Improve formatting of CSums and UUIDs

6 files changed, 318 insertions, 1 deletions

diff --git a/pkg/btrfs/crc32c.go b/pkg/btrfs/crc32c.go
index ab2d6e9..52058e8 100644
--- a/pkg/btrfs/crc32c.go
+++ b/pkg/btrfs/crc32c.go
@@ -2,14 +2,21 @@ package btrfs
 
 import (
 	"encoding/binary"
+	"encoding/hex"
 	"fmt"
 	"hash/crc32"
+
+	"lukeshu.com/btrfs-tools/pkg/util"
 )
 
 type CSum [0x20]byte
 
 func (csum CSum) String() string {
-	return fmt.Sprintf("%x", [0x20]byte(csum))
+	return hex.EncodeToString(csum[:])
+}
+
+func (csum CSum) Format(f fmt.State, verb rune) {
+	util.FormatByteArrayStringer(csum, csum[:], f, verb)
 }
 
 func CRC32c(data []byte) CSum {
diff --git a/pkg/btrfs/crc32c_test.go b/pkg/btrfs/crc32c_test.go
new file mode 100644
index 0000000..335b3cc
--- /dev/null
+++ b/pkg/btrfs/crc32c_test.go
@@ -0,0 +1,35 @@
+package btrfs_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"lukeshu.com/btrfs-tools/pkg/btrfs"
+)
+
+func TestCSumFormat(t *testing.T) {
+	t.Parallel()
+	type TestCase struct {
+		InputSum btrfs.CSum
+		InputFmt string
+		Output   string
+	}
+	csum := btrfs.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":   TestCase{InputSum: csum, InputFmt: "%s", Output: "bd7b41f400000000000000000000000000000000000000000000000000000000"},
+		"x":   TestCase{InputSum: csum, InputFmt: "%x", Output: "bd7b41f400000000000000000000000000000000000000000000000000000000"},
+		"v":   TestCase{InputSum: csum, InputFmt: "%v", Output: "bd7b41f400000000000000000000000000000000000000000000000000000000"},
+		"70s": TestCase{InputSum: csum, InputFmt: "|% 70s", Output: "|      bd7b41f400000000000000000000000000000000000000000000000000000000"},
+		"#180v":  TestCase{InputSum: csum, InputFmt: "%#180v", Output: "      btrfs.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)
+		})
+	}
+}
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)
+		})
+	}
+}
diff --git a/pkg/util/fmt.go b/pkg/util/fmt.go
new file mode 100644
index 0000000..c0ff596
--- /dev/null
+++ b/pkg/util/fmt.go
@@ -0,0 +1,67 @@
+package util
+
+import (
+	"fmt"
+	"strings"
+)
+
+// FmtStateString returns the fmt.Printf string that produced a given
+// fmt.State and verb.
+func FmtStateString(st fmt.State, verb rune) string {
+	var ret strings.Builder
+	ret.WriteByte('%')
+	for _, flag := range []int{'-', '+', '#', ' ', '0'} {
+		if st.Flag(flag) {
+			ret.WriteByte(byte(flag))
+		}
+	}
+	if width, ok := st.Width(); ok {
+		fmt.Fprintf(&ret, "%d", width)
+	}
+	if prec, ok := st.Precision(); ok {
+		if prec == 0 {
+			ret.WriteByte('.')
+		} else {
+			fmt.Fprintf(&ret, ".%d", prec)
+		}
+	}
+	ret.WriteRune(verb)
+	return ret.String()
+}
+
+// FormatByteArrayStringer is function for helping to implement
+// fmt.Formatter for []byte or [n]byte types that have a custom string
+// representation.  Use it like:
+//
+//     type MyType [16]byte
+//
+//     func (val MyType) String() string {
+//         …
