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reflect.go
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reflect.go
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package jsoniter
import (
"fmt"
"reflect"
"unsafe"
"github.com/modern-go/reflect2"
)
// ValDecoder is an internal type registered to cache as needed.
// Don't confuse jsoniter.ValDecoder with json.Decoder.
// For json.Decoder's adapter, refer to jsoniter.AdapterDecoder(todo link).
//
// Reflection on type to create decoders, which is then cached
// Reflection on value is avoided as we can, as the reflect.Value itself will allocate, with following exceptions
// 1. create instance of new value, for example *int will need a int to be allocated
// 2. append to slice, if the existing cap is not enough, allocate will be done using Reflect.New
// 3. assignment to map, both key and value will be reflect.Value
// For a simple struct binding, it will be reflect.Value free and allocation free
type ValDecoder interface {
Decode(ptr unsafe.Pointer, iter *Iterator)
}
// ValEncoder is an internal type registered to cache as needed.
// Don't confuse jsoniter.ValEncoder with json.Encoder.
// For json.Encoder's adapter, refer to jsoniter.AdapterEncoder(todo godoc link).
type ValEncoder interface {
IsEmpty(ptr unsafe.Pointer) bool
Encode(ptr unsafe.Pointer, stream *Stream)
}
type checkIsEmpty interface {
IsEmpty(ptr unsafe.Pointer) bool
}
type ctx struct {
*frozenConfig
prefix string
encoders map[reflect2.Type]ValEncoder
decoders map[reflect2.Type]ValDecoder
}
func (b *ctx) caseSensitive() bool {
if b.frozenConfig == nil {
// default is case-insensitive
return false
}
return b.frozenConfig.caseSensitive
}
func (b *ctx) append(prefix string) *ctx {
return &ctx{
frozenConfig: b.frozenConfig,
prefix: b.prefix + " " + prefix,
encoders: b.encoders,
decoders: b.decoders,
}
}
// ReadVal copy the underlying JSON into go interface, same as json.Unmarshal
func (iter *Iterator) ReadVal(obj interface{}) {
cacheKey := reflect2.RTypeOf(obj)
decoder := iter.cfg.getDecoderFromCache(cacheKey) // 1.先从本地缓存中获取对应的解码器
if decoder == nil {
typ := reflect2.TypeOf(obj) // 2.不存在 则重新创建一个新的解码器
if typ.Kind() != reflect.Ptr {
iter.ReportError("ReadVal", "can only unmarshal into pointer")
return
}
decoder = iter.cfg.DecoderOf(typ) // 创建新的解码器
}
ptr := reflect2.PtrOf(obj) // 3.获取对应的反序列化目标对象的指针
if ptr == nil {
iter.ReportError("ReadVal", "can not read into nil pointer")
return
}
decoder.Decode(ptr, iter) // 4.执行解码 指定对应的解码后对象类型的指针以及iterator
}
// WriteVal copy the go interface into underlying JSON, same as json.Marshal
func (stream *Stream) WriteVal(val interface{}) {
if nil == val {
stream.WriteNil()
return
}
cacheKey := reflect2.RTypeOf(val) // 根据输入的val获取其对应的指针pointer,再根据其返回类型ArbitraryType(任意类型) 进行类型转换到eface(rtype, data) 对应的key等于eface中的rtype的指针uintptr
encoder := stream.cfg.getEncoderFromCache(cacheKey) // 1.先从本地缓存中获取到对应的编码器
if encoder == nil {
typ := reflect2.TypeOf(val) // 2.缓存中不存在对应的编码器 需要重新创建一个 扔把前面根据输入的val获取其对应的eface的rtype的指针, 二次检查;若是仍未有,则会根据反射类型得到其对应的eface的data指针 也是首先从本地缓存中获取,若是没有则再根据其反射类型进行新类型的包装,同时可以指定类型的安全与否
