From d7d3c56a784c37549f16a7dd901d84ffba419849 Mon Sep 17 00:00:00 2001
From: Michael Vogt <mvo@ubuntu.com>
Date: Tue, 8 May 2018 18:04:26 +0200
Subject: [PATCH] fixes around fat32 and lfn support

---
 fat/directory.go         |  4 ++--
 fat/directory_cluster.go | 16 ++++++++++++++--
 fat/filesystem.go        |  3 ++-
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/fat/directory.go b/fat/directory.go
index 2dec26a..4cc1854 100644
--- a/fat/directory.go
+++ b/fat/directory.go
@@ -53,14 +53,14 @@ func DecodeDirectoryEntry(d *Directory, entries []*DirectoryClusterEntry) (*Dire
 	// We have a long entry, so we have to traverse to the point where
 	// we're done. Also, calculate out the name and such.
 	if entries[0].IsLong() {
-		lfnEntries := make([]*DirectoryClusterEntry, 0, 3)
+		lfnEntries = make([]*DirectoryClusterEntry, 0, 3)
 		for entries[0].IsLong() {
 			lfnEntries = append(lfnEntries, entries[0])
 			entries = entries[1:]
 		}
 
 		var nameBytes []rune
-		nameBytes = make([]rune, 13*len(lfnEntries))
+		nameBytes = make([]rune, 0, 13*len(lfnEntries))
 		for i := len(lfnEntries) - 1; i >= 0; i-- {
 			for _, char := range lfnEntries[i].longName {
 				nameBytes = append(nameBytes, char)
diff --git a/fat/directory_cluster.go b/fat/directory_cluster.go
index 6917106..fd10efb 100644
--- a/fat/directory_cluster.go
+++ b/fat/directory_cluster.go
@@ -80,6 +80,15 @@ func DecodeDirectoryCluster(startCluster uint32, device fs.BlockDevice, fat *FAT
 	return result, nil
 }
 
+// DecodeFAT32RootDirectory decodes the FAT32 root directory structure
+// from the device.
+func DecodeFAT32RootDirectoryCluster(device fs.BlockDevice, fat *FAT) (*DirectoryCluster, error) {
+	// 2 is typcially the root dir for fat32
+	// FIXME: read from BootSectorCommon and BPB_RootClus there
+	return DecodeDirectoryCluster(2, device, fat)
+
+}
+
 // DecodeFAT16RootDirectory decodes the FAT16 root directory structure
 // from the device.
 func DecodeFAT16RootDirectoryCluster(device fs.BlockDevice, bs *BootSectorCommon) (*DirectoryCluster, error) {
@@ -304,7 +313,7 @@ func (d *DirectoryClusterEntry) IsLong() bool {
 }
 
 func (d *DirectoryClusterEntry) IsVolumeId() bool {
-	return (d.attr & AttrVolumeId) == AttrVolumeId
+	return d.attr == AttrVolumeId
 }
 
 // DecodeDirectoryClusterEntry decodes a single directory entry in the
@@ -332,8 +341,11 @@ func DecodeDirectoryClusterEntry(data []byte) (*DirectoryClusterEntry, error) {
 			offset := 28 + (i * 2)
 			chars[i+11] = binary.LittleEndian.Uint16(data[offset : offset+2])
 		}
-
 		result.longName = string(utf16.Decode(chars))
+		idx := strings.IndexByte(result.longName, 0)
+		if idx > 0 {
+			result.longName = result.longName[:idx]
+		}
 		result.longChecksum = data[13]
 	} else {
 		result.deleted = data[0] == 0xE5
diff --git a/fat/filesystem.go b/fat/filesystem.go
index 3102e0e..6c8999a 100644
--- a/fat/filesystem.go
+++ b/fat/filesystem.go
@@ -28,7 +28,8 @@ func New(device fs.BlockDevice) (*FileSystem, error) {
 
 	var rootDir *DirectoryCluster
 	if bs.FATType() == FAT32 {
-		panic("FAT32 not implemented yet")
+		// WARNING: very experimental and incomplete
+		rootDir, err = DecodeFAT32RootDirectoryCluster(device, fat)
 	} else {
 		rootDir, err = DecodeFAT16RootDirectoryCluster(device, bs)
 		if err != nil {