rlcomp.c

/*-
 * Copyright (c) 2012, 2016 Izumi Tsutsui.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * dumb run-length compression
 */

#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>

#define DS_SIZE	8192

#define MAGIC	0x9c

static void
usage(void)
{
	const char *prog;

	prog = getprogname();
	fprintf(stderr, "usage: %s binfile outfile\n", prog);
	exit(EXIT_FAILURE);
}

int
main(int argc, char **argv)
{
	struct stat sb;
	int fd, ofd;
	const char *binfile, *outfile;
	uint8_t *buf, *outbuf;
	int count, size, i, outi;
	uint8_t data;

	if (argc != 3)
		usage();

	binfile = argv[1];
	outfile = argv[2];

	/*
	 * open and check input files
	 */
	if ((fd = open(binfile, O_RDONLY, 0600)) == -1)
		err(EXIT_FAILURE, "can't open input file `%s'", binfile);
	if (fstat(fd, &sb) != 0)
		err(EXIT_FAILURE, "can't stat %s", binfile);
	size = sb.st_size;
	if (size == 0 || size > DS_SIZE)
		err(EXIT_FAILURE, "invalid size of %s (%d)",
		    binfile, (int)sb.st_size);
	/* open output file */
	if ((ofd = open(outfile, O_WRONLY|O_CREAT, 0644)) == -1)
		err(EXIT_FAILURE, "can't open output file `%s'", binfile);

	/* allocate buffer for input file */
	buf = malloc(DS_SIZE);
	if (buf == NULL)
		err(1, "malloc input buffer");
	memset(buf, 0, DS_SIZE);

	count = read(fd, buf, size);
	if (count != size)
		err(EXIT_FAILURE, "failed to read input file");
	close(fd);

	/* allocate buffer for input file */
	outbuf = malloc(size);
	if (outbuf == NULL)
		err(1, "malloc output buffer");
	memset(outbuf, 0, size);

	outi  = 0;
	data = buf[0];
	count = 1;
	for (i = 1; i < size; i++) {
		if (data == buf[i] && count < 0xff && i != size - 1) {
			count++;
		} else {
			if (count <= 2) {
				if (data == MAGIC) {
					outbuf[outi++] = MAGIC;
					outbuf[outi++] = count;
					outbuf[outi++] = data;
				} else {
					int j;
					for (j = 0; j < count; j++) {
						outbuf[outi++] = data;
					}
				}
			} else {
				outbuf[outi++] = MAGIC;
				outbuf[outi++] = count;
				outbuf[outi++] = data;
			}
			data = buf[i];
			count = 1;
		}
	}
	outbuf[outi++] = data;

	count = write(ofd, outbuf, outi);
	if (count != outi)
		err(EXIT_FAILURE, "failed to write output file");

	free(outbuf);
	close(ofd);
	free(buf);

	exit(EXIT_SUCCESS);
}