encoder = stream.cfg.EncoderOf(typ)
}
encoder.Encode(reflect2.PtrOf(val), stream) // 3.执行编码 指定编码内容类型的指针 以及 stream
}
func (cfg *frozenConfig) DecoderOf(typ reflect2.Type) ValDecoder { // 创建解码器
cacheKey := typ.RType() // 根据解码目标对象的类型 得到其对应的本地缓存的key
decoder := cfg.getDecoderFromCache(cacheKey) // 获取本地缓存中的解码器decoder
if decoder != nil {
return decoder
}
ctx := &ctx{ // 当缓存中不存在解码器 需要手动创建 指定本地的编码器和解码器缓存
frozenConfig: cfg,
prefix: "",
decoders: map[reflect2.Type]ValDecoder{},
encoders: map[reflect2.Type]ValEncoder{},
}
ptrType := typ.(*reflect2.UnsafePtrType)
decoder = decoderOfType(ctx, ptrType.Elem()) // 构建解码器 根据解码目标类型而非指针
cfg.addDecoderToCache(cacheKey, decoder) // 存放到本地缓存中 便于下一次使用
return decoder
}
func decoderOfType(ctx *ctx, typ reflect2.Type) ValDecoder { // 根据类型解码
decoder := getTypeDecoderFromExtension(ctx, typ)
if decoder != nil {
return decoder
}
decoder = createDecoderOfType(ctx, typ)
for _, extension := range extensions {
decoder = extension.DecorateDecoder(typ, decoder)
}
decoder = ctx.decoderExtension.DecorateDecoder(typ, decoder)
for _, extension := range ctx.extraExtensions {
decoder = extension.DecorateDecoder(typ, decoder)
}
return decoder
}
func createDecoderOfType(ctx *ctx, typ reflect2.Type) ValDecoder {
decoder := ctx.decoders[typ]
if decoder != nil {
return decoder
}
placeholder := &placeholderDecoder{}
ctx.decoders[typ] = placeholder
decoder = _createDecoderOfType(ctx, typ)
placeholder.decoder = decoder
return decoder
}
func _createDecoderOfType(ctx *ctx, typ reflect2.Type) ValDecoder {
decoder := createDecoderOfJsonRawMessage(ctx, typ)
if decoder != nil {
return decoder
}
decoder = createDecoderOfJsonNumber(ctx, typ)
if decoder != nil {
return decoder
}
decoder = createDecoderOfMarshaler(ctx, typ)
if decoder != nil {
return decoder
}
decoder = createDecoderOfAny(ctx, typ)
if decoder != nil {
return decoder
}
decoder = createDecoderOfNative(ctx, typ)
if decoder != nil {
return decoder
}
switch typ.Kind() {
case reflect.Interface:
ifaceType, isIFace := typ.(*reflect2.UnsafeIFaceType)
if isIFace {
return &ifaceDecoder{valType: ifaceType}
}
return &efaceDecoder{}
case reflect.Struct:
return decoderOfStruct(ctx, typ)
case reflect.Array:
return decoderOfArray(ctx, typ)
case reflect.Slice:
return decoderOfSlice(ctx, typ)
case reflect.Map:
return decoderOfMap(ctx, typ)
case reflect.Ptr:
return decoderOfOptional(ctx, typ)
default:
return &lazyErrorDecoder{err: fmt.Errorf("%s%s is unsupported type", ctx.prefix, typ.String())}
}
}
func (cfg *frozenConfig) EncoderOf(typ reflect2.Type) ValEncoder {
cacheKey := typ.RType()
encoder := cfg.getEncoderFromCache(cacheKey)
if encoder != nil {
return encoder
}
ctx := &ctx{
frozenConfig: cfg,
prefix: "",
decoders: map[reflect2.Type]ValDecoder{},
encoders: map[reflect2.Type]ValEncoder{},
}
encoder = encoderOfType(ctx, typ)
if typ.LikePtr() {
encoder = &onePtrEncoder{encoder}
}
cfg.addEncoderToCache(cacheKey, encoder)
return encoder
}
type onePtrEncoder struct {
encoder ValEncoder
}
