From acbbfafa07922b458506b91a58f3a082da453fd1 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Sat, 11 Feb 2023 22:33:44 -0700
Subject: Try to avoid unnecessary allocations in enum-types' String methods

---
 lib/btrfs/btrfsitem/item_dir.go        | 47 +++++++++++++++++-----------------
 lib/btrfs/btrfsitem/item_fileextent.go | 36 ++++++++++++++------------
 2 files changed, 43 insertions(+), 40 deletions(-)

(limited to 'lib/btrfs/btrfsitem')

diff --git a/lib/btrfs/btrfsitem/item_dir.go b/lib/btrfs/btrfsitem/item_dir.go
index 0f263d5..c1b3c09 100644
--- a/lib/btrfs/btrfsitem/item_dir.go
+++ b/lib/btrfs/btrfsitem/item_dir.go
@@ -84,33 +84,34 @@ func (o DirEntry) MarshalBinary() ([]byte, error) {
 type FileType uint8
 
 const (
-	FT_UNKNOWN  FileType = 0
-	FT_REG_FILE FileType = 1
-	FT_DIR      FileType = 2
-	FT_CHRDEV   FileType = 3
-	FT_BLKDEV   FileType = 4
-	FT_FIFO     FileType = 5
-	FT_SOCK     FileType = 6
-	FT_SYMLINK  FileType = 7
-	FT_XATTR    FileType = 8
+	FT_UNKNOWN FileType = iota
+	FT_REG_FILE
+	FT_DIR
+	FT_CHRDEV
+	FT_BLKDEV
+	FT_FIFO
+	FT_SOCK
+	FT_SYMLINK
+	FT_XATTR
 
-	FT_MAX FileType = 9
+	FT_MAX
 )
 
+var fileTypeNames = []string{
+	"UNKNOWN",
+	"FILE", // NB: Just "FILE", despite corresponding to "REG_FILE"
+	"DIR",
+	"CHRDEV",
+	"BLKDEV",
+	"FIFO",
+	"SOCK",
+	"SYMLINK",
+	"XATTR",
+}
+
 func (ft FileType) String() string {
-	names := map[FileType]string{
-		FT_UNKNOWN:  "UNKNOWN",
-		FT_REG_FILE: "FILE", // XXX
-		FT_DIR:      "DIR",
-		FT_CHRDEV:   "CHRDEV",
-		FT_BLKDEV:   "BLKDEV",
-		FT_FIFO:     "FIFO",
-		FT_SOCK:     "SOCK",
-		FT_SYMLINK:  "SYMLINK",
-		FT_XATTR:    "XATTR",
-	}
-	if name, ok := names[ft]; ok {
-		return name
+	if ft < FT_MAX {
+		return fileTypeNames[ft]
 	}
 	return fmt.Sprintf("DIR_ITEM.%d", uint8(ft))
 }
diff --git a/lib/btrfs/btrfsitem/item_fileextent.go b/lib/btrfs/btrfsitem/item_fileextent.go
index ce6c45c..6b08897 100644
--- a/lib/btrfs/btrfsitem/item_fileextent.go
+++ b/lib/btrfs/btrfsitem/item_fileextent.go
@@ -106,6 +106,12 @@ const (
 	FILE_EXTENT_PREALLOC
 )
 
+var fileExtentTypeNames = []string{
+	"inline",
+	"regular",
+	"prealloc",
+}
+
 func (o FileExtent) Size() (int64, error) {
 	switch o.Type {
 	case FILE_EXTENT_INLINE:
@@ -118,14 +124,9 @@ func (o FileExtent) Size() (int64, error) {
 }
 
 func (fet FileExtentType) String() string {
-	names := map[FileExtentType]string{
-		FILE_EXTENT_INLINE:   "inline",
-		FILE_EXTENT_REG:      "regular",
-		FILE_EXTENT_PREALLOC: "prealloc",
-	}
-	name, ok := names[fet]
-	if !ok {
-		name = "unknown"
+	name := "unknown"
+	if int(fet) < len(fileExtentTypeNames) {
+		name = fileExtentTypeNames[fet]
 	}
 	return fmt.Sprintf("%d (%s)", fet, name)
 }
@@ -139,16 +140,17 @@ const (
 	COMPRESS_ZSTD
 )
 
+var compressionTypeNames = []string{
+	"none",
+	"zlib",
+	"lzo",
+	"zstd",
+}
+
 func (ct CompressionType) String() string {
-	names := map[CompressionType]string{
-		COMPRESS_NONE: "none",
-		COMPRESS_ZLIB: "zlib",
-		COMPRESS_LZO:  "lzo",
-		COMPRESS_ZSTD: "zstd",
-	}
-	name, ok := names[ct]
-	if !ok {
-		name = "unknown"
+	name := "unknown"
+	if int(ct) < len(compressionTypeNames) {
+		name = compressionTypeNames[ct]
 	}
 	return fmt.Sprintf("%d (%s)", ct, name)
 }
-- 
cgit v1.2.3-2-g168b