LIBHASHKIT(3)

NAME
libhashkit - libhashkit Documentation

SYNOPSIS

#include <libhashkit-1.0/hashkit.h>
    Compile and link with -lhashkit.

DESCRIPTION

libhashkit is a small and thread-safe client library that provides a collection of useful hashing algorithms.

libhashkit is distributed with libmemcached.

  Creating a hashkit structure

  SYNOPSIS

#include <libhashkit-1.0/hashkit.h>
    Compile and link with -lhashkit

typedef struct hashkit_st hashkit_st

hashkit_st *hashkit_create(hashkit_st *hash)

Parameters
    hash -- memory address of a hashkit_st struct; if a nullptr is passed, the struct will be dynamically allocated by libhashkit

Returns
    pointer to initialized hashkit_st structure

hashkit_st *hashkit_clone(hashkit_st *destination, const hashkit_st *ptr)

Parameters

•   destination -- memory address of a hashkit_st struct; if a nullptr is passed, the struct will be dynamically allocated by libhashkit

•   ptr -- pointer of the hashkit_st struct to copy

Returns
    pointer to a hashkit_st structure (destination, if not nullptr), initialized from ptr

void hashkit_free(hashkit_st *hash)

Parameters
    hash -- pointer to an initialized hashkit_st struct

bool hashkit_is_allocated(const hashkit_st *hash)

Parameters
    hash -- pointer to an initialized hashkit_st struct

Returns
    bool, whether the hash struct was dynamically allocated

  DESCRIPTION

The hashkit_create() function initializes a hashkit object for use. If you pass a nullptr argument for hash, then the memory for the object is allocated. If you specify a pre-allocated piece of memory, that is initialized for use.

The hashkit_clone() function initializes a hashkit object much like hashkit_create(), but instead of using default settings it will use the settings of the ptr hashkit object.

The hashkit_free() frees any resources being consumed by the hashkit objects that were initialized with hashkit_create() or hashkit_clone().

The hashkit_is_allocated() reports whether the memory was allocated for a hashkit object.

  RETURN VALUE

hashkit_create() and hashkit_clone() will return nullptr on failure or pointer to hashkit_st on success.

hashkit_is_allocated() returns true if the memory for the hashkit object was allocated inside of hashkit_create() or hashkit_clone(), otherwise it is false and was user-supplied memory.

  SEE ALSO

libhashkit(3) hashkit_value(3) hashkit_function3)

  Set Hash Function

  SYNOPSIS

#include <libhashkit-1.0/hashkit.h>
    Compile and link with -lhashkit

typedef uint32_t (*hashkit_hash_fn)(const char *key, size_t key_length, void *context)

Param key
    the key to generate a hash of

Param key_length
    the length of the key without any terminating zero byte

Param context
    the custom hash function context set through hashkit_set_custom_function() or hashkit_set_custom_distribution_function()

Returns
    the custom hash function should return a hash value for key as an unsigned 32bit integer

typedef enum hashkit_return_t hashkit_return_t

enum hashkit_return_t

enumerator HASHKIT_SUCCESS
    Operation succeeded.

enumerator HASHKIT_FAILURE
    Operation failed.

enumerator HASHKIT_MEMORY_ALLOCATION_FAILURE
    Memory allocation failed.

enumerator HASHKIT_INVALID_HASH
    Invalid hashkit_hash_algorithm_t passed.

enumerator HASHKIT_INVALID_ARGUMENT
    Invalid argument passed.

typedef enum hashkit_hash_algorithm_t hashkit_hash_algorithm_t

enum hashkit_hash_algorithm_t

enumerator HASHKIT_HASH_DEFAULT
    Default hash algorithm (one_at_a_time).

enumerator HASHKIT_HASH_MD5

enumerator HASHKIT_HASH_CRC

enumerator HASHKIT_HASH_FNV1_64

enumerator HASHKIT_HASH_FNV1A_64

enumerator HASHKIT_HASH_FNV1_32

enumerator HASHKIT_HASH_FNV1A_32

enumerator HASHKIT_HASH_HSIEH
    Only available if libhashkit hash been built with HSIEH support.

enumerator HASHKIT_HASH_MURMUR
    Only available if libhashkit has been built with MURMUR support.

enumerator HASHKIT_HASH_MURMUR3
    Only available if libhashkit has been built with MURMUR support.

enumerator HASHKIT_HASH_JENKINS

enumerator HASHKIT_HASH_CUSTOM
    Use custom hashkit_hash_fn function set through hashkit_set_custom_function() or hashkit_set_custom_distribution_function().

hashkit_return_t hashkit_set_function(hashkit_st *hash, hashkit_hash_algorithm_t hash_algorithm)

