diff --git a/encode.go b/encode.go
index 54e7150..5cce9ad 100644
--- a/encode.go
+++ b/encode.go
@@ -3,6 +3,7 @@ package json
 import (
 	"bytes"
 	"encoding"
+	"encoding/base64"
 	"io"
 	"math"
 	"reflect"
@@ -310,6 +311,22 @@ func (e *Encoder) encodeString(s string) {
 	}
 }
 
+func (e *Encoder) encodeByteSlice(b []byte) {
+	encodedLen := base64.StdEncoding.EncodedLen(len(b))
+	e.encodeByte('"')
+	pos := len(e.buf)
+	remainLen := cap(e.buf[pos:])
+	var buf []byte
+	if remainLen > encodedLen {
+		buf = e.buf[pos : pos+encodedLen]
+	} else {
+		buf = make([]byte, encodedLen)
+	}
+	base64.StdEncoding.Encode(buf, b)
+	e.encodeBytes(buf)
+	e.encodeByte('"')
+}
+
 func (e *Encoder) encodeByte(b byte) {
 	e.buf = append(e.buf, b)
 }
diff --git a/encode_vm.go b/encode_vm.go
index 8578965..9780a03 100644
--- a/encode_vm.go
+++ b/encode_vm.go
@@ -99,13 +99,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 			if ptr == 0 || header.Data == 0 {
 				e.encodeNull()
 			} else {
-				b := e.ptrToBytes(ptr)
-				encodedLen := base64.StdEncoding.EncodedLen(len(b))
-				e.encodeByte('"')
-				buf := make([]byte, encodedLen)
-				base64.StdEncoding.Encode(buf, b)
-				e.encodeBytes(buf)
-				e.encodeByte('"')
+				e.encodeByteSlice(e.ptrToBytes(ptr))
 			}
 			code = code.next
 		case opInterface:
@@ -1151,10 +1145,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 			} else {
 				e.encodeByte('{')
 				e.encodeBytes(code.key)
-				s := base64.StdEncoding.EncodeToString(e.ptrToBytes(ptr + code.offset))
-				e.encodeByte('"')
-				e.encodeBytes(*(*[]byte)(unsafe.Pointer(&s)))
-				e.encodeByte('"')
+				e.encodeByteSlice(e.ptrToBytes(ptr + code.offset))
 				code = code.next
 			}
 		case opStructFieldPtrAnonymousHeadBytes:
@@ -1166,10 +1157,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 				code = code.end
 			} else {
 				e.encodeBytes(code.key)
-				s := base64.StdEncoding.EncodeToString(e.ptrToBytes(ptr + code.offset))
-				e.encodeByte('"')
-				e.encodeBytes(*(*[]byte)(unsafe.Pointer(&s)))
-				e.encodeByte('"')
+				e.encodeByteSlice(e.ptrToBytes(ptr + code.offset))
 				code = code.next
 			}
 		case opStructFieldPtrHeadArray:
@@ -2347,10 +2335,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 					code = code.nextField
 				} else {
 					e.encodeBytes(code.key)
-					s := base64.StdEncoding.EncodeToString(v)
-					e.encodeByte('"')
-					e.encodeBytes(*(*[]byte)(unsafe.Pointer(&s)))
-					e.encodeByte('"')
+					e.encodeByteSlice(v)
 					code = code.next
 				}
 			}
@@ -2370,10 +2355,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 					code = code.nextField
 				} else {
 					e.encodeBytes(code.key)
-					s := base64.StdEncoding.EncodeToString(v)
-					e.encodeByte('"')
-					e.encodeBytes(*(*[]byte)(unsafe.Pointer(&s)))
-					e.encodeByte('"')
+					e.encodeByteSlice(v)
 					code = code.next
 				}
 			}
@@ -3459,12 +3441,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 			} else {
 				e.encodeByte('{')
 				e.encodeBytes(code.key)
-				s := base64.StdEncoding.EncodeToString(
-					e.ptrToBytes(ptr + code.offset),
-				)
-				e.encodeByte('"')
-				e.encodeBytes(*(*[]byte)(unsafe.Pointer(&s)))
-				e.encodeByte('"')
+				e.encodeByteSlice(e.ptrToBytes(ptr + code.offset))
 				code = code.next
 			}
 		case opStructFieldPtrAnonymousHeadStringTagBytes:
@@ -3479,12 +3456,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 				code = code.end.next
 			} else {
 				e.encodeBytes(code.key)
-				s := base64.StdEncoding.EncodeToString(
-					e.ptrToBytes(ptr + code.offset),
-				)
-				e.encodeByte('"')
-				e.encodeBytes(*(*[]byte)(unsafe.Pointer(&s)))
-				e.encodeByte('"')
+				e.encodeByteSlice(e.ptrToBytes(ptr + code.offset))
 				code = code.next
 			}
 		case opStructFieldPtrHeadStringTagMarshalJSON:
@@ -4088,10 +4060,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 			}
 			ptr := load(ctxptr, code.headIdx)
 			e.encodeBytes(code.key)
-			s := base64.StdEncoding.EncodeToString(e.ptrToBytes(ptr + code.offset))
-			e.encodeByte('"')
-			e.encodeBytes(*(*[]byte)(unsafe.Pointer(&s)))
-			e.encodeByte('"')
+			e.encodeByteSlice(e.ptrToBytes(ptr + code.offset))
 			code = code.next
 		case opStructFieldMarshalJSON:
 			if e.buf[len(e.buf)-1] != '{' {
@@ -4659,10 +4628,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 					e.encodeByte(',')
 				}
 				e.encodeBytes(code.key)
-				s := base64.StdEncoding.EncodeToString(v)
-				e.encodeByte('"')
-				e.encodeBytes(*(*[]byte)(unsafe.Pointer(&s)))
-				e.encodeByte('"')
+				e.encodeByteSlice(v)
 			}
 			code = code.next
 		case opStructFieldOmitEmptyMarshalJSON:
@@ -5211,10 +5177,7 @@ func (e *Encoder) run(ctx *encodeRuntimeContext, code *opcode) error {
 				e.encodeByte(',')
 			}
 			e.encodeBytes(code.key)
-			s := base64.StdEncoding.EncodeToString(v)
-			e.encodeByte('"')
-			e.encodeBytes(*(*[]byte)(unsafe.Pointer(&s)))
-			e.encodeByte('"')
+			e.encodeByteSlice(v)
 			code = code.next
 		case opStructFieldStringTagMarshalJSON:
 			ptr := load(ctxptr, code.headIdx)