Refactor buffering of encoder for improvement performance

encode.go

@@ -100,7 +100,8 @@ func (e *Encoder) EncodeWithOption(v interface{}, opts ...EncodeOption) error {
 			return err
 		}
 	}
-	if err := e.encode(v); err != nil {
+	var err error
+	if e.buf, err = e.encode(v); err != nil {
 		return err
 	}
 	if e.enabledIndent {
@@ -149,7 +150,8 @@ func (e *Encoder) reset() {
 }
 
 func (e *Encoder) encodeForMarshal(v interface{}) ([]byte, error) {
-	if err := e.encode(v); err != nil {
+	var err error
+	if e.buf, err = e.encode(v); err != nil {
 		return nil, err
 	}
 	if e.enabledIndent {
@@ -162,15 +164,16 @@ func (e *Encoder) encodeForMarshal(v interface{}) ([]byte, error) {
 	return copied, nil
 }
 
-func (e *Encoder) encode(v interface{}) error {
+func (e *Encoder) encode(v interface{}) ([]byte, error) {
+	b := e.buf
 	if v == nil {
-		e.encodeNull()
+		b = encodeNull(b)
 		if e.enabledIndent {
-			e.encodeBytes([]byte{',', '\n'})
+			b = encodeIndentComma(b)
 		} else {
-			e.encodeByte(',')
+			b = encodeComma(b)
 		}
-		return nil
+		return b, nil
 	}
 	header := (*interfaceHeader)(unsafe.Pointer(&v))
 	typ := header.typ
@@ -187,9 +190,9 @@ func (e *Encoder) encode(v interface{}) error {
 		ctx := codeSet.ctx.Get().(*encodeRuntimeContext)
 		p := uintptr(header.ptr)
 		ctx.init(p)
-		err := e.run(ctx, code)
+		b, err := e.run(ctx, b, code)
 		codeSet.ctx.Put(ctx)
-		return err
+		return b, err
 	}
 
 	// noescape trick for header.typ ( reflect.*rtype )
@@ -201,7 +204,7 @@ func (e *Encoder) encode(v interface{}) error {
 		withIndent: true,
 	})
 	if err != nil {
-		return err
+		return nil, err
 	}
 	code, err := e.compileHead(&encodeCompileContext{
 		typ:        copiedType,
@@ -209,7 +212,7 @@ func (e *Encoder) encode(v interface{}) error {
 		withIndent: false,
 	})
 	if err != nil {
-		return err
+		return nil, err
 	}
 	codeIndent = copyOpcode(codeIndent)
 	code = copyOpcode(code)
@@ -239,55 +242,56 @@ func (e *Encoder) encode(v interface{}) error {
 		c = code
 	}
 
-	if err := e.run(ctx, c); err != nil {
+	b, err = e.run(ctx, b, c)
+	if err != nil {
 		codeSet.ctx.Put(ctx)
-		return err
+		return nil, err
 	}
 	codeSet.ctx.Put(ctx)
-	return nil
+	return b, nil
 }
 
-func (e *Encoder) encodeInt(v int) {
+func encodeInt(b []byte, v int) []byte {
-	e.encodeInt64(int64(v))
+	return strconv.AppendInt(b, int64(v), 10)
 }
 
-func (e *Encoder) encodeInt8(v int8) {
+func encodeInt8(b []byte, v int8) []byte {
-	e.encodeInt64(int64(v))
+	return strconv.AppendInt(b, int64(v), 10)
 }
 
-func (e *Encoder) encodeInt16(v int16) {
+func encodeInt16(b []byte, v int16) []byte {
-	e.encodeInt64(int64(v))
+	return strconv.AppendInt(b, int64(v), 10)
 }
 
-func (e *Encoder) encodeInt32(v int32) {
+func encodeInt32(b []byte, v int32) []byte {
-	e.encodeInt64(int64(v))
+	return strconv.AppendInt(b, int64(v), 10)
 }
 
-func (e *Encoder) encodeInt64(v int64) {
+func encodeInt64(b []byte, v int64) []byte {
-	e.buf = strconv.AppendInt(e.buf, v, 10)
+	return strconv.AppendInt(b, v, 10)
 }
 