+//     }
+//
+//     func (val MyType) Format(f fmt.State, verb rune) {
+//         util.FormatByteArrayStringer(val, val[:], f, verb)
+//     }
+func FormatByteArrayStringer(
+	obj interface {
+		fmt.Stringer
+		fmt.Formatter
+	},
+	objBytes []byte,
+	f fmt.State, verb rune) {
+	switch verb {
+	case 'v':
+		if !f.Flag('#') {
+			FormatByteArrayStringer(obj, objBytes, f, 's') // as a string
+		} else {
+			byteStr := fmt.Sprintf("%#v", objBytes)
+			objType := fmt.Sprintf("%T", obj)
+			objStr := objType + strings.TrimPrefix(byteStr, "[]byte")
+			fmt.Fprintf(f, FmtStateString(f, 's'), objStr)
+		}
+	case 's', 'q': // string
+		fmt.Fprintf(f, FmtStateString(f, verb), obj.String())
+	default:
+		fmt.Fprintf(f, FmtStateString(f, verb), objBytes)
+	}
+}
diff --git a/pkg/util/fmt_test.go b/pkg/util/fmt_test.go
new file mode 100644
index 0000000..d2579d0
--- /dev/null
+++ b/pkg/util/fmt_test.go
@@ -0,0 +1,99 @@
+package util_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"lukeshu.com/btrfs-tools/pkg/util"
+)
+
+type FmtState struct {
+	MWidth     int
+	MPrec      int
+	MFlagMinus bool
+	MFlagPlus  bool
+	MFlagSharp bool
+	MFlagSpace bool
+	MFlagZero  bool
+}
+
+func (st FmtState) Width() (int, bool) {
+	if st.MWidth < 1 {
+		return 0, false
+	}
+	return st.MWidth, true
+}
+
+func (st FmtState) Precision() (int, bool) {
+	if st.MPrec < 1 {
+		return 0, false
+	}
+	return st.MPrec, true
+}
+
+func (st FmtState) Flag(b int) bool {
+	switch b {
+	case '-':
+		return st.MFlagMinus
+	case '+':
+		return st.MFlagPlus
+	case '#':
+		return st.MFlagSharp
+	case ' ':
+		return st.MFlagSpace
+	case '0':
+		return st.MFlagZero
+	}
+	return false
+}
+
+func (st FmtState) Write([]byte) (int, error) {
+	panic("not implemented")
+}
+
+func (dst *FmtState) Format(src fmt.State, verb rune) {
+	if width, ok := src.Width(); ok {
+		dst.MWidth = width
+	}
+	if prec, ok := src.Precision(); ok {
+		dst.MPrec = prec
+	}
+	dst.MFlagMinus = src.Flag('-')
+	dst.MFlagPlus = src.Flag('+')
+	dst.MFlagSharp = src.Flag('#')
+	dst.MFlagSpace = src.Flag(' ')
+	dst.MFlagZero = src.Flag('0')
+}
+
+// letters only? No 'p', 'T', or 'w'.
+const verbs = "abcdefghijklmnoqrstuvxyzABCDEFGHIJKLMNOPQRSUVWXYZ"
+
+func FuzzFmtStateString(f *testing.F) {
+	f.Fuzz(func(t *testing.T,
+		width, prec uint8,
+		flagMinus, flagPlus, flagSharp, flagSpace, flagZero bool,
+		verbIdx uint8,
+	) {
+		if flagMinus {
+			flagZero = false
+		}
+		input := FmtState{
+			MWidth:     int(width),
+			MPrec:      int(prec),
+			MFlagMinus: flagMinus,
+			MFlagPlus:  flagPlus,
+			MFlagSharp: flagSharp,
+			MFlagSpace: flagSpace,
+			MFlagZero:  flagZero,
+		}
+		verb := rune(verbs[int(verbIdx)%len(verbs)])
+
+		t.Logf("(%#v, %c) => %q", input, verb, util.FmtStateString(input, verb))
+
+		var output FmtState
+		assert.Equal(t, "", fmt.Sprintf(util.FmtStateString(input, verb), &output))
+		assert.Equal(t, input, output)
+	})
+}