func (encoder *onePtrEncoder) IsEmpty(ptr unsafe.Pointer) bool {
return encoder.encoder.IsEmpty(unsafe.Pointer(&ptr))
}
func (encoder *onePtrEncoder) Encode(ptr unsafe.Pointer, stream *Stream) {
encoder.encoder.Encode(unsafe.Pointer(&ptr), stream)
}
func encoderOfType(ctx *ctx, typ reflect2.Type) ValEncoder {
encoder := getTypeEncoderFromExtension(ctx, typ)
if encoder != nil {
return encoder
}
encoder = createEncoderOfType(ctx, typ) // 根据类型type创建对应的编码器
for _, extension := range extensions { // 根据扩展来进行编码器包装DecorateEncoder(type, encoder)目前该函数没做任何处理
encoder = extension.DecorateEncoder(typ, encoder)
}
encoder = ctx.encoderExtension.DecorateEncoder(typ, encoder) // 编码器扩展进行编码器包装
for _, extension := range ctx.extraExtensions { // 根据额外扩展来进行编码器包装DecorateEncoder(type, encoder)目前该函数没做任何处理
encoder = extension.DecorateEncoder(typ, encoder)
}
return encoder
}
func createEncoderOfType(ctx *ctx, typ reflect2.Type) ValEncoder {
encoder := ctx.encoders[typ]
if encoder != nil {
return encoder
}
placeholder := &placeholderEncoder{}
ctx.encoders[typ] = placeholder
encoder = _createEncoderOfType(ctx, typ)
placeholder.encoder = encoder
return encoder
}
func _createEncoderOfType(ctx *ctx, typ reflect2.Type) ValEncoder {
encoder := createEncoderOfJsonRawMessage(ctx, typ)
if encoder != nil {
return encoder
}
encoder = createEncoderOfJsonNumber(ctx, typ)
if encoder != nil {
return encoder
}
encoder = createEncoderOfMarshaler(ctx, typ)
if encoder != nil {
return encoder
}
encoder = createEncoderOfAny(ctx, typ)
if encoder != nil {
return encoder
}
encoder = createEncoderOfNative(ctx, typ)
if encoder != nil {
return encoder
}
kind := typ.Kind()
switch kind {
case reflect.Interface:
return &dynamicEncoder{typ}
case reflect.Struct:
return encoderOfStruct(ctx, typ)
case reflect.Array:
return encoderOfArray(ctx, typ)
case reflect.Slice:
return encoderOfSlice(ctx, typ)
case reflect.Map:
return encoderOfMap(ctx, typ)
case reflect.Ptr:
return encoderOfOptional(ctx, typ)
default:
return &lazyErrorEncoder{err: fmt.Errorf("%s%s is unsupported type", ctx.prefix, typ.String())}
}
}
type lazyErrorDecoder struct {
err error
}
func (decoder *lazyErrorDecoder) Decode(ptr unsafe.Pointer, iter *Iterator) {
if iter.WhatIsNext() != NilValue {
if iter.Error == nil {
iter.Error = decoder.err
}
} else {
iter.Skip()
}
}
type lazyErrorEncoder struct {
err error
}
func (encoder *lazyErrorEncoder) Encode(ptr unsafe.Pointer, stream *Stream) {
if ptr == nil {
stream.WriteNil()
} else if stream.Error == nil {
stream.Error = encoder.err
}
}
func (encoder *lazyErrorEncoder) IsEmpty(ptr unsafe.Pointer) bool {
return false
}
type placeholderDecoder struct {
decoder ValDecoder
}
func (decoder *placeholderDecoder) Decode(ptr unsafe.Pointer, iter *Iterator) {
decoder.decoder.Decode(ptr, iter)
}
type placeholderEncoder struct {
encoder ValEncoder
}
func (encoder *placeholderEncoder) Encode(ptr unsafe.Pointer, stream *Stream) {
encoder.encoder.Encode(ptr, stream)
}
func (encoder *placeholderEncoder) IsEmpty(ptr unsafe.Pointer) bool {
return encoder.encoder.IsEmpty(ptr)
}