tar: use external program for lzma/xz compression

The lzma and xz applets don't support compression.  Any attempt
to generate a tar file using these compressors should try to use
an external program.  (Which probably won't work on a typical
Windows system, but hey, at least we made the effort.)

See GitHub issue #222.

1 files changed, 9 insertions, 3 deletions

diff --git a/win32/popen.c b/win32/popen.c
index 8810b8de0..c9ea00ffd 100644
--- a/win32/popen.c
+++ b/win32/popen.c
@@ -315,11 +315,17 @@ pid_t mingw_fork_compressor(int fd, const char *compressor, const char *mode)
         int fd1;
         pid_t pid;
 
-        if (find_applet_by_name(compressor) >= 0)
+        if (find_applet_by_name(compressor) < 0
+#if ENABLE_XZ || ENABLE_LZMA
+                /* xz and lzma applets don't support compression, try using
+                 * an external program */
+                || (mode[0] == 'w' && index_in_strings("lzma\0xz\0", compressor) >= 0)
+#endif
+                )
+                cmd = xasprintf("%s -cf -", compressor);
+        else
                 cmd = xasprintf("%s --busybox %s -cf -", bb_busybox_exec_path,
                                         compressor);
-        else
-                cmd = xasprintf("%s -cf -", compressor);
 
         if ((fd1 = mingw_popen_fd(cmd, mode, fd, &pid)) == -1)
                 bb_perror_msg_and_die("can't execute '%s'", compressor);