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, 5 insertions, 30 deletions

diff --git a/archival/libarchive/get_header_tar.c b/archival/libarchive/get_header_tar.c
index 8c699754b..80a709144 100644
--- a/archival/libarchive/get_header_tar.c
+++ b/archival/libarchive/get_header_tar.c
@@ -235,43 +235,18 @@ char FAST_FUNC get_header_tar(archive_handle_t *archive_handle)
 	     || memcmp(tar.magic, "\0\0\0\0", 5) != 0)
 	) {
 #if ENABLE_FEATURE_TAR_AUTODETECT
-		char FAST_FUNC (*get_header_ptr)(archive_handle_t *);
-		uint16_t magic2;
-
  autodetect:
-		magic2 = *(bb__aliased_uint16_t*)tar.name;
-		/* tar gz/bz autodetect: check for gz/bz2 magic.
-		 * If we see the magic, and it is the very first block,
-		 * we can switch to get_header_tar_gz/bz2/lzma().
-		 * Needs seekable fd. I wish recv(MSG_PEEK) works
-		 * on any fd... */
-# if ENABLE_FEATURE_SEAMLESS_GZ
-		if (magic2 == GZIP_MAGIC) {
-			get_header_ptr = get_header_tar_gz;
-		} else
-# endif
-# if ENABLE_FEATURE_SEAMLESS_BZ2
-		if (magic2 == BZIP2_MAGIC
-		 && tar.name[2] == 'h' && isdigit(tar.name[3])
-		) { /* bzip2 */
-			get_header_ptr = get_header_tar_bz2;
-		} else
-# endif
-# if ENABLE_FEATURE_SEAMLESS_XZ
-		//TODO: if (magic2 == XZ_MAGIC1)...
-		//else
-# endif
-			goto err;
 		/* Two different causes for lseek() != 0:
 		 * unseekable fd (would like to support that too, but...),
 		 * or not first block (false positive, it's not .gz/.bz2!) */
 		if (lseek(archive_handle->src_fd, -i, SEEK_CUR) != 0)
 			goto err;
-		while (get_header_ptr(archive_handle) == EXIT_SUCCESS)
-			continue;
-		return EXIT_FAILURE;
+		if (setup_unzip_on_fd(archive_handle->src_fd, /*fail_if_not_detected:*/ 0) != 0)
  err:
-#endif /* FEATURE_TAR_AUTODETECT */
+			bb_error_msg_and_die("invalid tar magic");
+		archive_handle->offset = 0;
+		goto again_after_align;
+#endif
 		bb_error_msg_and_die("invalid tar magic");
 	}