-func (e *Encoder) encodeUint(v uint) {
+func encodeUint(b []byte, v uint) []byte {
-	e.encodeUint64(uint64(v))
+	return strconv.AppendUint(b, uint64(v), 10)
 }
 
-func (e *Encoder) encodeUint8(v uint8) {
+func encodeUint8(b []byte, v uint8) []byte {
-	e.encodeUint64(uint64(v))
+	return strconv.AppendUint(b, uint64(v), 10)
 }
 
-func (e *Encoder) encodeUint16(v uint16) {
+func encodeUint16(b []byte, v uint16) []byte {
-	e.encodeUint64(uint64(v))
+	return strconv.AppendUint(b, uint64(v), 10)
 }
 
-func (e *Encoder) encodeUint32(v uint32) {
+func encodeUint32(b []byte, v uint32) []byte {
-	e.encodeUint64(uint64(v))
+	return strconv.AppendUint(b, uint64(v), 10)
 }
 
-func (e *Encoder) encodeUint64(v uint64) {
+func encodeUint64(b []byte, v uint64) []byte {
-	e.buf = strconv.AppendUint(e.buf, v, 10)
+	return strconv.AppendUint(b, v, 10)
 }
 
-func (e *Encoder) encodeFloat32(v float32) {
+func encodeFloat32(b []byte, v float32) []byte {
 	f64 := float64(v)
 	abs := math.Abs(f64)
 	fmt := byte('f')
@@ -298,10 +302,10 @@ func (e *Encoder) encodeFloat32(v float32) {
 			fmt = 'e'
 		}
 	}
-	e.buf = strconv.AppendFloat(e.buf, f64, fmt, -1, 32)
+	return strconv.AppendFloat(b, f64, fmt, -1, 32)
 }
 
-func (e *Encoder) encodeFloat64(v float64) {
+func encodeFloat64(b []byte, v float64) []byte {
 	abs := math.Abs(v)
 	fmt := byte('f')
 	// Note: Must use float32 comparisons for underlying float32 value to get precise cutoffs right.
@@ -310,58 +314,62 @@ func (e *Encoder) encodeFloat64(v float64) {
 			fmt = 'e'
 		}
 	}
-	e.buf = strconv.AppendFloat(e.buf, v, fmt, -1, 64)
+	return strconv.AppendFloat(b, v, fmt, -1, 64)
 }
 
-func (e *Encoder) encodeBool(v bool) {
+func encodeBool(b []byte, v bool) []byte {
-	e.buf = strconv.AppendBool(e.buf, v)
+	if v {
-}
+		return append(b, "true"...)
-
-func (e *Encoder) encodeBytes(b []byte) {
-	e.buf = append(e.buf, b...)
-}
-
-func (e *Encoder) encodeNull() {
-	e.buf = append(e.buf, 'n', 'u', 'l', 'l')
-}
-
-func (e *Encoder) encodeKey(code *opcode) {
-	if e.enabledHTMLEscape {
-		e.encodeBytes(code.escapedKey)
-	} else {
-		e.encodeBytes(code.key)
 	}
+	return append(b, "false"...)
 }
 
-func (e *Encoder) encodeString(s string) {
+func encodeBytes(dst []byte, src []byte) []byte {
+	return append(dst, src...)
+}
+
+func encodeNull(b []byte) []byte {
+	return append(b, "null"...)
+}
+
+func encodeComma(b []byte) []byte {
+	return append(b, ',')
+}
+
+func encodeIndentComma(b []byte) []byte {
+	return append(b, ',', '\n')
+}
+
+func (e *Encoder) encodeKey(b []byte, code *opcode) []byte {
 	if e.enabledHTMLEscape {
-		e.encodeEscapedString(s)
+		return append(b, code.escapedKey...)
-	} else {
-		e.encodeNoEscapedString(s)
 	}
+	return append(b, code.key...)
 }
 
