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, 31 insertions, 42 deletions

diff --git a/archival/rpm2cpio.c b/archival/rpm2cpio.c
index 28b43a181..7256aae6b 100644
--- a/archival/rpm2cpio.c
+++ b/archival/rpm2cpio.c
@@ -42,6 +42,26 @@ static unsigned skip_header(void)
 	return sizeof(header) + len;
 }
 
+#if SEAMLESS_COMPRESSION
+static void handle_SIGCHLD(int signo UNUSED_PARAM)
+{
+	int status;
+
+	/* Wait for any child without blocking */
+	for (;;) {
+		if (wait_any_nohang(&status) < 0)
+			/* wait failed?! I'm confused... */
+			return;
+		if (WIFEXITED(status) && WEXITSTATUS(status) == 0)
+			/* this child exited with 0 */
+			continue;
+		/* Cannot happen?
+		if (!WIFSIGNALED(status) && !WIFEXITED(status)) ???; */
+		bb_got_signal = 1;
+	}
+}
+#endif
+
 /* No getopt required */
 int rpm2cpio_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int rpm2cpio_main(int argc UNUSED_PARAM, char **argv)
@@ -66,54 +86,23 @@ int rpm2cpio_main(int argc UNUSED_PARAM, char **argv)
 	/* Skip the main header */
 	skip_header();
 
-#if 0
+#if SEAMLESS_COMPRESSION
+	/* We need to know whether child (gzip/bzip/etc) exits abnormally */
+	signal(SIGCHLD, handle_SIGCHLD);
+#endif
+
 	/* This works, but doesn't report uncompress errors (they happen in child) */
-	setup_unzip_on_fd(rpm_fd /*fail_if_not_detected: 1*/);
+	setup_unzip_on_fd(rpm_fd, /*fail_if_not_detected:*/ 1);
 	if (bb_copyfd_eof(rpm_fd, STDOUT_FILENO) < 0)
 		bb_error_msg_and_die("error unpacking");
-#else
-	/* BLOAT */
-	{
-		union {
-			uint8_t b[4];
-			uint16_t b16[2];
-			uint32_t b32[1];
-		} magic;
-		IF_DESKTOP(long long) int FAST_FUNC (*unpack)(int src_fd, int dst_fd);
-
-		xread(rpm_fd, magic.b16, sizeof(magic.b16[0]));
-		if (magic.b16[0] == GZIP_MAGIC) {
-			unpack = unpack_gz_stream;
-		} else
-		if (ENABLE_FEATURE_SEAMLESS_BZ2
-		 && magic.b16[0] == BZIP2_MAGIC
-		) {
-			unpack = unpack_bz2_stream;
-		} else
-		if (ENABLE_FEATURE_SEAMLESS_XZ
-		 && magic.b16[0] == XZ_MAGIC1
-		) {
-			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 6, no need to seek */
-			//xlseek(rpm_fd, -6, SEEK_CUR);
-			unpack = unpack_xz_stream;
-		} else {
- no_magic:
-			bb_error_msg_and_die("no gzip"
-					IF_FEATURE_SEAMLESS_BZ2("/bzip2")
-					IF_FEATURE_SEAMLESS_XZ("/xz")
-					" magic");
-		}
-		if (unpack(rpm_fd, STDOUT_FILENO) < 0)
-			bb_error_msg_and_die("error unpacking");
-	}
-#endif
 
 	if (ENABLE_FEATURE_CLEAN_UP) {
 		close(rpm_fd);
 	}
 
-	return 0;
+#if SEAMLESS_COMPRESSION
+	return bb_got_signal;
+#else
+	return EXIT_SUCCESS;
+#endif
 }