blob: 69ac7e03c8db81c2ebcc5d14765e6b5a3a441215 [file] [log] [blame]
// Copyright 2010 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 implements encoding and decoding of JSON objects as defined in
// RFC 4627. The mapping between JSON objects and Go values is described
// in the documentation for the Marshal and Unmarshal functions.
//
// See "JSON and Go" for an introduction to this package:
// https://golang.org/doc/articles/json_and_go.html
package json
import (
"bytes"
"encoding"
"encoding/base64"
"fmt"
"math"
"reflect"
"runtime"
"sort"
"strconv"
"strings"
"sync"
"unicode"
"unicode/utf8"
)
// Marshal returns the JSON encoding of v.
//
// Marshal traverses the value v recursively.
// If an encountered value implements the Marshaler interface
// and is not a nil pointer, Marshal calls its MarshalJSON method
// to produce JSON. If no MarshalJSON method is present but the
// value implements encoding.TextMarshaler instead, Marshal calls
// its MarshalText method.
// The nil pointer exception is not strictly necessary
// but mimics a similar, necessary exception in the behavior of
// UnmarshalJSON.
//
// Otherwise, Marshal uses the following type-dependent default encodings:
//
// Boolean values encode as JSON booleans.
//
// Floating point, integer, and Number values encode as JSON numbers.
//
// String values encode as JSON strings coerced to valid UTF-8,
// replacing invalid bytes with the Unicode replacement rune.
// The angle brackets "<" and ">" are escaped to "\u003c" and "\u003e"
// to keep some browsers from misinterpreting JSON output as HTML.
// Ampersand "&" is also escaped to "\u0026" for the same reason.
//
// Array and slice values encode as JSON arrays, except that
// []byte encodes as a base64-encoded string, and a nil slice
// encodes as the null JSON object.
//
// Struct values encode as JSON objects. Each exported struct field
// becomes a member of the object unless
// - the field's tag is "-", or
// - the field is empty and its tag specifies the "omitempty" option.
// The empty values are false, 0, any
// nil pointer or interface value, and any array, slice, map, or string of
// length zero. The object's default key string is the struct field name
// but can be specified in the struct field's tag value. The "json" key in
// the struct field's tag value is the key name, followed by an optional comma
// and options. Examples:
//
// // Field is ignored by this package.
// Field int `json:"-"`
//
// // Field appears in JSON as key "myName".
// Field int `json:"myName"`
//
// // Field appears in JSON as key "myName" and
// // the field is omitted from the object if its value is empty,
// // as defined above.
// Field int `json:"myName,omitempty"`
//
// // Field appears in JSON as key "Field" (the default), but
// // the field is skipped if empty.
// // Note the leading comma.
// Field int `json:",omitempty"`
//
// The "string" option signals that a field is stored as JSON inside a
// JSON-encoded string. It applies only to fields of string, floating point,
// integer, or boolean types. This extra level of encoding is sometimes used
// when communicating with JavaScript programs:
//
// Int64String int64 `json:",string"`
//
// The key name will be used if it's a non-empty string consisting of
// only Unicode letters, digits, dollar signs, percent signs, hyphens,
// underscores and slashes.
//
// Anonymous struct fields are usually marshaled as if their inner exported fields
// were fields in the outer struct, subject to the usual Go visibility rules amended
// as described in the next paragraph.
// An anonymous struct field with a name given in its JSON tag is treated as
// having that name, rather than being anonymous.
// An anonymous struct field of interface type is treated the same as having
// that type as its name, rather than being anonymous.
//
// The Go visibility rules for struct fields are amended for JSON when
// deciding which field to marshal or unmarshal. If there are
// multiple fields at the same level, and that level is the least
// nested (and would therefore be the nesting level selected by the
// usual Go rules), the following extra rules apply:
//
// 1) Of those fields, if any are JSON-tagged, only tagged fields are considered,
// even if there are multiple untagged fields that would otherwise conflict.
// 2) If there is exactly one field (tagged or not according to the first rule), that is selected.