-func (e *Encoder) encodeByteSlice(b []byte) {
+func (e *Encoder) encodeString(b []byte, s string) []byte {
-	encodedLen := base64.StdEncoding.EncodedLen(len(b))
+	if e.enabledHTMLEscape {
-	e.encodeByte('"')
+		return encodeEscapedString(b, s)
-	pos := len(e.buf)
+	}
-	remainLen := cap(e.buf[pos:])
+	return encodeNoEscapedString(b, s)
+}
+
+func encodeByteSlice(b []byte, src []byte) []byte {
+	encodedLen := base64.StdEncoding.EncodedLen(len(src))
+	b = append(b, '"')
+	pos := len(b)
+	remainLen := cap(b[pos:])
 	var buf []byte
 	if remainLen > encodedLen {
-		buf = e.buf[pos : pos+encodedLen]
+		buf = b[pos : pos+encodedLen]
 	} else {
 		buf = make([]byte, encodedLen)
 	}
-	base64.StdEncoding.Encode(buf, b)
+	base64.StdEncoding.Encode(buf, src)
-	e.encodeBytes(buf)
+	return append(append(b, buf...), '"')
-	e.encodeByte('"')
 }
 
-func (e *Encoder) encodeByte(b byte) {
+func (e *Encoder) encodeIndent(b []byte, indent int) []byte {
-	e.buf = append(e.buf, b)
+	b = append(b, e.prefix...)
-}
+	return append(b, bytes.Repeat(e.indentStr, indent)...)
-
-func (e *Encoder) encodeIndent(indent int) {
-	e.buf = append(e.buf, e.prefix...)
-	e.buf = append(e.buf, bytes.Repeat(e.indentStr, indent)...)
 }

encode_compile.go

@@ -1007,7 +1007,7 @@ func (e *Encoder) compileStruct(ctx *encodeCompileContext, isPtr bool) (*opcode,
 
 		var buf bytes.Buffer
 		enc := NewEncoder(&buf)
-		enc.encodeEscapedString(tag.key)
+		enc.buf = encodeEscapedString(enc.buf, tag.key)
 		escapedKey := fmt.Sprintf(`%s:`, string(enc.buf))
 		enc.release()
 		fieldCode := &opcode{

encode_string.go

@@ -1,9 +1,352 @@
 package json
 
 import (
+	"math/bits"
+	"reflect"
 	"unicode/utf8"
+	"unsafe"
 )
 
