update seamless uncompression code

This change makes "tar tf hello_world.txz" work without
adding special-casing for ".txz" extension. It also removes
ever-growing magic checking code in rpm2cpio and get_header_tar -
we reuse one which lives in setup_unzip_on_fd.

function                                             old     new   delta
unpack_gz_stream                                       7     566    +559
check_signature16                                      -      70     +70
setup_unzip_on_fd                                     99     142     +43
handle_SIGCHLD                                         -      41     +41
unpack_bz2_stream                                    342     376     +34
unzip_main                                          2352    2385     +33
bbunpack                                             503     533     +30
open_transformer                                      74     102     +28
unpack_Z_stream                                     1278    1304     +26
unpack_gunzip                                        101     123     +22
init_transformer_aux_data                              -      18     +18
unpack_xz_stream                                    2388    2402     +14
open_zipped                                          131     141     +10
rpm_main                                            1358    1363      +5
get_header_tar_lzma                                   52      57      +5
get_header_tar_bz2                                    52      57      +5
unpack_lzma_stream                                  2698    2702      +4
hash_find                                            234     233      -1
get_header_tar                                      1759    1733     -26
get_header_tar_gz                                     92      57     -35
unpack_uncompress                                     51      12     -39
rpm2cpio_main                                        201     147     -54
unpack_unxz                                           67      12     -55
unpack_bz2_stream_prime                               55       -     -55
get_header_tar_Z                                      86       -     -86
unpack_gz_stream_with_info                           539       -    -539
------------------------------------------------------------------------------
(add/remove: 3/3 grow/shrink: 14/6 up/down: 947/-890)          Total: 57 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/archival/libarchive/decompress_unxz.c b/archival/libarchive/decompress_unxz.c
index 3e5d4ed..79b48a1 100644
--- a/archival/libarchive/decompress_unxz.c
+++ b/archival/libarchive/decompress_unxz.c
@@ -38,7 +38,7 @@ static uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc)
 #include "unxz/xz_dec_stream.c"
 
 IF_DESKTOP(long long) int FAST_FUNC
-unpack_xz_stream(int src_fd, int dst_fd)
+unpack_xz_stream(transformer_aux_data_t *aux, int src_fd, int dst_fd)
 {
 	struct xz_buf iobuf;
 	struct xz_dec *state;
@@ -49,13 +49,17 @@ unpack_xz_stream(int src_fd, int dst_fd)
 		global_crc32_table = crc32_filltable(NULL, /*endian:*/ 0);
 
 	memset(&iobuf, 0, sizeof(iobuf));
-	/* Preload XZ file signature */
-	membuf = (void*) strcpy(xmalloc(2 * BUFSIZ), HEADER_MAGIC);
+	membuf = xmalloc(2 * BUFSIZ);
 	iobuf.in = membuf;
-	iobuf.in_size = HEADER_MAGIC_SIZE;
 	iobuf.out = membuf + BUFSIZ;
 	iobuf.out_size = BUFSIZ;
 
+	if (!aux || aux->check_signature == 0) {
+		/* Preload XZ file signature */
+		strcpy((char*)membuf, HEADER_MAGIC);
+		iobuf.in_size = HEADER_MAGIC_SIZE;
+	} /* else: let xz code read & check it */
+
 	/* Limit memory usage to about 64 MiB. */
 	state = xz_dec_init(XZ_DYNALLOC, 64*1024*1024);