40 lines
1.4 KiB
C
40 lines
1.4 KiB
C
|
/******************************************************************************
|
||
|
|
|
||
|
|
gif_hash.h - magfic constants and declarations for GIF LZW
|
||
|
|
|
||
|
|
******************************************************************************/
|
||
|
|
|
||
|
|
#ifndef _GIF_HASH_H_
|
||
|
|
#define _GIF_HASH_H_
|
||
|
|
|
||
|
|
#include <unistd.h>
|
||
|
|
#include <stdint.h>
|
||
|
|
|
||
|
|
#define HT_SIZE 8192 /* 12bits = 4096 or twice as big! */
|
||
|
|
#define HT_KEY_MASK 0x1FFF /* 13bits keys */
|
||
|
|
#define HT_KEY_NUM_BITS 13 /* 13bits keys */
|
||
|
|
#define HT_MAX_KEY 8191 /* 13bits - 1, maximal code possible */
|
||
|
|
#define HT_MAX_CODE 4095 /* Biggest code possible in 12 bits. */
|
||
|
|
|
||
|
|
/* The 32 bits of the long are divided into two parts for the key & code: */
|
||
|
|
/* 1. The code is 12 bits as our compression algorithm is limited to 12bits */
|
||
|
|
/* 2. The key is 12 bits Prefix code + 8 bit new char or 20 bits. */
|
||
|
|
/* The key is the upper 20 bits. The code is the lower 12. */
|
||
|
|
#define HT_GET_KEY(l) (l >> 12)
|
||
|
|
#define HT_GET_CODE(l) (l & 0x0FFF)
|
||
|
|
#define HT_PUT_KEY(l) (l << 12)
|
||
|
|
#define HT_PUT_CODE(l) (l & 0x0FFF)
|
||
|
|
|
||
|
|
typedef struct GifHashTableType {
|
||
|
|
uint32_t HTable[HT_SIZE];
|
||
|
|
} GifHashTableType;
|
||
|
|
|
||
|
|
GifHashTableType *_InitHashTable(void);
|
||
|
|
void _ClearHashTable(GifHashTableType *HashTable);
|
||
|
|
void _InsertHashTable(GifHashTableType *HashTable, uint32_t Key, int Code);
|
||
|
|
int _ExistsHashTable(GifHashTableType *HashTable, uint32_t Key);
|
||
|
|
|
||
|
|
#endif /* _GIF_HASH_H_ */
|
||
|
|
|
||
|
|
/* end */
|