text: #include <stdlib.h>
  #include <string.h>
  
  #include "hashmap.h"
  
  internal ulong _hashmap_crc32s[256];
  
  internal ulong
  _hashmap_crc32(const byte *data, size_t length)
  {
  	const ubyte *udata = (ubyte *)data;
  	ulong crc = 0;
  	size_t i;
  
  	for (i = 0; i < length; i++)
  		crc = _hashmap_crc32s[(crc ^ udata[i]) & 0xff] ^ (crc >> 8);
  
  	return (crc);
  }
  
  internal ulong
  _hashmap_hash(struct hashmap *map, const str *key)
  {
  	ulong crc = _hashmap_crc32(key, strlen(key));
  
  	crc += crc << 12;
  	crc ^= crc >> 22;
  	crc += crc << 4;
  	crc ^= crc >> 9;
  	crc += crc << 10;
  	crc ^= crc >> 2;
  	crc += crc << 7;
  	crc ^= crc >> 12;
  
  	crc = (crc >> 3) * 2654435761;
  
  	return (crc % map->nelements);
  }
  
  internal long
  _hashmap_find_index(struct hashmap *map, const str *key)
  {
  	ulong i, hash;
  
  	if (map->size >= (map->nelements / 2))
  		return (HASHMAP_ERROR_FULL);
  
  	hash = _hashmap_hash(map, key);
  
  	for (i = 0; i < HASHMAP_MAX_CHAIN_LENGTH; i++)
  	{
  		if (map->elements[hash].key == null)
  			return (long)(hash);
  		
  		else if (strcmp(map->elements[hash].key, key) == 0)
  			return (long)(hash);
  
  		hash = (hash + 1) % map->nelements;
  	}
  
  	return (HASHMAP_ERROR_FULL);
  }
  
  internal int
  _hashmap_resize_and_rehash(struct hashmap *map)
  {
  	struct hashmap_element *new, *old;
  	size_t i, nelements;
  	int status;
  
  	if ((new = calloc(map->nelements * 2, sizeof(*new))) == null)
  		return (HASHMAP_ERROR_OUT_OF_MEMORY);
  
  	old = map->elements;
  	map->elements = new;
  
  	nelements = map->nelements;
  	map->nelements *= 2;
  	map->size = 0;
  
  	for (i = 0; i < nelements; i++)
  	{
  		if (old[i].key == null)
  			continue;
  
  		status = hashmap_insert(map, old[i].key, old[i].data);
  
  		if (status != HASHMAP_OK)
  			return (status);
  	}
  
  	free(old);
  
  	return (HASHMAP_OK);
  }
  
  struct hashmap *
  hashmap_create(void)
  {
  	struct hashmap *map;
  
  	if ((map = malloc(sizeof(*map))) == null)
  		return (null);
  
  	memset(map, 0, sizeof(*map));
  
  	return (map);
  }
  
  void
  hashmap_destroy(struct hashmap *map)
  {
  	free(map);
  }
  
  int
  hashmap_init(struct hashmap *map, size_t nelements)
  {
  	size_t size;
  
  	if (nelements == 0)
  		nelements = 1;
  
  	size = sizeof(*map->elements) * nelements;
  
  	if ((map->elements = malloc(size)) == null)
  		return (HASHMAP_ERROR_OUT_OF_MEMORY);
  
  	memset(map->elements, 0, size);
  	map->nelements = nelements;
  
  	return (HASHMAP_OK);
  }
  
  void
  hashmap_finish(struct hashmap *map)
  {
  	free(map->elements);
  
  	map->elements = null;
  	map->nelements = 0;
  	map->size = 0;
  }
  
  int
  hashmap_insert(struct hashmap *map, const str *key, void *data)
  {
  	long index;
  
  	while ((index = _hashmap_find_index(map, key)) == HASHMAP_ERROR_FULL)
  		if (_hashmap_resize_and_rehash(map) == HASHMAP_ERROR_OUT_OF_MEMORY)
  			return (HASHMAP_ERROR_OUT_OF_MEMORY);
  
  	map->elements[index].key = key;
  	map->elements[index].data = data;
  	map->size++;
  
  	return (HASHMAP_OK);
  }
  
  int
  hashmap_get(struct hashmap *map, const str *key, void **data)
  {
  	ulong i, hash;
  
  	hash = _hashmap_hash(map, key);
  
  	for (i = 0; i < HASHMAP_MAX_CHAIN_LENGTH; i++)
  	{
  		if (map->elements[hash].key && 
  			(strcmp(map->elements[hash].key, key) == 0))
  		{
  			*data = map->elements[hash].data;
  			return (HASHMAP_OK);
  		}
  
  		hash = (hash + 1) % map->nelements;
  	}
  
  	return (HASHMAP_ERROR_NO_SUCH_ELEMENT);
  }
  
  int
  hashmap_remove(struct hashmap *map, const str *key, void **data)
  {
  	ulong i, hash;
  
  	hash = _hashmap_hash(map, key);
  
  	for (i = 0; i < HASHMAP_MAX_CHAIN_LENGTH; i++)
  	{
  		if (map->elements[hash].key && 
  			(strcmp(map->elements[hash].key, key) == 0))
  		{
  			*data = map->elements[hash].data;
  
  			map->elements[hash].key = null;
  			map->elements[hash].data = null;
  			map->size--;
  			
  			return (HASHMAP_OK);
  		}
  
  		hash = (hash + 1) % map->nelements;
  	}
  
  	return (HASHMAP_ERROR_NO_SUCH_ELEMENT);
  }
  
  internal ulong _hashmap_crc32s[] =
  {
        0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L, 0x706af48fL, 0xe963a535L, 0x9e6495a3L, 
        0x0edb8832L, 0x79dcb8a4L, 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L, 0x90bf1d91L, 
        0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL, 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 
        0x136c9856L, 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L, 0xfa0f3d63L, 0x8d080df5L, 
        0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L, 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
        0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L, 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 
        0x26d930acL, 0x51de003aL, 0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 0xb8bda50fL, 
        0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L, 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 
        0x76dc4190L, 0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL, 0x9fbfe4a5L, 0xe8b8d433L, 
        0x7807c9a2L, 0x0f00f934L, 0x9609a88eL, 0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
        0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL, 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 
        0x65b0d9c6L, 0x12b7e950L, 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L, 0xfbd44c65L, 
        0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L, 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 
        0x4369e96aL, 0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L, 0xaa0a4c5fL, 0xdd0d7cc9L, 
        0x5005713cL, 0x270241aaL, 0xbe0b1010L, 0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
        0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L, 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 
        0xedb88320L, 0x9abfb3b6L, 0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L, 0x73dc1683L, 
        0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L, 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 
        0xf00f9344L, 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL, 0x196c3671L, 0x6e6b06e7L, 
        0xfed41b76L, 0x89d32be0L, 0x10da7a5aL, 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
        0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L, 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 
        0xd80d2bdaL, 0xaf0a1b4cL, 0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 0x4669be79L, 
        0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L, 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 
        0xc5ba3bbeL, 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L, 0x2cd99e8bL, 0x5bdeae1dL, 
        0x9b64c2b0L, 0xec63f226L, 0x756aa39cL, 0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
        0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL, 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 
        0x86d3d2d4L, 0xf1d4e242L, 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L, 0x18b74777L, 
        0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL, 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 
        0xa00ae278L, 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L, 0x4969474dL, 0x3e6e77dbL, 
        0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L, 
        0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L, 0xcdd70693L, 0x54de5729L, 0x23d967bfL, 
        0xb3667a2eL, 0xc4614ab8L, 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL, 0x2d02ef8dL,
  };
  