537 lines
13 KiB
Go
537 lines
13 KiB
Go
// Copyright (C) MongoDB, Inc. 2017-present.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may
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// not use this file except in compliance with the License. You may obtain
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// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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package bsoncodec
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import (
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"errors"
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"fmt"
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"reflect"
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"strings"
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"sync"
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"time"
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"go.mongodb.org/mongo-driver/bson/bsonoptions"
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"go.mongodb.org/mongo-driver/bson/bsonrw"
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"go.mongodb.org/mongo-driver/bson/bsontype"
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)
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var defaultStructCodec = &StructCodec{
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cache: make(map[reflect.Type]*structDescription),
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parser: DefaultStructTagParser,
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}
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// Zeroer allows custom struct types to implement a report of zero
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// state. All struct types that don't implement Zeroer or where IsZero
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// returns false are considered to be not zero.
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type Zeroer interface {
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IsZero() bool
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}
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// StructCodec is the Codec used for struct values.
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type StructCodec struct {
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cache map[reflect.Type]*structDescription
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l sync.RWMutex
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parser StructTagParser
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DecodeZeroStruct bool
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DecodeDeepZeroInline bool
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EncodeOmitDefaultStruct bool
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AllowUnexportedFields bool
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}
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var _ ValueEncoder = &StructCodec{}
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var _ ValueDecoder = &StructCodec{}
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// NewStructCodec returns a StructCodec that uses p for struct tag parsing.
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func NewStructCodec(p StructTagParser, opts ...*bsonoptions.StructCodecOptions) (*StructCodec, error) {
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if p == nil {
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return nil, errors.New("a StructTagParser must be provided to NewStructCodec")
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}
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structOpt := bsonoptions.MergeStructCodecOptions(opts...)
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codec := &StructCodec{
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cache: make(map[reflect.Type]*structDescription),
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parser: p,
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}
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if structOpt.DecodeZeroStruct != nil {
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codec.DecodeZeroStruct = *structOpt.DecodeZeroStruct
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}
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if structOpt.DecodeDeepZeroInline != nil {
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codec.DecodeDeepZeroInline = *structOpt.DecodeDeepZeroInline
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}
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if structOpt.EncodeOmitDefaultStruct != nil {
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codec.EncodeOmitDefaultStruct = *structOpt.EncodeOmitDefaultStruct
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}
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if structOpt.AllowUnexportedFields != nil {
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codec.AllowUnexportedFields = *structOpt.AllowUnexportedFields
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}
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return codec, nil
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}
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// EncodeValue handles encoding generic struct types.
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func (sc *StructCodec) EncodeValue(r EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
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if !val.IsValid() || val.Kind() != reflect.Struct {
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return ValueEncoderError{Name: "StructCodec.EncodeValue", Kinds: []reflect.Kind{reflect.Struct}, Received: val}
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}
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sd, err := sc.describeStruct(r.Registry, val.Type())
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if err != nil {
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return err
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}
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dw, err := vw.WriteDocument()
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if err != nil {
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return err
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}
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var rv reflect.Value
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for _, desc := range sd.fl {
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if desc.inline == nil {
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rv = val.Field(desc.idx)
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} else {
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rv, err = fieldByIndexErr(val, desc.inline)
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if err != nil {
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continue
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}
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}
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desc.encoder, rv, err = defaultValueEncoders.lookupElementEncoder(r, desc.encoder, rv)
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if err != nil && err != errInvalidValue {
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return err
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}
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if err == errInvalidValue {
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if desc.omitEmpty {
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continue
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}
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vw2, err := dw.WriteDocumentElement(desc.name)
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if err != nil {
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return err
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}
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err = vw2.WriteNull()
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if err != nil {
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return err
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}
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continue
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}
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if desc.encoder == nil {
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return ErrNoEncoder{Type: rv.Type()}
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}
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encoder := desc.encoder
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var isZero bool
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rvInterface := rv.Interface()
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if cz, ok := encoder.(CodecZeroer); ok {
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isZero = cz.IsTypeZero(rvInterface)
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} else if rv.Kind() == reflect.Interface {
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// sc.isZero will not treat an interface rv as an interface, so we need to check for the zero interface separately.
