introducing the short map

1 files changed, 964 insertions, 0 deletions

diff --git a/src/util/container_multishortmap.c b/src/util/container_multishortmap.c
new file mode 100644
index 000000000..71d1073b0
--- /dev/null
+++ b/src/util/container_multishortmap.c
@@ -0,0 +1,964 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2008, 2012 GNUnet e.V.
+
+     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., 51 Franklin Street, Fifth Floor,
+     Boston, MA 02110-1301, USA.
+*/
+/**
+ * @file util/container_multishortmap.c
+ * @brief hash map where the same key may be present multiple times
+ * @author Christian Grothoff
+ */
+
+#include "platform.h"
+#include "gnunet_util_lib.h"
+
+#define LOG(kind,...) GNUNET_log_from (kind, "util", __VA_ARGS__)
+
+/**
+ * An entry in the hash map with the full key.
+ */
+struct BigMapEntry
+{
+
+  /**
+   * Value of the entry.
+   */
+  void *value;
+
+  /**
+   * If there is a hash collision, we create a linked list.
+   */
+  struct BigMapEntry *next;
+
+  /**
+   * Key for the entry.
+   */
+  struct GNUNET_PeerIdentity key;
+
+};
+
+
+/**
+ * An entry in the hash map with just a pointer to the key.
+ */
+struct SmallMapEntry
+{
+
+  /**
+   * Value of the entry.
+   */
+  void *value;
+
+  /**
+   * If there is a hash collision, we create a linked list.
+   */
+  struct SmallMapEntry *next;
+
+  /**
+   * Key for the entry.
+   */
+  const struct GNUNET_PeerIdentity *key;
+
+};
+
+
+/**
+ * Entry in the map.
+ */
+union MapEntry
+{
+  /**
+   * Variant used if map entries only contain a pointer to the key.
+   */
+  struct SmallMapEntry *sme;
+
+  /**
+   * Variant used if map entries contain the full key.
+   */
+  struct BigMapEntry *bme;
+};
+
+
+/**
+ * Internal representation of the hash map.
+ */
+struct GNUNET_CONTAINER_MultiShortmap
+{
+  /**
+   * All of our buckets.
+   */
+  union MapEntry *map;
+
+  /**
+   * Number of entries in the map.
+   */
+  unsigned int size;
+
+  /**
+   * Length of the "map" array.
+   */
+  unsigned int map_length;
+
+  /**
+   * GNUNET_NO if the map entries are of type 'struct BigMapEntry',
+   * GNUNET_YES if the map entries are of type 'struct SmallMapEntry'.
+   */
+  int use_small_entries;
+
+  /**
+   * Counts the destructive modifications (grow, remove)
+   * to the map, so that iterators can check if they are still valid.
+   */
+  unsigned int modification_counter;
+};
+
+
+/**
+ * Cursor into a multishortmap.
+ * Allows to enumerate elements asynchronously.
+ */
+struct GNUNET_CONTAINER_MultiShortmapIterator
+{
+  /**
+   * Position in the bucket 'idx'
+   */
+  union MapEntry me;
+
+  /**
+   * Current bucket index.
+   */
+  unsigned int idx;
+
+  /**
+   * Modification counter as observed on the map when the iterator
+   * was created.
+   */
+  unsigned int modification_counter;
+
+  /**
+   * Map that we are iterating over.
+   */
+  const struct GNUNET_CONTAINER_MultiShortmap *map;
+};
+
+
+/**
+ * Create a multi hash map.