Parameters

•   hash -- pointer to an initialized hashkit_st struct

•   hash_algorithm -- valid hashkit_hash_algorithm_t constant

Returns
    hashkit_return_t indicating success or failure

hashkit_return_t hashkit_set_custom_function(hashkit_st *hash, hashkit_hash_fn function, void *context)

Parameters

•   hash -- pointer to initialized hashkit_st struct

•   function -- hashkit_hash_fn function pointer to use as hash function for HASHKIT_HASH_CUSTOM

•   context -- pointer to an opaque user managed context for the custom hash function

Returns
    hashkit_return_t indicating success or failure

hashkit_hash_algorithm_t hashkit_get_function(const hashkit_st *hash)

Parameters
    hash -- pointer to an initialized hashkit_st struct

Returns
    hashkit_hash_algorithm_t indicating the currently set hash algorithm to use

hashkit_return_t hashkit_set_distribution_function(hashkit_st *hash, hashkit_hash_algorithm_t hash_algorithm)

Parameters

•   hash -- pointer to an initialized hashkit_st struct

•   hash_algorithm -- valid hashkit_hash_algrothm_t constant

Returns
    hashkit_return_t indicating success or failure

hashkit_return_t hashkit_set_custom_distribution_function(hashkit_st *hash, hashkit_hash_fn function, void *context)

Parameters

•   hash -- pointer to initialized hashkit_st struct

•   function -- hashkit_hash_fn function pointer to use as distribution hash function for HASHKIT_HASH_CUSTOM

•   context -- pointer to an opaque user managed context for the custom distribution hash function

hashkit_hash_algorithm_t hashkit_get_distribution_function(const hashkit_st *hash)

Parameters
    hash -- pointer to an initialized hashkit_st struct

Returns
    hashkit_hash_algorithm_t indicating the currently set distribution hash algorithm to use

  DESCRIPTION

These functions are used to set and retrieve the key and distribution hash functions.

  RETURN VALUE

hashkit_set_function(), hashkit_set_custom_function() and the distribution equivalents return hashkit_return_t::HASHKIT_SUCCESS on success.

hashkit_get_function() and hashkit_get_distribution_function() return hashkit_hash_algorithm_t indicating the hash function used.

  SEE ALSO

libhashkit(3) hashkit_create(3) hashkit_functions(3)

  Available Hashes

  SYNOPSIS

#include <libhashkit-1.0/hashkit.h>
    Compile and link with -lhashkit

uint32_t hashkit_default(const char *key, size_t key_length)

uint32_t hashkit_fnv1_64(const char *key, size_t key_length)

uint32_t hashkit_fnv1a_64(const char *key, size_t key_length)

uint32_t hashkit_fnv1_32(const char *key, size_t key_length)

uint32_t hashkit_fnv1a_32(const char *key, size_t key_length)

uint32_t hashkit_crc32(const char *key, size_t key_length)

uint32_t hashkit_hsieh(const char *key, size_t key_length)

uint32_t hashkit_murmur(const char *key, size_t key_length)

uint32_t hashkit_murmur3(const char *key, size_t key_length)

uint32_t hashkit_jenkins(const char *key, size_t key_length)

uint32_t hashkit_md5(const char *key, size_t key_length)

  DESCRIPTION

These functions generate hash values from a key using a variety of algorithms. These functions can be used standalone, or will be used according to the algorithm set with hashkit_set_function() or hashkit_set_distribution_function().

The hashkit_hsieh(), hashkit_murmur() and hashkit_murmur3() functions are only available if the library is built with the appropriate flag enabled.

  RETURN VALUE

A 32-bit hash value.

  SEE ALSO

libhashkit(3) hashkit_create(3) hashkit_function(3)

  Generate hash value

  SYNOPSIS

#include <libhashkit-1.0/hashkit.h>
    Compile and link with -lhashkit

uint32_t hashkit_value(hashkit_st *hash, const char *key, size_t key_length)

Parameters

•   hash -- pointer to an initialized hashkit_st struct

•   key -- the key to genereate a hash of

•   key_length -- the length of the key without any terminating zero byte

  DESCRIPTION

The hashkit_value() function generates a 32-bit hash value from the given key and key_length. The hash argument is an initialized hashkit object, and distribution type and hash function is used from this object while generating the value.

  RETURN VALUE

A 32-bit hash value.

  SEE ALSO

libhashkit(3) hashkit_create(3) hashkit_function(3) hashkit_functions(3)

SEE ALSO

libmemcached(3) hashkit_create(3) hashkit_function(3) hashkit_functions(3) hashkit_value(3)