// 3) Otherwise there are multiple fields, and all are ignored; no error occurs.
//
// Handling of anonymous struct fields is new in Go 1.1.
// Prior to Go 1.1, anonymous struct fields were ignored. To force ignoring of
// an anonymous struct field in both current and earlier versions, give the field
// a JSON tag of "-".
//
// Map values encode as JSON objects.
// The map's key type must be string; the map keys are used as JSON object
// keys, subject to the UTF-8 coercion described for string values above.
//
// Pointer values encode as the value pointed to.
// A nil pointer encodes as the null JSON object.
//
// Interface values encode as the value contained in the interface.
// A nil interface value encodes as the null JSON object.
//
// Channel, complex, and function values cannot be encoded in JSON.
// Attempting to encode such a value causes Marshal to return
// an UnsupportedTypeError.
//
// JSON cannot represent cyclic data structures and Marshal does not
// handle them. Passing cyclic structures to Marshal will result in
// an infinite recursion.
//
func Marshal(v interface{}) ([]byte, error) {
e := &encodeState{}
err := e.marshal(v)
if err != nil {
return nil, err
}
return e.Bytes(), nil
}
// MarshalIndent is like Marshal but applies Indent to format the output.
func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error) {
b, err := Marshal(v)
if err != nil {
return nil, err
}
var buf bytes.Buffer
err = Indent(&buf, b, prefix, indent)
if err != nil {
return nil, err
}
return buf.Bytes(), nil
}
// HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029
// characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029
// so that the JSON will be safe to embed inside HTML <script> tags.
// For historical reasons, web browsers don't honor standard HTML
// escaping within <script> tags, so an alternative JSON encoding must
// be used.
func HTMLEscape(dst *bytes.Buffer, src []byte) {
// The characters can only appear in string literals,
// so just scan the string one byte at a time.
start := 0
for i, c := range src {
if c == '<' || c == '>' || c == '&' {
if start < i {
dst.Write(src[start:i])
}
dst.WriteString(`\u00`)
dst.WriteByte(hex[c>>4])
dst.WriteByte(hex[c&0xF])
start = i + 1
}
// Convert U+2028 and U+2029 (E2 80 A8 and E2 80 A9).
if c == 0xE2 && i+2 < len(src) && src[i+1] == 0x80 && src[i+2]&^1 == 0xA8 {
if start < i {
dst.Write(src[start:i])
}
dst.WriteString(`\u202`)
dst.WriteByte(hex[src[i+2]&0xF])
start = i + 3
}
}
if start < len(src) {
dst.Write(src[start:])
}
}
// Marshaler is the interface implemented by objects that
// can marshal themselves into valid JSON.
type Marshaler interface {
MarshalJSON() ([]byte, error)
}
// An UnsupportedTypeError is returned by Marshal when attempting
// to encode an unsupported value type.
type UnsupportedTypeError struct {
Type reflect.Type
}
func (e *UnsupportedTypeError) Error() string {
return "json: unsupported type: " + e.Type.String()
}
type UnsupportedValueError struct {
Value reflect.Value
Str string
}
func (e *UnsupportedValueError) Error() string {
return "json: unsupported value: " + e.Str
}
// Before Go 1.2, an InvalidUTF8Error was returned by Marshal when
// attempting to encode a string value with invalid UTF-8 sequences.
// As of Go 1.2, Marshal instead coerces the string to valid UTF-8 by
// replacing invalid bytes with the Unicode replacement rune U+FFFD.
