X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=lib%2Fshash.c;h=82791e31f76e77445ff2bf771df6eb78ee4c687d;hb=76ecc721793b29c8bae44b10a065ec9ac07a9e4b;hp=c4d3ccb8daa524b586dc4471d1365e40e401c65d;hpb=a90b56b7708a17e8bd689d4a3558348f04cb8dcb;p=openvswitch

diff --git a/lib/shash.c b/lib/shash.c
index c4d3ccb8..82791e31 100644
--- a/lib/shash.c
+++ b/lib/shash.c
@@ -19,6 +19,9 @@
 #include <assert.h>
 #include "hash.h"
 
+static struct shash_node *shash_find__(const struct shash *,
+                                       const char *name, size_t hash);
+
 static size_t
 hash_name(const char *name)
 {
@@ -100,18 +103,24 @@ shash_count(const struct shash *shash)
     return hmap_count(&shash->map);
 }
 
-/* It is the caller's responsibility to avoid duplicate names, if that is
- * desirable. */
-struct shash_node *
-shash_add_nocopy(struct shash *sh, char *name, const void *data)
+static struct shash_node *
+shash_add_nocopy__(struct shash *sh, char *name, const void *data, size_t hash)
 {
     struct shash_node *node = xmalloc(sizeof *node);
     node->name = name;
     node->data = (void *) data;
-    hmap_insert(&sh->map, &node->node, hash_name(name));
+    hmap_insert(&sh->map, &node->node, hash);
     return node;
 }
 
+/* It is the caller's responsibility to avoid duplicate names, if that is
+ * desirable. */
+struct shash_node *
+shash_add_nocopy(struct shash *sh, char *name, const void *data)
+{
+    return shash_add_nocopy__(sh, name, data, hash_name(name));
+}
+
 /* It is the caller's responsibility to avoid duplicate names, if that is
  * desirable. */
 struct shash_node *
@@ -138,22 +147,53 @@ 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, 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;
 }
 
-/* If there are duplicates, returns a random element. */
-struct shash_node *
-shash_find(const struct shash *sh, const char *name)
+static struct shash_node *
+shash_find__(const struct shash *sh, const char *name, size_t hash)
 {
     struct shash_node *node;
 
-    HMAP_FOR_EACH_WITH_HASH (node, struct shash_node, node,
-                             hash_name(name), &sh->map) {
+    HMAP_FOR_EACH_WITH_HASH (node, node, hash, &sh->map) {
         if (!strcmp(node->name, name)) {
             return node;
         }
@@ -161,6 +201,13 @@ shash_find(const struct shash *sh, const char *name)
     return NULL;
 }
 
+/* If there are duplicates, returns a random element. */
+struct shash_node *
+shash_find(const struct shash *sh, const char *name)
+{
+    return shash_find__(sh, name, hash_name(name));
+}
+
 void *
 shash_find_data(const struct shash *sh, const char *name)
 {
@@ -245,3 +292,14 @@ 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);
+}