// A modified version of Go's JSON implementation.
// Copyright 2010, 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package json
import (
"bytes"
"encoding/base64"
"errors"
"math"
"strconv"
"unicode/utf8"
"github.com/d5/tengo/v2"
)
// safeSet holds the value true if the ASCII character with the given array
// position can be represented inside a JSON string without any further
// escaping.
//
// All values are true except for the ASCII control characters (0-31), the
// double quote ("), and the backslash character ("\").
var safeSet = [utf8.RuneSelf]bool{
' ': true,
'!': true,
'"': false,
'#': true,
'$': true,
'%': true,
'&': true,
'\'': true,
'(': true,
')': true,
'*': true,
'+': true,
',': true,
'-': true,
'.': true,
'/': true,
'0': true,
'1': true,
'2': true,
'3': true,
'4': true,
'5': true,
'6': true,
'7': true,
'8': true,
'9': true,
':': true,
';': true,
'<': true,
'=': true,
'>': true,
'?': true,
'@': true,
'A': true,
'B': true,
'C': true,
'D': true,
'E': true,
'F': true,
'G': true,
'H': true,
'I': true,
'J': true,
'K': true,
'L': true,
'M': true,
'N': true,
'O': true,
'P': true,
'Q': true,
'R': true,
'S': true,
'T': true,
'U': true,
'V': true,
'W': true,
'X': true,
'Y': true,
'Z': true,
'[': true,
'\\': false,
']': true,
'^': true,
'_': true,
'`': true,
'a': true,
'b': true,
'c': true,
'd': true,
'e': true,
'f': true,
'g': true,
'h': true,
'i': true,
'j': true,
'k': true,
'l': true,
'm': true,
'n': true,
'o': true,
'p': true,
'q': true,
'r': true,
's': true,
't': true,
'u': true,
'v': true,
'w': true,
'x': true,
'y': true,
'z': true,
'{': true,
'|': true,
'}': true,
'~': true,
'\u007f': true,
}
var hex = "0123456789abcdef"
// Encode returns the JSON encoding of the object.
func Encode(o tengo.Object) ([]byte, error) {
var b []byte
switch o := o.(type) {
case *tengo.Array:
b = append(b, '[')
len1 := len(o.Value) - 1
for idx, elem := range o.Value {
eb, err := Encode(elem)
if err != nil {
return nil, err
}
b = append(b, eb...)
if idx < len1 {
b = append(b, ',')
}
}
b = append(b, ']')
case *tengo.ImmutableArray:
b = append(b, '[')
len1 := len(o.Value) - 1
for idx, elem := range o.Value {
eb, err := Encode(elem)
if err != nil {
return nil, err
}
b = append(b, eb...)
if idx < len1 {
b = append(b, ',')
}
}
b = append(b, ']')
case *tengo.Map:
b = append(b, '{')
len1 := len(o.Value) - 1
idx := 0
for key, value := range o.Value {
b = encodeString(b, key)
b = append(b, ':')
eb, err := Encode(value)
if err != nil {
return nil, err
}
b = append(b, eb...)
if idx < len1 {
b = append(b, ',')
}
idx++
}
b = append(b, '}')
case *tengo.ImmutableMap:
b = append(b, '{')
len1 := len(o.Value) - 1
idx := 0
for key, value := range o.Value {
b = encodeString(b, key)
b = append(b, ':')
eb, err := Encode(value)
if err != nil {
return nil, err
}
b = append(b, eb...)
if idx < len1 {
b = append(b, ',')
}
idx++
}
b = append(b, '}')
case *tengo.Bool:
if o.IsFalsy() {
b = strconv.AppendBool(b, false)
} else {
b = strconv.AppendBool(b, true)
}
case *tengo.Bytes:
b = append(b, '"')
encodedLen := base64.StdEncoding.EncodedLen(len(o.Value))
dst := make([]byte, encodedLen)
base64.StdEncoding.Encode(dst, o.Value)
b = append(b, dst...)
b = append(b, '"')
case *tengo.Char:
b = strconv.AppendInt(b, int64(o.Value), 10)
case *tengo.Float:
var y []byte
f := o.Value
if math.IsInf(f, 0) || math.IsNaN(f) {
return nil, errors.New("unsupported float value")
}
// Convert as if by ES6 number to string conversion.
// This matches most other JSON generators.
abs := math.Abs(f)
fmt := byte('f')
if abs != 0 {
if abs < 1e-6 || abs >= 1e21 {
fmt = 'e'
}
}
y = strconv.AppendFloat(y, f, fmt, -1, 64)
if fmt == 'e' {
// clean up e-09 to e-9
n := len(y)
if n >= 4 && y[n-4] == 'e' && y[n-3] == '-' && y[n-2] == '0' {
y[n-2] = y[n-1]
y = y[:n-1]
}
}
b = append(b, y...)
case *tengo.Int:
b = strconv.AppendInt(b, o.Value, 10)
case *tengo.String:
// string encoding bug is fixed with newly introduced function
// encodeString(). See: https://github.com/d5/tengo/issues/268
b = encodeString(b, o.Value)
case *tengo.Time:
y, err := o.Value.MarshalJSON()
if err != nil {
return nil, err
}
b = append(b, y...)
case *tengo.Undefined:
b = append(b, "null"...)
default:
// unknown type: ignore
}
return b, nil
}
// encodeString encodes given string as JSON string according to
// https://www.json.org/img/string.png
// Implementation is inspired by https://github.com/json-iterator/go
// See encodeStringSlowPath() for more information.
func encodeString(b []byte, val string) []byte {
valLen := len(val)
buf := bytes.NewBuffer(b)
buf.WriteByte('"')
// write string, the fast path, without utf8 and escape support
i := 0
for ; i < valLen; i++ {
c := val[i]
if c > 31 && c != '"' && c != '\\' {
buf.WriteByte(c)
} else {
break
}
}
if i == valLen {
buf.WriteByte('"')
return buf.Bytes()
}
encodeStringSlowPath(buf, i, val, valLen)
buf.WriteByte('"')
return buf.Bytes()
}
// encodeStringSlowPath is ported from Go 1.14.2 encoding/json package.
// U+2028 U+2029 JSONP security holes can be fixed with addition call to
// json.html_escape() thus it is removed from the implementation below.
// Note: Invalid runes are not checked as they are checked in original
// implementation.
func encodeStringSlowPath(buf *bytes.Buffer, i int, val string, valLen int) {
start := i
for i < valLen {
if b := val[i]; b < utf8.RuneSelf {
if safeSet[b] {
i++
continue
}
if start < i {
buf.WriteString(val[start:i])
}
buf.WriteByte('\\')
switch b {
case '\\', '"':
buf.WriteByte(b)
case '\n':
buf.WriteByte('n')
case '\r':
buf.WriteByte('r')
case '\t':
buf.WriteByte('t')
default:
// This encodes bytes < 0x20 except for \t, \n and \r.
// If escapeHTML is set, it also escapes <, >, and &
// because they can lead to security holes when
// user-controlled strings are rendered into JSON
// and served to some browsers.
buf.WriteString(`u00`)
buf.WriteByte(hex[b>>4])
buf.WriteByte(hex[b&0xF])
}
i++
start = i
continue
}
i++
continue
}
if start < valLen {
buf.WriteString(val[start:])
}
}