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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"
"sync"
"go.mongodb.org/mongo-driver/bson/bsontype"
)
// ErrNilType is returned when nil is passed to either LookupEncoder or LookupDecoder.
var ErrNilType = errors.New("cannot perform a decoder lookup on <nil>")
// ErrNotPointer is returned when a non-pointer type is provided to LookupDecoder.
var ErrNotPointer = errors.New("non-pointer provided to LookupDecoder")
// ErrNoEncoder is returned when there wasn't an encoder available for a type.
type ErrNoEncoder struct {
Type reflect.Type
}
func (ene ErrNoEncoder) Error() string {
if ene.Type == nil {
return "no encoder found for <nil>"
}
return "no encoder found for " + ene.Type.String()
}
// ErrNoDecoder is returned when there wasn't a decoder available for a type.
type ErrNoDecoder struct {
Type reflect.Type
}
func (end ErrNoDecoder) Error() string {
return "no decoder found for " + end.Type.String()
}
// ErrNoTypeMapEntry is returned when there wasn't a type available for the provided BSON type.
type ErrNoTypeMapEntry struct {
Type bsontype.Type
}
func (entme ErrNoTypeMapEntry) Error() string {
return "no type map entry found for " + entme.Type.String()
}
// ErrNotInterface is returned when the provided type is not an interface.
var ErrNotInterface = errors.New("The provided type is not an interface")
// A RegistryBuilder is used to build a Registry. This type is not goroutine
// safe.
type RegistryBuilder struct {
typeEncoders map[reflect.Type]ValueEncoder
interfaceEncoders []interfaceValueEncoder
kindEncoders map[reflect.Kind]ValueEncoder
typeDecoders map[reflect.Type]ValueDecoder
interfaceDecoders []interfaceValueDecoder
kindDecoders map[reflect.Kind]ValueDecoder
typeMap map[bsontype.Type]reflect.Type
}
// A Registry is used to store and retrieve codecs for types and interfaces. This type is the main
// typed passed around and Encoders and Decoders are constructed from it.
type Registry struct {
typeEncoders map[reflect.Type]ValueEncoder
typeDecoders map[reflect.Type]ValueDecoder
interfaceEncoders []interfaceValueEncoder
interfaceDecoders []interfaceValueDecoder
kindEncoders map[reflect.Kind]ValueEncoder
kindDecoders map[reflect.Kind]ValueDecoder
typeMap map[bsontype.Type]reflect.Type
mu sync.RWMutex
}
// NewRegistryBuilder creates a new empty RegistryBuilder.
func NewRegistryBuilder() *RegistryBuilder {
return &RegistryBuilder{
typeEncoders: make(map[reflect.Type]ValueEncoder),
typeDecoders: make(map[reflect.Type]ValueDecoder),
interfaceEncoders: make([]interfaceValueEncoder, 0),
interfaceDecoders: make([]interfaceValueDecoder, 0),
kindEncoders: make(map[reflect.Kind]ValueEncoder),
kindDecoders: make(map[reflect.Kind]ValueDecoder),
typeMap: make(map[bsontype.Type]reflect.Type),
}
}
func buildDefaultRegistry() *Registry {
rb := NewRegistryBuilder()
defaultValueEncoders.RegisterDefaultEncoders(rb)
defaultValueDecoders.RegisterDefaultDecoders(rb)
return rb.Build()
}
// RegisterCodec will register the provided ValueCodec for the provided type.
func (rb *RegistryBuilder) RegisterCodec(t reflect.Type, codec ValueCodec) *RegistryBuilder {
rb.RegisterTypeEncoder(t, codec)
rb.RegisterTypeDecoder(t, codec)
return rb
}
// RegisterTypeEncoder will register the provided ValueEncoder for the provided type.
//
// The type will be used directly, so an encoder can be registered for a type and a different encoder can be registered
// for a pointer to that type.
