forked from mongodb/mongo-go-driver
/
struct_codec.go
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/
struct_codec.go
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// Copyright (C) MongoDB, Inc. 2017-present.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
package bsoncodec
import (
"errors"
"fmt"
"reflect"
"strings"
"sync"
"time"
"go.mongodb.org/mongo-driver/bson/bsonoptions"
"go.mongodb.org/mongo-driver/bson/bsonrw"
"go.mongodb.org/mongo-driver/bson/bsontype"
)
var defaultStructCodec = &StructCodec{
cache: make(map[reflect.Type]*structDescription),
parser: DefaultStructTagParser,
}
// Zeroer allows custom struct types to implement a report of zero
// state. All struct types that don't implement Zeroer or where IsZero
// returns false are considered to be not zero.
type Zeroer interface {
IsZero() bool
}
// StructCodec is the Codec used for struct values.
type StructCodec struct {
cache map[reflect.Type]*structDescription
l sync.RWMutex
parser StructTagParser
DecodeZeroStruct bool
DecodeDeepZeroInline bool
EncodeOmitDefaultStruct bool
AllowUnexportedFields bool
}
var _ ValueEncoder = &StructCodec{}
var _ ValueDecoder = &StructCodec{}
// NewStructCodec returns a StructCodec that uses p for struct tag parsing.
func NewStructCodec(p StructTagParser, opts ...*bsonoptions.StructCodecOptions) (*StructCodec, error) {
if p == nil {
return nil, errors.New("a StructTagParser must be provided to NewStructCodec")
}
structOpt := bsonoptions.MergeStructCodecOptions(opts...)
codec := &StructCodec{
cache: make(map[reflect.Type]*structDescription),
parser: p,
}
if structOpt.DecodeZeroStruct != nil {
codec.DecodeZeroStruct = *structOpt.DecodeZeroStruct
}
if structOpt.DecodeDeepZeroInline != nil {
codec.DecodeDeepZeroInline = *structOpt.DecodeDeepZeroInline
}
if structOpt.EncodeOmitDefaultStruct != nil {
codec.EncodeOmitDefaultStruct = *structOpt.EncodeOmitDefaultStruct
}
if structOpt.AllowUnexportedFields != nil {
codec.AllowUnexportedFields = *structOpt.AllowUnexportedFields
}
return codec, nil
}
// EncodeValue handles encoding generic struct types.
func (sc *StructCodec) EncodeValue(r EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
if !val.IsValid() || val.Kind() != reflect.Struct {
return ValueEncoderError{Name: "StructCodec.EncodeValue", Kinds: []reflect.Kind{reflect.Struct}, Received: val}
}
sd, err := sc.describeStruct(r.Registry, val.Type())
if err != nil {
return err
}
dw, err := vw.WriteDocument()
if err != nil {
return err
}
var rv reflect.Value
for _, desc := range sd.fl {
if desc.inline == nil {
rv = val.Field(desc.idx)
} else {
rv, err = fieldByIndexErr(val, desc.inline)
if err != nil {
continue
}
}
desc.encoder, rv, err = defaultValueEncoders.lookupElementEncoder(r, desc.encoder, rv)
if err != nil && err != errInvalidValue {
return err
}
if err == errInvalidValue {
if desc.omitEmpty {
continue
}
vw2, err := dw.WriteDocumentElement(desc.name)
if err != nil {
return err
}
err = vw2.WriteNull()
if err != nil {
return err
}
continue
}
if desc.encoder == nil {
return ErrNoEncoder{Type: rv.Type()}
}
encoder := desc.encoder
var isZero bool
rvInterface := rv.Interface()
if cz, ok := encoder.(CodecZeroer); ok {
isZero = cz.IsTypeZero(rvInterface)
} else if rv.Kind() == reflect.Interface {
// sc.isZero will not treat an interface rv as an interface, so we need to check for the zero interface separately.
isZero = rv.IsNil()
} else {
isZero = sc.isZero(rvInterface)
}
if desc.omitEmpty && isZero {
continue
}
vw2, err := dw.WriteDocumentElement(desc.name)
if err != nil {
return err
}
ectx := EncodeContext{Registry: r.Registry, MinSize: desc.minSize}
err = encoder.EncodeValue(ectx, vw2, rv)
if err != nil {
return err
}
}
if sd.inlineMap >= 0 {
rv := val.Field(sd.inlineMap)
collisionFn := func(key string) bool {
_, exists := sd.fm[key]
return exists
}
return defaultMapCodec.mapEncodeValue(r, dw, rv, collisionFn)
}
return dw.WriteDocumentEnd()
}
// DecodeValue implements the Codec interface.
