2 files changed, 113 insertions, 0 deletions
diff --git a/pkg/btrfs/btrfssum/csum.go b/pkg/btrfs/btrfssum/csum.go
new file mode 100644
index 0000000..22d8149
--- /dev/null
+++ b/pkg/btrfs/btrfssum/csum.go
@@ -0,0 +1,78 @@
+package btrfssum
+
+import (
+	"encoding/binary"
+	"encoding/hex"
+	"fmt"
+	"hash/crc32"
+
+	"lukeshu.com/btrfs-tools/pkg/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)
+	}
+}
diff --git a/pkg/btrfs/btrfssum/csum_test.go b/pkg/btrfs/btrfssum/csum_test.go
new file mode 100644
index 0000000..c47409c
--- /dev/null
+++ b/pkg/btrfs/btrfssum/csum_test.go
@@ -0,0 +1,35 @@
+package btrfssum_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"lukeshu.com/btrfs-tools/pkg/btrfs/btrfssum"
+)
+
+func TestCSumFormat(t *testing.T) {
+	t.Parallel()
+	type TestCase struct {
+		InputSum btrfssum.CSum
+		InputFmt string
+		Output   string
+	}
+	csum := btrfssum.CSum{0xbd, 0x7b, 0x41, 0xf4, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}
+	testcases := map[string]TestCase{
+		"s":     {InputSum: csum, InputFmt: "%s", Output: "bd7b41f400000000000000000000000000000000000000000000000000000000"},
+		"x":     {InputSum: csum, InputFmt: "%x", Output: "bd7b41f400000000000000000000000000000000000000000000000000000000"},
+		"v":     {InputSum: csum, InputFmt: "%v", Output: "bd7b41f400000000000000000000000000000000000000000000000000000000"},
+		"70s":   {InputSum: csum, InputFmt: "|% 70s", Output: "|      bd7b41f400000000000000000000000000000000000000000000000000000000"},
+		"#180v": {InputSum: csum, InputFmt: "%#180v", Output: "   btrfssum.CSum{0xbd, 0x7b, 0x41, 0xf4, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}"},
+	}
+	for tcName, tc := range testcases {
+		tc := tc
+		t.Run(tcName, func(t *testing.T) {
+			t.Parallel()
+			actual := fmt.Sprintf(tc.InputFmt, tc.InputSum)
+			assert.Equal(t, tc.Output, actual)
+		})
+	}
+}