ANSI C Hash Table ("strmap")

This is Per Ola Kristensson's implementation of a hash map in ANSI C. The origin of the code in this repo and it's explanation can be found here.

The simple implementation is described to have the following functionality:

1. Inserting and retrieving key-value associations
2. Querying the existence of a key
3. Returning the total number of key-value associations
4. Iterating over all key-value associations

Usage

example.c:

// creating a new map
StrMap *map = sm_new(4);

// creating pairs
sm_put(map, "tag", "Digital Cannon");
sm_put(map, "character", "Electric Mouse");

// getting values
char buf[80];
int result = sm_get(map, "character", buf, sizeof(buf));
if (result) {
	printf("Character: %s\n", buf);
} else {
	printf("No character\n");
}

// delete map when it is no longer needed
sm_delete(map);

License

The code ("strmap") is licensed under the GNU Lesser General Public License.

The license as it was when the code was last updated is in LICENSE.txt.

Notes

First, the code is not thread-safe. Use external synchronization.

Second, the implementation copies values upon insertion and retrieval. This guarantees that no internal references are exposed to the client after the hash table has been deleted from memory. There is one exception, however. When iterating over all key-value associations, the internal strings are temporarily exposed as constant pointers to the internal string buffers. This is because it is very slow and cumbersome to copy all key-value associations to a buffer via a callback function interface. It is recommended not to keep the pointers to the internal string buffers around out of scope of the callback function. Otherwise, you risk having wild pointers in your code after you have deleted the hash table.