xz: support concatenated .xz streams

function                                             old     new   delta
xz_dec_reset                                           -      77     +77
unpack_xz_stream                                    2402    2397      -5

Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/archival/libarchive/decompress_unxz.c b/archival/libarchive/decompress_unxz.c
index 79b48a1..e9ddd37 100644 (file)
--- a/archival/libarchive/decompress_unxz.c
+++ b/archival/libarchive/decompress_unxz.c
@@ -40,6 +40,7 @@ static uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc)
 IF_DESKTOP(long long) int FAST_FUNC
 unpack_xz_stream(transformer_aux_data_t *aux, int src_fd, int dst_fd)
 {
+       enum xz_ret xz_result;
        struct xz_buf iobuf;
        struct xz_dec *state;
        unsigned char *membuf;
@@ -63,9 +64,8 @@ unpack_xz_stream(transformer_aux_data_t *aux, int src_fd, int dst_fd)
        /* Limit memory usage to about 64 MiB. */
        state = xz_dec_init(XZ_DYNALLOC, 64*1024*1024);
 
+       xz_result = X_OK;
        while (1) {
-               enum xz_ret r;
-
                if (iobuf.in_pos == iobuf.in_size) {
                        int rd = safe_read(src_fd, membuf, BUFSIZ);
                        if (rd < 0) {
@@ -73,28 +73,57 @@ unpack_xz_stream(transformer_aux_data_t *aux, int src_fd, int dst_fd)
                                total = -1;
                                break;
                        }
+                       if (rd == 0 && xz_result == XZ_STREAM_END)
+                               break;
                        iobuf.in_size = rd;
                        iobuf.in_pos = 0;
                }
+               if (xz_result == XZ_STREAM_END) {
+                       /*
+                        * Try to start decoding next concatenated stream.
+                        * Stream padding must always be a multiple of four
+                        * bytes to preserve four-byte alignment. To keep the
+                        * code slightly smaller, we aren't as strict here as
+                        * the .xz spec requires. We just skip all zero-bytes
+                        * without checking the alignment and thus can accept
+                        * files that aren't valid, e.g. the XZ utils test
+                        * files bad-0pad-empty.xz and bad-0catpad-empty.xz.
+                        */
+                       do {
+                               if (membuf[iobuf.in_pos] != 0) {
+                                       xz_dec_reset(state);
+                                       goto do_run;
+                               }
+                               iobuf.in_pos++;
+                       } while (iobuf.in_pos < iobuf.in_size);
+               }
+ do_run:
 //             bb_error_msg(">in pos:%d size:%d out pos:%d size:%d",
 //                             iobuf.in_pos, iobuf.in_size, iobuf.out_pos, iobuf.out_size);
-               r = xz_dec_run(state, &iobuf);
+               xz_result = xz_dec_run(state, &iobuf);
 //             bb_error_msg("<in pos:%d size:%d out pos:%d size:%d r:%d",
-//                             iobuf.in_pos, iobuf.in_size, iobuf.out_pos, iobuf.out_size, r);
+//                             iobuf.in_pos, iobuf.in_size, iobuf.out_pos, iobuf.out_size, xz_result);
                if (iobuf.out_pos) {
                        xwrite(dst_fd, iobuf.out, iobuf.out_pos);
                        IF_DESKTOP(total += iobuf.out_pos;)
                        iobuf.out_pos = 0;
                }
-               if (r == XZ_STREAM_END) {
-                       break;
+               if (xz_result == XZ_STREAM_END) {
+                       /*
+                        * Can just "break;" here, if not for concatenated
+                        * .xz streams.
+                        * Checking for padding may require buffer
+                        * replenishment. Can't do it here.
+                        */
+                       continue;
                }
-               if (r != XZ_OK && r != XZ_UNSUPPORTED_CHECK) {
+               if (xz_result != XZ_OK && xz_result != XZ_UNSUPPORTED_CHECK) {
                        bb_error_msg("corrupted data");
                        total = -1;
                        break;
                }
        }
+
        xz_dec_end(state);
        free(membuf);