rpm2cpio: extract cpio even if compression is not known

This is more useful than failing outright.

function                                             old     new   delta
rpm2cpio_main                                        110     144     +34
.rodata                                           105681  105715     +34
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 68/0)               Total: 68 bytes

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

1 files changed, 6 insertions, 1 deletions

diff --git a/archival/rpm.c b/archival/rpm.c
index 7fd2a2b46..95a8c79b6 100644
--- a/archival/rpm.c
+++ b/archival/rpm.c
@@ -533,6 +533,7 @@ int rpm2cpio_main(int argc UNUSED_PARAM, char **argv)
         //      /* We need to know whether child (gzip/bzip/etc) exits abnormally */
         //      signal(SIGCHLD, check_errors_in_children);
 
+        str = NULL;
         if (ENABLE_FEATURE_SEAMLESS_LZMA
          && (str = rpm_getstr0(TAG_PAYLOADCOMPRESSOR)) != NULL
          && strcmp(str, "lzma") == 0
@@ -541,7 +542,11 @@ int rpm2cpio_main(int argc UNUSED_PARAM, char **argv)
                 // set up decompressor without detection
                 setup_lzma_on_fd(rpm_fd);
         } else {
-                setup_unzip_on_fd(rpm_fd, /*die_if_not_compressed:*/ 1);
+                int signature_bytes = setup_unzip_on_fd(rpm_fd, /*die_if_not_compressed:*/ 0);
+                if (signature_bytes != 0) {
+                        xlseek(rpm_fd, - signature_bytes, SEEK_CUR);
+                        bb_error_msg("warning, unknown compression '%s'", str);
+                }
         }
 
         if (bb_copyfd_eof(rpm_fd, STDOUT_FILENO) < 0)