*: teach tar et. al. to understand .xz by heart

function                                             old     new   delta
unpack_xz_stream                                       -    4126   +4126
setup_unzip_on_fd                                     80     150     +70
open_zipped                                          113     131     +18
unpack_unxz                                            5      12      +7
send_tree                                            360     353      -7
unpack_xz_stream_stdin                              3953       -   -3953
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 3/1 up/down: 4221/-3960)        Total: 261 bytes

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

1 files changed, 36 insertions, 17 deletions

diff --git a/libbb/read.c b/libbb/read.c
index f3af144f0..cd6bbeb13 100644
--- a/libbb/read.c
+++ b/libbb/read.c
@@ -305,22 +305,26 @@ void* FAST_FUNC xmalloc_xopen_read_close(const char *filename, size_t *maxsz_p)
         return buf;
 }
 
+/* Used by e.g. rpm which gives us a fd without filename,
+ * thus we can't guess the format from filename's extension.
+ */
 #if ZIPPED
-int FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
+void FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
 {
         const int fail_if_not_detected = 1;
-        unsigned char magic[2];
-#if BB_MMU
+        unsigned char magic[8];
+        int offset = -2;
+# if BB_MMU
         IF_DESKTOP(long long) int FAST_FUNC (*xformer)(int src_fd, int dst_fd);
         enum { xformer_prog = 0 };
-#else
+# else
         enum { xformer = 0 };
         const char *xformer_prog;
-#endif
+# endif
 
         /* .gz and .bz2 both have 2-byte signature, and their
          * unpack_XXX_stream wants this header skipped. */
-        xread(fd, &magic, 2);
+        xread(fd, magic, 2);
         if (ENABLE_FEATURE_SEAMLESS_GZ
          && magic[0] == 0x1f && magic[1] == 0x8b
         ) {
@@ -341,28 +345,41 @@ int FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
 # endif
                 goto found_magic;
         }
-// TODO: xz format support. rpm adopted it, "rpm -i FILE.rpm" badly needs this.
-// Signature: 0xFD, '7', 'z', 'X', 'Z', 0x00
-// More info at: http://tukaani.org/xz/xz-file-format.txt
+        if (ENABLE_FEATURE_SEAMLESS_XZ
+         && magic[0] == 0xfd && magic[1] == '7'
+        ) {
+                /* .xz signature: 0xfd, '7', 'z', 'X', 'Z', 0x00 */
+                /* More info at: http://tukaani.org/xz/xz-file-format.txt */
+                offset = -6;
+                xread(fd, magic + 2, 4);
+                if (strcmp((char*)magic + 2, "zXZ") == 0) {
+# if BB_MMU
+                        xformer = unpack_xz_stream;
+# else
+                        xformer_prog = "unxz";
+# endif
+                        xlseek(fd, offset, SEEK_CUR);
+                        goto found_magic;
+                }
+        }
 
         /* No known magic seen */
         if (fail_if_not_detected)
                 bb_error_msg_and_die("no gzip"
                         IF_FEATURE_SEAMLESS_BZ2("/bzip2")
+                        IF_FEATURE_SEAMLESS_XZ("/xz")
                         " magic");
-        xlseek(fd, -2, SEEK_CUR);
-        return fd;
+        xlseek(fd, offset, SEEK_CUR);
+        return;
 
  found_magic:
 # if !BB_MMU
         /* NOMMU version of open_transformer execs
          * an external unzipper that wants
          * file position at the start of the file */
-        xlseek(fd, -2, SEEK_CUR);
+        xlseek(fd, offset, SEEK_CUR);
 # endif
         open_transformer(fd, xformer, xformer_prog);
-
-        return fd;
 }
 #endif /* ZIPPED */
 
@@ -380,12 +397,14 @@ int FAST_FUNC open_zipped(const char *fname)
 
         sfx = strrchr(fname, '.');
         if (sfx) {
-                if (ENABLE_FEATURE_SEAMLESS_LZMA && strcmp(sfx, ".lzma") == 0)
+                sfx++;
+                if (ENABLE_FEATURE_SEAMLESS_LZMA && strcmp(sfx, "lzma") == 0)
                         /* .lzma has no header/signature, just trust it */
                         open_transformer(fd, unpack_lzma_stream, "unlzma");
                 else
-                if ((ENABLE_FEATURE_SEAMLESS_GZ && strcmp(sfx, ".gz") == 0)
-                 || (ENABLE_FEATURE_SEAMLESS_BZ2 && strcmp(sfx, ".bz2") == 0)
+                if ((ENABLE_FEATURE_SEAMLESS_GZ && strcmp(sfx, "gz") == 0)
+                 || (ENABLE_FEATURE_SEAMLESS_BZ2 && strcmp(sfx, "bz2") == 0)
+                 || (ENABLE_FEATURE_SEAMLESS_XZ && strcmp(sfx, "xz") == 0)
                 ) {
                         setup_unzip_on_fd(fd /*, fail_if_not_detected: 1*/);
                 }