+ *
+ * @param len initial size (map will grow as needed)
+ * @param do_not_copy_keys GNUNET_NO is always safe and should be used by default;
+ *                         GNUNET_YES means that on 'put', the 'key' does not have
+ *                         to be copied as the destination of the pointer is
+ *                         guaranteed to be life as long as the value is stored in
+ *                         the hashmap.  This can significantly reduce memory
+ *                         consumption, but of course is also a recipie for
+ *                         heap corruption if the assumption is not true.  Only
+ *                         use this if (1) memory use is important in this case and
+ *                         (2) you have triple-checked that the invariant holds
+ * @return NULL on error
+ */
+struct GNUNET_CONTAINER_MultiShortmap *
+GNUNET_CONTAINER_multishortmap_create (unsigned int len,
+                                      int do_not_copy_keys)
+{
+  struct GNUNET_CONTAINER_MultiShortmap *map;
+
+  GNUNET_assert (len > 0);
+  map = GNUNET_new (struct GNUNET_CONTAINER_MultiShortmap);
+  map->map = GNUNET_malloc (len * sizeof (union MapEntry));
+  map->map_length = len;
+  map->use_small_entries = do_not_copy_keys;
+  return map;
+}
+
+
+/**
+ * Destroy a hash map.  Will not free any values
+ * stored in the hash map!
+ *
+ * @param map the map
+ */
+void
+GNUNET_CONTAINER_multishortmap_destroy (struct GNUNET_CONTAINER_MultiShortmap
+                                       *map)
+{
+  unsigned int i;
+  union MapEntry me;
+
+  for (i = 0; i < map->map_length; i++)
+  {
+    me = map->map[i];
+    if (map->use_small_entries)
+    {
+      struct SmallMapEntry *sme;
+      struct SmallMapEntry *nxt;
+
+      nxt = me.sme;
+      while (NULL != (sme = nxt))
+      {
+        nxt = sme->next;
+        GNUNET_free (sme);
+      }
+      me.sme = NULL;
+    }
+    else
+    {
+      struct BigMapEntry *bme;
+      struct BigMapEntry *nxt;
+
+      nxt = me.bme;
+      while (NULL != (bme = nxt))
+      {
+        nxt = bme->next;
+        GNUNET_free (bme);
+      }
+      me.bme = NULL;
+    }
+  }
+  GNUNET_free (map->map);
+  GNUNET_free (map);
+}
+
+
+/**
+ * Compute the index of the bucket for the given key.
+ *
+ * @param map hash map for which to compute the index
+ * @param key what key should the index be computed for
+ * @return offset into the "map" array of "map"
+ */
+static unsigned int
+idx_of (const struct GNUNET_CONTAINER_MultiShortmap *map,
+        const struct GNUNET_PeerIdentity *key)
+{
+  unsigned int kx;
+
+  GNUNET_assert (NULL != map);
+  GNUNET_memcpy (&kx, key, sizeof (kx));
+  return kx % map->map_length;
+}
+
+
+/**
+ * Get the number of key-value pairs in the map.
+ *
+ * @param map the map
+ * @return the number of key value pairs
+ */
+unsigned int
+GNUNET_CONTAINER_multishortmap_size (const struct GNUNET_CONTAINER_MultiShortmap *map)
+{
+  return map->size;
+}
+
+
+/**
+ * Given a key find a value in the map matching the key.
+ *
+ * @param map the map
+ * @param key what to look for
+ * @return NULL if no value was found; note that
+ *   this is indistinguishable from values that just
+ *   happen to be NULL; use "contains" to test for
+ *   key-value pairs with value NULL
+ */
+void *
+GNUNET_CONTAINER_multishortmap_get (const struct GNUNET_CONTAINER_MultiShortmap *map,
+                                    const struct GNUNET_PeerIdentity *key)
+{
+  union MapEntry me;
+
+  me = map->map[idx_of (map, key)];
+  if (map->use_small_entries)
+  {
+    struct SmallMapEntry *sme;
+
+    for (sme = me.sme; NULL != sme; sme = sme->next)
+      if (0 == memcmp (key, sme->key, sizeof (struct GNUNET_PeerIdentity)))
+        return sme->value;
+  }
+  else
+  {
+    struct BigMapEntry *bme;
+
+    for (bme = me.bme; NULL != bme; bme = bme->next)
+      if (0 == memcmp (key, &bme->key, sizeof (struct GNUNET_PeerIdentity)))
+        return bme->value;
+  }
+  return NULL;
+}
+
+
+/**
+ * Iterate over all entries in the map.
