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/* compress.c - deflate/inflate code for zip, gzip, zlib, and raw
*
* Copyright 2014 Rob Landley <rob@landley.net>
*
* The inflate/deflate code lives here, so the various things that use it
* either live here or call these commands to pipe data through them.
*
* Divergence from posix: replace obsolete "compress" with mutiplexer.
*
* See RFCs 1950 (zlib), 1951 (deflate), and 1952 (gzip)
* LSB 4.1 has gzip, gunzip, and zcat
* TODO: zip -d DIR -x LIST -list -quiet -no overwrite -overwrite -p to stdout
// Accept many different kinds of command line argument:
USE_COMPRESS(NEWTOY(compress, "zglrcd9[-cd][!zglr]", TOYFLAG_USR|TOYFLAG_BIN))
//zip unzip gzip gunzip zcat
config COMPRESS
bool "compress"
default n
help
usage: compress [-zglrcd9] [FILE]
Compress or decompress file (or stdin) using "deflate" algorithm.
-c compress
-d decompress
-g gzip
-l zlib
-r raw (default)
-z zip
*/
#define FOR_compress
#include "toys.h"
GLOBALS(
// base offset and extra bits tables (length and distance)
char lenbits[29], distbits[30];
unsigned short lenbase[29], distbase[30];
)
// little endian bit buffer
struct bitbuf {
int fd, pos, len, max;
char buf[];
};
struct bitbuf *get_bitbuf(int fd, int size)
{
struct bitbuf *bb = xmalloc(sizeof(struct bitbuf)+size);
memset(bb, 0, sizeof(struct bitbuf));
bb->max = size;
bb->fd = fd;
return bb;
}
int get_bits(struct bitbuf *bb, int bits)
{
int result = 0, offset = 0;
while (bits) {
int click = bb->pos >> 3, blow, blen;
// Load more data if buffer empty
if (click == bb->len) {
bb->len = read(bb->fd, bb->buf, bb->max);
if (bb->len < 1) perror_exit("inflate EOF");
bb->pos = click = 0;
}
// grab bits from next byte
blow = bb->pos & 7;
blen = 8-blow;
if (blen > bits) blen = bits;
result |= ((bb->buf[click] >> blow) & ((1<<blen)-1)) << offset;
offset += blen;
bits -= blen;
bb->pos += blen;
}
return result;
}
static int deflate(struct bitbuf *buf)
{
return 0;
}
static void init_deflate(void)
{
int i, n = 1;
// Calculate lenbits, lenbase, distbits, distbase
*TT.lenbase = 3;
for (i = 0; i<sizeof(TT.lenbits)-1; i++) {
if (i>4) {
if (!(i&3)) {
TT.lenbits[i]++;
n <<= 1;
}
if (i == 27) n--;
else TT.lenbits[i+1] = TT.lenbits[i];
}
TT.lenbase[i+1] = n + TT.lenbase[i];
}
n = 0;
for (i = 0; i<sizeof(TT.distbits); i++) {
TT.distbase[i] = 1<<n;
if (i) TT.distbase[i] += TT.distbase[i-1];
if (i>3 && !(i&1)) n++;
TT.distbits[i] = n;
}
}
// Return true/false whether we consumed a gzip header.
static int is_gzip(struct bitbuf *bb)
{
int flags;
// Confirm signature
if (get_bits(bb, 24) != 0x088b1f || (flags = get_bits(bb, 8)) > 31) return 0;
get_bits(bb, 6*8);
// Skip extra, name, comment, header CRC fields
if (flags & 4) get_bits(bb, 16);
if (flags & 8) while (get_bits(bb, 8));
if (flags & 16) while (get_bits(bb, 8));
if (flags & 2) get_bits(bb, 16);
return 1;
}
static void do_gzip(int fd, char *name)
{
struct bitbuf *bb = get_bitbuf(fd, sizeof(toybuf));
printf("is_gzip=%d\n", is_gzip(bb));
// tail: crc32, len32
free(bb);
}
// Parse many different kinds of command line argument:
void compress_main(void)
{
// 31, 139, 8
// &2 = skip 2 bytes
init_deflate();
loopfiles(toys.optargs, do_gzip);
}
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