1 files changed, 64 insertions, 10 deletions

diff --git a/libbb/gz_open.c b/libbb/gz_open.c
index 3997e72..bdc7564 100644
--- a/libbb/gz_open.c
+++ b/libbb/gz_open.c
@@ -29,33 +29,69 @@
 #include <unistd.h>
 #include "libbb.h"
 
+static int gz_use_vfork;
+
 FILE *
 gz_open(FILE *compressed_file, int *pid)
 {
 	int unzip_pipe[2];
+	off_t floc;
+	int cfile = -1;
+
+	gz_use_vfork = (getenv("OPKG_USE_VFORK") != NULL);
+
+	if (gz_use_vfork) {
+		/* Create a new file descriptor for the input stream
+		 * (it *must* be associated with a file), and lseek()
+		 * to the same position in that fd as the stream.
+		 */
+		cfile = dup(fileno(compressed_file));
+		floc = ftello(compressed_file);
+		lseek(cfile, floc, SEEK_SET);
+		setenv("GZIP", "--quiet", 0);
+	}
 
 	if (pipe(unzip_pipe)!=0) {
 		perror_msg("pipe");
 		return(NULL);
 	}
 
-    /* If we don't flush, we end up with two copies of anything pending,
-       one from the parent, one from the child */
-    fflush(stdout);
-    fflush(stderr);
+	/* If we don't flush, we end up with two copies of anything pending,
+	   one from the parent, one from the child */
+	fflush(stdout);
+	fflush(stderr);
 
-	if ((*pid = fork()) == -1) {
+	if (gz_use_vfork) {
+		*pid = vfork();
+	} else {
+		*pid = fork();
+	}
+
+	if (*pid<0) {
 		perror_msg("fork");
 		return(NULL);
 	}
+
 	if (*pid==0) {
 		/* child process */
 		close(unzip_pipe[0]);
-		unzip(compressed_file, fdopen(unzip_pipe[1], "w"));
-		fflush(NULL);
-		fclose(compressed_file);
-		close(unzip_pipe[1]);
-		_exit(EXIT_SUCCESS);
+		if (gz_use_vfork) {
+			dup2(unzip_pipe[1], 1);
+			dup2(cfile, 0);
+			execlp("gunzip","gunzip",NULL);
+			/* If we get here, we had a failure */
+			_exit(EXIT_FAILURE);
+		} else {
+			unzip(compressed_file, fdopen(unzip_pipe[1], "w"));
+			fflush(NULL);
+			fclose(compressed_file);
+			close(unzip_pipe[1]);
+			_exit(EXIT_SUCCESS);
+		}
+	}
+	/* Parent process is executing here */
+	if (gz_use_vfork) {
+		close(cfile);
 	}
 	close(unzip_pipe[1]);
 	return(fdopen(unzip_pipe[0], "r"));
@@ -67,11 +103,29 @@ gz_close(int gunzip_pid)
 	int status;
 	int ret;
 
+	if (gz_use_vfork) {
+		/* The gunzip process remains running in the background if we
+		 * used the vfork()/exec() technique - so we have to kill it
+		 * forcibly.  There might be a better way to do this, but that
+		 * affect a lot of other parts of opkg, and this works fine.
+		 */
+		if (kill(gunzip_pid, SIGTERM) == -1) {
+			perror_msg("gz_close(): unable to kill gunzip pid.");
+			return -1;
+		}
+	}
+
+
 	if (waitpid(gunzip_pid, &status, 0) == -1) {
 		perror_msg("waitpid");
 		return -1;
 	}
 
+	if (gz_use_vfork) {
+		/* Bail out here if we used the vfork()/exec() technique. */
+		return 0;
+	}
+
 	if (WIFSIGNALED(status)) {
 		error_msg("Unzip process killed by signal %d.\n",
 			WTERMSIG(status));