reservation was made has
+ * been stored and that whatever excess space might have been reserved
+ * can now be released.
+ *
+ * @param h handle to the datastore
+ * @param rid reservation ID (value of "success" in original continuation
+ *        from the "reserve" function).
+ * @param cont continuation to call when done
+ * @param cont_cls closure for cont
+ */
+void
+GNUNET_DATASTORE_release_reserve (struct GNUNET_DATASTORE_Handle *h,
+                                  int rid,
+                                  GNUNET_DATASTORE_ContinuationWithStatus cont,
+                                  void *cont_cls)
+{
+  cont (cont_cls, GNUNET_OK, NULL);
+}
+
+
+/**
+ * Update a value in the datastore.
+ *
+ * @param h handle to the datastore
+ * @param uid identifier for the value
+ * @param priority how much to increase the priority of the value
+ * @param expiration new expiration value should be MAX of existing and this argument
+ * @param cont continuation to call when done
+ * @param cont_cls closure for cont
+ */
+void
+GNUNET_DATASTORE_update (struct GNUNET_DATASTORE_Handle *h,
+                         unsigned long long uid,
+                         uint32_t priority,
+                         struct GNUNET_TIME_Absolute expiration,
+                         GNUNET_DATASTORE_ContinuationWithStatus cont,
+                         void *cont_cls)
+{
+  cont (cont_cls, GNUNET_SYSERR, "not implemented");
 }
 
 
@@ -210,6 +256,9 @@ GNUNET_DATASTORE_get (struct GNUNET_DATASTORE_Handle *h,
                       uint32_t type,
                       GNUNET_DATASTORE_Iterator iter, void *iter_cls)
 {
+  static struct GNUNET_TIME_Absolute zero;
+  iter (iter_cls,
+        NULL, 0, NULL, 0, 0, 0, zero, 0);
 }
 
 
@@ -240,12 +289,17 @@ GNUNET_DATASTORE_get_random (struct GNUNET_DATASTORE_Handle *h,
  * @param key key for the value
  * @param size number of bytes in data
  * @param data content stored
+ * @param cont continuation to call when done
+ * @param cont_cls closure for cont
  */
 void
 GNUNET_DATASTORE_remove (struct GNUNET_DATASTORE_Handle *h,
                          const GNUNET_HashCode * key,
-                         uint32_t size, const void *data)
+                         uint32_t size, const void *data,
+                         GNUNET_DATASTORE_ContinuationWithStatus cont,
+                         void *cont_cls)
 {
+  cont (cont_cls, GNUNET_SYSERR, "not implemented");
 }
 
 
diff --git a/src/datastore/gnunet-service-datastore.c b/src/datastore/gnunet-service-datastore.c
index fe7987632..db3524557 100644
--- a/src/datastore/gnunet-service-datastore.c
+++ b/src/datastore/gnunet-service-datastore.c
@@ -92,18 +92,28 @@ transmit (struct GNUNET_SERVER_Client *client,
 
 
 /**
- * Transmit the size of the current datastore to the client.
+ * Transmit a status code to the client.
+ *
+ * @param client receiver of the response
+ * @param code status code
+ * @param msg optional error message (can be NULL)
  */
 static void
-transmit_size (struct GNUNET_SERVER_Client *client)
+transmit_status (struct GNUNET_SERVER_Client *client,
+                 int code,
+                 const char *msg)
 {
-  struct SizeMessage sm;
-  
-  sm.header.size = htons(sizeof(struct SizeMessage));
-  sm.header.type = htons(GNUNET_MESSAGE_TYPE_DATASTORE_SIZE);
-  sm.reserved = htonl(0);
-  sm.size = GNUNET_htonll(plugin->api->get_size (plugin->api->cls));
-  transmit (client, &sm.header);
+  struct StatusMessage *sm;
+  size_t slen;
+
+  slen = (msg == NULL) ? 0 : strlen(msg) + 1;  
+  sm = GNUNET_malloc (sizeof(struct StatusMessage) + slen);
+  sm->header.size = htons(sizeof(struct StatusMessage) + slen);
+  sm->header.type = htons(GNUNET_MESSAGE_TYPE_DATASTORE_STATUS);
+  sm->status = htonl(code);
+  memcpy (&sm[1], msg, slen);  
+  transmit (client, &sm->header);
+  GNUNET_free (sm);
 }
 
