From 5ad44b42a877528448fd107a595ca9bf9f7c9b27 Mon Sep 17 00:00:00 2001
From: Joshua Boelter <joshua.boelter@intel.com>
Date: Sun, 24 Jan 2021 21:16:15 -0800
Subject: [PATCH] fixes zip64 headers

See also https://github.com/golang/go/issues/33116

The offset must be written into the central directory
as 0xFFFFFFFF if it's going to be written in the zip64
extended information field.

https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT

The following is the layout of the zip64 extended
information "extra" block. If one of the size or
offset fields in the Local or Central directory
record is too small to hold the required data,
a Zip64 extended information record is created.
The order of the fields in the zip64 extended
information record is fixed, but the fields MUST
only appear if the corresponding Local or Central
directory record field is set to 0xFFFF or 0xFFFFFFFF.
---
 zip/writer.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/zip/writer.go b/zip/writer.go
index 335b637c8f..f7eb90da45 100644
--- a/zip/writer.go
+++ b/zip/writer.go
@@ -129,7 +129,7 @@ func (w *Writer) Close() error {
 		b.uint16(uint16(len(h.Comment)))
 		b = b[4:] // skip disk number start and internal file attr (2x uint16)
 		b.uint32(h.ExternalAttrs)
-		if h.offset > uint32max {
+		if h.isZip64() || h.offset > uint32max {
 			b.uint32(uint32max)
 		} else {
 			b.uint32(uint32(h.offset))