+const (
+	lsb = 0x0101010101010101
+	msb = 0x8080808080808080
+)
+
+var needEscapeWithHTML = [256]bool{
+	'"':  true,
+	'&':  true,
+	'<':  true,
+	'>':  true,
+	'\\': true,
+	0x00: true,
+	0x01: true,
+	0x02: true,
+	0x03: true,
+	0x04: true,
+	0x05: true,
+	0x06: true,
+	0x07: true,
+	0x08: true,
+	0x09: true,
+	0x0a: true,
+	0x0b: true,
+	0x0c: true,
+	0x0d: true,
+	0x0e: true,
+	0x0f: true,
+	0x10: true,
+	0x11: true,
+	0x12: true,
+	0x13: true,
+	0x14: true,
+	0x15: true,
+	0x16: true,
+	0x17: true,
+	0x18: true,
+	0x19: true,
+	0x1a: true,
+	0x1b: true,
+	0x1c: true,
+	0x1d: true,
+	0x1e: true,
+	0x1f: true,
+	/* 0x20 - 0x7f */
+	0x80: true,
+	0x81: true,
+	0x82: true,
+	0x83: true,
+	0x84: true,
+	0x85: true,
+	0x86: true,
+	0x87: true,
+	0x88: true,
+	0x89: true,
+	0x8a: true,
+	0x8b: true,
+	0x8c: true,
+	0x8d: true,
+	0x8e: true,
+	0x8f: true,
+	0x90: true,
+	0x91: true,
+	0x92: true,
+	0x93: true,
+	0x94: true,
+	0x95: true,
+	0x96: true,
+	0x97: true,
+	0x98: true,
+	0x99: true,
+	0x9a: true,
+	0x9b: true,
+	0x9c: true,
+	0x9d: true,
+	0x9e: true,
+	0x9f: true,
+	0xa0: true,
+	0xa1: true,
+	0xa2: true,
+	0xa3: true,
+	0xa4: true,
+	0xa5: true,
+	0xa6: true,
+	0xa7: true,
+	0xa8: true,
+	0xa9: true,
+	0xaa: true,
+	0xab: true,
+	0xac: true,
+	0xad: true,
+	0xae: true,
+	0xaf: true,
+	0xb0: true,
+	0xb1: true,
+	0xb2: true,
+	0xb3: true,
+	0xb4: true,
+	0xb5: true,
+	0xb6: true,
+	0xb7: true,
+	0xb8: true,
+	0xb9: true,
+	0xba: true,
+	0xbb: true,
+	0xbc: true,
+	0xbd: true,
+	0xbe: true,
+	0xbf: true,
+	0xc0: true,
+	0xc1: true,
+	0xc2: true,
+	0xc3: true,
+	0xc4: true,
+	0xc5: true,
+	0xc6: true,
+	0xc7: true,
+	0xc8: true,
+	0xc9: true,
+	0xca: true,
+	0xcb: true,
+	0xcc: true,
+	0xcd: true,
+	0xce: true,
+	0xcf: true,
+	0xd0: true,
+	0xd1: true,
+	0xd2: true,
+	0xd3: true,
+	0xd4: true,
+	0xd5: true,
+	0xd6: true,
+	0xd7: true,
+	0xd8: true,
+	0xd9: true,
+	0xda: true,
+	0xdb: true,
+	0xdc: true,
+	0xdd: true,
+	0xde: true,
+	0xdf: true,
+	0xe0: true,
+	0xe1: true,
+	0xe2: true,
+	0xe3: true,
+	0xe4: true,
+	0xe5: true,
+	0xe6: true,
+	0xe7: true,
+	0xe8: true,
+	0xe9: true,
+	0xea: true,
+	0xeb: true,
+	0xec: true,
+	0xed: true,
+	0xee: true,
+	0xef: true,
+	0xf0: true,
+	0xf1: true,
+	0xf2: true,
+	0xf3: true,
+	0xf4: true,
+	0xf5: true,
+	0xf6: true,
+	0xf7: true,
+	0xf8: true,
+	0xf9: true,
+	0xfa: true,
+	0xfb: true,
+	0xfc: true,
+	0xfd: true,
+	0xfe: true,
+	0xff: true,
+}
+
+var needEscape = [256]bool{
+	'"':  true,
+	'\\': true,
+	0x00: true,
+	0x01: true,
