1 files changed, 13 insertions, 8 deletions

diff --git a/libbb/read.c b/libbb/read.c
index cd6bbeb13..b1eb3f24b 100644
--- a/libbb/read.c
+++ b/libbb/read.c
@@ -312,7 +312,11 @@ void* FAST_FUNC xmalloc_xopen_read_close(const char *filename, size_t *maxsz_p)
 void FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
 {
         const int fail_if_not_detected = 1;
-        unsigned char magic[8];
+        union {
+                uint8_t b[4];
+                uint16_t b16[2];
+                uint32_t b32[1];
+        } magic;
         int offset = -2;
 # if BB_MMU
         IF_DESKTOP(long long) int FAST_FUNC (*xformer)(int src_fd, int dst_fd);
@@ -324,9 +328,9 @@ void FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
 
         /* .gz and .bz2 both have 2-byte signature, and their
          * unpack_XXX_stream wants this header skipped. */
-        xread(fd, magic, 2);
+        xread(fd, magic.b16, sizeof(magic.b16));
         if (ENABLE_FEATURE_SEAMLESS_GZ
-         && magic[0] == 0x1f && magic[1] == 0x8b
+         && magic.b16[0] == GZIP_MAGIC
         ) {
 # if BB_MMU
                 xformer = unpack_gz_stream;
@@ -336,7 +340,7 @@ void FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
                 goto found_magic;
         }
         if (ENABLE_FEATURE_SEAMLESS_BZ2
-         && magic[0] == 'B' && magic[1] == 'Z'
+         && magic.b16[0] == BZIP2_MAGIC
         ) {
 # if BB_MMU
                 xformer = unpack_bz2_stream;
@@ -346,19 +350,20 @@ void FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
                 goto found_magic;
         }
         if (ENABLE_FEATURE_SEAMLESS_XZ
-         && magic[0] == 0xfd && magic[1] == '7'
+         && magic.b16[0] == XZ_MAGIC1
         ) {
                 /* .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) {
+                xread(fd, magic.b32, sizeof(magic.b32));
+                if (magic.b32[0] == XZ_MAGIC2) {
 # if BB_MMU
                         xformer = unpack_xz_stream;
+                        /* unpack_xz_stream wants fd at position 0 */
+                        xlseek(fd, offset, SEEK_CUR);
 # else
                         xformer_prog = "unxz";
 # endif
-                        xlseek(fd, offset, SEEK_CUR);
                         goto found_magic;
                 }
         }