1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
|
#include <zlib.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
void usage(char *exe) {
fprintf(stderr,"usage: %s <file>\n", exe);
exit(-1);
}
char *slurp(char *file, size_t *flen) {
struct stat stats;
char *out;
int fd;
if (stat(file, &stats) == -1) {
fprintf(stderr, "can't stat %s: %s\n", file, strerror(errno));
exit(-1);
}
*flen = stats.st_size;
if (flen == 0) {
fprintf(stderr, "file %s is zero length\n", file);
exit(-1);
}
if ( (out = malloc(stats.st_size)) == NULL) {
fprintf(stderr, "can't malloc space for %s\n", file);
exit(-1);
}
if ( (fd = open(file,O_RDONLY)) == -1) {
fprintf(stderr, "can't open %s: %s\n", file, strerror(errno));
exit(-1);
}
if ( read(fd, out, stats.st_size) != stats.st_size) {
fprintf(stderr, "short read on %s\n", file);
exit(-1);
}
close(fd);
return out;
}
int main( int argc, char *argv[]) {
if (argc < 2) usage(argv[0]);
int rc;
size_t flen;
char *file = argv[1];
char *data = slurp(file, &flen);
/* minimal required initialization of z_stream prior to deflateInit2 */
z_stream zs = {.next_in = data, .zalloc=Z_NULL, .zfree=Z_NULL, .opaque=NULL};
#define want_gzip 16
#define def_windowbits (15 + want_gzip)
#define def_memlevel 8
rc = deflateInit2(&zs, Z_DEFAULT_COMPRESSION, Z_DEFLATED, def_windowbits,
def_memlevel, Z_DEFAULT_STRATEGY);
if (rc != Z_OK) {
fprintf(stderr, "deflateInit failed: %s\n", zs.msg);
exit(-1);
}
/* calculate the max space needed to deflate this buffer in a single pass */
size_t gzmax = deflateBound(&zs, flen);
char *out = malloc(gzmax);
if (out == NULL) {
fprintf(stderr, "could not allocate %u bytes for compressed file\n",
(unsigned)gzmax);
exit(-1);
}
/* initialize the remaining parts of z_stream prior to actual deflate */
zs.avail_in = flen;
zs.next_out = out;
zs.avail_out = gzmax;
/* deflate it in one fell swoop */
rc = deflate(&zs, Z_FINISH);
if (rc != Z_STREAM_END) {
fprintf(stderr,"single-pass deflate failed: ");
if (rc == Z_OK) fprintf(stderr,"additional passes needed\n");
else if (rc == Z_STREAM_ERROR) fprintf(stderr,"stream error\n");
else if (rc == Z_BUF_ERROR) fprintf(stderr,"buffer unavailable\n");
else fprintf(stderr,"unknown error\n");
exit(-1);
}
rc = deflateEnd(&zs);
if (rc != Z_OK) fprintf(stderr,"deflateEnd error: %s\n", zs.msg);
fprintf(stderr,"Original size: %u\n", (unsigned)flen);
fprintf(stderr,"Deflated size: %u\n", (unsigned)zs.total_out);
if (write(STDOUT_FILENO, out, zs.total_out) != zs.total_out) {
fprintf(stderr,"error: partial write\n");
exit(-1);
}
return 0;
}
|
