pbm.c

/*\
 *  Yes, This Is Another Barcode Reader
 *  Copyright (C) 2013 Quentin SANTOS
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
\*/

#include "pbm.h"

#include <stdlib.h>
#include <string.h>



// please, refer to DOCUMENTATION for technical details



static byte nextint(FILE* f);
static byte nextbit(FILE* f, byte* buf, size_t* buf_avail);

static byte nextint(FILE* f)
{
	char c;
	do
	{
		if (feof(f))
		{
			fprintf(stderr, "Unexpected end of file\n");
			exit(1);
		}
		c = fgetc(f);

		if (c != '#')
			continue;

		// skip comments
		do
		{
			if (feof(f))
			{
				fprintf(stderr, "Unexpected end of file in comment\n");
				exit(1);
			}
			c = fgetc(f);
		}
		while (c != '\n');

	} while (strchr(" \n\r", c));

	if (!('0' <= c && c <= '9'))
	{
		fprintf(stderr, "Unexpected character '%c'\n", c);
		exit(1);
	}

	byte res = 0;
	while ('0' <= c && c <= '9')
	{
		res *= 10;
		res += c - '0';
		if (feof(f))
			break;
		c = fgetc(f);
	}
	return res;
}

static byte nextbit(FILE* f, byte* buf, size_t* buf_avail)
{
	if (!*buf_avail)
	{
		if (fread(buf, 1, 1, f) != 1)
		{
			fprintf(stderr, "Unexpected %s\n",
				feof(f) ? "end of file" : "error reading file");
			exit(1);
		}
		*buf_avail = 8;
	}
	return (*buf >> (--(*buf_avail))) & 1;
}

void load_pbm(scanner_t* scanner, FILE* f)
{
	fgetc(f); // reads 'P'
	char format = fgetc(f); // reads format (1-6)

	byte w = nextint(f);
	byte h = nextint(f);

	if (w != h)
	{
		fprintf(stderr, "I only handle square images\n");
		exit(1);
	}

	byte* d = (byte*) malloc(sizeof(byte) * w*h);
	if (!d)
	{
		fprintf(stderr, "Could not allocate memory\n");
		exit(1);
	}

	scanner->d = d;
	scanner->s = w;

	if (format == '1')
	{
		for (size_t i = 0; i < h; i++)
		for (size_t j = 0; j < w; j++)
			P(i, j) = nextint(f);
	}
	else if (format == '4')
	{
		byte buf = 0;
		size_t buf_avail = 0;
		for (size_t i = 0; i < h; i++)
		{
			for (size_t j = 0; j < w; j++)
				P(i, j) = nextbit(f, &buf, &buf_avail);
			buf_avail = 0;
		}
	}
	else
	{
		fprintf(stderr, "Unsupported format '%c'\n", format);
		exit(1);
	}
}