+ *
+ * @param map the map
+ * @param it function to call on each entry
+ * @param it_cls extra argument to @a it
+ * @return the number of key value pairs processed,
+ *         #GNUNET_SYSERR if it aborted iteration
+ */
+int
+GNUNET_CONTAINER_multishortmap_iterate (const struct GNUNET_CONTAINER_MultiShortmap *map,
+                                       GNUNET_CONTAINER_ShortmapIterator it,
+                                       void *it_cls)
+{
+  int count;
+  unsigned int i;
+  union MapEntry me;
+  struct GNUNET_PeerIdentity kc;
+
+  count = 0;
+  GNUNET_assert (NULL != map);
+  for (i = 0; i < map->map_length; i++)
+  {
+    me = map->map[i];
+    if (map->use_small_entries)
+    {
+      struct SmallMapEntry *sme;
+      struct SmallMapEntry *nxt;
+
+      nxt = me.sme;
+      while (NULL != (sme = nxt))
+      {
+        nxt = sme->next;
+        if (NULL != it)
+        {
+          if (GNUNET_OK != it (it_cls, sme->key, sme->value))
+            return GNUNET_SYSERR;
+        }
+        count++;
+      }
+    }
+    else
+    {
+      struct BigMapEntry *bme;
+      struct BigMapEntry *nxt;
+
+      nxt = me.bme;
+      while (NULL != (bme = nxt))
+      {
+        nxt = bme->next;
+        if (NULL != it)
+        {
+          kc = bme->key;
+          if (GNUNET_OK != it (it_cls, &kc, bme->value))
+            return GNUNET_SYSERR;
+        }
+        count++;
+      }
+    }
+  }
+  return count;
+}
+
+
+/**
+ * Remove the given key-value pair from the map.  Note that if the
+ * key-value pair is in the map multiple times, only one of the pairs
+ * will be removed.
+ *
+ * @param map the map
+ * @param key key of the key-value pair
+ * @param value value of the key-value pair
+ * @return #GNUNET_YES on success, #GNUNET_NO if the key-value pair
+ *  is not in the map
+ */
+int
+GNUNET_CONTAINER_multishortmap_remove (struct GNUNET_CONTAINER_MultiShortmap *map,
+                                       const struct GNUNET_PeerIdentity *key,
+                                       const void *value)
+{
+  union MapEntry me;
+  unsigned int i;
+
+  map->modification_counter++;
+
+  i = idx_of (map, key);
+  me = map->map[i];
+  if (map->use_small_entries)
+  {
+    struct SmallMapEntry *sme;
+    struct SmallMapEntry *p;
+
+    p = NULL;
+    for (sme = me.sme; NULL != sme; sme = sme->next)
+    {
+      if ((0 == memcmp (key, sme->key, sizeof (struct GNUNET_PeerIdentity))) &&
+          (value == sme->value))
+      {
+        if (NULL == p)
+          map->map[i].sme = sme->next;
+        else
+          p->next = sme->next;
+        GNUNET_free (sme);
+        map->size--;
+        return GNUNET_YES;
+      }
+      p = sme;
+    }
+  }
+  else
+  {
+    struct BigMapEntry *bme;
+    struct BigMapEntry *p;
+
+    p = NULL;
+    for (bme = me.bme; NULL != bme; bme = bme->next)
+    {
+      if ((0 == memcmp (key, &bme->key, sizeof (struct GNUNET_PeerIdentity))) &&
+          (value == bme->value))
+      {
+        if (NULL == p)
+          map->map[i].bme = bme->next;
+        else
+          p->next = bme->next;
+        GNUNET_free (bme);
+        map->size--;
+        return GNUNET_YES;
+      }
+      p = bme;
+    }
+  }
+  return GNUNET_NO;
+}
+
+
+/**
+ * Remove all entries for the given key from the map.
+ * Note that the values would not be "freed".