// By default, map types in val will not be cleared. If a map has existing key/value pairs, it will be extended with the new ones from vr.
// For slices, the decoder will set the length of the slice to zero and append all elements. The underlying array will not be cleared.
func (sc *StructCodec) DecodeValue(r DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
if !val.CanSet() || val.Kind() != reflect.Struct {
return ValueDecoderError{Name: "StructCodec.DecodeValue", Kinds: []reflect.Kind{reflect.Struct}, Received: val}
}
switch vr.Type() {
case bsontype.Type(0), bsontype.EmbeddedDocument:
default:
return fmt.Errorf("cannot decode %v into a %s", vr.Type(), val.Type())
}
sd, err := sc.describeStruct(r.Registry, val.Type())
if err != nil {
return err
}
if sc.DecodeZeroStruct {
val.Set(reflect.Zero(val.Type()))
}
if sc.DecodeDeepZeroInline && sd.inline {
val.Set(deepZero(val.Type()))
}
var decoder ValueDecoder
var inlineMap reflect.Value
if sd.inlineMap >= 0 {
inlineMap = val.Field(sd.inlineMap)
decoder, err = r.LookupDecoder(inlineMap.Type().Elem())
if err != nil {
return err
}
}
dr, err := vr.ReadDocument()
if err != nil {
return err
}
for {
name, vr, err := dr.ReadElement()
if err == bsonrw.ErrEOD {
break
}
if err != nil {
return err
}
fd, exists := sd.fm[name]
if !exists {
// if the original name isn't found in the struct description, try again with the name in lowercase
// this could match if a BSON tag isn't specified because by default, describeStruct lowercases all field
// names
fd, exists = sd.fm[strings.ToLower(name)]
}
if !exists {
if sd.inlineMap < 0 {
// The encoding/json package requires a flag to return on error for non-existent fields.
// This functionality seems appropriate for the struct codec.
err = vr.Skip()
if err != nil {
return err
}
continue
}
if inlineMap.IsNil() {
inlineMap.Set(reflect.MakeMap(inlineMap.Type()))
}
elem := reflect.New(inlineMap.Type().Elem()).Elem()
err = decoder.DecodeValue(r, vr, elem)
if err != nil {
return err
}
inlineMap.SetMapIndex(reflect.ValueOf(name), elem)
continue
}
var field reflect.Value
if fd.inline == nil {
field = val.Field(fd.idx)
} else {
field, err = getInlineField(val, fd.inline)
if err != nil {
return err
}
}
if !field.CanSet() { // Being settable is a super set of being addressable.
return fmt.Errorf("cannot decode element '%s' into field %v; it is not settable", name, field)
}
if field.Kind() == reflect.Ptr && field.IsNil() {
field.Set(reflect.New(field.Type().Elem()))
}
field = field.Addr()
dctx := DecodeContext{Registry: r.Registry, Truncate: fd.truncate || r.Truncate}
if fd.decoder == nil {
return ErrNoDecoder{Type: field.Elem().Type()}
}
if decoder, ok := fd.decoder.(ValueDecoder); ok {
err = decoder.DecodeValue(dctx, vr, field.Elem())
if err != nil {
return err
}
continue
}
err = fd.decoder.DecodeValue(dctx, vr, field)
if err != nil {
return err
}
}
return nil
}
func (sc *StructCodec) isZero(i interface{}) bool {
v := reflect.ValueOf(i)
// check the value validity
if !v.IsValid() {
return true
}
if z, ok := v.Interface().(Zeroer); ok && (v.Kind() != reflect.Ptr || !v.IsNil()) {
return z.IsZero()
}
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()
case reflect.Struct:
if sc.EncodeOmitDefaultStruct {
vt := v.Type()
if vt == tTime {
return v.Interface().(time.Time).IsZero()
}
for i := 0; i < v.NumField(); i++ {
if vt.Field(i).PkgPath != "" && !vt.Field(i).Anonymous {
continue // Private field
}
fld := v.Field(i)
if !sc.isZero(fld.Interface()) {
return false
}
}
return true
}
}
return false
}
type structDescription struct {
fm map[string]fieldDescription
fl []fieldDescription
inlineMap int
inline bool
}
type fieldDescription struct {
name string
idx int
omitEmpty bool
minSize bool
truncate bool
inline []int
encoder ValueEncoder
decoder ValueDecoder
}
func (sc *StructCodec) describeStruct(r *Registry, t reflect.Type) (*structDescription, error) {
// We need to analyze the struct, including getting the tags, collecting
// information about inlining, and create a map of the field name to the field.