// This error is no longer generated but is kept for backwards compatibility
// with programs that might mention it.
type InvalidUTF8Error struct {
S string // the whole string value that caused the error
}
func (e *InvalidUTF8Error) Error() string {
return "json: invalid UTF-8 in string: " + strconv.Quote(e.S)
}
type MarshalerError struct {
Type reflect.Type
Err error
}
func (e *MarshalerError) Error() string {
return "json: error calling MarshalJSON for type " + e.Type.String() + ": " + e.Err.Error()
}
var hex = "0123456789abcdef"
// An encodeState encodes JSON into a bytes.Buffer.
type encodeState struct {
bytes.Buffer // accumulated output
scratch [64]byte
}
var encodeStatePool sync.Pool
func newEncodeState() *encodeState {
if v := encodeStatePool.Get(); v != nil {
e := v.(*encodeState)
e.Reset()
return e
}
return new(encodeState)
}
func (e *encodeState) marshal(v interface{}) (err error) {
defer func() {
if r := recover(); r != nil {
if _, ok := r.(runtime.Error); ok {
panic(r)
}
if s, ok := r.(string); ok {
panic(s)
}
err = r.(error)
}
}()
e.reflectValue(reflect.ValueOf(v))
return nil
}
func (e *encodeState) error(err error) {
panic(err)
}
func isEmptyValue(v reflect.Value) bool {
switch v.Kind() {
case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
return v.Len() == 0
case reflect.Bool:
return !v.Bool()
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return v.Int() == 0
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return v.Uint() == 0
case reflect.Float32, reflect.Float64:
return v.Float() == 0
case reflect.Interface, reflect.Ptr:
return v.IsNil()
}
return false
}
func (e *encodeState) reflectValue(v reflect.Value) {
valueEncoder(v)(e, v, false)
}
type encoderFunc func(e *encodeState, v reflect.Value, quoted bool)
var encoderCache struct {
sync.RWMutex
m map[reflect.Type]encoderFunc
}
func valueEncoder(v reflect.Value) encoderFunc {
if !v.IsValid() {
return invalidValueEncoder
}
return typeEncoder(v.Type())
}
func typeEncoder(t reflect.Type) encoderFunc {
encoderCache.RLock()
f := encoderCache.m[t]
encoderCache.RUnlock()
if f != nil {
return f
}
// To deal with recursive types, populate the map with an
// indirect func before we build it. This type waits on the
// real func (f) to be ready and then calls it. This indirect
// func is only used for recursive types.
encoderCache.Lock()
if encoderCache.m == nil {
encoderCache.m = make(map[reflect.Type]encoderFunc)
}
var wg sync.WaitGroup
wg.Add(1)
encoderCache.m[t] = func(e *encodeState, v reflect.Value, quoted bool) {
wg.Wait()
f(e, v, quoted)
}
encoderCache.Unlock()
// Compute fields without lock.
// Might duplicate effort but won't hold other computations back.
f = newTypeEncoder(t, true)
wg.Done()
encoderCache.Lock()
encoderCache.m[t] = f
encoderCache.Unlock()
return f
}
var (
marshalerType = reflect.TypeOf(new(Marshaler)).Elem()
textMarshalerType = reflect.TypeOf(new(encoding.TextMarshaler)).Elem()
)
// newTypeEncoder constructs an encoderFunc for a type.
// The returned encoder only checks CanAddr when allowAddr is true.
func newTypeEncoder(t reflect.Type, allowAddr bool) encoderFunc {
if t.Implements(marshalerType) {
return marshalerEncoder
}
if t.Kind() != reflect.Ptr && allowAddr {
if reflect.PtrTo(t).Implements(marshalerType) {
return newCondAddrEncoder(addrMarshalerEncoder, newTypeEncoder(t, false))
}
}
if t.Implements(textMarshalerType) {
return textMarshalerEncoder
}
if t.Kind() != reflect.Ptr && allowAddr {
if reflect.PtrTo(t).Implements(textMarshalerType) {
return newCondAddrEncoder(addrTextMarshalerEncoder, newTypeEncoder(t, false))
}
}
switch t.Kind() {
case reflect.Bool:
return boolEncoder
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return intEncoder
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return uintEncoder
case reflect.Float32:
return float32Encoder
case reflect.Float64:
return float64Encoder
case reflect.String:
return stringEncoder
case reflect.Interface:
return interfaceEncoder
case reflect.Struct:
return newStructEncoder(t)
case reflect.Map:
return newMapEncoder(t)
case reflect.Slice:
return newSliceEncoder(t)
case reflect.Array:
return newArrayEncoder(t)
case reflect.Ptr:
return newPtrEncoder(t)
default:
return unsupportedTypeEncoder
}
}
func invalidValueEncoder(e *encodeState, v reflect.Value, quoted bool) {
e.WriteString("null")
}
func marshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
if v.Kind() == reflect.Ptr && v.IsNil() {
e.WriteString("null")
return
}
m := v.Interface().(Marshaler)
b, err := m.MarshalJSON()
if err == nil {
// copy JSON into buffer, checking validity.
