Try to avoid unnecessary allocations in enum-types' String methods

6 files changed, 173 insertions, 143 deletions

diff --git a/lib/btrfs/Makefile b/lib/btrfs/Makefile
index 015c3e1..b98a1b7 100644
--- a/lib/btrfs/Makefile
+++ b/lib/btrfs/Makefile
@@ -80,13 +80,10 @@ btrfsprim/itemtype.go: btrfsitem/items.txt $(MAKEFILE_LIST)
 	  sed -E 's,(.*)=([^:]*)(:.*)? (trivial|complex) (.*),\1_KEY ItemType=\2,' $< | uniq; \
 	  echo ')'; \
 	  echo 'func (t ItemType) String() string {'; \
-	  echo '  names := map[ItemType]string{'; \
-	  sed -E 's@(.*)=(.*) (trivial|complex) (.*)@\1_KEY: "\1",@' $< | sed 's/"UUID_/&KEY_/'; \
+	  echo '  switch t {'; \
+	  sed -E 's@(.*)=(.*) (trivial|complex) (.*)@case \1_KEY: return "\1"@' $< | sed 's/"UUID_/&KEY_/'; \
+	  echo '  default: return fmt.Sprintf("%d", t)'; \
 	  echo '  }'; \
-	  echo '  if name, ok := names[t]; ok {'; \
-	  echo '    return name'; \
-	  echo '  }'; \
-	  echo '  return fmt.Sprintf("%d", t)'; \
 	  echo '}'; \
 	} | gofmt >$@
 files += btrfsprim/itemtype.go
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)
 }
diff --git a/lib/btrfs/btrfsprim/itemtype.go b/lib/btrfs/btrfsprim/itemtype.go
index dba7ced..f33179a 100644
--- a/lib/btrfs/btrfsprim/itemtype.go
+++ b/lib/btrfs/btrfsprim/itemtype.go
@@ -42,42 +42,72 @@ const (
 )
 
 func (t ItemType) String() string {
-	names := map[ItemType]string{
-		BLOCK_GROUP_ITEM_KEY:     "BLOCK_GROUP_ITEM",
-		CHUNK_ITEM_KEY:           "CHUNK_ITEM",
-		DEV_EXTENT_KEY:           "DEV_EXTENT",
-		DEV_ITEM_KEY:             "DEV_ITEM",
-		DIR_INDEX_KEY:            "DIR_INDEX",
-		DIR_ITEM_KEY:             "DIR_ITEM",
-		EXTENT_CSUM_KEY:          "EXTENT_CSUM",
-		EXTENT_DATA_KEY:          "EXTENT_DATA",
-		EXTENT_DATA_REF_KEY:      "EXTENT_DATA_REF",
-		EXTENT_ITEM_KEY:          "EXTENT_ITEM",
-		FREE_SPACE_BITMAP_KEY:    "FREE_SPACE_BITMAP",
-		FREE_SPACE_EXTENT_KEY:    "FREE_SPACE_EXTENT",
-		FREE_SPACE_INFO_KEY:      "FREE_SPACE_INFO",
-		INODE_ITEM_KEY:           "INODE_ITEM",
-		INODE_REF_KEY:            "INODE_REF",
-		METADATA_ITEM_KEY:        "METADATA_ITEM",
-		ORPHAN_ITEM_KEY:          "ORPHAN_ITEM",
-		PERSISTENT_ITEM_KEY:      "PERSISTENT_ITEM",
-		QGROUP_INFO_KEY:          "QGROUP_INFO",
-		QGROUP_LIMIT_KEY:         "QGROUP_LIMIT",
-		QGROUP_RELATION_KEY:      "QGROUP_RELATION",
-		QGROUP_STATUS_KEY:        "QGROUP_STATUS",
