Add defined behavior for inserts with matching keys, and a test.

5 files changed, 88 insertions, 2 deletions

diff --git a/README b/README
index be2fe40..fb85a68 100644
--- a/README
+++ b/README
@@ -13,8 +13,10 @@ with rehashing.  The table stores for each entry:
  * pointer to the data.
 
 Inserts occur at key->hash % hash->size.  When an insert collides, the insert
-reattempts at (key->hash % hash->size + hash->reprobe) % hash->size, and
-onwards at increments of reprobe until a free or dead entry is found.
+steps through the table using the reprobe stride until a free or dead entry is
+found.  When an insert occurs with a key matching a key already in the table,
+the new data is associated with the key.  Note that old key/data is not freed,
+so if memory management is required, do a search before insert.
 
 When searching, the search starts at key % hash_size and continues at
 increments of reprobe as with inserts, until the matching entry or an
diff --git a/hash_table.c b/hash_table.c
index 6367ea3..e295472 100644
--- a/hash_table.c
+++ b/hash_table.c
@@ -255,6 +255,25 @@ hash_table_insert(struct hash_table *ht, uint32_t hash,
 			return entry;
 		}
 
+		/* Implement replacement when another insert happens
+		 * with a matching key.  This is a relatively common
+		 * feature of hash tables, with the alternative
+		 * generally being "insert the new value as well, and
+		 * return it first when the key is searched for".
+		 *
+		 * Note that the hash table doesn't have a delete
+		 * callback.  If freeing of old data pointers is
+		 * required to avoid memory leaks, perform a search
+		 * before inserting.
+		 */
+		if (entry->hash == hash &&
+		    ht->key_equals_function(key, entry->key)) {
+			entry->key = key;
+			entry->data = data;
+			return entry;
+		}
+
+
 		double_hash = 1 + hash % ht->rehash;
 
 		hash_address = (hash_address + double_hash) % ht->size;
diff --git a/tests/.gitignore b/tests/.gitignore
index 6c96e28..41ca9e7 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -5,3 +5,4 @@ insert_and_lookup
 insert_many
 null_destroy
 random_entry
+replacement
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 83610ba..e681df1 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -29,6 +29,7 @@ TESTS = \
 	insert_many \
 	null_destroy \
 	random_entry \
+	replacement \
 	$()
 
 EXTRA_PROGRAMS = $(TESTS)
diff --git a/tests/replacement.c b/tests/replacement.c
new file mode 100644
index 0000000..eb70906
--- /dev/null
+++ b/tests/replacement.c
@@ -0,0 +1,63 @@
+/*
+ * Copyright © 2011 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ *    Eric Anholt <eric@anholt.net>
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+#include "hash_table.h"
+#include "fnv_hash.h"
+
+int
+main(int argc, char **argv)
+{
+	struct hash_table *ht;
+	char *str1 = strdup("test1");
+	char *str2 = strdup("test1");
+	uint32_t hash_str1 = fnv1_hash_string(str1);
+	uint32_t hash_str2 = fnv1_hash_string(str2);
+	struct hash_entry *entry;
+
+	ht = hash_table_create(string_key_equals);
+
+	hash_table_insert(ht, hash_str1, str1, str1);
+	hash_table_insert(ht, hash_str2, str2, str2);
+
+	entry = hash_table_search(ht, hash_str1, str1);
+	assert(entry);
+	assert(entry->data == str2);
+
+	hash_table_remove(ht, entry);
+
+	entry = hash_table_search(ht, hash_str1, str1);
+	assert(!entry);
+
+	hash_table_destroy(ht, NULL);
+	free(str1);
+	free(str2);
+
+	return 0;
+}