Enable seamless compression for WIN32

In the archival code we pretend that WIN32 is a no-MMU platform and
use the new mingw_popen_fd routine to pipe data to/from commands
to compress/decompress.

The pretence is maintained by redefining MMU macros in bb_archive.h.
This is mostly used in the archival code but there are a handful
of places where it's used to access public interfaces.  The symbol
BB_ARCHIVE_PUBLIC is defined in these places.

With these changes:

   tar supports seamless compression/decompression
   rpm2cpio and dpkg-deb can be enabled

2 files changed, 25 insertions, 0 deletions

diff --git a/archival/libarchive/init_handle.c b/archival/libarchive/init_handle.c
index cbae06ac3..b1166d577 100644
--- a/archival/libarchive/init_handle.c
+++ b/archival/libarchive/init_handle.c
@@ -16,7 +16,12 @@ archive_handle_t* FAST_FUNC init_handle(void)
         archive_handle->action_header = header_skip;
         archive_handle->action_data = data_skip;
         archive_handle->filter = filter_accept_all;
+#if !ENABLE_PLATFORM_MINGW32
         archive_handle->seek = seek_by_jump;
+#else
+        /* can't reliably detect pipes on WIN32: default to seek_by_read */
+        archive_handle->seek = seek_by_read;
+#endif
 
         return archive_handle;
 }
diff --git a/archival/libarchive/open_transformer.c b/archival/libarchive/open_transformer.c
index 1c5c185d0..24524f6ee 100644
--- a/archival/libarchive/open_transformer.c
+++ b/archival/libarchive/open_transformer.c
@@ -69,6 +69,7 @@ ssize_t FAST_FUNC xtransformer_write(transformer_state_t *xstate, const void *bu
 }
 
 #if SEAMLESS_COMPRESSION
+#if !ENABLE_PLATFORM_MINGW32
 void check_errors_in_children(int signo)
 {
         int status;
@@ -155,6 +156,25 @@ void FAST_FUNC fork_transformer(int fd, const char *transform_prog)
         close(fd_pipe.wr); /* don't want to write to the child */
         xmove_fd(fd_pipe.rd, fd);
 }
+#else
+void FAST_FUNC fork_transformer(int fd, const char *transform_prog)
+{
+        char *cmd;
+        int fd1;
+
+        if (find_applet_by_name(transform_prog) >= 0) {
+                cmd = xasprintf("%s %s -cf -", bb_busybox_exec_path, transform_prog);
+        }
+        else {
+                cmd = xasprintf("%s -cf -", transform_prog);
+        }
+        if ( (fd1=mingw_popen_fd(cmd, "r", fd, NULL)) == -1 ) {
+                bb_perror_msg_and_die("can't execute '%s'", transform_prog);
+        }
+        free(cmd);
+        xmove_fd(fd1, fd);
+}
+#endif
 
 /* Used by e.g. rpm which gives us a fd without filename,
  * thus we can't guess the format from filename's extension.