+	0x02: true,
+	0x03: true,
+	0x04: true,
+	0x05: true,
+	0x06: true,
+	0x07: true,
+	0x08: true,
+	0x09: true,
+	0x0a: true,
+	0x0b: true,
+	0x0c: true,
+	0x0d: true,
+	0x0e: true,
+	0x0f: true,
+	0x10: true,
+	0x11: true,
+	0x12: true,
+	0x13: true,
+	0x14: true,
+	0x15: true,
+	0x16: true,
+	0x17: true,
+	0x18: true,
+	0x19: true,
+	0x1a: true,
+	0x1b: true,
+	0x1c: true,
+	0x1d: true,
+	0x1e: true,
+	0x1f: true,
+	/* 0x20 - 0x7f */
+	0x80: true,
+	0x81: true,
+	0x82: true,
+	0x83: true,
+	0x84: true,
+	0x85: true,
+	0x86: true,
+	0x87: true,
+	0x88: true,
+	0x89: true,
+	0x8a: true,
+	0x8b: true,
+	0x8c: true,
+	0x8d: true,
+	0x8e: true,
+	0x8f: true,
+	0x90: true,
+	0x91: true,
+	0x92: true,
+	0x93: true,
+	0x94: true,
+	0x95: true,
+	0x96: true,
+	0x97: true,
+	0x98: true,
+	0x99: true,
+	0x9a: true,
+	0x9b: true,
+	0x9c: true,
+	0x9d: true,
+	0x9e: true,
+	0x9f: true,
+	0xa0: true,
+	0xa1: true,
+	0xa2: true,
+	0xa3: true,
+	0xa4: true,
+	0xa5: true,
+	0xa6: true,
+	0xa7: true,
+	0xa8: true,
+	0xa9: true,
+	0xaa: true,
+	0xab: true,
+	0xac: true,
+	0xad: true,
+	0xae: true,
+	0xaf: true,
+	0xb0: true,
+	0xb1: true,
+	0xb2: true,
+	0xb3: true,
+	0xb4: true,
+	0xb5: true,
+	0xb6: true,
+	0xb7: true,
+	0xb8: true,
+	0xb9: true,
+	0xba: true,
+	0xbb: true,
+	0xbc: true,
+	0xbd: true,
+	0xbe: true,
+	0xbf: true,
+	0xc0: true,
+	0xc1: true,
+	0xc2: true,
+	0xc3: true,
+	0xc4: true,
+	0xc5: true,
+	0xc6: true,
+	0xc7: true,
+	0xc8: true,
+	0xc9: true,
+	0xca: true,
+	0xcb: true,
+	0xcc: true,
+	0xcd: true,
+	0xce: true,
+	0xcf: true,
+	0xd0: true,
+	0xd1: true,
+	0xd2: true,
+	0xd3: true,
+	0xd4: true,
+	0xd5: true,
+	0xd6: true,
+	0xd7: true,
+	0xd8: true,
+	0xd9: true,
+	0xda: true,
+	0xdb: true,
+	0xdc: true,
+	0xdd: true,
+	0xde: true,
+	0xdf: true,
+	0xe0: true,
+	0xe1: true,
+	0xe2: true,
+	0xe3: true,
+	0xe4: true,
+	0xe5: true,
+	0xe6: true,
+	0xe7: true,
+	0xe8: true,
+	0xe9: true,
+	0xea: true,
+	0xeb: true,
+	0xec: true,
+	0xed: true,
+	0xee: true,
+	0xef: true,
+	0xf0: true,
+	0xf1: true,
+	0xf2: true,
+	0xf3: true,
+	0xf4: true,
+	0xf5: true,
+	0xf6: true,
+	0xf7: true,
+	0xf8: true,
+	0xf9: true,
+	0xfa: true,
+	0xfb: true,
+	0xfc: true,
+	0xfd: true,
+	0xfe: true,
+	0xff: true,
+}
+
 // htmlSafeSet holds the value true if the ASCII character with the given
 // array position can be safely represented inside a JSON string, embedded
 // inside of HTML <script> tags, without any additional escaping.
@@ -345,69 +688,171 @@ var safeSet = [utf8.RuneSelf]bool{
 
