hashlib.c File Reference

the implementation of the hashing library More...

#include "config.h"
#include "defines.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <stddef.h>
#include "hashlib.h"

Go to the source code of this file.

Functions
ub4	lookup (register ub1 *k, register ub4 length, register ub4 level)
t_cf_hash *	cf_hash_new (t_cf_hash_cleanup cl)
int	cf_hash_set (t_cf_hash *hsh, unsigned char *key, size_t keylen, void *data, size_t datalen)
int	cf_hash_set_static (t_cf_hash *hsh, unsigned char *key, size_t keylen, void *data)
void *	cf_hash_get (t_cf_hash *hsh, unsigned char *key, size_t keylen)
int	cf_hash_entry_delete (t_cf_hash *hsh, unsigned char *key, size_t keylen)
void	cf_hash_destroy (t_cf_hash *hsh)

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Detailed Description

the implementation of the hashing library

Author:

Christian Kruse, <cjk@wwwtech.de>

The hashing library was developed within the Classic Forum project, <http://cforum.teamone.de/>

I use a hashing algorithm developed by Bob Jenkins, December 1996. This is (directly after the SDBM algorithm) the fastest hashing algorithm at this time, but the SDBM algorithm has more duplicates. The Fowler/Noll/Vo algorithm has no duplicates, but it is also the slowest of these three algorithms. So the Bob-Jenkins algorithm should be a moderate compromiss.

Definition in file hashlib.c.

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Function Documentation

void cf_hash_destroy (  t_cf_hash *  hsh  )

This function destroys a hash and frees all of its values. After this function call you have to create a new hash with cf_hash_new()! Parameters: hsh  The hash table to destroy. Definition at line 601 of file hashlib.c.

int cf_hash_entry_delete (  t_cf_hash *  hsh, unsigned char *  key, size_t  keylen )

This function deletes a hash entry in a hashtable. Parameters: hsh  The hash table key  The key of the entry keylen  The length of the key Returns: It returns 0 if the entry could not be found and 1 if the entry has been deleted successfully. Definition at line 555 of file hashlib.c.

void* cf_hash_get (  t_cf_hash *  hsh, unsigned char *  key, size_t  keylen )

This function looks up a hash entry in a hash table. If an entry with the key could not be found, NULL is returned. Parameters: hsh  The hash table key  The key of the entry keylen  The length of the key Returns: The data of the entry if it has been found or NULL if it could not be found. Definition at line 527 of file hashlib.c.

t_cf_hash* cf_hash_new (  t_cf_hash_cleanup  cl  )

This function constructs a new hash. It expects a pointer to a destructor function. This function will be called when a hash entry will be destroyed. This can happen if you call 'cf_hash_entry_delete' or if you call 'cf_hash_destroy'. You MUST NOT free the data object itself! This will be done internaly. You only should cleanup the structure if it is a complex data structure like a struct or an array of arrays. Parameters: cl  The destructor for a data entry of the hash table. If the function pointer is NULL, no cleanup function will be called. Returns: It returns the new created hash table object on success or NULL on failure Definition at line 175 of file hashlib.c.

int cf_hash_set (  t_cf_hash *  hsh, unsigned char *  key, size_t  keylen, void *  data, size_t  datalen )

This function saves a hash entry with the given key in the hash table. It can happen that the table has to be resized, but this should not happen very often (there's one double hashvalue in a 32 bit keylen and we accept 5 double hashvalues per entry). But *when* it happens, this call is very expensive... Parameters: hsh  The hash table key  The key of the entry keylen  The length of the key data  The data of the entry datalen  The size of the data Returns: 0 on failure, 1 if successful Definition at line 382 of file hashlib.c.

int cf_hash_set_static (  t_cf_hash *  hsh, unsigned char *  key, size_t  keylen, void *  data )

This function saves a hash entry with the given key in the hash table. It can happen that the table has to be resized, but this should not happen very often (there's one double hashvalue in a 32 bit keylen and we accept 5 double hashvalues per entry). But *when* it happens, this call is very expensive... The difference between cf_hash_set() is, that cf_hash_set() makes a copy from the data and cf_hash_set_static() assumes static data which needs not to be copied and needs no free() call Parameters: hsh  The hash table key  The key of the entry keylen  The length of the key data  The data of the entry Returns: 0 on failure, 1 if successful Definition at line 457 of file hashlib.c.

ub4 lookup (  register ub1 *  k, register ub4  length, register ub4  level )

This function is used to generate a hash sum from a given key. Parameters: k  The key to calculate the hashsum from length  The length of the key level  The entropy level. It is used to mix a little bit random into the keys. Not used by this hash table library. Returns: the hash sum Definition at line 114 of file hashlib.c.

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