lib: New data structure - smap.

[sliver-openvswitch.git] / lib / shash.c

diff --git a/lib/shash.c b/lib/shash.c
index e2b1fe2..7480176 100644 (file)
--- a/lib/shash.c
+++ b/lib/shash.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009, 2010 Nicira Networks.
+ * Copyright (c) 2009, 2010, 2011 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,7 +20,8 @@
 #include "hash.h"
 
 static struct shash_node *shash_find__(const struct shash *,
-                                       const char *name, size_t hash);
+                                       const char *name, size_t name_len,
+                                       size_t hash);
 
 static size_t
 hash_name(const char *name)
@@ -147,21 +148,55 @@ shash_add_assert(struct shash *sh, const char *name, const void *data)
     assert(added);
 }
 
+/* Searches for 'name' in 'sh'.  If it does not already exist, adds it along
+ * with 'data' and returns NULL.  If it does already exist, replaces its data
+ * by 'data' and returns the data that it formerly contained. */
+void *
+shash_replace(struct shash *sh, const char *name, const void *data)
+{
+    size_t hash = hash_name(name);
+    struct shash_node *node;
+
+    node = shash_find__(sh, name, strlen(name), hash);
+    if (!node) {
+        shash_add_nocopy__(sh, xstrdup(name), data, hash);
+        return NULL;
+    } else {
+        void *old_data = node->data;
+        node->data = (void *) data;
+        return old_data;
+    }
+}
+
+/* Deletes 'node' from 'sh' and frees the node's name.  The caller is still
+ * responsible for freeing the node's data, if necessary. */
 void
 shash_delete(struct shash *sh, struct shash_node *node)
 {
+    free(shash_steal(sh, node));
+}
+
+/* Deletes 'node' from 'sh'.  Neither the node's name nor its data is freed;
+ * instead, ownership is transferred to the caller.  Returns the node's
+ * name. */
+char *
+shash_steal(struct shash *sh, struct shash_node *node)
+{
+    char *name = node->name;
+
     hmap_remove(&sh->map, &node->node);
-    free(node->name);
     free(node);
+    return name;
 }
 
 static struct shash_node *
-shash_find__(const struct shash *sh, const char *name, size_t hash)
+shash_find__(const struct shash *sh, const char *name, size_t name_len,
+             size_t hash)
 {
     struct shash_node *node;
 
-    HMAP_FOR_EACH_WITH_HASH (node, struct shash_node, node, hash, &sh->map) {
-        if (!strcmp(node->name, name)) {
+    HMAP_FOR_EACH_WITH_HASH (node, node, hash, &sh->map) {
+        if (!strncmp(node->name, name, name_len) && !node->name[name_len]) {
             return node;
         }
     }
@@ -172,7 +207,15 @@ shash_find__(const struct shash *sh, const char *name, size_t hash)
 struct shash_node *
 shash_find(const struct shash *sh, const char *name)
 {
-    return shash_find__(sh, name, hash_name(name));
+    return shash_find__(sh, name, strlen(name), hash_name(name));
+}
+
+/* Finds and returns a shash_node within 'sh' that has the given 'name' that is
+ * exactly 'len' bytes long.  Returns NULL if no node in 'sh' has that name. */
+struct shash_node *
+shash_find_len(const struct shash *sh, const char *name, size_t len)
+{
+    return shash_find__(sh, name, len, hash_bytes(name, len, 0));
 }
 
 void *
@@ -259,3 +302,14 @@ shash_equal_keys(const struct shash *a, const struct shash *b)
     }
     return true;
 }
+
+/* Chooses and returns a randomly selected node from 'sh', which must not be
+ * empty.
+ *
+ * I wouldn't depend on this algorithm to be fair, since I haven't analyzed it.
+ * But it does at least ensure that any node in 'sh' can be chosen. */
+struct shash_node *
+shash_random_node(struct shash *sh)
+{
+    return CONTAINER_OF(hmap_random_node(&sh->map), struct shash_node, node);
+}