err = compact(&e.Buffer, b, true)
}
if err != nil {
e.error(&MarshalerError{v.Type(), err})
}
}
func addrMarshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
va := v.Addr()
if va.IsNil() {
e.WriteString("null")
return
}
m := va.Interface().(Marshaler)
b, err := m.MarshalJSON()
if err == nil {
// copy JSON into buffer, checking validity.
err = compact(&e.Buffer, b, true)
}
if err != nil {
e.error(&MarshalerError{v.Type(), err})
}
}
func textMarshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
if v.Kind() == reflect.Ptr && v.IsNil() {
e.WriteString("null")
return
}
m := v.Interface().(encoding.TextMarshaler)
b, err := m.MarshalText()
if err != nil {
e.error(&MarshalerError{v.Type(), err})
}
e.stringBytes(b)
}
func addrTextMarshalerEncoder(e *encodeState, v reflect.Value, quoted bool) {
va := v.Addr()
if va.IsNil() {
e.WriteString("null")
return
}
m := va.Interface().(encoding.TextMarshaler)
b, err := m.MarshalText()
if err != nil {
e.error(&MarshalerError{v.Type(), err})
}
e.stringBytes(b)
}
func boolEncoder(e *encodeState, v reflect.Value, quoted bool) {
if quoted {
e.WriteByte('"')
}
if v.Bool() {
e.WriteString("true")
} else {
e.WriteString("false")
}
if quoted {
e.WriteByte('"')
}
}
func intEncoder(e *encodeState, v reflect.Value, quoted bool) {
b := strconv.AppendInt(e.scratch[:0], v.Int(), 10)
if quoted {
e.WriteByte('"')
}
e.Write(b)
if quoted {
e.WriteByte('"')
}
}
func uintEncoder(e *encodeState, v reflect.Value, quoted bool) {
b := strconv.AppendUint(e.scratch[:0], v.Uint(), 10)
if quoted {
e.WriteByte('"')
}
e.Write(b)
if quoted {
e.WriteByte('"')
}
}
type floatEncoder int // number of bits
func (bits floatEncoder) encode(e *encodeState, v reflect.Value, quoted bool) {
f := v.Float()
if math.IsInf(f, 0) || math.IsNaN(f) {
e.error(&UnsupportedValueError{v, strconv.FormatFloat(f, 'g', -1, int(bits))})
}
b := strconv.AppendFloat(e.scratch[:0], f, 'g', -1, int(bits))
if quoted {
e.WriteByte('"')
}
e.Write(b)
if quoted {
e.WriteByte('"')
}
}
var (
float32Encoder = (floatEncoder(32)).encode
float64Encoder = (floatEncoder(64)).encode
)
func stringEncoder(e *encodeState, v reflect.Value, quoted bool) {
if v.Type() == numberType {
numStr := v.String()
// In Go1.5 the empty string encodes to "0", while this is not a valid number literal
// we keep compatibility so check validity after this.
