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#include <stdio.h>
#include <string.h>
#include <assert.h>
#include "meh.h"
#define GIF87a 0
#define GIF89a 1
#define MAX_CODES 4096
unsigned char *loadgif(FILE *infile, int *bufwidth, int *bufheight){
int version;
unsigned char *palette;
int pallen;
unsigned char *buf = NULL;
unsigned int bpp;
{
/* Read header*/
unsigned char packed;
unsigned char header[13];
if(fread(header, 1, 13, infile) != 13)
return NULL;
if(!memcmp("GIF89a", header, 6))
version = GIF89a;
else if(!memcmp("GIF87a", header, 6))
version = GIF87a;
else
return NULL;
*bufwidth = header[6] | header[7] << 8;
*bufheight = header[8] | header[9] << 8;
packed = header[10];
bpp = (packed & 7) + 1;
/* Read colormap */
if(packed & 0x80){
printf("Reading palette\n");
pallen = 1 << bpp;
printf("pallen: %i\n", pallen);
palette = malloc(3 * pallen);
fread(palette, 1, 3 * pallen, infile);
}
}
{
int blocktype;
while((blocktype = fgetc(infile)) != EOF){
if(blocktype == ';'){
printf("end of file\n");
break;
}else if(blocktype == '!'){
int bytecount, fncode;
if((fncode = fgetc(infile)) == EOF)
return NULL;
while(1){
bytecount = fgetc(infile);
printf("Skipping extblock 0x%x\n", fncode);
if(bytecount == EOF)
return NULL;
else if(bytecount > 0)
fseek(infile, bytecount, SEEK_CUR);
else
break;
}
}else if(blocktype == ','){
int imagex, imagey, imagew, imageh;
unsigned char imagedesc[9];
if(fread(imagedesc, 1, 9, infile) != 9)
return NULL;
if(imagedesc[8] & 0x80){
printf("ERROR: local palettes not supported\n");
return NULL;
}
if(imagedesc[8] & 0x40){
printf("ERROR: interlaced images\n");
return NULL;
}
imagex = imagedesc[0] | imagedesc[1] << 8;
imagey = imagedesc[2] | imagedesc[3] << 8;
imagew = imagedesc[4] | imagedesc[5] << 8;
imageh = imagedesc[6] | imagedesc[7] << 8;
if(imagex != 0 || imagey != 0 || imagew != *bufwidth || imageh != *bufheight){
printf("%ix%i %ix%i\n", imagex, imagey, imagew, imageh);
printf("TODO: allow this sort of thing\n");
return NULL;
}
buf = malloc((*bufwidth) * (*bufheight) * 3);
memset(buf, 0, (*bufwidth) * (*bufheight) * 3);
{
unsigned int initcodesize, curcodesize;
unsigned int clearcode, endcode, newcode;
int bytesleft = 0;
int i = 0;
/* Get code size */
initcodesize = fgetc(infile);
if(initcodesize < 1 || initcodesize > 9){
printf("bad code size %i\n", initcodesize);
return NULL;
}
curcodesize = initcodesize + 1;
clearcode = 1 << initcodesize;
endcode = clearcode + 1;
newcode = endcode + 1;
int count = 0;
int byte0 = -1, byte1 = -1, byteshift = 0;
unsigned int suffix[MAX_CODES * 3];
unsigned int prefix[MAX_CODES];
int length[MAX_CODES];
goto clear;
for(;;){
for(;;){
count++;
int a, b, c;
int code;
/* get code */
while(byte1 == -1){
if(!bytesleft){
bytesleft = fgetc(infile);
if(bytesleft < 0){
printf("unexpected EOF (0)\n");
return NULL;
}else if(bytesleft == 0)
break;
}
if((byte1 = fgetc(infile)) == EOF){
printf("unexpected EOF (1)\n");
return NULL;
}
if(byte0 == -1){
byte0 = byte1;
byte1 = -1;
}
bytesleft--;
}
code = ((byte0 | (byte1 << 8)) >> byteshift) & ((1 << curcodesize) - 1);
byteshift += curcodesize;
while(byteshift >= 8){
byte0 = byte1;
byte1 = -1;
byteshift -= 8;
}
if(code == clearcode){
clear:
printf("%i. clear\n", count);
curcodesize = initcodesize + 1;
newcode = endcode; /* endcode is also used as a sentinel */
for(a = 0; a < clearcode; a++){
length[a] = 0;
prefix[a] = 0;
suffix[a*3] = palette[a*3];
suffix[a*3+1] = palette[a*3+1];
suffix[a*3+2] = palette[a*3+2];
}
}else if(code == endcode){
printf("%i. endcode\n", count);
return buf;
}else{
assert(newcode < MAX_CODES);
printf("newcode: %x\n", newcode);
if(code <= newcode){
printf("%i. dict\n", count);
prefix[newcode+1] = i;
length[newcode+1] = length[code] + 1;
for(a = prefix[code]; a < prefix[code] + length[code]; a++){
buf[i*3] = buf[a*3];
buf[i*3+1] = buf[a*3+1];
buf[i*3+2] = buf[a*3+2];
i++;
}
buf[i*3] = suffix[code*3];
buf[i*3+1] = suffix[code*3+1];
buf[i*3+2] = suffix[code*3+1];
i++;
suffix[newcode*3 + 3] = suffix[newcode*3] = buf[prefix[newcode+1] * 3];
suffix[newcode*3 + 4] = suffix[newcode*3 + 1] = buf[prefix[newcode+1] * 3 + 1];
suffix[newcode*3 + 5] = suffix[newcode*3 + 2] = buf[prefix[newcode+1] * 3 + 2];
printf("codes[%x] = {%x,%x,%x}\n", newcode, prefix[newcode], length[newcode], suffix[newcode]);
}else{
printf("code > newcode (%x > %x)\n", code, newcode);
return buf;
//exit(1);
}
newcode++;
if(newcode == 1 << curcodesize){
curcodesize++;
}
}
}
}
/*for(i = 0; i < (*bufwidth) * (*bufheight); i++){
}*/
printf("good end\n");
return buf;
}
break;
}else{
printf("Unknown block type %i\n", blocktype);
return NULL;
}
}
}
printf("end\n");
return NULL;
}
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