+ *
+ * @param map the map
+ * @param key identifies values to be removed
+ * @return number of values removed
+ */
+int
+GNUNET_CONTAINER_multishortmap_remove_all (struct GNUNET_CONTAINER_MultiShortmap *map,
+                                           const struct GNUNET_PeerIdentity *key)
+{
+  union MapEntry me;
+  unsigned int i;
+  int ret;
+
+  map->modification_counter++;
+
+  ret = 0;
+  i = idx_of (map, key);
+  me = map->map[i];
+  if (map->use_small_entries)
+  {
+    struct SmallMapEntry *sme;
+    struct SmallMapEntry *p;
+
+    p = NULL;
+    sme = me.sme;
+    while (NULL != sme)
+    {
+      if (0 == memcmp (key, sme->key, sizeof (struct GNUNET_PeerIdentity)))
+      {
+        if (NULL == p)
+          map->map[i].sme = sme->next;
+        else
+          p->next = sme->next;
+        GNUNET_free (sme);
+        map->size--;
+        if (NULL == p)
+          sme = map->map[i].sme;
+        else
+          sme = p->next;
+        ret++;
+      }
+      else
+      {
+        p = sme;
+        sme = sme->next;
+      }
+    }
+  }
+  else
+  {
+    struct BigMapEntry *bme;
+    struct BigMapEntry *p;
+
+    p = NULL;
+    bme = me.bme;
+    while (NULL != bme)
+    {
+      if (0 == memcmp (key, &bme->key, sizeof (struct GNUNET_PeerIdentity)))
+      {
+        if (NULL == p)
+          map->map[i].bme = bme->next;
+        else
+          p->next = bme->next;
+        GNUNET_free (bme);
+        map->size--;
+        if (NULL == p)
+          bme = map->map[i].bme;
+        else
+          bme = p->next;
+        ret++;
+      }
+      else
+      {
+        p = bme;
+        bme = bme->next;
+      }
+    }
+  }
+  return ret;
+}
+
+
+/**
+ * Check if the map contains any value under the given
+ * key (including values that are NULL).
+ *
+ * @param map the map
+ * @param key the key to test if a value exists for it
+ * @return #GNUNET_YES if such a value exists,
+ *         #GNUNET_NO if not
+ */
+int
+GNUNET_CONTAINER_multishortmap_contains (const struct GNUNET_CONTAINER_MultiShortmap *map,
+                                         const struct GNUNET_PeerIdentity *key)
+{
+  union MapEntry me;
+
+  me = map->map[idx_of (map, key)];
+  if (map->use_small_entries)
+  {
+    struct SmallMapEntry *sme;
+
+    for (sme = me.sme; NULL != sme; sme = sme->next)
+      if (0 == memcmp (key, sme->key, sizeof (struct GNUNET_PeerIdentity)))
+        return GNUNET_YES;
+  }
+  else
+  {
+    struct BigMapEntry *bme;
+
+    for (bme = me.bme; NULL != bme; bme = bme->next)
+      if (0 == memcmp (key, &bme->key, sizeof (struct GNUNET_PeerIdentity)))
+        return GNUNET_YES;
+  }
+  return GNUNET_NO;
+}
+
+
+/**
+ * Check if the map contains the given value under the given
+ * key.
+ *
+ * @param map the map
+ * @param key the key to test if a value exists for it
+ * @param value value to test for
+ * @return #GNUNET_YES if such a value exists,
+ *         #GNUNET_NO if not
+ */
+int
+GNUNET_CONTAINER_multishortmap_contains_value (const struct GNUNET_CONTAINER_MultiShortmap *map,
+                                               const struct GNUNET_PeerIdentity *key,
+                                               const void *value)
+{
+  union MapEntry me;
+
+  me = map->map[idx_of (map, key)];
+  if (map->use_small_entries)
+  {
+    struct SmallMapEntry *sme;
+
+    for (sme = me.sme; NULL != sme; sme = sme->next)
+      if ( (0 == memcmp (key, sme->key, sizeof (struct GNUNET_PeerIdentity))) &&
+           (sme->value == value) )
+        return GNUNET_YES;
+  }
+  else
+  {
+    struct BigMapEntry *bme;
+
+    for (bme = me.bme; NULL != bme; bme = bme->next)
+      if ( (0 == memcmp (key, &bme->key, sizeof (struct GNUNET_PeerIdentity))) &&
+           (bme->value == value) )
+        return GNUNET_YES;
+  }
+  return GNUNET_NO;
+}
+
+
+/**
+ * Grow the given map to a more appropriate size.