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isZero = rv.IsNil()
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} else {
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isZero = sc.isZero(rvInterface)
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}
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if desc.omitEmpty && isZero {
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continue
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}
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vw2, err := dw.WriteDocumentElement(desc.name)
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if err != nil {
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return err
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}
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ectx := EncodeContext{Registry: r.Registry, MinSize: desc.minSize}
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err = encoder.EncodeValue(ectx, vw2, rv)
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if err != nil {
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return err
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}
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}
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if sd.inlineMap >= 0 {
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rv := val.Field(sd.inlineMap)
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collisionFn := func(key string) bool {
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_, exists := sd.fm[key]
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return exists
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}
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return defaultMapCodec.mapEncodeValue(r, dw, rv, collisionFn)
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}
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return dw.WriteDocumentEnd()
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}
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// DecodeValue implements the Codec interface.
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// 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.
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// For slices, the decoder will set the length of the slice to zero and append all elements. The underlying array will not be cleared.
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func (sc *StructCodec) DecodeValue(r DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
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if !val.CanSet() || val.Kind() != reflect.Struct {
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return ValueDecoderError{Name: "StructCodec.DecodeValue", Kinds: []reflect.Kind{reflect.Struct}, Received: val}
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}
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switch vrType := vr.Type(); vrType {
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case bsontype.Type(0), bsontype.EmbeddedDocument:
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case bsontype.Null:
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if err := vr.ReadNull(); err != nil {
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return err
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}
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val.Set(reflect.Zero(val.Type()))
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return nil
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default:
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return fmt.Errorf("cannot decode %v into a %s", vrType, val.Type())
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}
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sd, err := sc.describeStruct(r.Registry, val.Type())
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if err != nil {
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return err
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}
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if sc.DecodeZeroStruct {
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val.Set(reflect.Zero(val.Type()))
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}
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if sc.DecodeDeepZeroInline && sd.inline {
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val.Set(deepZero(val.Type()))
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}
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var decoder ValueDecoder
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var inlineMap reflect.Value
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if sd.inlineMap >= 0 {
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inlineMap = val.Field(sd.inlineMap)
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decoder, err = r.LookupDecoder(inlineMap.Type().Elem())
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if err != nil {
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return err
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}
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}
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dr, err := vr.ReadDocument()
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if err != nil {
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return err
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}
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for {
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name, vr, err := dr.ReadElement()
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if err == bsonrw.ErrEOD {
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break
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}
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if err != nil {
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return err
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}
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fd, exists := sd.fm[name]
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if !exists {
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// if the original name isn't found in the struct description, try again with the name in lowercase
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// this could match if a BSON tag isn't specified because by default, describeStruct lowercases all field
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// names
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fd, exists = sd.fm[strings.ToLower(name)]
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}
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if !exists {
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if sd.inlineMap < 0 {
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// The encoding/json package requires a flag to return on error for non-existent fields.
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// This functionality seems appropriate for the struct codec.
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err = vr.Skip()
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if err != nil {
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return err
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}
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continue
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}
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if inlineMap.IsNil() {
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inlineMap.Set(reflect.MakeMap(inlineMap.Type()))
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}
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elem := reflect.New(inlineMap.Type().Elem()).Elem()
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r.Ancestor = inlineMap.Type()
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err = decoder.DecodeValue(r, vr, elem)
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if err != nil {
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return err
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}
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inlineMap.SetMapIndex(reflect.ValueOf(name), elem)
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continue
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}
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var field reflect.Value
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if fd.inline == nil {
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field = val.Field(fd.idx)
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} else {
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field, err = getInlineField(val, fd.inline)
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if err != nil {
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return err
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}
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}
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if !field.CanSet() { // Being settable is a super set of being addressable.
