www.pudn.com > giflib12.zip > GIF_HASH.H

/****************************************************************************** 
* Declarations, global to other of the GIF-HASH.C module.		      * 
*									      * 
*					Written by Gershon Elber,  Jun 1989   * 
******************************************************************************* 
* History:								      * 
* 14 Jun 89 - Version 1.0 by Gershon Elber.				      * 
******************************************************************************/ 
 
#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.	    */ 
#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 { 
    unsigned long HTable[HT_SIZE]; 
} GifHashTableType; 
 
GifHashTableType *_InitHashTable(void); 
void _ClearHashTable(GifHashTableType *HashTable); 
void _InsertHashTable(GifHashTableType *HashTable, unsigned long Key, int Code); 
int _ExistsHashTable(GifHashTableType *HashTable, unsigned long Key);