encoding/hex: canonicalize error type names

Also simplify the tests.

Fixes #2849.

R=golang-dev, bradfitz, r
CC=golang-dev
https://golang.org/cl/5643045

src/pkg/encoding/hex/hex.go

@@ -7,8 +7,9 @@ package hex
 
 import (
 	"bytes"
+	"errors"
+	"fmt"
 	"io"
-	"strconv"
 )
 
 const hextable = "0123456789abcdef"
@@ -29,16 +30,14 @@ func Encode(dst, src []byte) int {
 	return len(src) * 2
 }
 
-// OddLengthInputError results from decoding an odd length slice.
-type OddLengthInputError struct{}
+// ErrLength results from decoding an odd length slice.
+var ErrLength = errors.New("encoding/hex: odd length hex string")
 
-func (OddLengthInputError) Error() string { return "odd length hex string" }
+// InvalidByteError values describe errors resulting from an invalid byte in a hex string.
+type InvalidByteError byte
 
-// InvalidHexCharError results from finding an invalid character in a hex string.
-type InvalidHexCharError byte
-
-func (e InvalidHexCharError) Error() string {
-	return "invalid hex char: " + strconv.Itoa(int(e))
+func (e InvalidByteError) Error() string {
+	return fmt.Sprintf("encoding/hex: invalid byte: %#U", rune(e))
 }
 
 func DecodedLen(x int) int { return x / 2 }
@@ -46,21 +45,20 @@ func DecodedLen(x int) int { return x / 2 }
 // Decode decodes src into DecodedLen(len(src)) bytes, returning the actual
 // number of bytes written to dst.
 //
-// If Decode encounters invalid input, it returns an OddLengthInputError or an
-// InvalidHexCharError.
+// If Decode encounters invalid input, it returns an error describing the failure.
 func Decode(dst, src []byte) (int, error) {
 	if len(src)%2 == 1 {
-		return 0, OddLengthInputError{}
+		return 0, ErrLength
 	}
 
 	for i := 0; i < len(src)/2; i++ {
 		a, ok := fromHexChar(src[i*2])
 		if !ok {
-			return 0, InvalidHexCharError(src[i*2])
+			return 0, InvalidByteError(src[i*2])
 		}
 		b, ok := fromHexChar(src[i*2+1])
 		if !ok {
-			return 0, InvalidHexCharError(src[i*2+1])
+			return 0, InvalidByteError(src[i*2+1])
 		}
 		dst[i] = (a << 4) | b
 	}

src/pkg/encoding/hex/hex_test.go

@@ -9,141 +9,98 @@ import (
 	"testing"
 )
 
-type encodeTest struct {
-	in, out []byte
+type encDecTest struct {
+	enc string
+	dec []byte
 }
 
-var encodeTests = []encodeTest{
-	{[]byte{}, []byte{}},
-	{[]byte{0x01}, []byte{'0', '1'}},
-	{[]byte{0xff}, []byte{'f', 'f'}},
-	{[]byte{0xff, 00}, []byte{'f', 'f', '0', '0'}},
-	{[]byte{0}, []byte{'0', '0'}},
-	{[]byte{1}, []byte{'0', '1'}},
-	{[]byte{2}, []byte{'0', '2'}},
-	{[]byte{3}, []byte{'0', '3'}},
-	{[]byte{4}, []byte{'0', '4'}},
-	{[]byte{5}, []byte{'0', '5'}},
-	{[]byte{6}, []byte{'0', '6'}},
-	{[]byte{7}, []byte{'0', '7'}},
-	{[]byte{8}, []byte{'0', '8'}},
-	{[]byte{9}, []byte{'0', '9'}},
-	{[]byte{10}, []byte{'0', 'a'}},
-	{[]byte{11}, []byte{'0', 'b'}},
-	{[]byte{12}, []byte{'0', 'c'}},
-	{[]byte{13}, []byte{'0', 'd'}},
-	{[]byte{14}, []byte{'0', 'e'}},
-	{[]byte{15}, []byte{'0', 'f'}},
+var encDecTests = []encDecTest{
+	{"", []byte{}},
+	{"0001020304050607", []byte{0, 1, 2, 3, 4, 5, 6, 7}},
+	{"08090a0b0c0d0e0f", []byte{8, 9, 10, 11, 12, 13, 14, 15}},
+	{"f0f1f2f3f4f5f6f7", []byte{0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7}},
+	{"f8f9fafbfcfdfeff", []byte{0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff}},
+	{"67", []byte{'g'}},
+	{"e3a1", []byte{0xe3, 0xa1}},
 }
 
 func TestEncode(t *testing.T) {
-	for i, test := range encodeTests {
-		dst := make([]byte, EncodedLen(len(test.in)))
-		n := Encode(dst, test.in)
+	for i, test := range encDecTests {
+		dst := make([]byte, EncodedLen(len(test.dec)))
+		n := Encode(dst, test.dec)
 		if n != len(dst) {
 			t.Errorf("#%d: bad return value: got: %d want: %d", i, n, len(dst))
 		}
-		if bytes.Compare(dst, test.out) != 0 {
-			t.Errorf("#%d: got: %#v want: %#v", i, dst, test.out)
+		if string(dst) != test.enc {
+			t.Errorf("#%d: got: %#v want: %#v", i, dst, test.enc)
 		}
 	}
 }
 