 var hex = "0123456789abcdef"
 
-func (e *Encoder) encodeEscapedString(s string) {
+// escapeIndex finds the index of the first char in `s` that requires escaping.
+// A char requires escaping if it's outside of the range of [0x20, 0x7F] or if
+// it includes a double quote or backslash.
+// If no chars in `s` require escaping, the return value is -1.
+func escapeIndex(s string) int {
+	chunks := stringToUint64Slice(s)
+	for _, n := range chunks {
+		// combine masks before checking for the MSB of each byte. We include
+		// `n` in the mask to check whether any of the *input* byte MSBs were
+		// set (i.e. the byte was outside the ASCII range).
+		mask := n | below(n, 0x20) | contains(n, '"') | contains(n, '\\')
+		if (mask & msb) != 0 {
+			return bits.TrailingZeros64(mask&msb) / 8
+		}
+	}
+
 	valLen := len(s)
-	// write string, the fast path, without utf8 and escape support
+	for i := len(chunks) * 8; i < valLen; i++ {
-	i := 0
+		if needEscape[s[i]] {
-	for ; i < valLen; i++ {
+			return i
-		if !htmlSafeSet[s[i]] {
-			break
 		}
 	}
-	e.buf = append(e.buf, '"')
+
-	if i == valLen {
+	return -1
-		e.buf = append(e.buf, s...)
-		e.buf = append(e.buf, '"')
-		return
-	}
-	e.buf = append(e.buf, s[:i]...)
-	e.writeStringSlowPathWithHTMLEscaped(i, s, valLen)
 }
 
