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xz compression detection: avoid the need to seek

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function                                             old     new   delta
unpack_unxz                                           12      67     +55
unpack_xz_stream                                    2357    2373     +16
xmalloc_read                                         197     199      +2
setup_unzip_on_fd                                    118      99     -19
rpm2cpio_main                                        222     203     -19
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/2 up/down: 73/-38)             Total: 35 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2010-07-01 05:12:28 +02:00
parent 620e863ba2
commit 45f66167fe
5 changed files with 30 additions and 14 deletions
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9
archival/bbunzip.c
View File

@ -373,6 +373,15 @@ int unlzma_main(int argc UNUSED_PARAM, char **argv)
static
IF_DESKTOP(long long) int FAST_FUNC unpack_unxz(unpack_info_t *info UNUSED_PARAM)
{
struct {
uint32_t v1;
uint16_t v2;
} magic;
xread(STDIN_FILENO, &magic, 6);
if (magic.v1 != XZ_MAGIC1a || magic.v2 != XZ_MAGIC2a) {
bb_error_msg("invalid magic");
return -1;
}
return unpack_xz_stream(STDIN_FILENO, STDOUT_FILENO);
}
int unxz_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;

4
archival/libunarchive/decompress_unxz.c
View File

@ -56,9 +56,11 @@ unpack_xz_stream(int src_fd, int dst_fd)
if (!crc32_table)
crc32_table = crc32_filltable(NULL, /*endian:*/ 0);
membuf = xmalloc(2 * BUFSIZ);
memset(&iobuf, 0, sizeof(iobuf));
/* Preload XZ file signature */
membuf = (void*) strcpy(xmalloc(2 * BUFSIZ), HEADER_MAGIC);
iobuf.in = membuf;
iobuf.in_size = HEADER_MAGIC_SIZE;
iobuf.out = membuf + BUFSIZ;
iobuf.out_size = BUFSIZ;

4
archival/rpm2cpio.c
View File

@ -92,8 +92,8 @@ int rpm2cpio_main(int argc UNUSED_PARAM, char **argv)
xread(rpm_fd, magic.b32, sizeof(magic.b32[0]));
if (magic.b32[0] != XZ_MAGIC2)
goto no_magic;
/* unpack_xz_stream wants fd at position 0 */
xlseek(rpm_fd, -6, SEEK_CUR);
/* unpack_xz_stream wants fd at position 6, no need to seek */
//xlseek(rpm_fd, -6, SEEK_CUR);
unpack = unpack_xz_stream;
} else {
no_magic:

23
include/unarchive.h
View File

@ -7,16 +7,21 @@ PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN
enum {
#if BB_BIG_ENDIAN
COMPRESS_MAGIC = 0x1f9d,
GZIP_MAGIC = 0x1f8b,
BZIP2_MAGIC = ('B'<<8) + 'Z',
XZ_MAGIC1 = (0xfd<<8) + '7',
XZ_MAGIC2 = ((((('z'<<8) + 'X')<<8) + 'Z')<<8) + 0,
GZIP_MAGIC = 0x1f8b,
BZIP2_MAGIC = 'B' * 256 + 'Z',
XZ_MAGIC1 = 0xfd * 256 + '7',
XZ_MAGIC2 = (('z' * 256 + 'X') * 256 + 'Z') * 256 + 0,
/* Different form: 32 bits, then 16 bits: */
XZ_MAGIC1a = ((0xfd * 256 + '7') * 256 + 'z') * 256 + 'X',
XZ_MAGIC2a = 'Z' * 256 + 0,
#else
COMPRESS_MAGIC = 0x9d1f,
GZIP_MAGIC = 0x8b1f,
BZIP2_MAGIC = ('Z'<<8) + 'B',
XZ_MAGIC1 = ('7'<<8) + 0xfd,
XZ_MAGIC2 = (((((0<<8) + 'Z')<<8) + 'X')<<8) + 'z',
GZIP_MAGIC = 0x8b1f,
BZIP2_MAGIC = 'Z' * 256 + 'B',
XZ_MAGIC1 = '7' * 256 + 0xfd,
XZ_MAGIC2 = ((0 * 256 + 'Z') * 256 + 'X') * 256 + 'z',
XZ_MAGIC1a = (('X' * 256 + 'z') * 256 + '7') * 256 + 0xfd,
XZ_MAGIC2a = 0 * 256 + 'Z',
#endif
};
@ -196,7 +201,7 @@ typedef struct inflate_unzip_result {
} inflate_unzip_result;
IF_DESKTOP(long long) int inflate_unzip(inflate_unzip_result *res, off_t compr_size, int src_fd, int dst_fd) FAST_FUNC;
/* xz unpacker takes .xz stream from offset 0 */
/* xz unpacker takes .xz stream from offset 6 */
IF_DESKTOP(long long) int unpack_xz_stream(int src_fd, int dst_fd) FAST_FUNC;
/* lzma unpacker takes .lzma stream from offset 0 */
IF_DESKTOP(long long) int unpack_lzma_stream(int src_fd, int dst_fd) FAST_FUNC;

4
libbb/read_printf.c
View File

@ -296,8 +296,8 @@ void FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
if (magic.b32[0] == XZ_MAGIC2) {
# if BB_MMU
xformer = unpack_xz_stream;
/* unpack_xz_stream wants fd at position 0 */
xlseek(fd, offset, SEEK_CUR);
/* unpack_xz_stream wants fd at position 6, no need to seek */
//xlseek(fd, offset, SEEK_CUR);
# else
xformer_prog = "unxz";
# endif