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return fmt.Errorf("cannot decode element '%s' into field %v; it is not settable", name, field)
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}
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if field.Kind() == reflect.Ptr && field.IsNil() {
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field.Set(reflect.New(field.Type().Elem()))
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}
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field = field.Addr()
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dctx := DecodeContext{Registry: r.Registry, Truncate: fd.truncate || r.Truncate}
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if fd.decoder == nil {
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return ErrNoDecoder{Type: field.Elem().Type()}
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}
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if decoder, ok := fd.decoder.(ValueDecoder); ok {
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err = decoder.DecodeValue(dctx, vr, field.Elem())
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if err != nil {
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return err
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}
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continue
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}
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err = fd.decoder.DecodeValue(dctx, vr, field)
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if err != nil {
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return err
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}
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}
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return nil
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}
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func (sc *StructCodec) isZero(i interface{}) bool {
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v := reflect.ValueOf(i)
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// check the value validity
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if !v.IsValid() {
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return true
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}
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if z, ok := v.Interface().(Zeroer); ok && (v.Kind() != reflect.Ptr || !v.IsNil()) {
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return z.IsZero()
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}
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switch v.Kind() {
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case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
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return v.Len() == 0
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case reflect.Bool:
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return !v.Bool()
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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return v.Int() == 0
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return v.Uint() == 0
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case reflect.Float32, reflect.Float64:
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return v.Float() == 0
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case reflect.Interface, reflect.Ptr:
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return v.IsNil()
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case reflect.Struct:
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if sc.EncodeOmitDefaultStruct {
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vt := v.Type()
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if vt == tTime {
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return v.Interface().(time.Time).IsZero()
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}
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for i := 0; i < v.NumField(); i++ {
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if vt.Field(i).PkgPath != "" && !vt.Field(i).Anonymous {
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continue // Private field
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}
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fld := v.Field(i)
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if !sc.isZero(fld.Interface()) {
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return false
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}
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}
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return true
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}
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}
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return false
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}
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type structDescription struct {
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fm map[string]fieldDescription
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fl []fieldDescription
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inlineMap int
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inline bool
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}
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type fieldDescription struct {
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name string
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idx int
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omitEmpty bool
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minSize bool
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truncate bool
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inline []int
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encoder ValueEncoder
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decoder ValueDecoder
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}
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func (sc *StructCodec) describeStruct(r *Registry, t reflect.Type) (*structDescription, error) {
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// We need to analyze the struct, including getting the tags, collecting
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// information about inlining, and create a map of the field name to the field.
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sc.l.RLock()
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ds, exists := sc.cache[t]
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sc.l.RUnlock()
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if exists {
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return ds, nil
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}
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numFields := t.NumField()
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sd := &structDescription{
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fm: make(map[string]fieldDescription, numFields),
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fl: make([]fieldDescription, 0, numFields),
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inlineMap: -1,
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}
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for i := 0; i < numFields; i++ {
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sf := t.Field(i)
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if sf.PkgPath != "" && (!sc.AllowUnexportedFields || !sf.Anonymous) {
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// field is private or unexported fields aren't allowed, ignore
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continue
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}
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sfType := sf.Type
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encoder, err := r.LookupEncoder(sfType)
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if err != nil {
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encoder = nil
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}
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decoder, err := r.LookupDecoder(sfType)
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if err != nil {
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decoder = nil
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}
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description := fieldDescription{idx: i, encoder: encoder, decoder: decoder}
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stags, err := sc.parser.ParseStructTags(sf)
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if err != nil {
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return nil, err
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}
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if stags.Skip {
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continue
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}
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description.name = stags.Name
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description.omitEmpty = stags.OmitEmpty
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description.minSize = stags.MinSize
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description.truncate = stags.Truncate
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if stags.Inline {
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sd.inline = true
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switch sfType.Kind() {
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case reflect.Map:
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if sd.inlineMap >= 0 {
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return nil, errors.New("(struct " + t.String() + ") multiple inline maps")
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}
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if sfType.Key() != tString {
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return nil, errors.New("(struct " + t.String() + ") inline map must have a string keys")
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}
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sd.inlineMap = description.idx
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case reflect.Ptr:
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sfType = sfType.Elem()
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if sfType.Kind() != reflect.Struct {
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return nil, fmt.Errorf("(struct %s) inline fields must be a struct, a struct pointer, or a map", t.String())
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}
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fallthrough
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case reflect.Struct:
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inlinesf, err := sc.describeStruct(r, sfType)
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if err != nil {
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return nil, err
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}
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for _, fd := range inlinesf.fl {
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if _, exists := sd.fm[fd.name]; exists {
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return nil, fmt.Errorf("(struct %s) duplicated key %s", t.String(), fd.name)
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}
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if fd.inline == nil {
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fd.inline = []int{i, fd.idx}
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} else {
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fd.inline = append([]int{i}, fd.inline...)
