lib/gifcomp.c File Reference

#include "common.h"
#include <setjmp.h>

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Defines
#define	UBYTE   unsigned char
#define	LARGEST_CODE   4095
#define	TABLE_SIZE   (8*1024)
Functions
static void	init_table (short min_code_size)
static void	flush (size_t n)
static void	write_code (short code)
static short	compress_data (int min_code_size)
short	gif_compress_data (int min_code_size, unsigned char *pt, long size, FILE *out)
Variables
static char const	rcsid [] = "$Id: gifcomp.c,v 1.7 2003/05/21 21:03:22 kent Exp $"
static UBYTE	gif_byte_buff [256+3]
static FILE *	gif_file
static unsigned char *	gif_wpt
static long	gif_wcount
static jmp_buf	recover
static short *	prior_codes
static short *	code_ids
static unsigned char *	added_chars
static short	code_size
static short	clear_code
static short	eof_code
static short	bit_offset
static short	max_code
static short	free_code

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Define Documentation

#define LARGEST_CODE   4095

Definition at line 64 of file gifcomp.c.

Referenced by compress_data().

#define TABLE_SIZE   (8*1024)

Definition at line 65 of file gifcomp.c.

Referenced by compress_data(), gif_compress_data(), and init_table().

#define UBYTE   unsigned char

Definition at line 61 of file gifcomp.c.

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Function Documentation

static short compress_data

(

int

min_code_size

)

[static]

Definition at line 161 of file gifcomp.c.

References added_chars, bit_offset, clear_code, code_ids, code_size, eof_code, flush(), free_code, gif_byte_buff, gif_wcount, gif_wpt, init_table(), LARGEST_CODE, max_code, prior_codes, recover, TABLE_SIZE, UBYTE, and write_code().

Referenced by gif_compress_data().

{
short status;
short prefix_code;
short d;
register int hx;
register short suffix_char;

status = setjmp(recover);

if (status != 0)
    {
    return status;
    }

bit_offset = 0;
init_table(min_code_size);
write_code(clear_code);
suffix_char = *gif_wpt++;
gif_wcount -= 1;

prefix_code = suffix_char;

while (--gif_wcount >= 0)
    {
    suffix_char = *gif_wpt++;
    hx = prefix_code ^ suffix_char << 5;
    d = 1;

    for (;;)
        {
        if (code_ids[hx] == 0)
            {
            write_code(prefix_code);

            d = free_code;

            if (free_code <= LARGEST_CODE)
                {
                prior_codes[hx] = prefix_code;
                added_chars[hx] = (UBYTE)suffix_char;
                code_ids[hx] = free_code;
                free_code++;
                }

            if (d == max_code)
                {
                if (code_size < 12)
                    {
                    code_size++;
                    max_code <<= 1;
                    }
                else
                    {
                    write_code(clear_code);
                    init_table(min_code_size);
                    }
                }

            prefix_code = suffix_char;
            break;
            }

        if (prior_codes[hx] == prefix_code &&
                added_chars[hx] == suffix_char)
            {
            prefix_code = code_ids[hx];
            break;
            }

        hx += d;
        d += 2;
        if (hx >= TABLE_SIZE)
            hx -= TABLE_SIZE;
        }
    }

write_code(prefix_code);

write_code(eof_code);


/* Make sure the code buffer is flushed */

if (bit_offset > 0)
    {
    int byte_offset = (bit_offset >> 3);
    if (byte_offset == 255)     /* Make sure we don't write a zero by mistake. */
        {
        int bits_left = bit_offset & 7;
        flush(255);
        if (bits_left)
            {
            gif_byte_buff[0] = gif_byte_buff[byte_offset];
            flush(1);
            }
        }
    else
        {
        flush((bit_offset + 7)/8);
        }
    }

flush(0);                               /* end-of-data */
return 0;
}

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static void flush

(

size_t

n

)

[static]

Definition at line 99 of file gifcomp.c.

References gif_byte_buff, gif_file, and recover.

Referenced by compress_data(), and write_code().

{
if (fputc(n,gif_file) < 0)
    {
    longjmp(recover, -3);
    }
if (fwrite(gif_byte_buff, 1, n, gif_file) < n)
    {
    longjmp(recover, -3);
    }
}

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short gif_compress_data	(	int	min_code_size,
		unsigned char *	pt,
		long	size,
		FILE *	out
	)

Definition at line 268 of file gifcomp.c.

References added_chars, code_ids, compress_data(), gentleFree(), gif_file, gif_wcount, gif_wpt, needMem(), prior_codes, and TABLE_SIZE.

Referenced by mgSaveToGif().