 
@@ -148,16 +158,16 @@ transmit_item (void *cls,
       transmit (client, &end);
       return GNUNET_OK;
     }
-  /* FIXME: make use of 'uid' for efficient priority/expiration update! */
   dm = GNUNET_malloc (sizeof(struct DataMessage) + size);
   dm->header.size = htons(sizeof(struct DataMessage) + size);
   dm->header.type = htons(GNUNET_MESSAGE_TYPE_DATASTORE_DATA);
-  dm->reserved = htonl(0);
+  dm->rid = htonl(0);
   dm->size = htonl(size);
   dm->type = htonl(type);
   dm->priority = htonl(priority);
   dm->anonymity = htonl(anonymity);
   dm->expiration = GNUNET_TIME_absolute_hton(expiration);
+  dm->uid = GNUNET_htonll(uid);
   dm->key = *key;
   memcpy (&dm[1], data, size);
   transmit (client, &dm->header);
@@ -167,18 +177,35 @@ transmit_item (void *cls,
 
 
 /**
- * Handle INIT-message.
+ * Handle RESERVE-message.
  *
  * @param cls closure
  * @param client identification of the client
  * @param message the actual message
  */
 static void
-handle_init (void *cls,
+handle_reserve (void *cls,
              struct GNUNET_SERVER_Client *client,
              const struct GNUNET_MessageHeader *message)
 {
-  transmit_size (client);
+  transmit_status (client, GNUNET_SYSERR, "not implemented");
+  GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+}
+
+
+/**
+ * Handle RELEASE_RESERVE-message.
+ *
+ * @param cls closure
+ * @param client identification of the client
+ * @param message the actual message
+ */
+static void
+handle_release_reserve (void *cls,
+                        struct GNUNET_SERVER_Client *client,
+                        const struct GNUNET_MessageHeader *message)
+{
+  transmit_status (client, GNUNET_SYSERR, "not implemented");
   GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
 }
 
@@ -208,8 +235,7 @@ check_data (const struct GNUNET_MessageHeader *message)
       GNUNET_break (0);
       return NULL;
     }
-  if ( (ntohl(dm->type) == 0) ||
-       (ntohl(dm->reserved) != 0) )
+  if (ntohl(dm->type) == 0) 
     {
       GNUNET_break (0);
       return NULL;
@@ -231,21 +257,33 @@ handle_put (void *cls,
             const struct GNUNET_MessageHeader *message)
 {
   const struct DataMessage *dm = check_data (message);
+  char *msg;
+  int ret;
+  int rid;
+
   if (dm == NULL)
     {
       GNUNET_break (0);
       GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
       return;
     }
-  plugin->api->put (plugin->api->cls,
-                    &dm->key,
-                    ntohl(dm->size),
-                    &dm[1],
-                    ntohl(dm->type),
-                    ntohl(dm->priority),
-                    ntohl(dm->anonymity),
-                    GNUNET_TIME_absolute_ntoh(dm->expiration));
-  transmit_size (client);
+  rid = ntohl(dm->rid);
+  if (rid > 0)
+    {
+      /* FIXME: find reservation, update remaining! */
+    }
+  msg = NULL;
+  ret = plugin->api->put (plugin->api->cls,
+                          &dm->key,
+                          ntohl(dm->size),
+                          &dm[1],
+                          ntohl(dm->type),
+                          ntohl(dm->priority),
+                          ntohl(dm->anonymity),
+                          GNUNET_TIME_absolute_ntoh(dm->expiration),
+                          &msg);
+  transmit_status (client, ret, msg);
+  GNUNET_free_non_null (msg);
   GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
 }
 
