| // 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 bson |
| |
| import ( |
| "errors" |
| "fmt" |
| "reflect" |
| "sync" |
| |
| "github.com/mongodb/mongo-go-driver/bson/bsoncodec" |
| "github.com/mongodb/mongo-go-driver/bson/bsonrw" |
| ) |
| |
| // This pool is used to keep the allocations of Decoders down. This is only used for the Marshal* |
| // methods and is not consumable from outside of this package. The Decoders retrieved from this pool |
| // must have both Reset and SetRegistry called on them. |
| var decPool = sync.Pool{ |
| New: func() interface{} { |
| return new(Decoder) |
| }, |
| } |
| |
| // A Decoder reads and decodes BSON documents from a stream. It reads from a bsonrw.ValueReader as |
| // the source of BSON data. |
| type Decoder struct { |
| dc bsoncodec.DecodeContext |
| vr bsonrw.ValueReader |
| } |
| |
| // NewDecoder returns a new decoder that uses the DefaultRegistry to read from vr. |
| func NewDecoder(vr bsonrw.ValueReader) (*Decoder, error) { |
| if vr == nil { |
| return nil, errors.New("cannot create a new Decoder with a nil ValueReader") |
| } |
| |
| return &Decoder{ |
| dc: bsoncodec.DecodeContext{Registry: DefaultRegistry}, |
| vr: vr, |
| }, nil |
| } |
| |
| // NewDecoderWithContext returns a new decoder that uses DecodeContext dc to read from vr. |
| func NewDecoderWithContext(dc bsoncodec.DecodeContext, vr bsonrw.ValueReader) (*Decoder, error) { |
| if dc.Registry == nil { |
| dc.Registry = DefaultRegistry |
| } |
| if vr == nil { |
| return nil, errors.New("cannot create a new Decoder with a nil ValueReader") |
| } |
| |
| return &Decoder{ |
| dc: dc, |
| vr: vr, |
| }, nil |
| } |
| |
| // Decode reads the next BSON document from the stream and decodes it into the |
| // value pointed to by val. |
| // |
| // The documentation for Unmarshal contains details about of BSON into a Go |
| // value. |
| func (d *Decoder) Decode(val interface{}) error { |
| if unmarshaler, ok := val.(Unmarshaler); ok { |
| // TODO(skriptble): Reuse a []byte here and use the AppendDocumentBytes method. |
| buf, err := bsonrw.Copier{}.CopyDocumentToBytes(d.vr) |
| if err != nil { |
| return err |
| } |
| return unmarshaler.UnmarshalBSON(buf) |
| } |
| |
| rval := reflect.ValueOf(val) |
| if rval.Kind() != reflect.Ptr { |
| return fmt.Errorf("argument to Decode must be a pointer to a type, but got %v", rval) |
| } |
| rval = rval.Elem() |
| decoder, err := d.dc.LookupDecoder(rval.Type()) |
| if err != nil { |
| return err |
| } |
| return decoder.DecodeValue(d.dc, d.vr, rval) |
| } |
| |
| // Reset will reset the state of the decoder, using the same *DecodeContext used in |
| // the original construction but using vr for reading. |
| func (d *Decoder) Reset(vr bsonrw.ValueReader) error { |
| d.vr = vr |
| return nil |
| } |
| |
| // SetRegistry replaces the current registry of the decoder with r. |
| func (d *Decoder) SetRegistry(r *bsoncodec.Registry) error { |
| d.dc.Registry = r |
| return nil |
| } |
| |
| // SetContext replaces the current registry of the decoder with dc. |
| func (d *Decoder) SetContext(dc bsoncodec.DecodeContext) error { |
| d.dc = dc |
| return nil |
| } |