+ *
+ * @param map the hash map to grow
+ */
+static void
+grow (struct GNUNET_CONTAINER_MultiShortmap *map)
+{
+  union MapEntry *old_map;
+  union MapEntry *new_map;
+  unsigned int old_len;
+  unsigned int new_len;
+  unsigned int idx;
+  unsigned int i;
+
+  map->modification_counter++;
+
+  old_map = map->map;
+  old_len = map->map_length;
+  new_len = old_len * 2;
+  new_map = GNUNET_malloc (sizeof (union MapEntry) * new_len);
+  map->map_length = new_len;
+  map->map = new_map;
+  for (i = 0; i < old_len; i++)
+  {
+    if (map->use_small_entries)
+    {
+      struct SmallMapEntry *sme;
+
+      while (NULL != (sme = old_map[i].sme))
+      {
+        old_map[i].sme = sme->next;
+        idx = idx_of (map, sme->key);
+        sme->next = new_map[idx].sme;
+        new_map[idx].sme = sme;
+      }
+    }
+    else
+    {
+      struct BigMapEntry *bme;
+
+      while (NULL != (bme = old_map[i].bme))
+      {
+        old_map[i].bme = bme->next;
+        idx = idx_of (map, &bme->key);
+        bme->next = new_map[idx].bme;
+        new_map[idx].bme = bme;
+      }
+    }
+  }
+  GNUNET_free (old_map);
+}
+
+
+/**
+ * Store a key-value pair in the map.
+ *
+ * @param map the map
+ * @param key key to use
+ * @param value value to use
+ * @param opt options for put
+ * @return #GNUNET_OK on success,
+ *         #GNUNET_NO if a value was replaced (with REPLACE)
+ *         #GNUNET_SYSERR if GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY was the option and the
+ *                       value already exists
+ */
+int
+GNUNET_CONTAINER_multishortmap_put (struct GNUNET_CONTAINER_MultiShortmap *map,
+                                    const struct GNUNET_PeerIdentity *key,
+                                    void *value,
+                                    enum GNUNET_CONTAINER_MultiHashMapOption opt)
+{
+  union MapEntry me;
+  unsigned int i;
+
+  i = idx_of (map, key);
+  if ((opt != GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE) &&
+      (opt != GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_FAST))
+  {
+    me = map->map[i];
+    if (map->use_small_entries)
+    {
+      struct SmallMapEntry *sme;
+
+      for (sme = me.sme; NULL != sme; sme = sme->next)
+        if (0 == memcmp (key, sme->key, sizeof (struct GNUNET_PeerIdentity)))
+        {
+          if (opt == GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY)
+            return GNUNET_SYSERR;
+          sme->value = value;
+          return GNUNET_NO;
+        }
+    }
+    else
+    {
+      struct BigMapEntry *bme;
+
+      for (bme = me.bme; NULL != bme; bme = bme->next)
+        if (0 == memcmp (key, &bme->key, sizeof (struct GNUNET_PeerIdentity)))
+        {
+          if (opt == GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY)
+            return GNUNET_SYSERR;
+          bme->value = value;
+          return GNUNET_NO;
+        }
+    }
+  }
+  if (map->size / 3 >= map->map_length / 4)
+  {
+    grow (map);
+    i = idx_of (map, key);
+  }
+  if (map->use_small_entries)
+  {
+    struct SmallMapEntry *sme;
+
+    sme = GNUNET_new (struct SmallMapEntry);
+    sme->key = key;
+    sme->value = value;
+    sme->next = map->map[i].sme;
+    map->map[i].sme = sme;
+  }
+  else
+  {
+    struct BigMapEntry *bme;
+
+    bme = GNUNET_new (struct BigMapEntry);
+    bme->key = *key;
+    bme->value = value;
+    bme->next = map->map[i].bme;
+    map->map[i].bme = bme;
+  }
+  map->size++;
+  return GNUNET_OK;
+}
+
+
+/**
+ * Iterate over all entries in the map that match a particular key.
