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// Standard C
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// System
#include <unistd.h>
// zlib
#include <zlib.h>
static void
usage(void)
{
(void) fprintf(stderr, "compress [-d] infile outfile\n");
}
static void
error(const char *msg)
{
perror(msg);
exit(EXIT_FAILURE);
}
size_t
get_filesize(FILE *file)
{
long current_pos = ftell(file);
if ( current_pos == -1 ) {
error("ftell() failed");
}
if ( fseek(file, 0, SEEK_END) != 0 ) {
error("fseek() failed");
}
long size = ftell(file);
if ( size == -1 ) {
error("ftell() failed");
}
if ( fseek(file, current_pos, SEEK_SET) != 0 ) {
error("fseek() failed");
}
return (size_t) size;
}
void
do_compress(FILE *in_file, FILE *out_file, int compress_level)
{
size_t in_size = get_filesize(in_file);
(void) fwrite(&in_size, sizeof in_size, 1, out_file);
unsigned char *in_data = malloc(in_size);
(void) fread(in_data, 1, in_size, in_file);
size_t out_size = compressBound(in_size);
unsigned char *out_data = malloc(out_size);
const int error = compress2(out_data, &out_size,
in_data, in_size,
compress_level);
if ( !error ) {
(void) fwrite(out_data, 1, out_size, out_file);
}
else {
(void) fprintf(stderr, "Error: %s\n", zError(error));
}
free(out_data);
free(in_data);
}
void
do_uncompress(FILE *in_file, FILE *out_file)
{
size_t in_size = get_filesize(in_file);
unsigned char *in_data = malloc(in_size);
(void) fread(in_data, 1, in_size, in_file);
size_t out_size = 0;
memcpy(&out_size, in_data, sizeof out_size);
unsigned char *out_data = malloc(out_size);
const size_t compressed_data_size = in_size - sizeof(size_t);
size_t consumed_size = compressed_data_size;
const int error = uncompress2(out_data, &out_size,
in_data + sizeof(size_t),
&consumed_size);
if ( !error ) {
if ( compressed_data_size != consumed_size ) {
(void) fputs("Warning: Trailing data detected.\n", stderr);
}
(void) fwrite(out_data, 1, out_size, out_file);
}
else {
(void) fprintf(stderr, "Error: %s\n", zError(error));
}
free(out_data);
free(in_data);
}
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 ) {
do_compress(in_file, out_file, compress_level);
}
else {
do_uncompress(in_file, out_file);
}
(void) fclose(out_file);
(void) fclose(in_file);
return EXIT_SUCCESS;
}
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