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// Standard C
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// System
#include <unistd.h>
// zlib
#include <zlib.h>
enum { BUFFER_SIZE = 8192 };
static void
usage(void)
{
(void) fprintf(stderr, "compress [-d] infile outfile\n");
}
static void
print_zlib_error(const char *operation, int error)
{
if ( error == Z_ERRNO ) {
(void) fprintf(stderr, "%s error: %s\n", operation, strerror(errno));
}
else {
(void) fprintf(stderr, "%s error: %s\n", operation, zError(error));
}
}
int
do_compress(FILE *in_file, FILE *out_file, int compress_level)
{
z_stream strm = { 0 };
int error = deflateInit(&strm, compress_level);
if ( error ) {
return error;
}
unsigned char in_buffer[BUFFER_SIZE];
unsigned char out_buffer[BUFFER_SIZE];
int flush = Z_NO_FLUSH;
do {
strm.avail_in = fread(in_buffer, 1, BUFFER_SIZE, in_file);
if ( ferror(in_file) ) {
deflateEnd(&strm);
return Z_ERRNO;
}
flush = feof(in_file) ? Z_FINISH : Z_NO_FLUSH;
strm.next_in = in_buffer;
do {
strm.avail_out = BUFFER_SIZE;
strm.next_out = out_buffer;
error = deflate(&strm, flush);
size_t have = BUFFER_SIZE - strm.avail_out;
if ( fwrite(out_buffer, 1, have, out_file) != have || ferror(out_file) ) {
deflateEnd(&strm);
return Z_ERRNO;
}
} while ( strm.avail_out == 0 );
} while ( flush != Z_FINISH );
deflateEnd(&strm);
return Z_OK;
}
int
do_uncompress(FILE *in_file, FILE *out_file)
{
z_stream strm = { 0 };
int error = inflateInit(&strm);
if ( error ) {
return error;
}
unsigned char in_buffer[BUFFER_SIZE];
unsigned char out_buffer[BUFFER_SIZE];
do {
strm.avail_in = fread(in_buffer, 1, BUFFER_SIZE, in_file);
if ( ferror(in_file) ) {
inflateEnd(&strm);
return Z_ERRNO;
}
if ( strm.avail_in == 0 ) {
break;
}
strm.next_in = in_buffer;
do {
strm.avail_out = BUFFER_SIZE;
strm.next_out = out_buffer;
error = inflate(&strm, Z_NO_FLUSH);
switch ( error ) {
case Z_NEED_DICT:
error = Z_DATA_ERROR; /* and fall through */
case Z_DATA_ERROR:
case Z_MEM_ERROR:
(void) inflateEnd(&strm);
return error;
default:
break;
}
size_t have = BUFFER_SIZE - strm.avail_out;
if ( fwrite(out_buffer, 1, have, out_file) != have || ferror(out_file) ) {
(void) inflateEnd(&strm);
return Z_ERRNO;
}
} while ( strm.avail_out == 0 );
} while ( error != Z_STREAM_END );
inflateEnd(&strm);
return error == Z_STREAM_END ? Z_OK : Z_DATA_ERROR;
}
int
main(int argc, char *argv[])
{
enum {
COMPRESSION_STD = 5,
COMPRESSION_BEST = 9
};
int decompress = 0;
int compress_level = COMPRESSION_STD;
int opt = 0;
while ( (opt = getopt(argc, argv, "dl")) != -1 ) {
switch ( opt ) {
case 'd':
decompress = 1;
break;
case 'l':
compress_level = COMPRESSION_BEST;
break;
case '?':
default:
usage();
return EXIT_SUCCESS;
}
}
argc -= optind;
argv += optind;
if ( argc != 2 ) {
usage();
}
FILE *in_file = fopen(argv[0], "rb");
FILE *out_file = fopen(argv[1], "wb");
if ( !decompress ) {
int error = do_compress(in_file, out_file, compress_level);
if ( error ) {
print_zlib_error("compression", error);
}
}
else {
int error = do_uncompress(in_file, out_file);
if ( error ) {
print_zlib_error("extraction", error);
}
}
(void) fclose(out_file);
(void) fclose(in_file);
return EXIT_SUCCESS;
}
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