-		ROOT_BACKREF_KEY:         "ROOT_BACKREF",
-		ROOT_ITEM_KEY:            "ROOT_ITEM",
-		ROOT_REF_KEY:             "ROOT_REF",
-		SHARED_BLOCK_REF_KEY:     "SHARED_BLOCK_REF",
-		SHARED_DATA_REF_KEY:      "SHARED_DATA_REF",
-		TREE_BLOCK_REF_KEY:       "TREE_BLOCK_REF",
-		UNTYPED_KEY:              "UNTYPED",
-		UUID_RECEIVED_SUBVOL_KEY: "UUID_KEY_RECEIVED_SUBVOL",
-		UUID_SUBVOL_KEY:          "UUID_KEY_SUBVOL",
-		XATTR_ITEM_KEY:           "XATTR_ITEM",
+	switch t {
+	case BLOCK_GROUP_ITEM_KEY:
+		return "BLOCK_GROUP_ITEM"
+	case CHUNK_ITEM_KEY:
+		return "CHUNK_ITEM"
+	case DEV_EXTENT_KEY:
+		return "DEV_EXTENT"
+	case DEV_ITEM_KEY:
+		return "DEV_ITEM"
+	case DIR_INDEX_KEY:
+		return "DIR_INDEX"
+	case DIR_ITEM_KEY:
+		return "DIR_ITEM"
+	case EXTENT_CSUM_KEY:
+		return "EXTENT_CSUM"
+	case EXTENT_DATA_KEY:
+		return "EXTENT_DATA"
+	case EXTENT_DATA_REF_KEY:
+		return "EXTENT_DATA_REF"
+	case EXTENT_ITEM_KEY:
+		return "EXTENT_ITEM"
+	case FREE_SPACE_BITMAP_KEY:
+		return "FREE_SPACE_BITMAP"
+	case FREE_SPACE_EXTENT_KEY:
+		return "FREE_SPACE_EXTENT"
+	case FREE_SPACE_INFO_KEY:
+		return "FREE_SPACE_INFO"
+	case INODE_ITEM_KEY:
+		return "INODE_ITEM"
+	case INODE_REF_KEY:
+		return "INODE_REF"
+	case METADATA_ITEM_KEY:
+		return "METADATA_ITEM"
+	case ORPHAN_ITEM_KEY:
+		return "ORPHAN_ITEM"
+	case PERSISTENT_ITEM_KEY:
+		return "PERSISTENT_ITEM"
+	case QGROUP_INFO_KEY:
+		return "QGROUP_INFO"
+	case QGROUP_LIMIT_KEY:
+		return "QGROUP_LIMIT"
+	case QGROUP_RELATION_KEY:
+		return "QGROUP_RELATION"
+	case QGROUP_STATUS_KEY:
+		return "QGROUP_STATUS"
+	case ROOT_BACKREF_KEY:
+		return "ROOT_BACKREF"
+	case ROOT_ITEM_KEY:
+		return "ROOT_ITEM"
+	case ROOT_REF_KEY:
+		return "ROOT_REF"
+	case SHARED_BLOCK_REF_KEY:
+		return "SHARED_BLOCK_REF"
+	case SHARED_DATA_REF_KEY:
+		return "SHARED_DATA_REF"
+	case TREE_BLOCK_REF_KEY:
+		return "TREE_BLOCK_REF"
+	case UNTYPED_KEY:
+		return "UNTYPED"
+	case UUID_RECEIVED_SUBVOL_KEY:
+		return "UUID_KEY_RECEIVED_SUBVOL"
+	case UUID_SUBVOL_KEY:
+		return "UUID_KEY_SUBVOL"
+	case XATTR_ITEM_KEY:
+		return "XATTR_ITEM"
+	default:
+		return fmt.Sprintf("%d", t)
 	}
-	if name, ok := names[t]; ok {
-		return name
-	}
-	return fmt.Sprintf("%d", t)
 }
diff --git a/lib/btrfs/btrfsprim/objid.go b/lib/btrfs/btrfsprim/objid.go
index 8ca1fbb..1aea030 100644
--- a/lib/btrfs/btrfsprim/objid.go
+++ b/lib/btrfs/btrfsprim/objid.go