+ *
+ * @param map the map
+ * @param key key that the entries must correspond to
+ * @param it function to call on each entry
+ * @param it_cls extra argument to @a it
+ * @return the number of key value pairs processed,
+ *         #GNUNET_SYSERR if it aborted iteration
+ */
+int
+GNUNET_CONTAINER_multishortmap_get_multiple (const struct GNUNET_CONTAINER_MultiShortmap *map,
+                                             const struct GNUNET_PeerIdentity *key,
+                                             GNUNET_CONTAINER_ShortmapIterator it,
+                                             void *it_cls)
+{
+  int count;
+  union MapEntry me;
+
+  count = 0;
+  me = map->map[idx_of (map, key)];
+  if (map->use_small_entries)
+  {
+    struct SmallMapEntry *sme;
+    struct SmallMapEntry *nxt;
+
+    nxt = me.sme;
+    while (NULL != (sme = nxt))
+    {
+      nxt = sme->next;
+      if (0 != memcmp (key, sme->key, sizeof (struct GNUNET_PeerIdentity)))
+        continue;
+      if ((it != NULL) && (GNUNET_OK != it (it_cls, key, sme->value)))
+        return GNUNET_SYSERR;
+      count++;
+    }
+  }
+  else
+  {
+    struct BigMapEntry *bme;
+    struct BigMapEntry *nxt;
+
+    nxt = me.bme;
+    while (NULL != (bme = nxt))
+    {
+      nxt = bme->next;
+      if (0 != memcmp (key, &bme->key, sizeof (struct GNUNET_PeerIdentity)))
+        continue;
+      if ((it != NULL) && (GNUNET_OK != it (it_cls, key, bme->value)))
+        return GNUNET_SYSERR;
+      count++;
+    }
+  }
+  return count;
+}
+
+
+/**
+ * @ingroup hashmap
+ * Call @a it on a random value from the map, or not at all
+ * if the map is empty.  Note that this function has linear
+ * complexity (in the size of the map).
+ *
+ * @param map the map
+ * @param it function to call on a random entry
+ * @param it_cls extra argument to @a it
+ * @return the number of key value pairs processed, zero or one.
+ */
+unsigned int
+GNUNET_CONTAINER_multishortmap_get_random (const struct GNUNET_CONTAINER_MultiShortmap *map,
+                                          GNUNET_CONTAINER_ShortmapIterator it,
+                                          void *it_cls)
+{
+  unsigned int off;
+  unsigned int idx;
+  union MapEntry me;
+
+  if (0 == map->size)
+    return 0;
+  if (NULL == it)
+    return 1;
+  off = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE,
+                                  map->size);
+  for (idx = 0; idx < map->map_length; idx++)
+  {
+    me = map->map[idx];
+    if (map->use_small_entries)
+    {
+      struct SmallMapEntry *sme;
+      struct SmallMapEntry *nxt;
+
+      nxt = me.sme;
+      while (NULL != (sme = nxt))
+      {
+        nxt = sme->next;
+        if (0 == off)
+        {
+          if (GNUNET_OK != it (it_cls,
+                               sme->key,
+                               sme->value))
+            return GNUNET_SYSERR;
+          return 1;
+        }
+        off--;
+      }
+    }
+    else
+    {
+      struct BigMapEntry *bme;
+      struct BigMapEntry *nxt;
+
+      nxt = me.bme;
+      while (NULL != (bme = nxt))
+      {
+        nxt = bme->next;
+        if (0 == off)
+        {
+          if (GNUNET_OK != it (it_cls,
+                               &bme->key, bme->value))
+            return GNUNET_SYSERR;
+          return 1;
+        }
+        off--;
+      }
+    }
+  }
+  GNUNET_break (0);
+  return GNUNET_SYSERR;
+}
+
+
+/**
+ * Create an iterator for a multishortmap.
