From e25847c90cf3c574e1024e83e0f8993cfc04c7d1 Mon Sep 17 00:00:00 2001
From: calluo <calluo@tencent.com>
Date: Wed, 2 Nov 2022 15:22:21 +0800
Subject: [PATCH] archive50 parse header, impl file redirection to get link
 file info

---
 archive50.go | 24 +++++++++++++++++++++++-
 reader.go    |  9 +++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/archive50.go b/archive50.go
index 1d8f850..1cd7837 100644
--- a/archive50.go
+++ b/archive50.go
@@ -47,6 +47,13 @@ const (
 	file5EncCheckPresent = 0x0001 // password check data is present
 	file5EncUseMac       = 0x0002 // use MAC instead of plain checksum
 
+	// file system redirection flags
+	file5UnixSymlink     = 0x0001
+	file5WindowsSymlink  = 0x0002
+	file5WindowsJunction = 0x0003
+	file5HardLink        = 0x0004
+	file5FileCopy        = 0x0005
+
 	cacheSize50   = 4
 	maxPbkdf2Salt = 64
 	pwCheckSize   = 8
@@ -250,6 +257,21 @@ func (a *archive50) parseFileEncryptionRecord(b readBuf, f *fileBlockHeader) err
 	return nil
 }
 
+// parseFileRedirectionRecord processes the file reddirection record from a file header
+func (a *archive50) parseFileRedirectionRecord(b readBuf, f *fileBlockHeader) error {
+	types := b.uvarint()
+	if types&file5WindowsSymlink > 0 || types&file5UnixSymlink > 0 {
+		f.LinkType = TypeSymlink
+	} else if types&file5HardLink > 0 {
+		f.LinkType = TypeLink
+	}
+	// pass link target flags
+	b.uvarint()
+	lenName := int(b.uvarint())
+	f.LinkName = string(b.bytes(lenName))
+	return nil
+}
+
 func (a *archive50) parseFileHeader(h *blockHeader50) (*fileBlockHeader, error) {
 	a.checksum.sum = nil
 	a.checksum.key = nil
@@ -324,7 +346,7 @@ func (a *archive50) parseFileHeader(h *blockHeader50) (*fileBlockHeader, error)
 			_ = e.data.uvarint() // ignore flags field
 			f.Version = int(e.data.uvarint())
 		case 5:
-			// TODO: redirection
+			err = a.parseFileRedirectionRecord(e.data, f)
 		case 6:
 			// TODO: owner
 		}
diff --git a/reader.go b/reader.go
index 11adc4f..db9ab31 100644
--- a/reader.go
+++ b/reader.go
@@ -25,6 +25,13 @@ const (
 	maxPassword = 128
 )
 
+const (
+	// Type '0' indicates a regular file.
+	TypeReg     = '0'
+	TypeLink    = '1' // Hard link
+	TypeSymlink = '2' // Symbolic link
+)
+
 var (
 	errShortFile        = errors.New("rardecode: decoded file too short")
 	errInvalidFileBlock = errors.New("rardecode: invalid file block")
@@ -105,6 +112,8 @@ type FileHeader struct {
 	CreationTime     time.Time // creation time (non-zero if set)
 	AccessTime       time.Time // access time (non-zero if set)
 	Version          int       // file version
+	LinkType         byte      //
+	LinkName         string    // link name
 }
 
 // Mode returns an os.FileMode for the file, calculated from the Attributes field.