# This patchset updates the libbb stuff to use a vfork() version of
# gz_open, called gzvopen.  This is done because a standard fork will
# duplicate the entire address space.  This will invoke the OOM
# (out of memory) killer on small-memory machines, because most often
# by the time we unzip any package, we've read the entire package
# database into memory already.  By using vfork() and immediatly
# execing the external gunzip utility, we avoid the need to clone the
# entire address space.
#
# Yes, this is actually **LESS** efficient than the original way!
# But there is no way to (currently) dodge the OOM killer on a
# per-process basis, so the alternatives are to either change the
# OOM killer behavior system-wide, or to use this workaround.
#
# Mike Westerhof, Dec 2008

--- orig/libbb/gz_open.c	2008-03-01 12:55:33.000000000 -0600
+++ opkg/libbb/gz_open.c	2008-12-21 21:41:13.000000000 -0600
@@ -56,3 +56,78 @@
 	}
 	return(fdopen(unzip_pipe[0], "r"));
 }
+
+/* gz_open implementation using gunzip and a vfork/exec -- dodges OOM killer */
+extern FILE *gzvopen(FILE *compressed_file, int *pid)
+{
+	int unzip_pipe[2];
+	off_t floc;
+	int cfile;
+
+	/* create a new file descriptor for the input stream
+	 * (it *must* be associated with a file)
+	 * and seek to the same position in that fd as the stream.
+	 */
+	cfile = dup(fileno(compressed_file));
+	floc = ftello(compressed_file);
+	lseek(cfile, floc, SEEK_SET);
+
+	/* create the pipe */
+	if (pipe(unzip_pipe)!=0) {
+		error_msg("gzvopen(): pipe error");
+		return(NULL);
+	}
+
+	*pid = vfork();
+
+	if (*pid < 0) {
+		error_msg("gzvopen(): fork failed");
+		return(NULL);
+	}
+
+	if (*pid==0) {
+		/* child process - reads STDIN, writes to pipe */
+
+		/* close unused read end of pipe */
+		close(unzip_pipe[0]);
+
+		/* connect child's stdout to the pipe write end */
+		dup2(unzip_pipe[1], 1);
+
+		/* connect child's stdin to the fd passed in to us */
+		dup2(cfile, 0);
+
+		/* execute the gunzip utility */
+		execlp("gunzip","gunzip",NULL);
+
+		/* if we get here, we had a failure - since we are
+		 * using vfork(), we cannot call exit(), must call _exit().
+		 */
+		_exit(-1);
+	}
+
+	/* Parent process is executing here */
+
+	/* we have no more need of the duplicate fd */
+	close(cfile);
+
+	/* close the write end of the pipe */
+	close(unzip_pipe[1]);
+
+	/* return the read end of the pipe as a FILE */
+	return(fdopen(unzip_pipe[0], "r"));
+}
+
+extern void gzvclose(int gunzip_pid)
+{
+        if (kill(gunzip_pid, SIGTERM) == -1) {
+		perror("gzvclose()");
+                fprintf(stderr,"%s: unable to kill gunzip pid.\n",
+			__FUNCTION__);
+        }
+
+        if (waitpid(gunzip_pid, NULL, 0) == -1) {
+                fprintf(stderr,"%s: unable to wait on gunzip pid.\n",
+			__FUNCTION__);
+        }
+}
--- orig/libbb/libbb.h	2008-12-20 15:06:51.000000000 -0600
+++ opkg/libbb/libbb.h	2008-12-21 21:41:13.000000000 -0600
@@ -270,6 +270,8 @@
 extern int unzip(FILE *l_in_file, FILE *l_out_file);
 extern void gz_close(int gunzip_pid);
 extern FILE *gz_open(FILE *compressed_file, int *pid);
+extern void gzvclose(int gunzip_pid);
+extern FILE *gzvopen(FILE *compressed_file, int *pid);
 
 extern struct hostent *xgethostbyname(const char *name);
 extern int create_icmp_socket(void);
--- orig/libbb/unarchive.c	2008-09-10 11:48:23.000000000 -0500
+++ opkg/libbb/unarchive.c	2008-12-21 21:41:13.000000000 -0600
@@ -749,7 +749,7 @@
 		while ((ar_header = get_header_ar(deb_stream)) != NULL) {
 			if (strcmp(ared_file, ar_header->name) == 0) {
 				/* open a stream of decompressed data */
-				uncompressed_stream = gz_open(deb_stream, &gunzip_pid);
+				uncompressed_stream = gzvopen(deb_stream, &gunzip_pid);
 				archive_offset = 0;
 				output_buffer = unarchive(uncompressed_stream, out_stream, get_header_tar, free_header_tar, extract_function, prefix, file_list);
 			}
@@ -757,7 +757,7 @@
 			free (ar_header->name);
 			free (ar_header);
 		}
-		gz_close(gunzip_pid);
+		gzvclose(gunzip_pid);
 		fclose(deb_stream);
 		fclose(uncompressed_stream);
 		free(ared_file);
@@ -769,7 +769,7 @@
 		file_header_t *tar_header;
 		archive_offset = 0;
 		fseek(deb_stream, 0, SEEK_SET);
-		unzipped_opkg_stream = gz_open(deb_stream, &unzipped_opkg_pid);
+		unzipped_opkg_stream = gzvopen(deb_stream, &unzipped_opkg_pid);
 		
                 /*fprintf(stderr, __FUNCTION__ ": processing opkg %s -- ared_file=%s\n", package_filename, ared_file);*/
 		/* walk through outer tar file to find ared_file */
@@ -779,7 +779,7 @@
                                 name_offset = 2;
 			if (strcmp(ared_file, tar_header->name+name_offset) == 0) {
 				/* open a stream of decompressed data */
-				uncompressed_stream = gz_open(unzipped_opkg_stream, &gunzip_pid);
+				uncompressed_stream = gzvopen(unzipped_opkg_stream, &gunzip_pid);
 				archive_offset = 0;
                                 /*fprintf(stderr, __FUNCTION__ ":%d: here -- found file\n", __LINE__);*/
 				output_buffer = unarchive(uncompressed_stream, 
@@ -791,14 +791,14 @@
 							  file_list);
                                 /*fprintf(stderr, __FUNCTION__ ":%d: unarchive complete\n", __LINE__);*/
 				free_header_tar(tar_header);
-				gz_close(gunzip_pid);
+				gzvclose(gunzip_pid);
 				fclose(uncompressed_stream);
 				break;
 			}
 			seek_sub_file(unzipped_opkg_stream, tar_header->size);
 			free_header_tar(tar_header);
 		}
-		gz_close(unzipped_opkg_pid);
+		gzvclose(unzipped_opkg_pid);
 		fclose(unzipped_opkg_stream);
 		fclose(deb_stream);
 		free(ared_file);