@@ -285,6 +323,35 @@ handle_get (void *cls,
 
 
 /**
+ * Handle UPDATE-message.
+ *
+ * @param cls closure
+ * @param client identification of the client
+ * @param message the actual message
+ */
+static void
+handle_update (void *cls,
+               struct GNUNET_SERVER_Client *client,
+               const struct GNUNET_MessageHeader *message)
+{
+  const struct UpdateMessage *msg;
+  int ret;
+  char *emsg;
+
+  msg = (const struct UpdateMessage*) message;
+  emsg = NULL;
+  ret = plugin->api->update (plugin->api->cls,
+                             GNUNET_ntohll(msg->uid),
+                             (int32_t) ntohl(msg->priority),
+                             GNUNET_TIME_absolute_ntoh(msg->expiration),
+                             &emsg);
+  transmit_status (client, ret, emsg);
+  GNUNET_free_non_null (emsg);
+  GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
+}
+
+
+/**
  * Handle GET_RANDOM-message.
  *
  * @param cls closure
@@ -319,6 +386,8 @@ remove_callback (void *cls,
                  struct GNUNET_TIME_Absolute
                  expiration, unsigned long long uid)
 {
+  int *found = cls;
+  *found = GNUNET_YES;
   return GNUNET_NO;
 }
 
@@ -337,6 +406,7 @@ handle_remove (void *cls,
 {
   const struct DataMessage *dm = check_data (message);
   GNUNET_HashCode vhash;
+  int found;
 
   if (dm == NULL)
     {
@@ -344,6 +414,7 @@ handle_remove (void *cls,
       GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
       return;
     }
+  found = GNUNET_NO;
   GNUNET_CRYPTO_hash (&dm[1],
                       ntohl(dm->size),
                       &vhash);
@@ -352,8 +423,11 @@ handle_remove (void *cls,
                     &vhash,
                     ntohl(dm->type),
                     &remove_callback,
-                    NULL);
-  transmit_size (client);
+                    &found);
+  if (GNUNET_YES == found)
+    transmit_status (client, GNUNET_OK, NULL);
+  else
+    transmit_status (client, GNUNET_SYSERR, _("Content not found"));
   GNUNET_SERVER_receive_done (client, GNUNET_OK);
 }
 
@@ -380,9 +454,13 @@ handle_drop (void *cls,
  * service.
  */
 static struct GNUNET_SERVER_MessageHandler handlers[] = {
-  {&handle_init, NULL, GNUNET_MESSAGE_TYPE_DATASTORE_INIT, 
-   sizeof(struct GNUNET_MessageHeader) }, 
+  {&handle_reserve, NULL, GNUNET_MESSAGE_TYPE_DATASTORE_RESERVE, 
+   sizeof(struct ReserveMessage) }, 
+  {&handle_release_reserve, NULL, GNUNET_MESSAGE_TYPE_DATASTORE_RELEASE_RESERVE, 
+   sizeof(struct ReleaseReserveMessage) }, 
   {&handle_put, NULL, GNUNET_MESSAGE_TYPE_DATASTORE_PUT, 0 }, 
+  {&handle_update, NULL, GNUNET_MESSAGE_TYPE_DATASTORE_UPDATE, 
+   sizeof (struct UpdateMessage) }, 
   {&handle_get, NULL, GNUNET_MESSAGE_TYPE_DATASTORE_GET, 0 }, 
   {&handle_get_random, NULL, GNUNET_MESSAGE_TYPE_DATASTORE_GET_RANDOM, 
    sizeof(struct GNUNET_MessageHeader) }, 
diff --git a/src/datastore/plugin_datastore.h b/src/datastore/plugin_datastore.h
index 1c038bf19..cc68f3557 100644
--- a/src/datastore/plugin_datastore.h
+++ b/src/datastore/plugin_datastore.h
@@ -73,8 +73,10 @@ typedef unsigned long long (*GNUNET_DATASTORE_GetSize) (void *cls);
  * @param priority priority of the content
  * @param anonymity anonymity-level for the content
  * @param expiration expiration time for the content
+ * @param msg set to an error message (on failure)
+ * @return GNUNET_OK on success, GNUNET_SYSERR on failure
  */
-typedef void
+typedef int
   (*GNUNET_DATASTORE_Put) (void *cls,
                            const GNUNET_HashCode * key,
                            uint32_t size,
@@ -82,7 +84,8 @@ typedef void
                            uint32_t type,
                            uint32_t priority,
                            uint32_t anonymity,
-                           struct GNUNET_TIME_Absolute expiration);
+                           struct GNUNET_TIME_Absolute expiration,
+                           char **msg);
 