+ * The iterator can be used to retrieve all the elements in the multishortmap
+ * one by one, without having to handle all elements at once (in contrast to
+ * #GNUNET_CONTAINER_multishortmap_iterate).  Note that the iterator can not be
+ * used anymore if elements have been removed from 'map' after the creation of
+ * the iterator, or 'map' has been destroyed.  Adding elements to 'map' may
+ * result in skipped or repeated elements.
+ *
+ * @param map the map to create an iterator for
+ * @return an iterator over the given multishortmap 'map'
+ */
+struct GNUNET_CONTAINER_MultiShortmapIterator *
+GNUNET_CONTAINER_multishortmap_iterator_create (const struct GNUNET_CONTAINER_MultiShortmap *map)
+{
+  struct GNUNET_CONTAINER_MultiShortmapIterator *iter;
+
+  iter = GNUNET_new (struct GNUNET_CONTAINER_MultiShortmapIterator);
+  iter->map = map;
+  iter->modification_counter = map->modification_counter;
+  iter->me = map->map[0];
+  return iter;
+}
+
+
+/**
+ * Retrieve the next element from the hash map at the iterator's position.
+ * If there are no elements left, GNUNET_NO is returned, and 'key' and 'value'
+ * are not modified.
+ * This operation is only allowed if no elements have been removed from the
+ * multishortmap since the creation of 'iter', and the map has not been destroyed.
+ * Adding elements may result in repeating or skipping elements.
+ *
+ * @param iter the iterator to get the next element from
+ * @param key pointer to store the key in, can be NULL
+ * @param value pointer to store the value in, can be NULL
+ * @return #GNUNET_YES we returned an element,
+ *         #GNUNET_NO if we are out of elements
+ */
+int
+GNUNET_CONTAINER_multishortmap_iterator_next (struct GNUNET_CONTAINER_MultiShortmapIterator *iter,
+                                             struct GNUNET_PeerIdentity *key, const void **value)
+{
+  /* make sure the map has not been modified */
+  GNUNET_assert (iter->modification_counter == iter->map->modification_counter);
+
+  /* look for the next entry, skipping empty buckets */
+  while (1)
+  {
+    if (iter->idx >= iter->map->map_length)
+      return GNUNET_NO;
+    if (GNUNET_YES == iter->map->use_small_entries)
+    {
+      if (NULL != iter->me.sme)
+      {
+        if (NULL != key)
+          *key = *iter->me.sme->key;
+        if (NULL != value)
+          *value = iter->me.sme->value;
+        iter->me.sme = iter->me.sme->next;
+        return GNUNET_YES;
+      }
+    }
+    else
+    {
+      if (NULL != iter->me.bme)
+      {
+        if (NULL != key)
+          *key = iter->me.bme->key;
+        if (NULL != value)
+          *value = iter->me.bme->value;
+        iter->me.bme = iter->me.bme->next;
+        return GNUNET_YES;
+      }
+    }
+    iter->idx += 1;
+    if (iter->idx < iter->map->map_length)
+      iter->me = iter->map->map[iter->idx];
+  }
+}
+
+
+/**
+ * Destroy a multishortmap iterator.
+ *
+ * @param iter the iterator to destroy
+ */
+void
+GNUNET_CONTAINER_multishortmap_iterator_destroy (struct GNUNET_CONTAINER_MultiShortmapIterator *iter)
+{
+  GNUNET_free (iter);
+}
+
+
+/* end of container_multishortmap.c */