-func (e *Encoder) writeStringSlowPathWithHTMLEscaped(i int, s string, valLen int) {
+// escapeIndex finds the index of the first char in `s` that requires escaping.
-	start := i
+// A char requires escaping if it's outside of the range of [0x20, 0x7F] or if
-	// for the remaining parts, we process them char by char
+// it includes a double quote or backslash.
-	for i < valLen {
+// Also, the chars <, > and & require escaping.
-		if b := s[i]; b < utf8.RuneSelf {
+// If no chars in `s` require escaping, the return value is -1.
-			if htmlSafeSet[b] {
+func escapeIndexWithHTMLEscape(s string) int {
-				i++
+	chunks := stringToUint64Slice(s)
+	for _, n := range chunks {
+		// combine masks before checking for the MSB of each byte. We include
+		// `n` in the mask to check whether any of the *input* byte MSBs were
+		// set (i.e. the byte was outside the ASCII range).
+		mask := n | below(n, 0x20) | contains(n, '"') | contains(n, '\\') | contains(n, '<') | contains(n, '>') | contains(n, '&')
+		if (mask & msb) != 0 {
+			return bits.TrailingZeros64(mask&msb) / 8
+		}
+	}
+
+	valLen := len(s)
+	for i := len(chunks) * 8; i < valLen; i++ {
+		if needEscapeWithHTML[s[i]] {
+			return i
+		}
+	}
+
+	return -1
+}
+
+// below return a mask that can be used to determine if any of the bytes
+// in `n` are below `b`. If a byte's MSB is set in the mask then that byte was
+// below `b`. The result is only valid if `b`, and each byte in `n`, is below
+// 0x80.
+func below(n uint64, b byte) uint64 {
+	return n - expand(b)
+}
+
+// contains returns a mask that can be used to determine if any of the
+// bytes in `n` are equal to `b`. If a byte's MSB is set in the mask then
+// that byte is equal to `b`. The result is only valid if `b`, and each
+// byte in `n`, is below 0x80.
+func contains(n uint64, b byte) uint64 {
+	return (n ^ expand(b)) - lsb
+}
+
+// expand puts the specified byte into each of the 8 bytes of a uint64.
+func expand(b byte) uint64 {
+	return lsb * uint64(b)
+}
+
+func stringToUint64Slice(s string) []uint64 {
+	return *(*[]uint64)(unsafe.Pointer(&reflect.SliceHeader{
+		Data: ((*reflect.StringHeader)(unsafe.Pointer(&s))).Data,
+		Len:  len(s) / 8,
+		Cap:  len(s) / 8,
+	}))
+}
+
+func encodeEscapedString(buf []byte, s string) []byte {
+	valLen := len(s)
+	if valLen == 0 {
+		return append(buf, `""`...)
+	}
+	buf = append(buf, '"')
+	var escapeIdx int
+	if valLen >= 8 {
+		if escapeIdx = escapeIndexWithHTMLEscape(s); escapeIdx < 0 {
+			return append(append(buf, s...), '"')
+		}
+	}
+	i := 0
+	j := escapeIdx
+	for j < valLen {
+		c := s[j]
+
+		if c >= 0x20 && c <= 0x7f && c != '\\' && c != '"' && (c != '<' && c != '>' && c != '&') {
+			// fast path: most of the time, printable ascii characters are used
+			j++
 			continue
 		}
-			if start < i {
+
-				e.buf = append(e.buf, s[start:i]...)
+		switch c {
-			}
-			switch b {
 		case '\\', '"':
-				e.buf = append(e.buf, '\\', b)
+			buf = append(buf, s[i:j]...)
+			buf = append(buf, '\\', c)
+			i = j + 1
+			j = j + 1
+			continue
+
 		case '\n':
-				e.buf = append(e.buf, '\\', 'n')
+			buf = append(buf, s[i:j]...)
+			buf = append(buf, '\\', 'n')
+			i = j + 1
+			j = j + 1
+			continue
+
 		case '\r':
-				e.buf = append(e.buf, '\\', 'r')
+			buf = append(buf, s[i:j]...)
+			buf = append(buf, '\\', 'r')
+			i = j + 1
+			j = j + 1
+			continue
+
 		case '\t':
-				e.buf = append(e.buf, '\\', 't')
+			buf = append(buf, s[i:j]...)
-			default:
+			buf = append(buf, '\\', 't')
+			i = j + 1
+			j = j + 1
+			continue
+
+		case '<', '>', '&':
+			buf = append(buf, s[i:j]...)
+			buf = append(buf, `\u00`...)
+			buf = append(buf, hex[c>>4], hex[c&0xF])
+			i = j + 1
+			j = j + 1
+			continue
+		}
+
 		// This encodes bytes < 0x20 except for \t, \n and \r.
-				// If escapeHTML is set, it also escapes <, >, and &
+		if c < 0x20 {
-				// because they can lead to security holes when
+			buf = append(buf, s[i:j]...)
-				// user-controlled strings are rendered into JSON
+			buf = append(buf, `\u00`...)
-				// and served to some browsers.
+			buf = append(buf, hex[c>>4], hex[c&0xF])
-				e.buf = append(e.buf, `\u00`...)
+			i = j + 1
-				e.buf = append(e.buf, hex[b>>4], hex[b&0xF])
+			j = j + 1
-			}
-			i++
-			start = i
 			continue
 		}
-		c, size := utf8.DecodeRuneInString(s[i:])
+
-		if c == utf8.RuneError && size == 1 {
+		r, size := utf8.DecodeRuneInString(s[j:])
-			if start < i {
+
-				e.buf = append(e.buf, s[start:i]...)
+		if r == utf8.RuneError && size == 1 {
-			}
+			buf = append(buf, s[i:j]...)
-			e.buf = append(e.buf, `\ufffd`...)
+			buf = append(buf, `\ufffd`...)
-			i++
+			i = j + size
-			start = i
+			j = j + size
 			continue
 		}
+
+		switch r {
+		case '\u2028', '\u2029':
 			// U+2028 is LINE SEPARATOR.
 			// U+2029 is PARAGRAPH SEPARATOR.
 			// They are both technically valid characters in JSON strings,
@@ -415,84 +860,121 @@ func (e *Encoder) writeStringSlowPathWithHTMLEscaped(i int, s string, valLen int
 			// and can lead to security holes there. It is valid JSON to
 			// escape them, so we do so unconditionally.
 			// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
-		if c == '\u2028' || c == '\u2029' {
+			buf = append(buf, s[i:j]...)
-			if start < i {
+			buf = append(buf, `\u202`...)
-				e.buf = append(e.buf, s[start:i]...)
+			buf = append(buf, hex[r&0xF])
-			}
+			i = j + size
-			e.buf = append(e.buf, `\u202`...)
+			j = j + size
-			e.buf = append(e.buf, hex[c&0xF])
-			i += size
-			start = i
 			continue
 		}
-		i += size
+
+		j += size
 	}
-	if start < len(s) {
+
-		e.buf = append(e.buf, s[start:]...)
+	return append(append(buf, s[i:]...), '"')
-	}
-	e.buf = append(e.buf, '"')
 }
 
