From e46a815cbcaa5270acfb2893b66791150f4d2a87 Mon Sep 17 00:00:00 2001
From: Vincent Batts <vbatts@hashbangbash.com>
Date: Tue, 11 Aug 2015 15:51:52 -0400
Subject: [PATCH] archive/tar: fix carry-over of bytes for GNU types

Archives produced with GNU tar can have types of TypeGNULongName and
TypeGNULongLink.
These fields effectively appear like two file entries in the tar
archive. While golang's `archive/tar` transparently provide the file
name and headers and file payload, the access to the raw bytes is still
needed.

This fixes the access to the longlink header, it's payload (of the long
file path name), and the following file header and actual file payload.
---
 archive/tar/reader.go | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/archive/tar/reader.go b/archive/tar/reader.go
index a89957e..f817956 100644
--- a/archive/tar/reader.go
+++ b/archive/tar/reader.go
@@ -154,44 +154,60 @@ func (tr *Reader) Next() (*Header, error) {
 		}
 		return hdr, nil
 	case TypeGNULongName:
+		var b *bytes.Buffer
+		if tr.RawAccounting {
+			b = bytes.NewBuffer(tr.RawBytes())
+		}
 		// We have a GNU long name header. Its contents are the real file name.
 		realname, err := ioutil.ReadAll(tr)
 		if err != nil {
 			return nil, err
 		}
-		var b []byte
 		if tr.RawAccounting {
+			if _, err = tr.rawBytes.Write(b.Bytes()); err != nil {
+				return nil, err
+			}
 			if _, err = tr.rawBytes.Write(realname); err != nil {
 				return nil, err
 			}
-			b = tr.RawBytes()
+			b.Reset()
+			b.Write(tr.RawBytes())
 		}
 		hdr, err := tr.Next()
 		// since the above call to Next() resets the buffer, we need to throw the bytes over
 		if tr.RawAccounting {
-			if _, err = tr.rawBytes.Write(b); err != nil {
+			b.Write(tr.RawBytes())
+			if _, err = tr.rawBytes.Write(b.Bytes()); err != nil {
 				return nil, err
 			}
 		}
 		hdr.Name = cString(realname)
 		return hdr, err
 	case TypeGNULongLink:
+		var b *bytes.Buffer
+		if tr.RawAccounting {
+			b = bytes.NewBuffer(tr.RawBytes())
+		}
 		// We have a GNU long link header.
 		realname, err := ioutil.ReadAll(tr)
 		if err != nil {
 			return nil, err
 		}
-		var b []byte
 		if tr.RawAccounting {
+			if _, err = tr.rawBytes.Write(b.Bytes()); err != nil {
+				return nil, err
+			}
 			if _, err = tr.rawBytes.Write(realname); err != nil {
 				return nil, err
 			}
-			b = tr.RawBytes()
+			b.Reset()
+			b.Write(tr.RawBytes())
 		}
 		hdr, err := tr.Next()
 		// since the above call to Next() resets the buffer, we need to throw the bytes over
 		if tr.RawAccounting {
-			if _, err = tr.rawBytes.Write(b); err != nil {
+			b.Write(tr.RawBytes())
+			if _, err = tr.rawBytes.Write(b.Bytes()); err != nil {
 				return nil, err
 			}
 		}