@@ -54,13 +54,45 @@ const (
 	EMPTY_SUBVOL_DIR_OBJECTID ObjID = 2
 )
 
+var (
+	objidCommonNames = map[ObjID]string{
+		BALANCE_OBJECTID:         "BALANCE",
+		ORPHAN_OBJECTID:          "ORPHAN",
+		TREE_LOG_OBJECTID:        "TREE_LOG",
+		TREE_LOG_FIXUP_OBJECTID:  "TREE_LOG_FIXUP",
+		TREE_RELOC_OBJECTID:      "TREE_RELOC",
+		DATA_RELOC_TREE_OBJECTID: "DATA_RELOC_TREE",
+		EXTENT_CSUM_OBJECTID:     "EXTENT_CSUM",
+		FREE_SPACE_OBJECTID:      "FREE_SPACE",
+		FREE_INO_OBJECTID:        "FREE_INO",
+		MULTIPLE_OBJECTIDS:       "MULTIPLE",
+	}
+	objidDevTreeNames = map[ObjID]string{
+		DEV_STATS_OBJECTID: "DEV_STATS",
+	}
+	objidChunkTreeNames = map[ObjID]string{
+		DEV_ITEMS_OBJECTID:        "DEV_ITEMS",
+		FIRST_CHUNK_TREE_OBJECTID: "FIRST_CHUNK_TREE",
+	}
+	objidRootTreeNames = map[ObjID]string{
+		ROOT_TREE_OBJECTID:        "ROOT_TREE",
+		EXTENT_TREE_OBJECTID:      "EXTENT_TREE",
+		CHUNK_TREE_OBJECTID:       "CHUNK_TREE",
+		DEV_TREE_OBJECTID:         "DEV_TREE",
+		FS_TREE_OBJECTID:          "FS_TREE",
+		ROOT_TREE_DIR_OBJECTID:    "ROOT_TREE_DIR",
+		CSUM_TREE_OBJECTID:        "CSUM_TREE",
+		QUOTA_TREE_OBJECTID:       "QUOTA_TREE",
+		UUID_TREE_OBJECTID:        "UUID_TREE",
+		FREE_SPACE_TREE_OBJECTID:  "FREE_SPACE_TREE",
+		BLOCK_GROUP_TREE_OBJECTID: "BLOCK_GROUP_TREE",
+	}
+)
+
 func (id ObjID) Format(tree ObjID) string {
 	switch tree {
 	case DEV_TREE_OBJECTID:
-		names := map[ObjID]string{
-			DEV_STATS_OBJECTID: "DEV_STATS",
-		}
-		if name, ok := names[id]; ok {
+		if name, ok := objidDevTreeNames[id]; ok {
 			return name
 		}
 		return fmt.Sprintf("%d", int64(id))
@@ -75,51 +107,18 @@ func (id ObjID) Format(tree ObjID) string {
 	case UUID_TREE_OBJECTID:
 		return fmt.Sprintf("%#016x", uint64(id))
 	case CHUNK_TREE_OBJECTID:
-		names := map[ObjID]string{
-			BALANCE_OBJECTID:         "BALANCE",
-			ORPHAN_OBJECTID:          "ORPHAN",
-			TREE_LOG_OBJECTID:        "TREE_LOG",
-			TREE_LOG_FIXUP_OBJECTID:  "TREE_LOG_FIXUP",
-			TREE_RELOC_OBJECTID:      "TREE_RELOC",
-			DATA_RELOC_TREE_OBJECTID: "DATA_RELOC_TREE",
-			EXTENT_CSUM_OBJECTID:     "EXTENT_CSUM",
-			FREE_SPACE_OBJECTID:      "FREE_SPACE",
-			FREE_INO_OBJECTID:        "FREE_INO",
-			MULTIPLE_OBJECTIDS:       "MULTIPLE",
-
-			DEV_ITEMS_OBJECTID:        "DEV_ITEMS",
-			FIRST_CHUNK_TREE_OBJECTID: "FIRST_CHUNK_TREE",
+		if name, ok := objidCommonNames[id]; ok {
+			return name