 
 /**
@@ -129,11 +132,14 @@ typedef void
  * @param expire new expiration time should be the
  *     MAX of any existing expiration time and
  *     this value
+ * @param msg set to an error message (on error)
+ * @return GNUNET_OK on success
  */
-typedef void
+typedef int
   (*GNUNET_DATASTORE_Update) (void *cls,
                               unsigned long long uid,
-                              int delta, struct GNUNET_TIME_Absolute expire);
+                              int delta, struct GNUNET_TIME_Absolute expire,
+                              char **msg);
 
 
 /**
diff --git a/src/datastore/plugin_datastore_sqlite.c b/src/datastore/plugin_datastore_sqlite.c
index 486b9b96e..234519079 100644
--- a/src/datastore/plugin_datastore_sqlite.c
+++ b/src/datastore/plugin_datastore_sqlite.c
@@ -62,8 +62,10 @@ static unsigned long long sqlite_plugin_get_size (void *cls)
  * @param priority priority of the content
  * @param anonymity anonymity-level for the content
  * @param expiration expiration time for the content
+ * @param msg set to an error message
+ * @return GNUNET_OK on success
  */
-static void
+static int
 sqlite_plugin_put (void *cls,
                    const GNUNET_HashCode * key,
                    uint32_t size,
@@ -71,8 +73,11 @@ sqlite_plugin_put (void *cls,
                    uint32_t type,
                    uint32_t priority,
                    uint32_t anonymity,
-                   struct GNUNET_TIME_Absolute expiration)
+                   struct GNUNET_TIME_Absolute expiration,
+                   char ** msg)
 {
+  *msg = GNUNET_strdup("not implemented");
+  return GNUNET_SYSERR;
 }
 
 
@@ -100,6 +105,8 @@ sqlite_plugin_get (void *cls,
                    uint32_t type,
                    GNUNET_DATASTORE_Iterator iter, void *iter_cls)
 {
+  static struct GNUNET_TIME_Absolute zero;
+  iter (iter_cls, NULL, 0, NULL, 0, 0, 0, zero, 0);
 }
 
 
@@ -122,12 +129,17 @@ sqlite_plugin_get (void *cls,
  * @param expire new expiration time should be the
  *     MAX of any existing expiration time and
  *     this value
+ * @param msg set to an error message
+ * @return GNUNET_OK on success
  */
-static void
+static int
 sqlite_plugin_update (void *cls,
                       unsigned long long uid,
-                      int delta, struct GNUNET_TIME_Absolute expire)
+                      int delta, struct GNUNET_TIME_Absolute expire,
+                      char **msg)
 {
+  *msg = GNUNET_strdup ("not implemented");
+  return GNUNET_SYSERR;
 }
 
 
@@ -147,10 +159,11 @@ sqlite_plugin_iter_low_priority (void *cls,
                         GNUNET_DATASTORE_Iterator iter,
                         void *iter_cls)
 {
+  static struct GNUNET_TIME_Absolute zero;
+  iter (iter_cls, NULL, 0, NULL, 0, 0, 0, zero, 0);
 }
 
 
-
 /**
  * Select a subset of the items in the datastore and call
  * the given iterator for each of them.
@@ -167,6 +180,8 @@ sqlite_plugin_iter_zero_anonymity (void *cls,
                         GNUNET_DATASTORE_Iterator iter,
                         void *iter_cls)
 {
+  static struct GNUNET_TIME_Absolute zero;
+  iter (iter_cls, NULL, 0, NULL, 0, 0, 0, zero, 0);
 }
 
 
@@ -187,6 +202,8 @@ sqlite_plugin_iter_ascending_expiration (void *cls,
                         GNUNET_DATASTORE_Iterator iter,
                         void *iter_cls)
 {
+  static struct GNUNET_TIME_Absolute zero;
+  iter (iter_cls, NULL, 0, NULL, 0, 0, 0, zero, 0);
 }
 
 
@@ -207,6 +224,8 @@ sqlite_plugin_iter_migration_order (void *cls,
                         GNUNET_DATASTORE_Iterator iter,
                         void *iter_cls)
 {
+  static struct GNUNET_TIME_Absolute zero;
+  iter (iter_cls, NULL, 0, NULL, 0, 0, 0, zero, 0);
 }
 
