/* libpbm2.c - pbm utility library part 2
**
** Copyright (C) 1988 by Jef Poskanzer.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation.  This software is provided "as is" without express or
** implied warranty.
*/

#include <stdio.h>
#include "pbm.h"
#include "libpbm.h"

static bit
pbm_getbit( file )
FILE *file;
    {
    register char ch;

    do
	{
	ch = pbm_getc( file );
	}
    while ( ch == ' ' || ch == '\t' || ch == '\n' );

    if ( ch != '0' && ch != '1' )
	pm_error( "junk in file where bits should be", 0,0,0,0,0 );

    return ( ch == '1' ) ? 1 : 0;
    }

int
pbm_readmagicnumber( file )
FILE *file;
    {
    int ich1, ich2;

    ich1 = getc( file );
    if ( ich1 == EOF )
	pm_error( "premature EOF reading magic number", 0,0,0,0,0 );
    ich2 = getc( file );
    if ( ich2 == EOF )
	pm_error( "premature EOF reading magic number", 0,0,0,0,0 );
    return ich1 * 256 + ich2;
    }

void
pbm_readpbminitrest( file, colsP, rowsP )
FILE *file;
int *colsP, *rowsP;
    {
    /* Read size. */
    *colsP = pbm_getint( file );
    *rowsP = pbm_getint( file );
    }

void
pbm_readpbminit( file, colsP, rowsP, formatP )
FILE *file;
int *colsP, *rowsP, *formatP;
    {
    /* Check magic number. */
    *formatP = pbm_readmagicnumber( file );
    switch ( *formatP )
	{
        case PBM_FORMAT:
        case RPBM_FORMAT:
	pbm_readpbminitrest( file, colsP, rowsP );
	break;

	default:
	pm_error( "bad magic number - not a pbm file", 0,0,0,0,0 );
	}
    }

void
pbm_readpbmrow( file, bitrow, cols, format )
FILE *file;
bit *bitrow;
int cols, format;
    {
    register int col, bitshift;
    register unsigned char item;
    register bit *bP;

    switch ( format )
	{
	case PBM_FORMAT:
	for ( col = 0, bP = bitrow; col < cols; col++, bP++ )
	    *bP = pbm_getbit( file );
	break;

	case RPBM_FORMAT:
	bitshift = -1;
	for ( col = 0, bP = bitrow; col < cols; col++, bP++ )
	    {
	    if ( bitshift == -1 )
		{
		item = pbm_getrawbyte( file );
		bitshift = 7;
		}
	    *bP = ( item >> bitshift ) & 1;
	    bitshift--;
	    }
	break;

	default:
	pm_error( "can't happen", 0,0,0,0,0 );
	}
    }

bit **
pbm_readpbm( file, colsP, rowsP )
FILE *file;
int *colsP, *rowsP;
    {
    register bit **bits;
    int format, row;

    pbm_readpbminit( file, colsP, rowsP, &format );

    bits = pbm_allocarray( *colsP, *rowsP );

    for ( row = 0; row < *rowsP; row++ )
	pbm_readpbmrow( file, bits[row], *colsP, format );

    return bits;
    }