if numStr == "" {
numStr = "0" // Number's zero-val
}
if !isValidNumber(numStr) {
e.error(fmt.Errorf("json: invalid number literal %q", numStr))
}
e.WriteString(numStr)
return
}
if quoted {
sb, err := Marshal(v.String())
if err != nil {
e.error(err)
}
e.string(string(sb))
} else {
e.string(v.String())
}
}
func interfaceEncoder(e *encodeState, v reflect.Value, quoted bool) {
if v.IsNil() {
e.WriteString("null")
return
}
e.reflectValue(v.Elem())
}
func unsupportedTypeEncoder(e *encodeState, v reflect.Value, quoted bool) {
e.error(&UnsupportedTypeError{v.Type()})
}
type structEncoder struct {
fields []field
fieldEncs []encoderFunc
}
func (se *structEncoder) encode(e *encodeState, v reflect.Value, quoted bool) {
e.WriteByte('{')
first := true
for i, f := range se.fields {
fv := fieldByIndex(v, f.index)
if !fv.IsValid() || f.omitEmpty && isEmptyValue(fv) {
continue
}
if first {
first = false
} else {
e.WriteByte(',')
}
e.string(f.name)
e.WriteByte(':')
se.fieldEncs[i](e, fv, f.quoted)
}
e.WriteByte('}')
}
func newStructEncoder(t reflect.Type) encoderFunc {
fields := cachedTypeFields(t)
se := &structEncoder{
fields: fields,
fieldEncs: make([]encoderFunc, len(fields)),
}
for i, f := range fields {
se.fieldEncs[i] = typeEncoder(typeByIndex(t, f.index))
}
return se.encode
}
type mapEncoder struct {
elemEnc encoderFunc
}
func (me *mapEncoder) encode(e *encodeState, v reflect.Value, _ bool) {
if v.IsNil() {
e.WriteString("null")
return
}
e.WriteByte('{')
var sv stringValues = v.MapKeys()
sort.Sort(sv)
for i, k := range sv {
if i > 0 {
e.WriteByte(',')
}
e.string(k.String())
e.WriteByte(':')
me.elemEnc(e, v.MapIndex(k), false)
}
e.WriteByte('}')
}
func newMapEncoder(t reflect.Type) encoderFunc {
if t.Key().Kind() != reflect.String {
return unsupportedTypeEncoder
}
me := &mapEncoder{typeEncoder(t.Elem())}
return me.encode
}
func encodeByteSlice(e *encodeState, v reflect.Value, _ bool) {
if v.IsNil() {
e.WriteString("null")
return
}
s := v.Bytes()
e.WriteByte('"')
if len(s) < 1024 {
// for small buffers, using Encode directly is much faster.
dst := make([]byte, base64.StdEncoding.EncodedLen(len(s)))
base64.StdEncoding.Encode(dst, s)
e.Write(dst)
} else {
// for large buffers, avoid unnecessary extra temporary
// buffer space.
enc := base64.NewEncoder(base64.StdEncoding, e)
enc.Write(s)
enc.Close()
}
e.WriteByte('"')
}
// sliceEncoder just wraps an arrayEncoder, checking to make sure the value isn't nil.
type sliceEncoder struct {
arrayEnc encoderFunc
}
func (se *sliceEncoder) encode(e *encodeState, v reflect.Value, _ bool) {
if v.IsNil() {
e.WriteString("null")
return
}
se.arrayEnc(e, v, false)
}
func newSliceEncoder(t reflect.Type) encoderFunc {
// Byte slices get special treatment; arrays don't.
if t.Elem().Kind() == reflect.Uint8 {
return encodeByteSlice
}
enc := &sliceEncoder{newArrayEncoder(t)}
return enc.encode
}
type arrayEncoder struct {
elemEnc encoderFunc
}
func (ae *arrayEncoder) encode(e *encodeState, v reflect.Value, _ bool) {
e.WriteByte('[')
n := v.Len()
for i := 0; i < n; i++ {
if i > 0 {
e.WriteByte(',')
}
ae.elemEnc(e, v.Index(i), false)
}
e.WriteByte(']')
}
func newArrayEncoder(t reflect.Type) encoderFunc {
enc := &arrayEncoder{typeEncoder(t.Elem())}
return enc.encode
}
type ptrEncoder struct {
elemEnc encoderFunc
}
func (pe *ptrEncoder) encode(e *encodeState, v reflect.Value, quoted bool) {
if v.IsNil() {
e.WriteString("null")
return
}
pe.elemEnc(e, v.Elem(), quoted)
}
func newPtrEncoder(t reflect.Type) encoderFunc {
enc := &ptrEncoder{typeEncoder(t.Elem())}
return enc.encode
}
type condAddrEncoder struct {
canAddrEnc, elseEnc encoderFunc
}
func (ce *condAddrEncoder) encode(e *encodeState, v reflect.Value, quoted bool) {
if v.CanAddr() {
ce.canAddrEnc(e, v, quoted)
} else {
ce.elseEnc(e, v, quoted)
}
}
// newCondAddrEncoder returns an encoder that checks whether its value
// CanAddr and delegates to canAddrEnc if so, else to elseEnc.