 
@@ -227,6 +246,8 @@ sqlite_plugin_iter_all_now (void *cls,
                         GNUNET_DATASTORE_Iterator iter,
                         void *iter_cls)
 {
+  static struct GNUNET_TIME_Absolute zero;
+  iter (iter_cls, NULL, 0, NULL, 0, 0, 0, zero, 0);
 }
 
 
diff --git a/src/datastore/plugin_datastore_template.c b/src/datastore/plugin_datastore_template.c
index 70b8c635e..1e3d4343b 100644
--- a/src/datastore/plugin_datastore_template.c
+++ b/src/datastore/plugin_datastore_template.c
@@ -62,8 +62,10 @@ static unsigned long long template_plugin_get_size (void *cls)
  * @param priority priority of the content
  * @param anonymity anonymity-level for the content
  * @param expiration expiration time for the content
+ * @param msg set to error message
+ * @return GNUNET_OK on success
  */
-static void
+static int
 template_plugin_put (void *cls,
                    const GNUNET_HashCode * key,
                    uint32_t size,
@@ -71,8 +73,11 @@ template_plugin_put (void *cls,
                    uint32_t type,
                    uint32_t priority,
                    uint32_t anonymity,
-                   struct GNUNET_TIME_Absolute expiration)
+                     struct GNUNET_TIME_Absolute expiration,
+                     char **msg)
 {
+  *msg = GNUNET_strdup ("not implemented");
+  return GNUNET_SYSERR;
 }
 
 
@@ -122,12 +127,17 @@ template_plugin_get (void *cls,
  * @param expire new expiration time should be the
  *     MAX of any existing expiration time and
  *     this value
+ * @param msg set to error message
+ * @return GNUNET_OK on success
  */
-static void
+static int
 template_plugin_update (void *cls,
-                      unsigned long long uid,
-                      int delta, struct GNUNET_TIME_Absolute expire)
+                        unsigned long long uid,
+                        int delta, struct GNUNET_TIME_Absolute expire,
+                        char **msg)
 {
+  *msg = GNUNET_strdup ("not implemented");
+  return GNUNET_SYSERR;
 }
 
 
diff --git a/src/include/gnunet_datastore_service.h b/src/include/gnunet_datastore_service.h
index 2f7fce6d8..626a5afcc 100644
--- a/src/include/gnunet_datastore_service.h
+++ b/src/include/gnunet_datastore_service.h
@@ -49,33 +49,6 @@ struct GNUNET_DATASTORE_Handle;
 
 
 /**
- * An iterator over a set of items stored in the datastore.
- *
- * @param cls closure
- * @param key key for the content
- * @param size number of bytes in data
- * @param data content stored
- * @param type type of the content
- * @param priority priority of the content
- * @param anonymity anonymity-level for the content
- * @param expiration expiration time for the content
- * @param uid unique identifier for the datum;
- *        maybe 0 if no unique identifier is available
- *
- * @return GNUNET_SYSERR to abort the iteration, GNUNET_OK to continue,
- *         GNUNET_NO to delete the item and continue (if supported)
- */
-typedef int (*GNUNET_DATASTORE_Iterator) (void *cls,
-                                          const GNUNET_HashCode * key,
-                                          uint32_t size,
-                                          const void *data,
-                                          uint32_t type,
-                                          uint32_t priority,
-                                          uint32_t anonymity,
-                                          struct GNUNET_TIME_Absolute
-                                          expiration, unsigned long long uid);
-
-/**
  * Connect to the datastore service.
  *
  * @param cfg configuration to use
@@ -102,11 +75,36 @@ void GNUNET_DATASTORE_disconnect (struct GNUNET_DATASTORE_Handle *h,
 