{
int ret;

/* Make sure min_code_size is reasonable. */
if (min_code_size < 2 || min_code_size > 9)
    {
    if (min_code_size == 1)
        min_code_size = 2;
    else
        return -3;
    }

/* Store input parameters where rest of routines can use. */
gif_file = out;
gif_wpt = pt;
gif_wcount = size;

ret = -2;       /* out of memory default */
prior_codes = NULL;
code_ids = NULL;
added_chars = NULL;
if ((prior_codes = (short*)needMem(TABLE_SIZE*sizeof(short))) == NULL)
        goto OUT;
if ((code_ids = (short*)needMem(TABLE_SIZE*sizeof(short))) == NULL)
        goto OUT;
if ((added_chars = (unsigned char*)needMem(TABLE_SIZE)) == NULL)
        goto OUT;

ret = compress_data(min_code_size);

OUT:
gentleFree(prior_codes);
gentleFree(code_ids);
gentleFree(added_chars);
return(ret);
}

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static void init_table

(

short

min_code_size

)

[static]

Definition at line 87 of file gifcomp.c.

References clear_code, code_ids, code_size, eof_code, free_code, max_code, TABLE_SIZE, and zeroBytes().

Referenced by compress_data().

{
code_size = min_code_size + 1;
clear_code = 1 << min_code_size;
eof_code = clear_code + 1;
free_code = clear_code + 2;
max_code = 1 << code_size;

zeroBytes(code_ids, TABLE_SIZE*sizeof(code_ids[0]));
}

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static void write_code

(

short

code

)

[static]

Definition at line 112 of file gifcomp.c.

References bit_offset, code_size, flush(), gif_byte_buff, and UBYTE.

Referenced by compress_data().

{
long temp;
register short byte_offset; 
register short bits_left;

byte_offset = bit_offset >> 3;
bits_left = bit_offset & 7;

if (byte_offset >= 254)
        {
        flush(byte_offset);
        gif_byte_buff[0] = gif_byte_buff[byte_offset];
        bit_offset = bits_left;
        byte_offset = 0;
        }

if (bits_left > 0)
        {
        temp = ((long) code << bits_left) | gif_byte_buff[byte_offset];
        gif_byte_buff[byte_offset] = (UBYTE)temp;
        gif_byte_buff[byte_offset + 1] = (UBYTE)(temp >> 8);
        gif_byte_buff[byte_offset + 2] = (UBYTE)(temp >> 16);
        }
else
        {
        gif_byte_buff[byte_offset] = (UBYTE)code;
        gif_byte_buff[byte_offset + 1] = (UBYTE)(code >> 8);
        }
bit_offset += code_size;
}

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Variable Documentation

unsigned char* added_chars [static]

Definition at line 77 of file gifcomp.c.

Referenced by compress_data(), and gif_compress_data().

short bit_offset [static]

Definition at line 82 of file gifcomp.c.

Referenced by compress_data(), and write_code().

short clear_code [static]

Definition at line 80 of file gifcomp.c.

Referenced by compress_data(), and init_table().

short* code_ids [static]

Definition at line 76 of file gifcomp.c.

Referenced by compress_data(), gif_compress_data(), and init_table().

short code_size [static]

Definition at line 79 of file gifcomp.c.

Referenced by compress_data(), init_table(), and write_code().

short eof_code [static]

Definition at line 81 of file gifcomp.c.

Referenced by compress_data(), and init_table().

short free_code [static]

Definition at line 84 of file gifcomp.c.

Referenced by compress_data(), and init_table().

UBYTE gif_byte_buff[256+3] [static]

Definition at line 67 of file gifcomp.c.

Referenced by compress_data(), flush(), get_next_code(), and write_code().

FILE* gif_file [static]

Definition at line 68 of file gifcomp.c.

Referenced by flush(), gif_compress_data(), gif_get_byte(), and mgLoadGif().

long gif_wcount [static]

Definition at line 71 of file gifcomp.c.

Referenced by compress_data(), gif_compress_data(), and mgSaveToGif().

unsigned char* gif_wpt [static]

Definition at line 70 of file gifcomp.c.

Referenced by compress_data(), and gif_compress_data().

short max_code [static]

Definition at line 83 of file gifcomp.c.

Referenced by compress_data(), and init_table().

short* prior_codes [static]

Definition at line 75 of file gifcomp.c.

Referenced by compress_data(), and gif_compress_data().

char const rcsid[] = "$Id: gifcomp.c,v 1.7 2003/05/21 21:03:22 kent Exp $" [static]

Definition at line 59 of file gifcomp.c.

jmp_buf recover [static]

Definition at line 73 of file gifcomp.c.

Referenced by compress_data(), and flush().

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