Don Newton | 379ae25 | 2019-04-01 12:17:06 -0400 | [diff] [blame^] | 1 | // Copyright (C) MongoDB, Inc. 2017-present. |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); you may |
| 4 | // not use this file except in compliance with the License. You may obtain |
| 5 | // a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 |
| 6 | |
| 7 | package bson |
| 8 | |
| 9 | import ( |
| 10 | "errors" |
| 11 | "fmt" |
| 12 | "reflect" |
| 13 | "sync" |
| 14 | |
| 15 | "github.com/mongodb/mongo-go-driver/bson/bsoncodec" |
| 16 | "github.com/mongodb/mongo-go-driver/bson/bsonrw" |
| 17 | ) |
| 18 | |
| 19 | // This pool is used to keep the allocations of Decoders down. This is only used for the Marshal* |
| 20 | // methods and is not consumable from outside of this package. The Decoders retrieved from this pool |
| 21 | // must have both Reset and SetRegistry called on them. |
| 22 | var decPool = sync.Pool{ |
| 23 | New: func() interface{} { |
| 24 | return new(Decoder) |
| 25 | }, |
| 26 | } |
| 27 | |
| 28 | // A Decoder reads and decodes BSON documents from a stream. It reads from a bsonrw.ValueReader as |
| 29 | // the source of BSON data. |
| 30 | type Decoder struct { |
| 31 | dc bsoncodec.DecodeContext |
| 32 | vr bsonrw.ValueReader |
| 33 | } |
| 34 | |
| 35 | // NewDecoder returns a new decoder that uses the DefaultRegistry to read from vr. |
| 36 | func NewDecoder(vr bsonrw.ValueReader) (*Decoder, error) { |
| 37 | if vr == nil { |
| 38 | return nil, errors.New("cannot create a new Decoder with a nil ValueReader") |
| 39 | } |
| 40 | |
| 41 | return &Decoder{ |
| 42 | dc: bsoncodec.DecodeContext{Registry: DefaultRegistry}, |
| 43 | vr: vr, |
| 44 | }, nil |
| 45 | } |
| 46 | |
| 47 | // NewDecoderWithContext returns a new decoder that uses DecodeContext dc to read from vr. |
| 48 | func NewDecoderWithContext(dc bsoncodec.DecodeContext, vr bsonrw.ValueReader) (*Decoder, error) { |
| 49 | if dc.Registry == nil { |
| 50 | dc.Registry = DefaultRegistry |
| 51 | } |
| 52 | if vr == nil { |
| 53 | return nil, errors.New("cannot create a new Decoder with a nil ValueReader") |
| 54 | } |
| 55 | |
| 56 | return &Decoder{ |
| 57 | dc: dc, |
| 58 | vr: vr, |
| 59 | }, nil |
| 60 | } |
| 61 | |
| 62 | // Decode reads the next BSON document from the stream and decodes it into the |
| 63 | // value pointed to by val. |
| 64 | // |
| 65 | // The documentation for Unmarshal contains details about of BSON into a Go |
| 66 | // value. |
| 67 | func (d *Decoder) Decode(val interface{}) error { |
| 68 | if unmarshaler, ok := val.(Unmarshaler); ok { |
| 69 | // TODO(skriptble): Reuse a []byte here and use the AppendDocumentBytes method. |
| 70 | buf, err := bsonrw.Copier{}.CopyDocumentToBytes(d.vr) |
| 71 | if err != nil { |
| 72 | return err |
| 73 | } |
| 74 | return unmarshaler.UnmarshalBSON(buf) |
| 75 | } |
| 76 | |
| 77 | rval := reflect.ValueOf(val) |
| 78 | if rval.Kind() != reflect.Ptr { |
| 79 | return fmt.Errorf("argument to Decode must be a pointer to a type, but got %v", rval) |
| 80 | } |
| 81 | rval = rval.Elem() |
| 82 | decoder, err := d.dc.LookupDecoder(rval.Type()) |
| 83 | if err != nil { |
| 84 | return err |
| 85 | } |
| 86 | return decoder.DecodeValue(d.dc, d.vr, rval) |
| 87 | } |
| 88 | |
| 89 | // Reset will reset the state of the decoder, using the same *DecodeContext used in |
| 90 | // the original construction but using vr for reading. |
| 91 | func (d *Decoder) Reset(vr bsonrw.ValueReader) error { |
| 92 | d.vr = vr |
| 93 | return nil |
| 94 | } |
| 95 | |
| 96 | // SetRegistry replaces the current registry of the decoder with r. |
| 97 | func (d *Decoder) SetRegistry(r *bsoncodec.Registry) error { |
| 98 | d.dc.Registry = r |
| 99 | return nil |
| 100 | } |
| 101 | |
| 102 | // SetContext replaces the current registry of the decoder with dc. |
| 103 | func (d *Decoder) SetContext(dc bsoncodec.DecodeContext) error { |
| 104 | d.dc = dc |
| 105 | return nil |
| 106 | } |