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/* pbm.c
* code for reading the header of an ASCII PBM file
* Copyright (c) 1998 Tim Norman. See LICENSE for details
* 2-25-98
*
* Mar 18, 1998 Jim Peterson <jspeter@birch.ee.vt.edu>
*
* Restructured to encapsulate more of the PBM handling.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "ppapbm.h"
int make_pbm_stat(pbm_stat* pbm,FILE* fptr)
{
char line[1024];
pbm->fptr=fptr;
pbm->version=none;
pbm->current_line=0;
pbm->unread = 0;
if (fgets (line, 1024, fptr) == NULL)
return 0;
line[strlen(line)-1] = 0;
if(!strcmp(line,"P1")) pbm->version=P1;
if(!strcmp(line,"P4")) pbm->version=P4;
if(pbm->version == none)
{
fprintf(stderr,"pbm_readheader(): unknown PBM magic '%s'\n",line);
return 0;
}
do
if (fgets (line, 1024, fptr) == NULL)
return 0;
while (line[0] == '#');
if (2 != sscanf (line, "%d %d", &pbm->width, &pbm->height))
return 0;
return 1;
}
static int getbytes(FILE *fptr,int width,unsigned char* data)
{
unsigned char mask,acc,*place;
int num;
if(!width) return 0;
for(mask=0x80, acc=0, num=0, place=data; num<width; )
{
switch(getc(fptr))
{
case EOF:
return 0;
case '1':
acc|=mask;
/* fall through */
case '0':
mask>>=1;
num++;
if(!mask) /* if(num%8 == 0) */
{
*place++ = acc;
acc=0;
mask=0x80;
}
}
}
if(width%8)
*place=acc;
return 1;
}
/* Reads a single line into data which must be at least (pbm->width+7)/8
bytes of storage */
int pbm_readline(pbm_stat* pbm,unsigned char* data)
{
int tmp,tmp2;
if(pbm->current_line >= pbm->height) return 0;
if (pbm->unread)
{
memcpy (data, pbm->revdata, (pbm->width+7)/8);
pbm->current_line++;
pbm->unread = 0;
free (pbm->revdata);
pbm->revdata = NULL;
return 1;
}
switch(pbm->version)
{
case P1:
if(getbytes(pbm->fptr,pbm->width,data))
{
pbm->current_line++;
return 1;
}
return 0;
case P4:
tmp=(pbm->width+7)/8;
tmp2=fread(data,1,tmp,pbm->fptr);
if(tmp2 == tmp)
{
pbm->current_line++;
return 1;
}
fprintf(stderr,"pbm_readline(): error reading line data (%d)\n",tmp2);
return 0;
default:
fprintf(stderr,"pbm_readline(): unknown PBM version\n");
return 0;
}
}
/* push a line back into the buffer; we read too much! */
void pbm_unreadline (pbm_stat *pbm, void *data)
{
/* can only store one line in the unread buffer */
if (pbm->unread)
return;
pbm->unread = 1;
pbm->revdata = malloc ((pbm->width+7)/8);
memcpy (pbm->revdata, data, (pbm->width+7)/8);
pbm->current_line--;
}
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