New common unarchive code.

archival/libunarchive/data_align.c

@@ -0,0 +1,13 @@
+#include <errno.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include "unarchive.h"
+#include "libbb.h"
+
+extern const unsigned short data_align(const int src_fd, const unsigned int offset, const unsigned short align_to)
+{
+	const unsigned short skip_amount = (align_to - (offset % align_to)) % align_to;
+	seek_sub_file(src_fd, skip_amount);
+
+	return(skip_amount);
+}