1 files changed, 78 insertions, 0 deletions
diff --git a/lib/btrfs/btrfssum/csum.go b/lib/btrfs/btrfssum/csum.go
new file mode 100644
index 0000000..11a8385
--- /dev/null
+++ b/lib/btrfs/btrfssum/csum.go
@@ -0,0 +1,78 @@
+package btrfssum
+
+import (
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+	"hash/crc32"
+
+	"git.lukeshu.com/btrfs-progs-ng/lib/util"
+)
+
+type CSum [0x20]byte
+
+func (csum CSum) String() string {
+	return hex.EncodeToString(csum[:])
+}
+
+func (csum CSum) Fmt(typ CSumType) string {
+	return hex.EncodeToString(csum[:typ.Size()])
+}
+
+func (csum CSum) Format(f fmt.State, verb rune) {
+	util.FormatByteArrayStringer(csum, csum[:], f, verb)
+}
+
+type CSumType uint16
+
+const (
+	TYPE_CRC32 = CSumType(iota)
+	TYPE_XXHASH
+	TYPE_SHA256
+	TYPE_BLAKE2
+)
+
+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
+	}
+	return fmt.Sprintf("%d", typ)
+}
+
+func (typ CSumType) Size() int {
+	sizes := map[CSumType]int{
+		TYPE_CRC32:  4,
+		TYPE_XXHASH: 8,
+		TYPE_SHA256: 32,
+		TYPE_BLAKE2: 32,
+	}
+	if size, ok := sizes[typ]; ok {
+		return size
+	}
+	return len(CSum{})
+}
+
+func (typ CSumType) Sum(data []byte) (CSum, error) {
+	switch typ {
+	case TYPE_CRC32:
+		crc := crc32.Update(0, crc32.MakeTable(crc32.Castagnoli), data)
+
+		var ret CSum
+		binary.LittleEndian.PutUint32(ret[:], crc)
+		return ret, nil
+	case TYPE_XXHASH:
+		panic("not implemented")
+	case TYPE_SHA256:
+		panic("not implemented")
+	case TYPE_BLAKE2:
+		panic("not implemented")
+	default:
+		return CSum{}, fmt.Errorf("unknown checksum type: %v", typ)
+	}
+}