libgo: update to Go 1.14.6 release

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/243317

2 files changed, 48 insertions, 42 deletions

diff --git a/libgo/go/encoding/json/decode.go b/libgo/go/encoding/json/decode.go
index b60e2bb..86d8a69 100644
--- a/libgo/go/encoding/json/decode.go
+++ b/libgo/go/encoding/json/decode.go
@@ -213,9 +213,6 @@ type decodeState struct {
 	savedError            error
 	useNumber             bool
 	disallowUnknownFields bool
-	// safeUnquote is the number of current string literal bytes that don't
-	// need to be unquoted. When negative, no bytes need unquoting.
-	safeUnquote int
 }
 
 // readIndex returns the position of the last byte read.
@@ -317,27 +314,13 @@ func (d *decodeState) rescanLiteral() {
 Switch:
 	switch data[i-1] {
 	case '"': // string
-		// safeUnquote is initialized at -1, which means that all bytes
-		// checked so far can be unquoted at a later time with no work
-		// at all. When reaching the closing '"', if safeUnquote is
-		// still -1, all bytes can be unquoted with no work. Otherwise,
-		// only those bytes up until the first '\\' or non-ascii rune
-		// can be safely unquoted.
-		safeUnquote := -1
 		for ; i < len(data); i++ {
-			if c := data[i]; c == '\\' {
-				if safeUnquote < 0 { // first unsafe byte
-					safeUnquote = int(i - d.off)
-				}
+			switch data[i] {
+			case '\\':
 				i++ // escaped char
-			} else if c == '"' {
-				d.safeUnquote = safeUnquote
+			case '"':
 				i++ // tokenize the closing quote too
 				break Switch
-			} else if c >= utf8.RuneSelf {
-				if safeUnquote < 0 { // first unsafe byte
-					safeUnquote = int(i - d.off)
-				}
 			}
 		}
 	case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-': // number
@@ -691,7 +674,7 @@ func (d *decodeState) object(v reflect.Value) error {
 		start := d.readIndex()
 		d.rescanLiteral()
 		item := d.data[start:d.readIndex()]
-		key, ok := d.unquoteBytes(item)
+		key, ok := unquoteBytes(item)
 		if !ok {
 			panic(phasePanicMsg)
 		}
@@ -892,7 +875,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 			d.saveError(&UnmarshalTypeError{Value: val, Type: v.Type(), Offset: int64(d.readIndex())})
 			return nil
 		}
-		s, ok := d.unquoteBytes(item)
+		s, ok := unquoteBytes(item)
 		if !ok {
 			if fromQuoted {
 				return fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type())
@@ -943,7 +926,7 @@ func (d *decodeState) literalStore(item []byte, v reflect.Value, fromQuoted bool
 		}
 
 	case '"': // string
-		s, ok := d.unquoteBytes(item)
+		s, ok := unquoteBytes(item)
 		if !ok {
 			if fromQuoted {
 				return fmt.Errorf("json: invalid use of ,string struct tag, trying to unmarshal %q into %v", item, v.Type())
@@ -1103,7 +1086,7 @@ func (d *decodeState) objectInterface() map[string]interface{} {
 		start := d.readIndex()
 		d.rescanLiteral()
 		item := d.data[start:d.readIndex()]
-		key, ok := d.unquote(item)
+		key, ok := unquote(item)
 		if !ok {
 			panic(phasePanicMsg)
 		}
@@ -1152,7 +1135,7 @@ func (d *decodeState) literalInterface() interface{} {
 		return c == 't'
 
 	case '"': // string
-		s, ok := d.unquote(item)
+		s, ok := unquote(item)
 		if !ok {
 			panic(phasePanicMsg)
 		}
@@ -1195,33 +1178,40 @@ func getu4(s []byte) rune {
 
 // unquote converts a quoted JSON string literal s into an actual string t.
 // The rules are different than for Go, so cannot use strconv.Unquote.
-// The first byte in s must be '"'.
-func (d *decodeState) unquote(s []byte) (t string, ok bool) {
-	s, ok = d.unquoteBytes(s)
+func unquote(s []byte) (t string, ok bool) {
+	s, ok = unquoteBytes(s)
 	t = string(s)
 	return
 }
 
-func (d *decodeState) unquoteBytes(s []byte) (t []byte, ok bool) {
-	// We already know that s[0] == '"'. However, we don't know that the
-	// closing quote exists in all cases, such as when the string is nested
-	// via the ",string" option.
-	if len(s) < 2 || s[len(s)-1] != '"' {
+func unquoteBytes(s []byte) (t []byte, ok bool) {
+	if len(s) < 2 || s[0] != '"' || s[len(s)-1] != '"' {
 		return
 	}
 	s = s[1 : len(s)-1]
 
-	// If there are no unusual characters, no unquoting is needed, so return
-	// a slice of the original bytes.
-	r := d.safeUnquote
-	if r == -1 {
+	// Check for unusual characters. If there are none,
+	// then no unquoting is needed, so return a slice of the
+	// original bytes.
+	r := 0
+	for r < len(s) {
+		c := s[r]
+		if c == '\\' || c == '"' || c < ' ' {
+			break
+		}
+		if c < utf8.RuneSelf {
+			r++
+			continue
+		}
+		rr, size := utf8.DecodeRune(s[r:])
+		if rr == utf8.RuneError && size == 1 {
+			break
+		}
+		r += size
+	}
+	if r == len(s) {
 		return s, true
 	}
-	// Only perform up to one safe unquote for each re-scanned string
-	// literal. In some edge cases, the decoder unquotes a literal a second
-	// time, even after another literal has been re-scanned. Thus, only the
-	// first unquote can safely use safeUnquote.
-	d.safeUnquote = 0
 
 	b := make([]byte, len(s)+2*utf8.UTFMax)
 	w := copy(b, s[0:r])
diff --git a/libgo/go/encoding/json/decode_test.go b/libgo/go/encoding/json/decode_test.go
index a49181e..689cc34 100644
--- a/libgo/go/encoding/json/decode_test.go
+++ b/libgo/go/encoding/json/decode_test.go
@@ -2459,4 +2459,20 @@ func TestUnmarshalRescanLiteralMangledUnquote(t *testing.T) {
 	if t1 != t2 {
 		t.Errorf("Marshal and Unmarshal roundtrip mismatch: want %q got %q", t1, t2)
 	}
+
+	// See golang.org/issues/39555.
+	input := map[textUnmarshalerString]string{"FOO": "", `"`: ""}
+
+	encoded, err := Marshal(input)
+	if err != nil {
+		t.Fatalf("Marshal unexpected error: %v", err)
+	}
+	var got map[textUnmarshalerString]string
+	if err := Unmarshal(encoded, &got); err != nil {
+		t.Fatalf("Unmarshal unexpected error: %v", err)
+	}
+	want := map[textUnmarshalerString]string{"foo": "", `"`: ""}
+	if !reflect.DeepEqual(want, got) {
+		t.Fatalf("Unexpected roundtrip result:\nwant: %q\ngot:  %q", want, got)
+	}
 }