 
 /**
- * Get the current on-disk size of the datastore.
+ * Continuation called to notify client about result of the
+ * operation.
+ *
+ * @param cls closure
+ * @param success GNUNET_SYSERR on failure
+ * @param msg NULL on success, otherwise an error message
+ */
+typedef void (*GNUNET_DATASTORE_ContinuationWithStatus)(void *cls,
+                                                        int success,
+                                                        const char *msg);
+
+
+/**
+ * Reserve space in the datastore.  This function should be used
+ * to avoid "out of space" failures during a longer sequence of "put"
+ * operations (for example, when a file is being inserted).
+ *
  * @param h handle to the datastore
- * @return size estimate, -1 if datastore is not available (yet)
+ * @param amount how much space (in bytes) should be reserved (for content only)
+ * @param entries how many entries will be created (to calculate per-entry overhead)
+ * @param cont continuation to call when done; "success" will be set to
+ *             a positive reservation value if space could be reserved.
+ * @param cont_cls closure for cont
  */
-unsigned long long GNUNET_DATASTORE_size (struct GNUNET_DATASTORE_Handle *h);
+void
+GNUNET_DATASTORE_reserve (struct GNUNET_DATASTORE_Handle *h,
+                          uint64_t amount,
+                          uint64_t entries,
+                          GNUNET_DATASTORE_ContinuationWithStatus cont,
+                          void *cont_cls);
 
 
 /**
@@ -115,6 +113,8 @@ unsigned long long GNUNET_DATASTORE_size (struct GNUNET_DATASTORE_Handle *h);
  * lower anonymity level is used.
  *
  * @param h handle to the datastore
+ * @param rid reservation ID to use (from "reserve"); use 0 if no
+ *            prior reservation was made
  * @param key key for the value
  * @param size number of bytes in data
  * @param data content stored
@@ -122,16 +122,87 @@ unsigned long long GNUNET_DATASTORE_size (struct GNUNET_DATASTORE_Handle *h);
  * @param priority priority of the content
  * @param anonymity anonymity-level for the content
  * @param expiration expiration time for the content
+ * @param cont continuation to call when done
+ * @param cont_cls closure for cont
  */
 void
 GNUNET_DATASTORE_put (struct GNUNET_DATASTORE_Handle *h,
+                      int rid,
                       const GNUNET_HashCode * key,
                       uint32_t size,
                       const void *data,
                       uint32_t type,
                       uint32_t priority,
                       uint32_t anonymity,
-                      struct GNUNET_TIME_Absolute expiration);
+                      struct GNUNET_TIME_Absolute expiration,
+                      GNUNET_DATASTORE_ContinuationWithStatus cont,
+                      void *cont_cls);
+
+
+/**
+ * Signal that all of the data for which a reservation was made has
+ * been stored and that whatever excess space might have been reserved
+ * can now be released.
+ *
+ * @param h handle to the datastore
+ * @param rid reservation ID (value of "success" in original continuation
+ *        from the "reserve" function).
+ * @param cont continuation to call when done
+ * @param cont_cls closure for cont
+ */
+void
+GNUNET_DATASTORE_release_reserve (struct GNUNET_DATASTORE_Handle *h,
+                                  int rid,
+                                  GNUNET_DATASTORE_ContinuationWithStatus cont,
+                                  void *cont_cls);
+
+
+/**
+ * Update a value in the datastore.
+ *
+ * @param h handle to the datastore
+ * @param uid identifier for the value
+ * @param priority how much to increase the priority of the value
+ * @param expiration new expiration value should be MAX of existing and this argument
+ * @param cont continuation to call when done
+ * @param cont_cls closure for cont
+ */
+void
+GNUNET_DATASTORE_update (struct GNUNET_DATASTORE_Handle *h,
+                         unsigned long long uid,
+                         uint32_t priority,
+                         struct GNUNET_TIME_Absolute expiration,
+                         GNUNET_DATASTORE_ContinuationWithStatus cont,
+                         void *cont_cls);
+
+
+/**
+ * An iterator over a set of items stored in the datastore.
+ *
+ * @param cls closure
+ * @param key key for the content
+ * @param size number of bytes in data
+ * @param data content stored
+ * @param type type of the content
+ * @param priority priority of the content
+ * @param anonymity anonymity-level for the content
+ * @param expiration expiration time for the content
+ * @param uid unique identifier for the datum;
+ *        maybe 0 if no unique identifier is available
+ *
+ * @return GNUNET_SYSERR to abort the iteration, GNUNET_OK to continue,
+ *         GNUNET_NO to delete the item and continue (if supported)
+ */
+typedef int (*GNUNET_DATASTORE_Iterator) (void *cls,
+                                          const GNUNET_HashCode * key,
+                                          uint32_t size,
+                                          const void *data,
+                                          uint32_t type,
+                                          uint32_t priority,
+                                          uint32_t anonymity,
+                                          struct GNUNET_TIME_Absolute
+                                          expiration, unsigned long long uid);
+
 
