/*
* The Python Imaging Library.
* $Id$
*
* Declarations for a fast, suspendable GIF decoder.
*
* Copyright (c) Fredrik Lundh 1995-96.
*/
/* Max size for a LZW code word. */
#define GIFBITS 12
#define GIFTABLE (1<<GIFBITS)
#define GIFBUFFER (1<<GIFBITS)
typedef struct {
/* CONFIGURATION */
/* Initial number of bits. The caller should clear all fields in
this structure and set this field before calling the decoder
the first time. */
int bits;
/* If set, this is an interlaced image. Process it the following way:
* 1st pass: start at top line, lines are 8 pixels high, step 8 pixels
* 2nd pass: start at line 4, lines are 4 pixels high, step 8 pixels
* 3rd pass: start at line 2, lines are 2 pixels high, step 4 pixels
* 4th pass: start at line 1, lines are 1 pixels high, step 2 pixels
*/
int interlace;
/* PRIVATE CONTEXT (set by decoder) */
/* Interlace parameters */
int step, repeat;
/* Input bit buffer */
INT32 bitbuffer;
int bitcount;
int blocksize;
/* Code buffer */
int codesize;
int codemask;
/* Constant symbol codes */
int clear, end;
/* Symbol history */
int lastcode;
unsigned char lastdata;
/* History buffer */
int bufferindex;
unsigned char buffer[GIFTABLE];
/* Symbol table */
UINT16 link[GIFTABLE];
unsigned char data[GIFTABLE];
int next;
} GIFDECODERSTATE;
typedef struct GIFENCODERBLOCK_T
{
struct GIFENCODERBLOCK_T *next;
int size;
UINT8 data[255];
} GIFENCODERBLOCK;
typedef struct {
/* CONFIGURATION */
/* Initial number of bits. The caller should clear all fields in
this structure and set this field before calling the encoder
the first time. */
int bits;
/* NOTE: the expanding encoder ignores this field */
/* If set, write an interlaced image (see above) */
int interlace;
/* PRIVATE CONTEXT (set by encoder) */
/* Interlace parameters */
int step, repeat;
/* Output bit buffer */
INT32 bitbuffer;
int bitcount;
/* Output buffer list (linked list) */
GIFENCODERBLOCK* block; /* current block */
GIFENCODERBLOCK* flush; /* output queue */
GIFENCODERBLOCK* free; /* if not null, use this */
/* Fields used for run-length encoding */
int first; /* true if we haven't read the first pixel */
int last; /* last byte value seen */
int count; /* how many bytes with that value we've seen */
int lastcode;
} GIFENCODERSTATE;
