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hashmap.c
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hashmap.c
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/*
hashmap.c : hash map routines
Copyright (C)2010 Rob Neff - All rights reserved.
Source code licensed under the new/simplified 2-clause BSD OSI license.
*/
#include <stdio.h>
#include <memory.h>
#include <malloc.h>
#include "hashmap.h"
#define HASH_MAP_MAGIC 0x6d686470 // 'pdhm'
/*
unsigned int hash16(unsigned char* p, unsigned int len)
Purpose
To calculate a 16-bit hash of a buffer of memory
Params
p - ptr to memory
len - length of buffer to sum
Returns
a 16-bit hash
Notes
This is a modified version of the Fletcher hash algorithm
*/
static unsigned int hash16(unsigned char* buf, unsigned int len)
{
register short int sum1;
register unsigned int sum2;
register unsigned char* p;
sum2 = sum1 = 0;
p = buf;
while (len--)
{
sum1 += *p++;
if (sum1 >= 255) sum1 -= 255;
sum2 += sum1;
}
sum2 %= 255;
return ( (sum2 << 8) | sum1 );
}
/***********************************************************
hash_map_t* hash_map_alloc(unsigned int buckets)
Purpose
To allow memory for the hashmap
Params
buckets - power of 2 number of buckets
Returns
ptr to hashmap, null ptr if error
*/
struct hash_map_t* hash_map_alloc(unsigned int buckets)
{
struct hash_map_t *pHashMap;
unsigned int len;
/* ensure correct buckets bitmask */
if ( buckets == 0 )
return (struct hash_map_t*)0;
/* we don't support hashmaps > 32K */
if ( buckets > 0x8000 )
buckets = 0x8000;
/* find uppermost bit */
len = (1 << ((sizeof(int)*8) - 1));
while ( (buckets & len) == 0 )
len = len >> 1;
len--; /* create the mask */
buckets = len; /* assign bucket size / bit mask */
/* alloc memory space */
len = sizeof(struct hash_map_t);
len += ((buckets + 1) * sizeof(void*));
pHashMap = malloc(len);
if ( pHashMap )
{
memset(pHashMap, 0, len);
pHashMap->magic = HASH_MAP_MAGIC;
pHashMap->buckets = buckets;
}
return pHashMap;
}
/******************************************************************************************
struct bst_node_t* hash_map_find(struct hash_map_t* pHashMap, void *key, unsigned int klen)
Purpose
To find a node within the hashmap containing key
Params
pHashMap - ptr to hash map to search
key - ptr to key to search for
klen - length of key
Returns
ptr to node if found, otherwise null
*/
struct bst_node_t* hash_map_find(struct hash_map_t* pHashMap, void *key, unsigned int klen)
{
unsigned int hash;
struct bst_node_t** root;
#if 0
/* compute the 32-bit hash value of key */
hash = FNV1Hash(key, klen, 2166136261);
/* xor-fold into 16-bit value */
hash = (((hash >> 16) ^ hash) & pHashMap->buckets);
#endif
hash = hash16(key, klen) & pHashMap->buckets;
root = (struct bst_node_t**)((char*)(((char*)pHashMap) + sizeof(struct hash_map_t)) + (hash * sizeof(void*)));
return binarytree_find_node(root, key, klen);
}
/*************************************************************************************************************
int hash_map_insert(struct hash_map_t* pHashMap, void *key, unsigned int klen, char *value, unsigned int vlen)
Purpose
To insert a node within the hashmap containing key/value pair
Params
pHashMap - ptr to hash map to insert into
key - ptr to key to insert
klen - length of key
value - data corresponding to key
vlen - length of data value
Returns
0 if successful, otherwise error code
Notes
value may be null or vlen may be zero if using the hash map for keys only.
Duplicate keys are not supported.
*/
int hash_map_insert(struct hash_map_t* pHashMap, void *key, unsigned int klen, void *value, unsigned int vlen)
{
unsigned int hash;
struct bst_node_t *node;
struct bst_node_t **root;
#ifdef _DEBUG
static int cCollisions = 0;
static int cInserts = 0;
#endif
#if 0
/* compute the 32-bit hash value of key */
hash = FNV1Hash(key, klen, 2166136261);
/* xor-fold into 16-bit value */
hash = (((hash >> 16) ^ hash) & pHashMap->buckets);
#endif
hash = hash16(key, klen) & pHashMap->buckets;
node = binarytree_alloc_node(key, klen, value, vlen);
if ( !node )
return 2; /* insufficient memory error */
#ifdef _DEBUG
cInserts++;
printf("Hash=0x%04x : Total of %d inserts\n", hash, cInserts);
#endif
root = (struct bst_node_t**)((char*)(((char*)pHashMap) + sizeof(struct hash_map_t)) + (hash * sizeof(void*)));
/* check for existing entry, if any */
if ( *root == 0 )
{
/* assert: no collision, put new root node entry here */
*root = node;
}
else
{
#ifdef _DEBUG
cCollisions++;
printf("Hash=0x%04x : Total of %d collisions\n", hash, cCollisions);
#endif
return binarytree_insert_node(root, node);
}
return 0;
}
/*****************************************************************************
int hash_map_delete(struct hash_map_t* pHashMap, void *key, unsigned int klen)
Purpose
To delete a node from the hashmap containing key
Params
pHashMap - ptr to hash map to insert into
key - ptr to key to delete
klen - length of key
Returns
0 if successful, otherwise error code
Notes
*/
int hash_map_delete(struct hash_map_t* pHashMap, void *key, unsigned int klen)
{
unsigned int hash;
struct bst_node_t** root;
#if 0
/* compute the 32-bit hash value of key */
hash = FNV1Hash(key, klen, 2166136261);
/* xor-fold into 16-bit value */
hash = (((hash >> 16) ^ hash) & pHashMap->buckets);
#endif
hash = hash16(key, klen) & pHashMap->buckets;
root = (struct bst_node_t**)((char*)(((char*)pHashMap) + sizeof(struct hash_map_t)) + (hash * sizeof(void*)));
return binarytree_delete_node(root, key, klen);
}
/*****************************************************************************
int hash_map_free(struct hash_map_t *pHashMap)
Purpose
To delete all nodes from the hashmap
Params
pHashMap - ptr to hash map to delete
Returns
0 if successful, otherwise error code
Notes
*/
int hash_map_free(struct hash_map_t *pHashMap)
{
unsigned int i;
struct bst_node_t** root;
if ( !pHashMap )
return 1; /* param error */
if ( pHashMap->magic != HASH_MAP_MAGIC )
return 1; /* param error */
for ( i = 0; i < pHashMap->buckets; i++ )
{
/* delete all binary trees */
root = (struct bst_node_t**)((char*)(((char*)pHashMap) + sizeof(struct hash_map_t)) + (i * sizeof(void*)));
if ( *root )
binarytree_delete_tree(root);
}
pHashMap->magic = 0;
free(pHashMap);
return 0;
}