2 files changed, 109 insertions, 0 deletions
diff --git a/pkg/btrfs/internal/uuid.go b/pkg/btrfs/internal/uuid.go
index 6169638..cb2c800 100644
--- a/pkg/btrfs/internal/uuid.go
+++ b/pkg/btrfs/internal/uuid.go
@@ -2,7 +2,10 @@ package internal
 
 import (
 	"encoding/hex"
+	"fmt"
 	"strings"
+
+	"lukeshu.com/btrfs-tools/pkg/util"
 )
 
 type UUID [16]byte
@@ -17,3 +20,46 @@ func (uuid UUID) String() string {
 		str[20:32],
 	}, "-")
 }
+
+func (uuid UUID) Format(f fmt.State, verb rune) {
+	util.FormatByteArrayStringer(uuid, uuid[:], f, verb)
+}
+
+func ParseUUID(str string) (UUID, error) {
+	var ret UUID
+	j := 0
+	for i := 0; i < len(str); i++ {
+		if j >= len(ret)*2 {
+			return UUID{}, fmt.Errorf("too long to be a UUID: %q|%q", str[:i], str[i:])
+		}
+		c := str[i]
+		var v byte
+		switch {
+		case '0' <= c && c <= '9':
+			v = c - '0'
+		case 'a' <= c && c <= 'f':
+			v = c - 'a' + 10
+		case 'A' <= c && c <= 'F':
+			v = c - 'A' + 10
+		case c == '-':
+			continue
+		default:
+			return UUID{}, fmt.Errorf("illegal byte in UUID: %q|%q|%q", str[:i], str[i:i+1], str[i+1:])
+		}
+		if j%2 == 0 {
+			ret[j/2] = v << 4
+		} else {
+			ret[j/2] = (ret[j/2] & 0xf0) | (v & 0x0f)
+		}
+		j++
+	}
+	return ret, nil
+}
+
+func MustParseUUID(str string) UUID {
+	ret, err := ParseUUID(str)
+	if err != nil {
+		panic(err)
+	}
+	return ret
+}
diff --git a/pkg/btrfs/internal/uuid_test.go b/pkg/btrfs/internal/uuid_test.go
new file mode 100644
index 0000000..8c78570
--- /dev/null
+++ b/pkg/btrfs/internal/uuid_test.go
@@ -0,0 +1,63 @@
+package internal_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"lukeshu.com/btrfs-tools/pkg/btrfs/internal"
+)
+
+func TestParseUUID(t *testing.T) {
+	t.Parallel()
+	type TestCase struct {
+		Input     string
+		OutputVal internal.UUID
+		OutputErr string
+	}
+	testcases := map[string]TestCase{
+		"basic":    TestCase{Input: "a0dd94ed-e60c-42e8-8632-64e8d4765a43", OutputVal: internal.UUID{0xa0, 0xdd, 0x94, 0xed, 0xe6, 0x0c, 0x42, 0xe8, 0x86, 0x32, 0x64, 0xe8, 0xd4, 0x76, 0x5a, 0x43}},
+		"too-long": TestCase{Input: "a0dd94ed-e60c-42e8-8632-64e8d4765a43a", OutputErr: `too long to be a UUID: "a0dd94ed-e60c-42e8-8632-64e8d4765a43"|"a"`},
+		"bad char": TestCase{Input: "a0dd94ej-e60c-42e8-8632-64e8d4765a43a", OutputErr: `illegal byte in UUID: "a0dd94e"|"j"|"-e60c-42e8-8632-64e8d4765a43a"`},
+	}
+	for tcName, tc := range testcases {
+		tc := tc
+		t.Run(tcName, func(t *testing.T) {
+			t.Parallel()
+			val, err := internal.ParseUUID(tc.Input)
+			assert.Equal(t, tc.OutputVal, val)
+			if tc.OutputErr == "" {
+				assert.NoError(t, err)
+			} else {
+				assert.EqualError(t, err, tc.OutputErr)
+			}
+		})
+	}
+}
+
+func TestUUIDFormat(t *testing.T) {
+	t.Parallel()
+	type TestCase struct {
+		InputUUID internal.UUID
+		InputFmt  string
+		Output    string
+	}
+	uuid := internal.MustParseUUID("a0dd94ed-e60c-42e8-8632-64e8d4765a43")
+	testcases := map[string]TestCase{
+		"s":     TestCase{InputUUID: uuid, InputFmt: "%s", Output: "a0dd94ed-e60c-42e8-8632-64e8d4765a43"},
+		"x":     TestCase{InputUUID: uuid, InputFmt: "%x", Output: "a0dd94ede60c42e8863264e8d4765a43"},
+		"X":     TestCase{InputUUID: uuid, InputFmt: "%X", Output: "A0DD94EDE60C42E8863264E8D4765A43"},
+		"v":     TestCase{InputUUID: uuid, InputFmt: "%v", Output: "a0dd94ed-e60c-42e8-8632-64e8d4765a43"},
+		"40s":   TestCase{InputUUID: uuid, InputFmt: "|% 40s", Output: "|    a0dd94ed-e60c-42e8-8632-64e8d4765a43"},
+		"#115v": TestCase{InputUUID: uuid, InputFmt: "|%#115v", Output: "|       internal.UUID{0xa0, 0xdd, 0x94, 0xed, 0xe6, 0xc, 0x42, 0xe8, 0x86, 0x32, 0x64, 0xe8, 0xd4, 0x76, 0x5a, 0x43}"},
+	}
+	for tcName, tc := range testcases {
+		tc := tc
+		t.Run(tcName, func(t *testing.T) {
+			t.Parallel()
+			actual := fmt.Sprintf(tc.InputFmt, tc.InputUUID)
+			assert.Equal(t, tc.Output, actual)
+		})
+	}
+}