func newCondAddrEncoder(canAddrEnc, elseEnc encoderFunc) encoderFunc {
enc := &condAddrEncoder{canAddrEnc: canAddrEnc, elseEnc: elseEnc}
return enc.encode
}
func isValidTag(s string) bool {
if s == "" {
return false
}
for _, c := range s {
switch {
case strings.ContainsRune("!#$%&()*+-./:<=>?@[]^_{|}~ ", c):
// Backslash and quote chars are reserved, but
// otherwise any punctuation chars are allowed
// in a tag name.
default:
if !unicode.IsLetter(c) && !unicode.IsDigit(c) {
return false
}
}
}
return true
}
func fieldByIndex(v reflect.Value, index []int) reflect.Value {
for _, i := range index {
if v.Kind() == reflect.Ptr {
if v.IsNil() {
return reflect.Value{}
}
v = v.Elem()
}
v = v.Field(i)
}
return v
}
func typeByIndex(t reflect.Type, index []int) reflect.Type {
for _, i := range index {
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
t = t.Field(i).Type
}
return t
}
// stringValues is a slice of reflect.Value holding *reflect.StringValue.
// It implements the methods to sort by string.
type stringValues []reflect.Value
func (sv stringValues) Len() int { return len(sv) }
func (sv stringValues) Swap(i, j int) { sv[i], sv[j] = sv[j], sv[i] }
func (sv stringValues) Less(i, j int) bool { return sv.get(i) < sv.get(j) }
func (sv stringValues) get(i int) string { return sv[i].String() }
// NOTE: keep in sync with stringBytes below.
func (e *encodeState) string(s string) int {
len0 := e.Len()
e.WriteByte('"')
start := 0
for i := 0; i < len(s); {
if b := s[i]; b < utf8.RuneSelf {
if 0x20 <= b && b != '\\' && b != '"' && b != '<' && b != '>' && b != '&' {
i++
continue
}
if start < i {
e.WriteString(s[start:i])
}
switch b {
case '\\', '"':
e.WriteByte('\\')
e.WriteByte(b)
case '\n':
e.WriteByte('\\')
e.WriteByte('n')
case '\r':
e.WriteByte('\\')
e.WriteByte('r')
case '\t':
e.WriteByte('\\')
e.WriteByte('t')
default:
// This encodes bytes < 0x20 except for \n and \r,
// as well as <, > and &. The latter are escaped because they
// can lead to security holes when user-controlled strings
// are rendered into JSON and served to some browsers.
e.WriteString(`\u00`)
e.WriteByte(hex[b>>4])
e.WriteByte(hex[b&0xF])
}
i++
start = i
continue
}
c, size := utf8.DecodeRuneInString(s[i:])
if c == utf8.RuneError && size == 1 {
if start < i {
e.WriteString(s[start:i])
}
e.WriteString(`\ufffd`)
i += size
start = i
continue
}
// 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.
if c == '\u2028' || c == '\u2029' {
if start < i {
e.WriteString(s[start:i])
}
e.WriteString(`\u202`)
e.WriteByte(hex[c&0xF])
i += size
start = i
continue
}
i += size
}
if start < len(s) {
e.WriteString(s[start:])
}
e.WriteByte('"')
return e.Len() - len0
}
// NOTE: keep in sync with string above.
