/* 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

  {

    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--;

}