1/******************************************************************************
2
3gif_hash.h - magfic constants and declarations for GIF LZW
4
5******************************************************************************/
6
7#ifndef _GIF_HASH_H_
8#define _GIF_HASH_H_
9
10#include <unistd.h>
11#include <stdint.h>
12
13#define HT_SIZE			8192	   /* 12bits = 4096 or twice as big! */
14#define HT_KEY_MASK		0x1FFF			      /* 13bits keys */
15#define HT_KEY_NUM_BITS		13			      /* 13bits keys */
16#define HT_MAX_KEY		8191	/* 13bits - 1, maximal code possible */
17#define HT_MAX_CODE		4095	/* Biggest code possible in 12 bits. */
18
19/* The 32 bits of the long are divided into two parts for the key & code:   */
20/* 1. The code is 12 bits as our compression algorithm is limited to 12bits */
21/* 2. The key is 12 bits Prefix code + 8 bit new char or 20 bits.	    */
22/* The key is the upper 20 bits.  The code is the lower 12. */
23#define HT_GET_KEY(l)	(l >> 12)
24#define HT_GET_CODE(l)	(l & 0x0FFF)
25#define HT_PUT_KEY(l)	(l << 12)
26#define HT_PUT_CODE(l)	(l & 0x0FFF)
27
28typedef struct GifHashTableType {
29    uint32_t HTable[HT_SIZE];
30} GifHashTableType;
31
32GifHashTableType *_InitHashTable(void);
33void _ClearHashTable(GifHashTableType *HashTable);
34void _InsertHashTable(GifHashTableType *HashTable, uint32_t Key, int Code);
35int _ExistsHashTable(GifHashTableType *HashTable, uint32_t Key);
36
37#endif /* _GIF_HASH_H_ */
38
39/* end */
40