func (e *encodeState) stringBytes(s []byte) int {
len0 := e.Len()
e.WriteByte('"')
start := 0
for i := 0; i < len(s); {
if b := s[i]; b < utf8.RuneSelf {
if 0x20 <= b && b != '\\' && b != '"' && b != '<' && b != '>' && b != '&' {
i++
continue
}
if start < i {
e.Write(s[start:i])
}
switch b {
case '\\', '"':
e.WriteByte('\\')
e.WriteByte(b)
case '\n':
e.WriteByte('\\')
e.WriteByte('n')
case '\r':
e.WriteByte('\\')
e.WriteByte('r')
case '\t':
e.WriteByte('\\')
e.WriteByte('t')
default:
// This encodes bytes < 0x20 except for \n and \r,
// as well as <, >, and &. The latter are escaped because they
// can lead to security holes when user-controlled strings
// are rendered into JSON and served to some browsers.
e.WriteString(`\u00`)
e.WriteByte(hex[b>>4])
e.WriteByte(hex[b&0xF])
}
i++
start = i
continue
}
c, size := utf8.DecodeRune(s[i:])
if c == utf8.RuneError && size == 1 {
if start < i {
e.Write(s[start:i])
}
e.WriteString(`\ufffd`)
i += size
start = i
continue
}
// 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.
if c == '\u2028' || c == '\u2029' {
if start < i {
e.Write(s[start:i])
}
e.WriteString(`\u202`)
e.WriteByte(hex[c&0xF])
i += size
start = i
continue
}
i += size
}
if start < len(s) {
e.Write(s[start:])
}
e.WriteByte('"')
return e.Len() - len0
}
// A field represents a single field found in a struct.
type field struct {
name string
nameBytes []byte // []byte(name)
equalFold func(s, t []byte) bool // bytes.EqualFold or equivalent
tag bool
index []int
typ reflect.Type
omitEmpty bool
quoted bool
}
func fillField(f field) field {
f.nameBytes = []byte(f.name)
f.equalFold = foldFunc(f.nameBytes)
return f
}
// byName sorts field by name, breaking ties with depth,
// then breaking ties with "name came from json tag", then
// breaking ties with index sequence.
type byName []field
func (x byName) Len() int { return len(x) }
func (x byName) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
func (x byName) Less(i, j int) bool {
if x[i].name != x[j].name {
return x[i].name < x[j].name
}
if len(x[i].index) != len(x[j].index) {
return len(x[i].index) < len(x[j].index)
}
if x[i].tag != x[j].tag {
return x[i].tag
}
return byIndex(x).Less(i, j)
}
// byIndex sorts field by index sequence.
type byIndex []field
func (x byIndex) Len() int { return len(x) }
func (x byIndex) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
func (x byIndex) Less(i, j int) bool {
for k, xik := range x[i].index {
if k >= len(x[j].index) {
return false
}
if xik != x[j].index[k] {
return xik < x[j].index[k]
}
}
return len(x[i].index) < len(x[j].index)
}
// typeFields returns a list of fields that JSON should recognize for the given type.
// The algorithm is breadth-first search over the set of structs to include - the top struct
// and then any reachable anonymous structs.
func typeFields(t reflect.Type) []field {
// Anonymous fields to explore at the current level and the next.
current := []field{}
next := []field{{typ: t}}
// Count of queued names for current level and the next.
count := map[reflect.Type]int{}
nextCount := map[reflect.Type]int{}
// Types already visited at an earlier level.
visited := map[reflect.Type]bool{}
// Fields found.
var fields []field
for len(next) > 0 {
current, next = next, current[:0]
count, nextCount = nextCount, map[reflect.Type]int{}
for _, f := range current {
if visited[f.typ] {
continue
}
visited[f.typ] = true
// Scan f.typ for fields to include.
for i := 0; i < f.typ.NumField(); i++ {
sf := f.typ.Field(i)
if sf.PkgPath != "" && !sf.Anonymous { // unexported
continue
}
tag := sf.Tag.Get("json")
if tag == "-" {
continue
}
name, opts := parseTag(tag)
if !isValidTag(name) {
name = ""
}
index := make([]int, len(f.index)+1)
copy(index, f.index)
index[len(f.index)] = i
ft := sf.Type
if ft.Name() == "" && ft.Kind() == reflect.Ptr {
// Follow pointer.