 		}
-		if name, ok := names[id]; ok {
+		if name, ok := objidChunkTreeNames[id]; ok {
 			return name
 		}
 		return fmt.Sprintf("%d", int64(id))
 	default:
-		names := map[ObjID]string{
-			BALANCE_OBJECTID:         "BALANCE",
-			ORPHAN_OBJECTID:          "ORPHAN",
-			TREE_LOG_OBJECTID:        "TREE_LOG",
-			TREE_LOG_FIXUP_OBJECTID:  "TREE_LOG_FIXUP",
-			TREE_RELOC_OBJECTID:      "TREE_RELOC",
-			DATA_RELOC_TREE_OBJECTID: "DATA_RELOC_TREE",
-			EXTENT_CSUM_OBJECTID:     "EXTENT_CSUM",
-			FREE_SPACE_OBJECTID:      "FREE_SPACE",
-			FREE_INO_OBJECTID:        "FREE_INO",
-			MULTIPLE_OBJECTIDS:       "MULTIPLE",
-
-			ROOT_TREE_OBJECTID:        "ROOT_TREE",
-			EXTENT_TREE_OBJECTID:      "EXTENT_TREE",
-			CHUNK_TREE_OBJECTID:       "CHUNK_TREE",
-			DEV_TREE_OBJECTID:         "DEV_TREE",
-			FS_TREE_OBJECTID:          "FS_TREE",
-			ROOT_TREE_DIR_OBJECTID:    "ROOT_TREE_DIR",
-			CSUM_TREE_OBJECTID:        "CSUM_TREE",
-			QUOTA_TREE_OBJECTID:       "QUOTA_TREE",
-			UUID_TREE_OBJECTID:        "UUID_TREE",
-			FREE_SPACE_TREE_OBJECTID:  "FREE_SPACE_TREE",
-			BLOCK_GROUP_TREE_OBJECTID: "BLOCK_GROUP_TREE",
+		if name, ok := objidCommonNames[id]; ok {
+			return name
 		}
-		if name, ok := names[id]; ok {
+		if name, ok := objidRootTreeNames[id]; ok {
 			return name
 		}
 		return fmt.Sprintf("%d", int64(id))
diff --git a/lib/btrfs/btrfssum/csum.go b/lib/btrfs/btrfssum/csum.go
index bce43f9..157371e 100644
--- a/lib/btrfs/btrfssum/csum.go
+++ b/lib/btrfs/btrfssum/csum.go
@@ -58,29 +58,30 @@ const (
 	TYPE_BLAKE2
 )
 
+var csumTypeNames = []string{
+	"crc32c",
+	"xxhash64",
+	"sha256",
+	"blake2",
+}
+
+var csumTypeSizes = []int{
+	4,
+	8,
+	32,
+	32,
+}
+
 func (typ CSumType) String() string {
-	names := map[CSumType]string{
-		TYPE_CRC32:  "crc32c",
-		TYPE_XXHASH: "xxhash64",
-		TYPE_SHA256: "sha256",
-		TYPE_BLAKE2: "blake2",
-	}
-	if name, ok := names[typ]; ok {
-		return name
+	if int(typ) < len(csumTypeNames) {
+		return csumTypeNames[typ]
 	}
 	return fmt.Sprintf("%d", typ)
 }
 
 func (typ CSumType) Size() int {
-	//nolint:gomnd // This is where we define the magic numbers.
-	sizes := map[CSumType]int{
-		TYPE_CRC32:  4,
-		TYPE_XXHASH: 8,
-		TYPE_SHA256: 32,
-		TYPE_BLAKE2: 32,
-	}
-	if size, ok := sizes[typ]; ok {
-		return size
+	if int(typ) < len(csumTypeSizes) {
+		return csumTypeSizes[typ]
 	}
 	return len(CSum{})
 }