1/******************************************************************************
2
3gif_hash.h - magfic constants and declarations for GIF LZW
4
5SPDX-License-Identifier: MIT
6
7******************************************************************************/
8
9#ifndef _GIF_HASH_H_
10#define _GIF_HASH_H_
11
12//#include <unistd.h>
13#include <stdint.h>
14
15#define HT_SIZE 8192 /* 12bits = 4096 or twice as big! */
16#define HT_KEY_MASK 0x1FFF /* 13bits keys */
17#define HT_KEY_NUM_BITS 13 /* 13bits keys */
18#define HT_MAX_KEY 8191 /* 13bits - 1, maximal code possible */
19#define HT_MAX_CODE 4095 /* Biggest code possible in 12 bits. */
20
21/* The 32 bits of the long are divided into two parts for the key & code: */
22/* 1. The code is 12 bits as our compression algorithm is limited to 12bits */
23/* 2. The key is 12 bits Prefix code + 8 bit new char or 20 bits. */
24/* The key is the upper 20 bits. The code is the lower 12. */
25#define HT_GET_KEY(l) (l >> 12)
26#define HT_GET_CODE(l) (l & 0x0FFF)
27#define HT_PUT_KEY(l) (l << 12)
28#define HT_PUT_CODE(l) (l & 0x0FFF)
29
30typedef struct GifHashTableType {
31 uint32_t HTable[HT_SIZE];
32} GifHashTableType;
33
34GifHashTableType *_InitHashTable(void);
35void _ClearHashTable(GifHashTableType *HashTable);
36void _InsertHashTable(GifHashTableType *HashTable, uint32_t Key, int Code);
37int _ExistsHashTable(GifHashTableType *HashTable, uint32_t Key);
38
39#endif /* _GIF_HASH_H_ */
40
41/* end */
42