TypeSafeSchwalbe / c-hashmap

A simple hashmap implementation in C.

c-hashmap

A simple hashmap implementation in C.

hmap.h

Types

typedef size_t (*Hasher)(size_t length, char* data);

A hash function.

• length - The number of bytes to hash
• data - The data to hash. Must be able to access the next length bytes.

typedef struct HashMap {
    Hasher hasher; 
    double load_factor; 
    size_t size;
    /* ... */
} HashMap;

The hashmap structure.

• hasher - The hash function to use to hash the keys. May be changed to another function to hash that specific key type.
• load_factor - Used to configure when the hash map size increases. The hash map bucket count doubles when size >= bucket_count * load_factor.
• size - The current number of key-value pairs in the map. May only be read from.

Macros

#define HashMap(K, V) ...

Creates a new hash map starting with 16 buckets and hmap_hash being the hash function (which may be changed), returning a HashMap*. The hash map must later be deallocated with hmap_free.

• K - The key type.
• V - The value type.

Functions

HashMap* hmap_new(size_t key_size, size_t val_size, size_t buckets)

Creates a new hash map. The returned pointer must later be passed to hmap_free for deallocation. The created map will use hmap_hash for hashing, which may be changed afterwards.

• key_size - The size of the keys used in the map in bytes.
• value_size - The size of the values used in the map in bytes.
• buckets - The number of buckets to start off with.

void hmap_set(HashMap* map, void* key, void* value)

Sets the value for key to value.

• map - The map to configure.
• key - A pointer to the key data. If the map holds keys of type K, this must be a K*. If the map holds keys of type char*, this must be a char**.
• value - A pointer to the value data. If the map holds values of type V, this must be a V*. If the map holds values of type int, this must be an int*.

void* hmap_get(HashMap* map, void* key)

Gets the value for key.

• map - The map to read from.
• key - A pointer to the key data. If the map holds keys of type K, this must be a K*. If the map holds keys of type char*, this must be a char**.

size_t hmap_hash(size_t length, char* data)

The default hash function used by the map.

void hmap_free(HashMap* map)

Frees all memory associated with map.

• map - The map to deallocate.