sc.l.RLock()
ds, exists := sc.cache[t]
sc.l.RUnlock()
if exists {
return ds, nil
}
numFields := t.NumField()
sd := &structDescription{
fm: make(map[string]fieldDescription, numFields),
fl: make([]fieldDescription, 0, numFields),
inlineMap: -1,
}
for i := 0; i < numFields; i++ {
sf := t.Field(i)
if sf.PkgPath != "" && (!sc.AllowUnexportedFields || !sf.Anonymous) {
// field is private or unexported fields aren't allowed, ignore
continue
}
sfType := sf.Type
encoder, err := r.LookupEncoder(sfType)
if err != nil {
encoder = nil
}
decoder, err := r.LookupDecoder(sfType)
if err != nil {
decoder = nil
}
description := fieldDescription{idx: i, encoder: encoder, decoder: decoder}
stags, err := sc.parser.ParseStructTags(sf)
if err != nil {
return nil, err
}
if stags.Skip {
continue
}
description.name = stags.Name
description.omitEmpty = stags.OmitEmpty
description.minSize = stags.MinSize
description.truncate = stags.Truncate
if stags.Inline {
sd.inline = true
switch sfType.Kind() {
case reflect.Map:
if sd.inlineMap >= 0 {
return nil, errors.New("(struct " + t.String() + ") multiple inline maps")
}
if sfType.Key() != tString {
return nil, errors.New("(struct " + t.String() + ") inline map must have a string keys")
}
sd.inlineMap = description.idx
case reflect.Ptr:
sfType = sfType.Elem()
if sfType.Kind() != reflect.Struct {
return nil, fmt.Errorf("(struct %s) inline fields must be a struct, a struct pointer, or a map", t.String())
}
fallthrough
case reflect.Struct:
inlinesf, err := sc.describeStruct(r, sfType)
if err != nil {
return nil, err
}
for _, fd := range inlinesf.fl {
if _, exists := sd.fm[fd.name]; exists {
return nil, fmt.Errorf("(struct %s) duplicated key %s", t.String(), fd.name)
}
if fd.inline == nil {
fd.inline = []int{i, fd.idx}
} else {
fd.inline = append([]int{i}, fd.inline...)
}
sd.fm[fd.name] = fd
sd.fl = append(sd.fl, fd)
}
default:
return nil, fmt.Errorf("(struct %s) inline fields must be a struct, a struct pointer, or a map", t.String())
}
continue
}
if _, exists := sd.fm[description.name]; exists {
return nil, fmt.Errorf("struct %s) duplicated key %s", t.String(), description.name)
}
sd.fm[description.name] = description
sd.fl = append(sd.fl, description)
}
sc.l.Lock()
sc.cache[t] = sd
sc.l.Unlock()
return sd, nil
}
func fieldByIndexErr(v reflect.Value, index []int) (result reflect.Value, err error) {
defer func() {
if recovered := recover(); recovered != nil {
switch r := recovered.(type) {
case string:
err = fmt.Errorf("%s", r)
case error:
err = r
}
}
}()
result = v.FieldByIndex(index)
return
}
func getInlineField(val reflect.Value, index []int) (reflect.Value, error) {
field, err := fieldByIndexErr(val, index)
if err == nil {
return field, nil
}
// if parent of this element doesn't exist, fix its parent
inlineParent := index[:len(index)-1]
var fParent reflect.Value
if fParent, err = fieldByIndexErr(val, inlineParent); err != nil {
fParent, err = getInlineField(val, inlineParent)
if err != nil {
return fParent, err
}
}
fParent.Set(reflect.New(fParent.Type().Elem()))
return fieldByIndexErr(val, index)
}
// DeepZero returns recursive zero object
func deepZero(st reflect.Type) (result reflect.Value) {
result = reflect.Indirect(reflect.New(st))
if result.Kind() == reflect.Struct {
for i := 0; i < result.NumField(); i++ {
if f := result.Field(i); f.Kind() == reflect.Ptr {
if f.CanInterface() {
if ft := reflect.TypeOf(f.Interface()); ft.Elem().Kind() == reflect.Struct {
result.Field(i).Set(recursivePointerTo(deepZero(ft.Elem())))
}
}
}
}
}
return
}
// recursivePointerTo calls reflect.New(v.Type) but recursively for its fields inside
func recursivePointerTo(v reflect.Value) reflect.Value {
v = reflect.Indirect(v)
result := reflect.New(v.Type())
if v.Kind() == reflect.Struct {
for i := 0; i < v.NumField(); i++ {
if f := v.Field(i); f.Kind() == reflect.Ptr {
if f.Elem().Kind() == reflect.Struct {
result.Elem().Field(i).Set(recursivePointerTo(f))
}
}
}
}
return result
}