-type decodeTest struct {
-	in, out []byte
-	ok      bool
-}
-
-var decodeTests = []decodeTest{
-	{[]byte{}, []byte{}, true},
-	{[]byte{'0'}, []byte{}, false},
-	{[]byte{'0', 'g'}, []byte{}, false},
-	{[]byte{'0', '\x01'}, []byte{}, false},
-	{[]byte{'0', '0'}, []byte{0}, true},
-	{[]byte{'0', '1'}, []byte{1}, true},
-	{[]byte{'0', '2'}, []byte{2}, true},
-	{[]byte{'0', '3'}, []byte{3}, true},
-	{[]byte{'0', '4'}, []byte{4}, true},
-	{[]byte{'0', '5'}, []byte{5}, true},
-	{[]byte{'0', '6'}, []byte{6}, true},
-	{[]byte{'0', '7'}, []byte{7}, true},
-	{[]byte{'0', '8'}, []byte{8}, true},
-	{[]byte{'0', '9'}, []byte{9}, true},
-	{[]byte{'0', 'a'}, []byte{10}, true},
-	{[]byte{'0', 'b'}, []byte{11}, true},
-	{[]byte{'0', 'c'}, []byte{12}, true},
-	{[]byte{'0', 'd'}, []byte{13}, true},
-	{[]byte{'0', 'e'}, []byte{14}, true},
-	{[]byte{'0', 'f'}, []byte{15}, true},
-	{[]byte{'0', 'A'}, []byte{10}, true},
-	{[]byte{'0', 'B'}, []byte{11}, true},
-	{[]byte{'0', 'C'}, []byte{12}, true},
-	{[]byte{'0', 'D'}, []byte{13}, true},
-	{[]byte{'0', 'E'}, []byte{14}, true},
-	{[]byte{'0', 'F'}, []byte{15}, true},
-}
-
 func TestDecode(t *testing.T) {
-	for i, test := range decodeTests {
-		dst := make([]byte, DecodedLen(len(test.in)))
-		n, err := Decode(dst, test.in)
-		if err == nil && n != len(dst) {
+	for i, test := range encDecTests {
+		dst := make([]byte, DecodedLen(len(test.enc)))
+		n, err := Decode(dst, []byte(test.enc))
+		if err != nil {
 			t.Errorf("#%d: bad return value: got:%d want:%d", i, n, len(dst))
-		}
-		if test.ok != (err == nil) {
-			t.Errorf("#%d: unexpected err value: %s", i, err)
-		}
-		if err == nil && bytes.Compare(dst, test.out) != 0 {
-			t.Errorf("#%d: got: %#v want: %#v", i, dst, test.out)
+		} else if !bytes.Equal(dst, test.dec) {
+			t.Errorf("#%d: got: %#v want: %#v", i, dst, test.dec)
 		}
 	}
 }
 
-type encodeStringTest struct {
-	in  []byte
-	out string
-}
-
-var encodeStringTests = []encodeStringTest{
-	{[]byte{}, ""},
-	{[]byte{0}, "00"},
-	{[]byte{0, 1}, "0001"},
-	{[]byte{0, 1, 255}, "0001ff"},
+func TestEncodeToString(t *testing.T) {
+	for i, test := range encDecTests {
+		s := EncodeToString(test.dec)
+		if s != test.enc {
+			t.Errorf("#%d got:%s want:%s", i, s, test.enc)
+		}
+	}
 }
 
-func TestEncodeToString(t *testing.T) {
-	for i, test := range encodeStringTests {
-		s := EncodeToString(test.in)
-		if s != test.out {
-			t.Errorf("#%d got:%s want:%s", i, s, test.out)
+func TestDecodeString(t *testing.T) {
+	for i, test := range encDecTests {
+		dst, err := DecodeString(test.enc)
+		if err != nil {
+			t.Errorf("#%d: unexpected err value: %s", i, err)
+			continue
+		}
+		if bytes.Compare(dst, test.dec) != 0 {
+			t.Errorf("#%d: got: %#v want: #%v", i, dst, test.dec)
 		}
 	}
 }
 
-type decodeStringTest struct {
+type errTest struct {
 	in  string
-	out []byte
-	ok  bool
+	err string
 }
 
-var decodeStringTests = []decodeStringTest{
-	{"", []byte{}, true},
-	{"0", []byte{}, false},
-	{"00", []byte{0}, true},
-	{"0\x01", []byte{}, false},
-	{"0g", []byte{}, false},
-	{"00ff00", []byte{0, 255, 0}, true},
-	{"0000ff", []byte{0, 0, 255}, true},
+var errTests = []errTest{
+	{"0", "encoding/hex: odd length hex string"},
+	{"0g", "encoding/hex: invalid byte: U+0067 'g'"},
+	{"0\x01", "encoding/hex: invalid byte: U+0001"},
 }
 
-func TestDecodeString(t *testing.T) {
-	for i, test := range decodeStringTests {
-		dst, err := DecodeString(test.in)
-		if test.ok != (err == nil) {
-			t.Errorf("#%d: unexpected err value: %s", i, err)
+func TestInvalidErr(t *testing.T) {
+	for i, test := range errTests {
+		dst := make([]byte, DecodedLen(len(test.in)))
+		_, err := Decode(dst, []byte(test.in))
+		if err == nil {
+			t.Errorf("#%d: expected error; got none")
+		} else if err.Error() != test.err {
+			t.Errorf("#%d: got: %v want: %v", i, err, test.err)
+		}
 	}
-		if err == nil && bytes.Compare(dst, test.out) != 0 {
-			t.Errorf("#%d: got: %#v want: #%v", i, dst, test.out)
+}
+
+func TestInvalidStringErr(t *testing.T) {
+	for i, test := range errTests {
+		_, err := DecodeString(test.in)
+		if err == nil {
+			t.Errorf("#%d: expected error; got none")
+		} else if err.Error() != test.err {
+			t.Errorf("#%d: got: %v want: %v", i, err, test.err)
 		}
 	}
 }