ft = ft.Elem()
}
// Only strings, floats, integers, and booleans can be quoted.
quoted := false
if opts.Contains("string") {
switch ft.Kind() {
case reflect.Bool,
reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
reflect.Float32, reflect.Float64,
reflect.String:
quoted = true
}
}
// Record found field and index sequence.
if name != "" || !sf.Anonymous || ft.Kind() != reflect.Struct {
tagged := name != ""
if name == "" {
name = sf.Name
}
fields = append(fields, fillField(field{
name: name,
tag: tagged,
index: index,
typ: ft,
omitEmpty: opts.Contains("omitempty"),
quoted: quoted,
}))
if count[f.typ] > 1 {
// If there were multiple instances, add a second,
// so that the annihilation code will see a duplicate.
// It only cares about the distinction between 1 or 2,
// so don't bother generating any more copies.
fields = append(fields, fields[len(fields)-1])
}
continue
}
// Record new anonymous struct to explore in next round.
nextCount[ft]++
if nextCount[ft] == 1 {
next = append(next, fillField(field{name: ft.Name(), index: index, typ: ft}))
}
}
}
}
sort.Sort(byName(fields))
// Delete all fields that are hidden by the Go rules for embedded fields,
// except that fields with JSON tags are promoted.
// The fields are sorted in primary order of name, secondary order
// of field index length. Loop over names; for each name, delete
// hidden fields by choosing the one dominant field that survives.
out := fields[:0]
for advance, i := 0, 0; i < len(fields); i += advance {
// One iteration per name.
// Find the sequence of fields with the name of this first field.
fi := fields[i]
name := fi.name
for advance = 1; i+advance < len(fields); advance++ {
fj := fields[i+advance]
if fj.name != name {
break
}
}
if advance == 1 { // Only one field with this name
out = append(out, fi)
continue
}
dominant, ok := dominantField(fields[i : i+advance])
if ok {
out = append(out, dominant)
}
}
fields = out
sort.Sort(byIndex(fields))
return fields
}
// dominantField looks through the fields, all of which are known to
// have the same name, to find the single field that dominates the
// others using Go's embedding rules, modified by the presence of
// JSON tags. If there are multiple top-level fields, the boolean
// will be false: This condition is an error in Go and we skip all
// the fields.
func dominantField(fields []field) (field, bool) {
// The fields are sorted in increasing index-length order. The winner
// must therefore be one with the shortest index length. Drop all
// longer entries, which is easy: just truncate the slice.
length := len(fields[0].index)
tagged := -1 // Index of first tagged field.
for i, f := range fields {
if len(f.index) > length {
fields = fields[:i]
break
}
if f.tag {
if tagged >= 0 {
// Multiple tagged fields at the same level: conflict.
// Return no field.
return field{}, false
}
tagged = i
}
}
if tagged >= 0 {
return fields[tagged], true
}
// All remaining fields have the same length. If there's more than one,
// we have a conflict (two fields named "X" at the same level) and we
// return no field.
if len(fields) > 1 {
return field{}, false
}
return fields[0], true
}
var fieldCache struct {
sync.RWMutex
m map[reflect.Type][]field
}
// cachedTypeFields is like typeFields but uses a cache to avoid repeated work.
func cachedTypeFields(t reflect.Type) []field {
fieldCache.RLock()
f := fieldCache.m[t]
fieldCache.RUnlock()
if f != nil {
return f
}
// Compute fields without lock.
// Might duplicate effort but won't hold other computations back.
f = typeFields(t)
if f == nil {
f = []field{}
}
fieldCache.Lock()
if fieldCache.m == nil {
fieldCache.m = map[reflect.Type][]field{}
}
fieldCache.m[t] = f
fieldCache.Unlock()
return f
}