128 lines
4.4 KiB
Go
128 lines
4.4 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 mgocompat
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import (
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"reflect"
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"go.mongodb.org/mongo-driver/bson"
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"go.mongodb.org/mongo-driver/bson/bsoncodec"
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"go.mongodb.org/mongo-driver/bson/bsonrw"
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)
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// Setter interface: a value implementing the bson.Setter interface will receive the BSON
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// value via the SetBSON method during unmarshaling, and the object
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// itself will not be changed as usual.
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//
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// If setting the value works, the method should return nil or alternatively
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// mgocompat.ErrSetZero to set the respective field to its zero value (nil for
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// pointer types). If SetBSON returns a non-nil error, the unmarshalling
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// procedure will stop and error out with the provided value.
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//
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// This interface is generally useful in pointer receivers, since the method
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// will want to change the receiver. A type field that implements the Setter
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// interface doesn't have to be a pointer, though.
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//
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// For example:
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//
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// type MyString string
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//
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// func (s *MyString) SetBSON(raw bson.RawValue) error {
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// return raw.Unmarshal(s)
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// }
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type Setter interface {
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SetBSON(raw bson.RawValue) error
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}
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// Getter interface: a value implementing the bson.Getter interface will have its GetBSON
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// method called when the given value has to be marshalled, and the result
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// of this method will be marshaled in place of the actual object.
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//
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// If GetBSON returns return a non-nil error, the marshalling procedure
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// will stop and error out with the provided value.
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type Getter interface {
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GetBSON() (interface{}, error)
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}
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// SetterDecodeValue is the ValueDecoderFunc for Setter types.
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func SetterDecodeValue(dc bsoncodec.DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
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if !val.IsValid() || (!val.Type().Implements(tSetter) && !reflect.PtrTo(val.Type()).Implements(tSetter)) {
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return bsoncodec.ValueDecoderError{Name: "SetterDecodeValue", Types: []reflect.Type{tSetter}, Received: val}
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}
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if val.Kind() == reflect.Ptr && val.IsNil() {
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if !val.CanSet() {
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return bsoncodec.ValueDecoderError{Name: "SetterDecodeValue", Types: []reflect.Type{tSetter}, Received: val}
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}
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val.Set(reflect.New(val.Type().Elem()))
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}
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if !val.Type().Implements(tSetter) {
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if !val.CanAddr() {
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return bsoncodec.ValueDecoderError{Name: "ValueUnmarshalerDecodeValue", Types: []reflect.Type{tSetter}, Received: val}
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}
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val = val.Addr() // If the type doesn't implement the interface, a pointer to it must.
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}
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t, src, err := bsonrw.Copier{}.CopyValueToBytes(vr)
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if err != nil {
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return err
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}
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fn := val.Convert(tSetter).MethodByName("SetBSON")
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errVal := fn.Call([]reflect.Value{reflect.ValueOf(bson.RawValue{Type: t, Value: src})})[0]
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if !errVal.IsNil() {
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err = errVal.Interface().(error)
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if err == ErrSetZero {
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val.Set(reflect.Zero(val.Type()))
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return nil
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}
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return err
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}
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return nil
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}
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// GetterEncodeValue is the ValueEncoderFunc for Getter types.
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func GetterEncodeValue(ec bsoncodec.EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
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// Either val or a pointer to val must implement Getter
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switch {
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case !val.IsValid():
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return bsoncodec.ValueEncoderError{Name: "GetterEncodeValue", Types: []reflect.Type{tGetter}, Received: val}
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case val.Type().Implements(tGetter):
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// If Getter is implemented on a concrete type, make sure that val isn't a nil pointer
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if isImplementationNil(val, tGetter) {
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return vw.WriteNull()
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}
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case reflect.PtrTo(val.Type()).Implements(tGetter) && val.CanAddr():
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val = val.Addr()
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default:
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return bsoncodec.ValueEncoderError{Name: "GetterEncodeValue", Types: []reflect.Type{tGetter}, Received: val}
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}
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fn := val.Convert(tGetter).MethodByName("GetBSON")
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returns := fn.Call(nil)
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if !returns[1].IsNil() {
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return returns[1].Interface().(error)
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}
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intermediate := returns[0]
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encoder, err := ec.Registry.LookupEncoder(intermediate.Type())
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if err != nil {
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return err
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}
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return encoder.EncodeValue(ec, vw, intermediate)
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}
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// isImplementationNil returns if val is a nil pointer and inter is implemented on a concrete type
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func isImplementationNil(val reflect.Value, inter reflect.Type) bool {
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vt := val.Type()
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for vt.Kind() == reflect.Ptr {
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vt = vt.Elem()
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}
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return vt.Implements(inter) && val.Kind() == reflect.Ptr && val.IsNil()
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}
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