//
// If the given type is an interface, the encoder will be called when marshalling a type that is that interface. It
// will not be called when marshalling a non-interface type that implements the interface.
func (rb *RegistryBuilder) RegisterTypeEncoder(t reflect.Type, enc ValueEncoder) *RegistryBuilder {
rb.typeEncoders[t] = enc
return rb
}
// RegisterHookEncoder will register an encoder for the provided interface type t. This encoder will be called when
// marshalling a type if the type implements t or a pointer to the type implements t. If the provided type is not
// an interface (i.e. t.Kind() != reflect.Interface), this method will panic.
func (rb *RegistryBuilder) RegisterHookEncoder(t reflect.Type, enc ValueEncoder) *RegistryBuilder {
if t.Kind() != reflect.Interface {
panicStr := fmt.Sprintf("RegisterHookEncoder expects a type with kind reflect.Interface, "+
"got type %s with kind %s", t, t.Kind())
panic(panicStr)
}
for idx, encoder := range rb.interfaceEncoders {
if encoder.i == t {
rb.interfaceEncoders[idx].ve = enc
return rb
}
}
rb.interfaceEncoders = append(rb.interfaceEncoders, interfaceValueEncoder{i: t, ve: enc})
return rb
}
// RegisterTypeDecoder will register the provided ValueDecoder for the provided type.
//
// The type will be used directly, so a decoder can be registered for a type and a different decoder can be registered
// for a pointer to that type.
//
// If the given type is an interface, the decoder will be called when unmarshalling into a type that is that interface.
// It will not be called when unmarshalling into a non-interface type that implements the interface.
func (rb *RegistryBuilder) RegisterTypeDecoder(t reflect.Type, dec ValueDecoder) *RegistryBuilder {
rb.typeDecoders[t] = dec
return rb
}
// RegisterHookDecoder will register an decoder for the provided interface type t. This decoder will be called when
// unmarshalling into a type if the type implements t or a pointer to the type implements t. If the provided type is not
// an interface (i.e. t.Kind() != reflect.Interface), this method will panic.
func (rb *RegistryBuilder) RegisterHookDecoder(t reflect.Type, dec ValueDecoder) *RegistryBuilder {
if t.Kind() != reflect.Interface {
panicStr := fmt.Sprintf("RegisterHookDecoder expects a type with kind reflect.Interface, "+
"got type %s with kind %s", t, t.Kind())
panic(panicStr)
}
for idx, decoder := range rb.interfaceDecoders {
if decoder.i == t {
rb.interfaceDecoders[idx].vd = dec
return rb
}
}
rb.interfaceDecoders = append(rb.interfaceDecoders, interfaceValueDecoder{i: t, vd: dec})
return rb
}
// RegisterEncoder registers the provided type and encoder pair.
//
// Deprecated: Use RegisterTypeEncoder or RegisterHookEncoder instead.
func (rb *RegistryBuilder) RegisterEncoder(t reflect.Type, enc ValueEncoder) *RegistryBuilder {
if t == tEmpty {
rb.typeEncoders[t] = enc
return rb
}
switch t.Kind() {
case reflect.Interface:
for idx, ir := range rb.interfaceEncoders {
if ir.i == t {
rb.interfaceEncoders[idx].ve = enc
return rb
}
}
rb.interfaceEncoders = append(rb.interfaceEncoders, interfaceValueEncoder{i: t, ve: enc})
default:
rb.typeEncoders[t] = enc
}
return rb
}
// RegisterDecoder registers the provided type and decoder pair.
//
// Deprecated: Use RegisterTypeDecoder or RegisterHookDecoder instead.
func (rb *RegistryBuilder) RegisterDecoder(t reflect.Type, dec ValueDecoder) *RegistryBuilder {
if t == nil {
rb.typeDecoders[nil] = dec
return rb
}
if t == tEmpty {
rb.typeDecoders[t] = dec
return rb
}
switch t.Kind() {
case reflect.Interface:
for idx, ir := range rb.interfaceDecoders {
if ir.i == t {
rb.interfaceDecoders[idx].vd = dec
return rb
}
}
rb.interfaceDecoders = append(rb.interfaceDecoders, interfaceValueDecoder{i: t, vd: dec})
default:
rb.typeDecoders[t] = dec
}
return rb
}
// RegisterDefaultEncoder will registr the provided ValueEncoder to the provided
// kind.
