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 | "reflect" |
| 12 | "sync" |
| 13 | |
| 14 | "github.com/mongodb/mongo-go-driver/bson/bsoncodec" |
| 15 | "github.com/mongodb/mongo-go-driver/bson/bsonrw" |
| 16 | ) |
| 17 | |
| 18 | // This pool is used to keep the allocations of Encoders down. This is only used for the Marshal* |
| 19 | // methods and is not consumable from outside of this package. The Encoders retrieved from this pool |
| 20 | // must have both Reset and SetRegistry called on them. |
| 21 | var encPool = sync.Pool{ |
| 22 | New: func() interface{} { |
| 23 | return new(Encoder) |
| 24 | }, |
| 25 | } |
| 26 | |
| 27 | // An Encoder writes a serialization format to an output stream. It writes to a bsonrw.ValueWriter |
| 28 | // as the destination of BSON data. |
| 29 | type Encoder struct { |
| 30 | ec bsoncodec.EncodeContext |
| 31 | vw bsonrw.ValueWriter |
| 32 | } |
| 33 | |
| 34 | // NewEncoder returns a new encoder that uses the DefaultRegistry to write to vw. |
| 35 | func NewEncoder(vw bsonrw.ValueWriter) (*Encoder, error) { |
| 36 | if vw == nil { |
| 37 | return nil, errors.New("cannot create a new Encoder with a nil ValueWriter") |
| 38 | } |
| 39 | |
| 40 | return &Encoder{ |
| 41 | ec: bsoncodec.EncodeContext{Registry: DefaultRegistry}, |
| 42 | vw: vw, |
| 43 | }, nil |
| 44 | } |
| 45 | |
| 46 | // NewEncoderWithContext returns a new encoder that uses EncodeContext ec to write to vw. |
| 47 | func NewEncoderWithContext(ec bsoncodec.EncodeContext, vw bsonrw.ValueWriter) (*Encoder, error) { |
| 48 | if ec.Registry == nil { |
| 49 | ec = bsoncodec.EncodeContext{Registry: DefaultRegistry} |
| 50 | } |
| 51 | if vw == nil { |
| 52 | return nil, errors.New("cannot create a new Encoder with a nil ValueWriter") |
| 53 | } |
| 54 | |
| 55 | return &Encoder{ |
| 56 | ec: ec, |
| 57 | vw: vw, |
| 58 | }, nil |
| 59 | } |
| 60 | |
| 61 | // Encode writes the BSON encoding of val to the stream. |
| 62 | // |
| 63 | // The documentation for Marshal contains details about the conversion of Go |
| 64 | // values to BSON. |
| 65 | func (e *Encoder) Encode(val interface{}) error { |
| 66 | if marshaler, ok := val.(Marshaler); ok { |
| 67 | // TODO(skriptble): Should we have a MarshalAppender interface so that we can have []byte reuse? |
| 68 | buf, err := marshaler.MarshalBSON() |
| 69 | if err != nil { |
| 70 | return err |
| 71 | } |
| 72 | return bsonrw.Copier{}.CopyDocumentFromBytes(e.vw, buf) |
| 73 | } |
| 74 | |
| 75 | encoder, err := e.ec.LookupEncoder(reflect.TypeOf(val)) |
| 76 | if err != nil { |
| 77 | return err |
| 78 | } |
| 79 | return encoder.EncodeValue(e.ec, e.vw, reflect.ValueOf(val)) |
| 80 | } |
| 81 | |
| 82 | // Reset will reset the state of the encoder, using the same *EncodeContext used in |
| 83 | // the original construction but using vw. |
| 84 | func (e *Encoder) Reset(vw bsonrw.ValueWriter) error { |
| 85 | e.vw = vw |
| 86 | return nil |
| 87 | } |
| 88 | |
| 89 | // SetRegistry replaces the current registry of the encoder with r. |
| 90 | func (e *Encoder) SetRegistry(r *bsoncodec.Registry) error { |
| 91 | e.ec.Registry = r |
| 92 | return nil |
| 93 | } |
| 94 | |
| 95 | // SetContext replaces the current EncodeContext of the encoder with er. |
| 96 | func (e *Encoder) SetContext(ec bsoncodec.EncodeContext) error { |
| 97 | e.ec = ec |
| 98 | return nil |
| 99 | } |