--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libzip/lib/zip_file_get_offset.c	Wed Feb 24 21:19:28 2016 +0100
@@ -0,0 +1,73 @@
+/*
+  zip_file_get_offset.c -- get offset of file data in archive.
+  Copyright (C) 1999-2015 Dieter Baron and Thomas Klausner
+
+  This file is part of libzip, a library to manipulate ZIP archives.
+  The authors can be contacted at <libzip@nih.at>
+
+  Redistribution and use in source and binary forms, with or without
+  modification, are permitted provided that the following conditions
+  are met:
+  1. Redistributions of source code must retain the above copyright
+     notice, this list of conditions and the following disclaimer.
+  2. Redistributions in binary form must reproduce the above copyright
+     notice, this list of conditions and the following disclaimer in
+     the documentation and/or other materials provided with the
+     distribution.
+  3. The names of the authors may not be used to endorse or promote
+     products derived from this software without specific prior
+     written permission.
+ 
+  THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS
+  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
+  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
+  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
+  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
+  IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "zipint.h"
+
+
+/* _zip_file_get_offset(za, ze):
+   Returns the offset of the file data for entry ze.
+
+   On error, fills in za->error and returns 0.
+*/
+
+zip_uint64_t
+_zip_file_get_offset(const zip_t *za, zip_uint64_t idx, zip_error_t *error)
+{
+    zip_uint64_t offset;
+    zip_int32_t size;
+
+    offset = za->entry[idx].orig->offset;
+
+    if (zip_source_seek(za->src, (zip_int64_t)offset, SEEK_SET) < 0) {
+	_zip_error_set_from_source(error, za->src);
+	return 0;
+    }
+
+    /* TODO: cache? */
+    if ((size=_zip_dirent_size(za->src, ZIP_EF_LOCAL, error)) < 0)
+	return 0;
+
+    if (offset+(zip_uint32_t)size > ZIP_INT64_MAX) {
+        zip_error_set(error, ZIP_ER_SEEK, EFBIG);
+        return 0;
+    }
+    
+    return offset + (zip_uint32_t)size;
+}