func (rb *RegistryBuilder) RegisterDefaultEncoder(kind reflect.Kind, enc ValueEncoder) *RegistryBuilder {
rb.kindEncoders[kind] = enc
return rb
}
// RegisterDefaultDecoder will register the provided ValueDecoder to the
// provided kind.
func (rb *RegistryBuilder) RegisterDefaultDecoder(kind reflect.Kind, dec ValueDecoder) *RegistryBuilder {
rb.kindDecoders[kind] = dec
return rb
}
// RegisterTypeMapEntry will register the provided type to the BSON type. The primary usage for this
// mapping is decoding situations where an empty interface is used and a default type needs to be
// created and decoded into.
//
// By default, BSON documents will decode into interface{} values as bson.D. To change the default type for BSON
// documents, a type map entry for bsontype.EmbeddedDocument should be registered. For example, to force BSON documents
// to decode to bson.Raw, use the following code:
// rb.RegisterTypeMapEntry(bsontype.EmbeddedDocument, reflect.TypeOf(bson.Raw{}))
func (rb *RegistryBuilder) RegisterTypeMapEntry(bt bsontype.Type, rt reflect.Type) *RegistryBuilder {
rb.typeMap[bt] = rt
return rb
}
// Build creates a Registry from the current state of this RegistryBuilder.
func (rb *RegistryBuilder) Build() *Registry {
registry := new(Registry)
registry.typeEncoders = make(map[reflect.Type]ValueEncoder)
for t, enc := range rb.typeEncoders {
registry.typeEncoders[t] = enc
}
registry.typeDecoders = make(map[reflect.Type]ValueDecoder)
for t, dec := range rb.typeDecoders {
registry.typeDecoders[t] = dec
}
registry.interfaceEncoders = make([]interfaceValueEncoder, len(rb.interfaceEncoders))
copy(registry.interfaceEncoders, rb.interfaceEncoders)
registry.interfaceDecoders = make([]interfaceValueDecoder, len(rb.interfaceDecoders))
copy(registry.interfaceDecoders, rb.interfaceDecoders)
registry.kindEncoders = make(map[reflect.Kind]ValueEncoder)
for kind, enc := range rb.kindEncoders {
registry.kindEncoders[kind] = enc
}
registry.kindDecoders = make(map[reflect.Kind]ValueDecoder)
for kind, dec := range rb.kindDecoders {
registry.kindDecoders[kind] = dec
}
registry.typeMap = make(map[bsontype.Type]reflect.Type)
for bt, rt := range rb.typeMap {
registry.typeMap[bt] = rt
}
return registry
}
// LookupEncoder inspects the registry for an encoder for the given type. The lookup precendence works as follows:
//
// 1. An encoder registered for the exact type. If the given type represents an interface, an encoder registered using
// RegisterTypeEncoder for the interface will be selected.
//
// 2. An encoder registered using RegisterHookEncoder for an interface implemented by the type or by a pointer to the
// type.
//
// 3. An encoder registered for the reflect.Kind of the value.
//
// If no encoder is found, an error of type ErrNoEncoder is returned.
func (r *Registry) LookupEncoder(t reflect.Type) (ValueEncoder, error) {
encodererr := ErrNoEncoder{Type: t}
r.mu.RLock()
enc, found := r.lookupTypeEncoder(t)
r.mu.RUnlock()
if found {
if enc == nil {
return nil, ErrNoEncoder{Type: t}
}
return enc, nil
}
enc, found = r.lookupInterfaceEncoder(t, true)
if found {
r.mu.Lock()
r.typeEncoders[t] = enc
r.mu.Unlock()
return enc, nil
}
if t == nil {
r.mu.Lock()
r.typeEncoders[t] = nil
r.mu.Unlock()
return nil, encodererr
}
enc, found = r.kindEncoders[t.Kind()]
if !found {
r.mu.Lock()
r.typeEncoders[t] = nil
r.mu.Unlock()
return nil, encodererr
}
r.mu.Lock()
r.typeEncoders[t] = enc
r.mu.Unlock()
return enc, nil
}
func (r *Registry) lookupTypeEncoder(t reflect.Type) (ValueEncoder, bool) {
enc, found := r.typeEncoders[t]
return enc, found
}
func (r *Registry) lookupInterfaceEncoder(t reflect.Type, allowAddr bool) (ValueEncoder, bool) {
if t == nil {
return nil, false
}
for _, ienc := range r.interfaceEncoders {
if t.Implements(ienc.i) {
return ienc.ve, true
}
if allowAddr && t.Kind() != reflect.Ptr && reflect.PtrTo(t).Implements(ienc.i) {
// if *t implements an interface, this will catch if t implements an interface further ahead
// in interfaceEncoders
defaultEnc, found := r.lookupInterfaceEncoder(t, false)
if !found {
defaultEnc = r.kindEncoders[t.Kind()]
}
return newCondAddrEncoder(ienc.ve, defaultEnc), true
}
}
return nil, false
}
// LookupDecoder inspects the registry for an decoder for the given type. The lookup precendence works as follows:
//
// 1. A decoder registered for the exact type. If the given type represents an interface, a decoder registered using
// RegisterTypeDecoder for the interface will be selected.
//
// 2. A decoder registered using RegisterHookDecoder for an interface implemented by the type or by a pointer to the
// type.
//
// 3. A decoder registered for the reflect.Kind of the value.
//
// If no decoder is found, an error of type ErrNoDecoder is returned.
func (r *Registry) LookupDecoder(t reflect.Type) (ValueDecoder, error) {
if t == nil {
return nil, ErrNilType
}
decodererr := ErrNoDecoder{Type: t}
r.mu.RLock()
dec, found := r.lookupTypeDecoder(t)
r.mu.RUnlock()
if found {
if dec == nil {
return nil, ErrNoDecoder{Type: t}
}
return dec, nil
}
dec, found = r.lookupInterfaceDecoder(t, true)
if found {
r.mu.Lock()
r.typeDecoders[t] = dec
r.mu.Unlock()
return dec, nil
}
dec, found = r.kindDecoders[t.Kind()]
if !found {
r.mu.Lock()
r.typeDecoders[t] = nil
r.mu.Unlock()
return nil, decodererr
}
r.mu.Lock()
r.typeDecoders[t] = dec
r.mu.Unlock()
return dec, nil
}
func (r *Registry) lookupTypeDecoder(t reflect.Type) (ValueDecoder, bool) {
dec, found := r.typeDecoders[t]
return dec, found
}
func (r *Registry) lookupInterfaceDecoder(t reflect.Type, allowAddr bool) (ValueDecoder, bool) {
for _, idec := range r.interfaceDecoders {
if t.Implements(idec.i) {
return idec.vd, true
}
if allowAddr && t.Kind() != reflect.Ptr && reflect.PtrTo(t).Implements(idec.i) {
// if *t implements an interface, this will catch if t implements an interface further ahead
// in interfaceDecoders
defaultDec, found := r.lookupInterfaceDecoder(t, false)
if !found {
defaultDec = r.kindDecoders[t.Kind()]
}
return newCondAddrDecoder(idec.vd, defaultDec), true
}
}
return nil, false
}
// LookupTypeMapEntry inspects the registry's type map for a Go type for the corresponding BSON
// type. If no type is found, ErrNoTypeMapEntry is returned.
func (r *Registry) LookupTypeMapEntry(bt bsontype.Type) (reflect.Type, error) {
t, ok := r.typeMap[bt]
if !ok || t == nil {
return nil, ErrNoTypeMapEntry{Type: bt}
}
return t, nil
}
type interfaceValueEncoder struct {
i reflect.Type
ve ValueEncoder
}
type interfaceValueDecoder struct {
i reflect.Type
vd ValueDecoder
}
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