libhashkit - Man Page

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)
Parameters
  • key -- the key to generate a hash of
  • key_length -- the length of the key without any terminating zero byte
  • 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)

Referenced By

hashkit_clone(3), hashkit_crc32(3), hashkit_create(3), hashkit_fnv1_32(3), hashkit_fnv1_64(3), hashkit_fnv1a_32(3), hashkit_fnv1a_64(3), hashkit_free(3), hashkit_function(3), hashkit_functions(3), hashkit_get_distribution_function(3), hashkit_get_function(3), hashkit_hsieh(3), hashkit_is_allocated(3), hashkit_jenkins(3), hashkit_md5(3), hashkit_murmur(3), hashkit_set_custom_distribution_function(3), hashkit_set_custom_function(3), hashkit_set_distribution_function(3), hashkit_set_function(3), hashkit_value(3), libmemcached(3), memcached_generate_hash(3), memcached_generate_hash_value(3).

Sep 20, 2021 1.1 libmemcached-awesome