 /**
  * Iterate over the results for a particular key
@@ -172,11 +243,15 @@ GNUNET_DATASTORE_get_random (struct GNUNET_DATASTORE_Handle *h,
  * @param key key for the value
  * @param size number of bytes in data
  * @param data content stored
+ * @param cont continuation to call when done
+ * @param cont_cls closure for cont
  */
 void
 GNUNET_DATASTORE_remove (struct GNUNET_DATASTORE_Handle *h,
                          const GNUNET_HashCode *key,
-                         uint32_t size, const void *data);
+                         uint32_t size, const void *data,
+                         GNUNET_DATASTORE_ContinuationWithStatus cont,
+                         void *cont_cls);
 
 
 #if 0                           /* keep Emacsens' auto-indent happy */
diff --git a/src/include/gnunet_protocols.h b/src/include/gnunet_protocols.h
index 04bfe2a4f..f78464593 100644
--- a/src/include/gnunet_protocols.h
+++ b/src/include/gnunet_protocols.h
@@ -306,51 +306,62 @@ extern "C"
 /**
  * Message sent by datastore client on join.
  */
-#define GNUNET_MESSAGE_TYPE_DATASTORE_INIT 92
+#define GNUNET_MESSAGE_TYPE_DATASTORE_RESERVE 92
 
 /**
- * Message sent by datastore to client informing about size.
- * (in response to JOIN, PUT and REMOVE requests).
+ * Message sent by datastore client on join.
+ */
+#define GNUNET_MESSAGE_TYPE_DATASTORE_RELEASE_RESERVE 93
+
+/**
+ * Message sent by datastore to client informing about status
+ * processing a request
+ * (in response to RESERVE, RELEASE_RESERVE, PUT, UPDATE and REMOVE requests).
  */
-#define GNUNET_MESSAGE_TYPE_DATASTORE_SIZE 93
+#define GNUNET_MESSAGE_TYPE_DATASTORE_STATUS 94
 
 /**
  * Message sent by datastore client to store data.
  */
-#define GNUNET_MESSAGE_TYPE_DATASTORE_PUT 94
+#define GNUNET_MESSAGE_TYPE_DATASTORE_PUT 95
+
+/**
+ * Message sent by datastore client to update data.
+ */
+#define GNUNET_MESSAGE_TYPE_DATASTORE_UPDATE 96
 
 /**
  * Message sent by datastore client to get data.
  */
-#define GNUNET_MESSAGE_TYPE_DATASTORE_GET 95
+#define GNUNET_MESSAGE_TYPE_DATASTORE_GET 97
 
 /**
  * Message sent by datastore client to get random data.
  */
-#define GNUNET_MESSAGE_TYPE_DATASTORE_GET_RANDOM 96
+#define GNUNET_MESSAGE_TYPE_DATASTORE_GET_RANDOM 98
 
 /**
  * Message sent by datastore to client providing requested data
  * (in response to GET or GET_RANDOM request).
  */
-#define GNUNET_MESSAGE_TYPE_DATASTORE_DATA 97
+#define GNUNET_MESSAGE_TYPE_DATASTORE_DATA 99
 
 /**
  * Message sent by datastore to client signaling end of matching data.
  * This message will also be sent for "GET_RANDOM", even though
  * "GET_RANDOM" returns at most one data item.
  */
-#define GNUNET_MESSAGE_TYPE_DATASTORE_DATA_END 98
+#define GNUNET_MESSAGE_TYPE_DATASTORE_DATA_END 100
 
 /**
  * Message sent by datastore client to remove data.
  */
-#define GNUNET_MESSAGE_TYPE_DATASTORE_REMOVE 99
+#define GNUNET_MESSAGE_TYPE_DATASTORE_REMOVE 101
 
 /**
  * Message sent by datastore client to drop the database.
  */
-#define GNUNET_MESSAGE_TYPE_DATASTORE_DROP 100
+#define GNUNET_MESSAGE_TYPE_DATASTORE_DROP 102
 
 /*
   TODO: