X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Futil%2Fcontainer_multihashmap.c;h=46379b34efe2d8a62f029863423a1c98715ac7d4;hb=93fba12ad8159dc6b683f9e7ce9f0528a11047f5;hp=ac19052010c28d8e5735c2fe30e70f0ec58cc86d;hpb=7e7e68018805b6566060d063d81f7ae5e5bb03e4;p=oweals%2Fgnunet.git

diff --git a/src/util/container_multihashmap.c b/src/util/container_multihashmap.c
index ac1905201..46379b34e 100644
--- a/src/util/container_multihashmap.c
+++ b/src/util/container_multihashmap.c
@@ -1,10 +1,10 @@
 /*
      This file is part of GNUnet.
-     (C) 2008 Christian Grothoff (and other contributing authors)
+     Copyright (C) 2008, 2012 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 2, or (at your
+     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
@@ -24,20 +24,39 @@
  */
 
 #include "platform.h"
-#include "gnunet_common.h"
 #include "gnunet_container_lib.h"
-#include "gnunet_crypto_lib.h"
+
+#define LOG(kind,...) GNUNET_log_from (kind, "util", __VA_ARGS__)
 
 /**
- * An entry in the hash map.
+ * An entry in the hash map with the full key.
  */
-struct MapEntry
+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.
    */
-  GNUNET_HashCode key;
+  struct GNUNET_HashCode key;
+
+};
+
+
+/**
+ * An entry in the hash map with just a pointer to the key.
+ */
+struct SmallMapEntry
+{
 
   /**
    * Value of the entry.
@@ -47,20 +66,42 @@ struct MapEntry
   /**
    * If there is a hash collision, we create a linked list.
    */
-  struct MapEntry *next;
+  struct SmallMapEntry *next;
+
+  /**
+   * Key for the entry.
+   */
+  const struct GNUNET_HashCode *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_MultiHashMap
 {
-
   /**
    * All of our buckets.
    */
-  struct MapEntry **map;
+  union MapEntry *map;
 
   /**
    * Number of entries in the map.
@@ -71,6 +112,47 @@ struct GNUNET_CONTAINER_MultiHashMap
    * 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 multihashmap.
+ * Allows to enumerate elements asynchronously.
+ */
+struct GNUNET_CONTAINER_MultiHashMapIterator
+{
+  /**
+   * 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_MultiHashMap *map;
 };
 
 
@@ -78,17 +160,29 @@ struct GNUNET_CONTAINER_MultiHashMap
  * 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_MultiHashMap *
-GNUNET_CONTAINER_multihashmap_create (unsigned int len)
+GNUNET_CONTAINER_multihashmap_create (unsigned int len,
+				      int do_not_copy_keys)
 {
-  struct GNUNET_CONTAINER_MultiHashMap *ret;
-
-  ret = GNUNET_malloc (sizeof (struct GNUNET_CONTAINER_MultiHashMap));
-  ret->map = GNUNET_malloc (len * sizeof (struct MapEntry *));
-  ret->map_length = len;
-  return ret;
+  struct GNUNET_CONTAINER_MultiHashMap *map;
+
+  GNUNET_assert (len > 0);
+  map = GNUNET_new (struct GNUNET_CONTAINER_MultiHashMap);
+  map->map = GNUNET_malloc (len * sizeof (union MapEntry));
+  map->map_length = len;
+  map->use_small_entries = do_not_copy_keys;
+  return map;
 }
 
 
@@ -103,16 +197,38 @@ GNUNET_CONTAINER_multihashmap_destroy (struct GNUNET_CONTAINER_MultiHashMap
                                        *map)
 {
   unsigned int i;
-  struct MapEntry *e;
+  union MapEntry me;
 
   for (i = 0; i < map->map_length; i++)
+  {
+    me = map->map[i];
+    if (map->use_small_entries)
     {
-      while (NULL != (e = map->map[i]))
-        {
-          map->map[i] = e->next;
-          GNUNET_free (e);
-        }
+      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);
 }
@@ -121,15 +237,16 @@ GNUNET_CONTAINER_multihashmap_destroy (struct GNUNET_CONTAINER_MultiHashMap
 /**
  * Compute the index of the bucket for the given key.
  *
- * @param m hash map for which to compute the index
+ * @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 "m"
+ * @return offset into the "map" array of "map"
  */
 static unsigned int
-idx_of (const struct GNUNET_CONTAINER_MultiHashMap *m,
-        const GNUNET_HashCode * key)
+idx_of (const struct GNUNET_CONTAINER_MultiHashMap *map,
+        const struct GNUNET_HashCode *key)
 {
-  return (*(unsigned int *) key) % m->map_length;
+  GNUNET_assert (map != NULL);
+  return (*(unsigned int *) key) % map->map_length;
 }
 
 
@@ -158,18 +275,28 @@ GNUNET_CONTAINER_multihashmap_size (const struct GNUNET_CONTAINER_MultiHashMap
  *   key-value pairs with value NULL
  */
 void *
-GNUNET_CONTAINER_multihashmap_get (const struct GNUNET_CONTAINER_MultiHashMap
-                                   *map, const GNUNET_HashCode * key)
+GNUNET_CONTAINER_multihashmap_get (const struct GNUNET_CONTAINER_MultiHashMap *map,
+                                   const struct GNUNET_HashCode *key)
 {
-  struct MapEntry *e;
-
-  e = map->map[idx_of (map, key)];
-  while (e != NULL)
-    {
-      if (0 == memcmp (key, &e->key, sizeof (GNUNET_HashCode)))
-        return e->value;
-      e = e->next;
-    }
+  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_HashCode)))
+	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_HashCode)))
+	return bme->value;
+  }
   return NULL;
 }
 
@@ -179,9 +306,9 @@ GNUNET_CONTAINER_multihashmap_get (const struct GNUNET_CONTAINER_MultiHashMap
  *
  * @param map the map
  * @param it function to call on each entry
- * @param it_cls extra argument to it
+ * @param it_cls extra argument to @a it
  * @return the number of key value pairs processed,
- *         GNUNET_SYSERR if it aborted iteration
+ *         #GNUNET_SYSERR if it aborted iteration
  */
 int
 GNUNET_CONTAINER_multihashmap_iterate (const struct
@@ -191,21 +318,50 @@ GNUNET_CONTAINER_multihashmap_iterate (const struct
 {
   int count;
   unsigned int i;
-  struct MapEntry *e;
+  union MapEntry me;
+  struct GNUNET_HashCode kc;
 
   count = 0;
+  GNUNET_assert (NULL != map);
   for (i = 0; i < map->map_length; i++)
+  {
+    me = map->map[i];
+    if (map->use_small_entries)
     {
-      e = map->map[i];
-      while (e != NULL)
-        {
-          if ( (NULL != it) && 
-	       (GNUNET_OK != it (it_cls, &e->key, e->value)) )
-            return GNUNET_SYSERR;
-          count++;
-          e = e->next;
-        }
+      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;
 }
 
@@ -218,37 +374,65 @@ GNUNET_CONTAINER_multihashmap_iterate (const struct
  * @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
+ * @return #GNUNET_YES on success, #GNUNET_NO if the key-value pair
  *  is not in the map
  */
 int
-GNUNET_CONTAINER_multihashmap_remove (struct GNUNET_CONTAINER_MultiHashMap
-                                      *map, const GNUNET_HashCode * key,
-                                      void *value)
+GNUNET_CONTAINER_multihashmap_remove (struct GNUNET_CONTAINER_MultiHashMap *map,
+                                      const struct GNUNET_HashCode *key,
+				      const void *value)
 {
-  struct MapEntry *e;
-  struct MapEntry *p;
+  union MapEntry me;
   unsigned int i;
 
+  map->modification_counter++;
+
   i = idx_of (map, key);
-  p = NULL;
-  e = map->map[i];
-  while (e != NULL)
+  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, &e->key, sizeof (GNUNET_HashCode))) &&
-	   (value == e->value))
-        {
-          if (p == NULL)
-            map->map[i] = e->next;
-          else
-            p->next = e->next;
-          GNUNET_free (e);
-          map->size--;
-          return GNUNET_YES;
-        }
-      p = e;
-      e = e->next;
+      if ((0 == memcmp (key, sme->key, sizeof (struct GNUNET_HashCode))) &&
+	  (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_HashCode))) &&
+	  (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;
 }
 
@@ -262,40 +446,121 @@ GNUNET_CONTAINER_multihashmap_remove (struct GNUNET_CONTAINER_MultiHashMap
  * @return number of values removed
  */
 int
-GNUNET_CONTAINER_multihashmap_remove_all (struct GNUNET_CONTAINER_MultiHashMap
-                                          *map, const GNUNET_HashCode * key)
+GNUNET_CONTAINER_multihashmap_remove_all (struct GNUNET_CONTAINER_MultiHashMap *map,
+                                          const struct GNUNET_HashCode *key)
 {
-  struct MapEntry *e;
-  struct MapEntry *p;
+  union MapEntry me;
   unsigned int i;
   int ret;
 
+  map->modification_counter++;
+
   ret = 0;
   i = idx_of (map, key);
-  p = NULL;
-  e = map->map[i];
-  while (e != NULL)
+  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, &e->key, sizeof (GNUNET_HashCode)))
-        {
-          if (p == NULL)
-            map->map[i] = e->next;
-          else
-            p->next = e->next;
-          GNUNET_free (e);
-          map->size--;
-          if (p == NULL)
-            e = map->map[i];
-          else
-            e = p->next;
-          ret++;
-        }
+      if (0 == memcmp (key, sme->key, sizeof (struct GNUNET_HashCode)))
+      {
+	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 = e;
-          e = e->next;
-        }
+      {
+	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_HashCode)))
+      {
+	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;
+}
+
+
+/**
+ * Callback used to remove all entries from the map.
+ *
+ * @param cls the `struct GNUNET_CONTAINER_MultiHashMap`
+ * @param key the key
+ * @param value the value
+ * @return #GNUNET_OK (continue to iterate)
+ */
+static int
+remove_all (void *cls,
+            const struct GNUNET_HashCode *key,
+            void *value)
+{
+  struct GNUNET_CONTAINER_MultiHashMap *map = cls;
+
+  GNUNET_CONTAINER_multihashmap_remove (map,
+                                        key,
+                                        value);
+  return GNUNET_OK;
+}
+
+
+/**
+ * @ingroup hashmap
+ * Remove all entries from the map.
+ * Note that the values would not be "freed".
+ *
+ * @param map the map
+ * @return number of values removed
+ */
+unsigned int
+GNUNET_CONTAINER_multihashmap_clear (struct GNUNET_CONTAINER_MultiHashMap *map)
+{
+  unsigned int ret;
+
+  ret = map->size;
+  GNUNET_CONTAINER_multihashmap_iterate (map,
+                                         &remove_all,
+                                         map);
   return ret;
 }
 
@@ -306,23 +571,74 @@ GNUNET_CONTAINER_multihashmap_remove_all (struct GNUNET_CONTAINER_MultiHashMap
  *
  * @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
+ * @return #GNUNET_YES if such a value exists,
+ *         #GNUNET_NO if not
  */
 int
 GNUNET_CONTAINER_multihashmap_contains (const struct
                                         GNUNET_CONTAINER_MultiHashMap *map,
-                                        const GNUNET_HashCode * key)
+                                        const struct GNUNET_HashCode *key)
 {
-  struct MapEntry *e;
+  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_HashCode)))
+	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_HashCode)))
+	return GNUNET_YES;
+  }
+  return GNUNET_NO;
+}
 
-  e = map->map[idx_of (map, key)];
-  while (e != NULL)
-    {
-      if (0 == memcmp (key, &e->key, sizeof (GNUNET_HashCode)))
-        return GNUNET_YES;
-      e = e->next;
-    }
+
+/**
+ * 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_multihashmap_contains_value (const struct
+                                              GNUNET_CONTAINER_MultiHashMap
+                                              *map, const struct GNUNET_HashCode *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_HashCode))) &&
+	   (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_HashCode))) &&
+	   (bme->value == value) )
+	return GNUNET_YES;
+  }
   return GNUNET_NO;
 }
 
@@ -335,30 +651,48 @@ GNUNET_CONTAINER_multihashmap_contains (const struct
 static void
 grow (struct GNUNET_CONTAINER_MultiHashMap *map)
 {
-  struct MapEntry **old_map;
-  struct MapEntry **new_map;
-  struct MapEntry *e;
+  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 (struct MapEntry *) * new_len);
+  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)
     {
-      while (NULL != (e = old_map[i]))
-        {
-          old_map[i] = e->next;
-	  idx = idx_of (map, &e->key);
-          e->next = new_map[idx];
-          new_map[idx] = e;
-        }
+      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);
 }
 
@@ -370,45 +704,77 @@ grow (struct GNUNET_CONTAINER_MultiHashMap *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 UNIQUE_ONLY was the option and the
+ * @return #GNUNET_OK on success,
+ *         #GNUNET_NO if a value was replaced (with REPLACE)
+ *         #GNUNET_SYSERR if UNIQUE_ONLY was the option and the
  *                       value already exists
  */
 int
 GNUNET_CONTAINER_multihashmap_put (struct GNUNET_CONTAINER_MultiHashMap *map,
-                                   const GNUNET_HashCode * key,
-                                   void *value,
-                                   enum GNUNET_CONTAINER_MultiHashMapOption
-                                   opt)
+                                   const struct GNUNET_HashCode *key,
+				   void *value,
+                                   enum GNUNET_CONTAINER_MultiHashMapOption opt)
 {
-  struct MapEntry *e;
+  union MapEntry me;
   unsigned int i;
 
   i = idx_of (map, key);
-  if ( (opt != GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE) &&
-       (opt != GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_FAST) )
+  if ((opt != GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE) &&
+      (opt != GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_FAST))
+  {
+    me = map->map[i];
+    if (map->use_small_entries)
     {
-      e = map->map[i];
-      while (e != NULL)
-        {
-          if (0 == memcmp (key, &e->key, sizeof (GNUNET_HashCode)))
-            {
-              if (opt == GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY)
-                return GNUNET_SYSERR;
-              e->value = value;
-              return GNUNET_NO;
-            }
-          e = e->next;
-        }
+      struct SmallMapEntry *sme;
+
+      for (sme = me.sme; NULL != sme; sme = sme->next)
+	if (0 == memcmp (key, sme->key, sizeof (struct GNUNET_HashCode)))
+	{
+	  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_HashCode)))
+	{
+	  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);
-  e = GNUNET_malloc (sizeof (struct MapEntry));
-  e->key = *key;
-  e->value = value;
-  e->next = map->map[i];
-  map->map[i] = e;
+    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;
 }
@@ -422,62 +788,222 @@ GNUNET_CONTAINER_multihashmap_put (struct GNUNET_CONTAINER_MultiHashMap *map,
  * @param it function to call on each entry
  * @param it_cls extra argument to it
  * @return the number of key value pairs processed,
- *         GNUNET_SYSERR if it aborted iteration
+ *         #GNUNET_SYSERR if it aborted iteration
  */
 int
 GNUNET_CONTAINER_multihashmap_get_multiple (const struct
-                                            GNUNET_CONTAINER_MultiHashMap
-                                            *map, const GNUNET_HashCode * key,
-                                            GNUNET_CONTAINER_HashMapIterator
-                                            it, void *it_cls)
+                                            GNUNET_CONTAINER_MultiHashMap *map,
+                                            const struct GNUNET_HashCode *key,
+                                            GNUNET_CONTAINER_HashMapIterator it,
+                                            void *it_cls)
 {
   int count;
-  struct MapEntry *e;
+  union MapEntry me;
 
   count = 0;
-  e = map->map[idx_of (map, key)];
-  while (e != NULL)
+  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))
     {
-      if (0 == memcmp (key, &e->key, sizeof (GNUNET_HashCode)))
+      nxt = sme->next;
+      if (0 != memcmp (key, sme->key, sizeof (struct GNUNET_HashCode)))
+	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_HashCode)))
+	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_multihashmap_get_random (const struct GNUNET_CONTAINER_MultiHashMap *map,
+                                          GNUNET_CONTAINER_HashMapIterator 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 ( (it != NULL) && 
-	       (GNUNET_OK != it (it_cls, &e->key, e->value)) )
+          if (GNUNET_OK != it (it_cls,
+                               sme->key,
+                               sme->value))
             return GNUNET_SYSERR;
-          count++;
+          return 1;
         }
-      e = e->next;
+        off--;
+      }
     }
-  return count;
+    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;
 }
 
 
 /**
- * Returns the stored value of a random non-null entry in the hash
- * table.  Returns only the first value, does not go inside bucket
- * linked list (yet).  Runs with a worst case time of N, so it's not
- * efficient in any way shape or form!!!!.
+ * Create an iterator for a multihashmap.
+ * The iterator can be used to retrieve all the elements in the multihashmap
+ * one by one, without having to handle all elements at once (in contrast to
+ * GNUNET_CONTAINER_multihashmap_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
- * @return value associated with a random key
+ * @param map the map to create an iterator for
+ * @return an iterator over the given multihashmap 'map'
  */
-void *
-GNUNET_CONTAINER_multihashmap_get_random (const struct
-                                          GNUNET_CONTAINER_MultiHashMap *map)
+struct GNUNET_CONTAINER_MultiHashMapIterator *
+GNUNET_CONTAINER_multihashmap_iterator_create (const struct GNUNET_CONTAINER_MultiHashMap *map)
 {
-  unsigned int rand;
-  struct MapEntry *e;
+  struct GNUNET_CONTAINER_MultiHashMapIterator *iter;
 
-  if (map->size == 0)
-    return NULL;
+  iter = GNUNET_new (struct GNUNET_CONTAINER_MultiHashMapIterator);
+  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
+ * multihashmap 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_multihashmap_iterator_next (struct GNUNET_CONTAINER_MultiHashMapIterator *iter,
+                                             struct GNUNET_HashCode *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)
     {
-      rand =
-        GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
-                                  map->map_length);
-      if (NULL != (e = map->map[rand]))
-	return e->value;
+      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;
+      }
     }
-  return e->value;
+    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 multihashmap iterator.
+ *
+ * @param iter the iterator to destroy
+ */
+void
+GNUNET_CONTAINER_multihashmap_iterator_destroy (struct GNUNET_CONTAINER_MultiHashMapIterator *iter)
+{
+  GNUNET_free (iter);
 }