-func (e *Encoder) encodeNoEscapedString(s string) {
+func encodeNoEscapedString(buf []byte, s string) []byte {
 	valLen := len(s)
+	if valLen == 0 {
+		return append(buf, `""`...)
+	}
+	buf = append(buf, '"')
+	var escapeIdx int
+	if valLen >= 8 {
+		if escapeIdx = escapeIndex(s); escapeIdx < 0 {
+			return append(append(buf, s...), '"')
+		}
+	}
 
-	// write string, the fast path, without utf8 and escape support
 	i := 0
-	for ; i < valLen; i++ {
+	j := escapeIdx
-		c := s[i]
+	for j < valLen {
-		if c <= 31 || c == '"' || c == '\\' {
+		c := s[j]
-			break
-		}
-	}
-	e.buf = append(e.buf, '"')
-	if i == valLen {
-		e.buf = append(e.buf, s...)
-		e.buf = append(e.buf, '"')
-		return
-	}
-	e.buf = append(e.buf, s[:i]...)
-	e.writeStringSlowPath(i, s, valLen)
-}
 
-func (e *Encoder) writeStringSlowPath(i int, s string, valLen int) {
+		if c >= 0x20 && c <= 0x7f && c != '\\' && c != '"' {
-	start := i
+			// fast path: most of the time, printable ascii characters are used
-	// for the remaining parts, we process them char by char
+			j++
-	for i < valLen {
-		if b := s[i]; b < utf8.RuneSelf {
-			if safeSet[b] {
-				i++
 			continue
 		}
-			if start < i {
+
-				e.buf = append(e.buf, s[start:i]...)
+		switch c {
-			}
-			switch b {
 		case '\\', '"':
-				e.buf = append(e.buf, '\\', b)
+			buf = append(buf, s[i:j]...)
+			buf = append(buf, '\\', c)
+			i = j + 1
+			j = j + 1
+			continue
+
 		case '\n':
-				e.buf = append(e.buf, '\\', 'n')
+			buf = append(buf, s[i:j]...)
+			buf = append(buf, '\\', 'n')
+			i = j + 1
+			j = j + 1
+			continue
+
 		case '\r':
-				e.buf = append(e.buf, '\\', 'r')
+			buf = append(buf, s[i:j]...)
+			buf = append(buf, '\\', 'r')
+			i = j + 1
+			j = j + 1
+			continue
+
 		case '\t':
-				e.buf = append(e.buf, '\\', 't')
+			buf = append(buf, s[i:j]...)
-			default:
+			buf = append(buf, '\\', 't')
+			i = j + 1
+			j = j + 1
+			continue
+
+		case '<', '>', '&':
+			buf = append(buf, s[i:j]...)
+			buf = append(buf, `\u00`...)
+			buf = append(buf, hex[c>>4], hex[c&0xF])
+			i = j + 1
+			j = j + 1
+			continue
+		}
+
 		// This encodes bytes < 0x20 except for \t, \n and \r.
-				// If escapeHTML is set, it also escapes <, >, and &
+		if c < 0x20 {
-				// because they can lead to security holes when
+			buf = append(buf, s[i:j]...)
-				// user-controlled strings are rendered into JSON
+			buf = append(buf, `\u00`...)
-				// and served to some browsers.
+			buf = append(buf, hex[c>>4], hex[c&0xF])
-				e.buf = append(e.buf, []byte(`\u00`)...)
+			i = j + 1
-				e.buf = append(e.buf, hex[b>>4], hex[b&0xF])
+			j = j + 1
-			}
-			i++
-			start = i
 			continue
 		}
-		i++
+
+		r, size := utf8.DecodeRuneInString(s[j:])
+
+		if r == utf8.RuneError && size == 1 {
+			buf = append(buf, s[i:j]...)
+			buf = append(buf, `\ufffd`...)
+			i = j + size
+			j = j + size
 			continue
 		}
-	if start < len(s) {
+
-		e.buf = append(e.buf, s[start:]...)
+		switch r {
+		case '\u2028', '\u2029':
+			// U+2028 is LINE SEPARATOR.
+			// U+2029 is PARAGRAPH SEPARATOR.
+			// They are both technically valid characters in JSON strings,
+			// but don't work in JSONP, which has to be evaluated as JavaScript,
+			// and can lead to security holes there. It is valid JSON to
+			// escape them, so we do so unconditionally.
+			// See http://timelessrepo.com/json-isnt-a-javascript-subset for discussion.
+			buf = append(buf, s[i:j]...)
+			buf = append(buf, `\u202`...)
+			buf = append(buf, hex[r&0xF])
+			i = j + size
+			j = j + size
+			continue
 		}
-	e.buf = append(e.buf, '"')
+
+		j += size
+	}
+
+	return append(append(buf, s[i:]...), '"')
 }

json.go

@@ -393,7 +393,7 @@ func HTMLEscape(dst *bytes.Buffer, src []byte) {
 	}
 	enc := NewEncoder(dst)
 	enc.SetEscapeHTML(true)
-	enc.encode(v)
+	enc.buf, _ = enc.encode(v)
 	dst.Write(enc.buf[:len(enc.buf)-1]) // remove last ',' character
 }