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}
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sd.fm[fd.name] = fd
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sd.fl = append(sd.fl, fd)
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}
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default:
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return nil, fmt.Errorf("(struct %s) inline fields must be a struct, a struct pointer, or a map", t.String())
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}
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continue
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}
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if _, exists := sd.fm[description.name]; exists {
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return nil, fmt.Errorf("struct %s) duplicated key %s", t.String(), description.name)
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}
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sd.fm[description.name] = description
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sd.fl = append(sd.fl, description)
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}
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sc.l.Lock()
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sc.cache[t] = sd
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sc.l.Unlock()
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return sd, nil
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}
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func fieldByIndexErr(v reflect.Value, index []int) (result reflect.Value, err error) {
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defer func() {
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if recovered := recover(); recovered != nil {
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switch r := recovered.(type) {
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case string:
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err = fmt.Errorf("%s", r)
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case error:
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err = r
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}
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}
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}()
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result = v.FieldByIndex(index)
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return
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}
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func getInlineField(val reflect.Value, index []int) (reflect.Value, error) {
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field, err := fieldByIndexErr(val, index)
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if err == nil {
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return field, nil
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}
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// if parent of this element doesn't exist, fix its parent
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inlineParent := index[:len(index)-1]
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var fParent reflect.Value
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if fParent, err = fieldByIndexErr(val, inlineParent); err != nil {
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fParent, err = getInlineField(val, inlineParent)
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if err != nil {
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return fParent, err
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}
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}
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fParent.Set(reflect.New(fParent.Type().Elem()))
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return fieldByIndexErr(val, index)
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}
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// DeepZero returns recursive zero object
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func deepZero(st reflect.Type) (result reflect.Value) {
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result = reflect.Indirect(reflect.New(st))
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if result.Kind() == reflect.Struct {
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for i := 0; i < result.NumField(); i++ {
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if f := result.Field(i); f.Kind() == reflect.Ptr {
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if f.CanInterface() {
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if ft := reflect.TypeOf(f.Interface()); ft.Elem().Kind() == reflect.Struct {
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result.Field(i).Set(recursivePointerTo(deepZero(ft.Elem())))
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}
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}
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}
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}
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}
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return
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}
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// recursivePointerTo calls reflect.New(v.Type) but recursively for its fields inside
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func recursivePointerTo(v reflect.Value) reflect.Value {
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v = reflect.Indirect(v)
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result := reflect.New(v.Type())
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if v.Kind() == reflect.Struct {
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for i := 0; i < v.NumField(); i++ {
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if f := v.Field(i); f.Kind() == reflect.Ptr {
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if f.Elem().Kind() == reflect.Struct {
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result.Elem().Field(i).Set(recursivePointerTo(f))
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}
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}
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}
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}
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return result
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}
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