Serge Bazanski | cc25bdf | 2018-10-25 14:02:58 +0200 | [diff] [blame] | 1 | package bson |
| 2 | |
| 3 | import ( |
| 4 | "bytes" |
| 5 | "encoding/binary" |
| 6 | "fmt" |
| 7 | "io" |
| 8 | ) |
| 9 | |
| 10 | const ( |
| 11 | // MinDocumentSize is the size of the smallest possible valid BSON document: |
| 12 | // an int32 size header + 0x00 (end of document). |
| 13 | MinDocumentSize = 5 |
| 14 | |
| 15 | // MaxDocumentSize is the largest possible size for a BSON document allowed by MongoDB, |
| 16 | // that is, 16 MiB (see https://docs.mongodb.com/manual/reference/limits/). |
| 17 | MaxDocumentSize = 16777216 |
| 18 | ) |
| 19 | |
| 20 | // ErrInvalidDocumentSize is an error returned when a BSON document's header |
| 21 | // contains a size smaller than MinDocumentSize or greater than MaxDocumentSize. |
| 22 | type ErrInvalidDocumentSize struct { |
| 23 | DocumentSize int32 |
| 24 | } |
| 25 | |
| 26 | func (e ErrInvalidDocumentSize) Error() string { |
| 27 | return fmt.Sprintf("invalid document size %d", e.DocumentSize) |
| 28 | } |
| 29 | |
| 30 | // A Decoder reads and decodes BSON values from an input stream. |
| 31 | type Decoder struct { |
| 32 | source io.Reader |
| 33 | } |
| 34 | |
| 35 | // NewDecoder returns a new Decoder that reads from source. |
| 36 | // It does not add any extra buffering, and may not read data from source beyond the BSON values requested. |
| 37 | func NewDecoder(source io.Reader) *Decoder { |
| 38 | return &Decoder{source: source} |
| 39 | } |
| 40 | |
| 41 | // Decode reads the next BSON-encoded value from its input and stores it in the value pointed to by v. |
| 42 | // See the documentation for Unmarshal for details about the conversion of BSON into a Go value. |
| 43 | func (dec *Decoder) Decode(v interface{}) (err error) { |
| 44 | // BSON documents start with their size as a *signed* int32. |
| 45 | var docSize int32 |
| 46 | if err = binary.Read(dec.source, binary.LittleEndian, &docSize); err != nil { |
| 47 | return |
| 48 | } |
| 49 | |
| 50 | if docSize < MinDocumentSize || docSize > MaxDocumentSize { |
| 51 | return ErrInvalidDocumentSize{DocumentSize: docSize} |
| 52 | } |
| 53 | |
| 54 | docBuffer := bytes.NewBuffer(make([]byte, 0, docSize)) |
| 55 | if err = binary.Write(docBuffer, binary.LittleEndian, docSize); err != nil { |
| 56 | return |
| 57 | } |
| 58 | |
| 59 | // docSize is the *full* document's size (including the 4-byte size header, |
| 60 | // which has already been read). |
| 61 | if _, err = io.CopyN(docBuffer, dec.source, int64(docSize-4)); err != nil { |
| 62 | return |
| 63 | } |
| 64 | |
| 65 | // Let Unmarshal handle the rest. |
| 66 | defer handleErr(&err) |
| 67 | return Unmarshal(docBuffer.Bytes(), v) |
| 68 | } |
| 69 | |
| 70 | // An Encoder encodes and writes BSON values to an output stream. |
| 71 | type Encoder struct { |
| 72 | target io.Writer |
| 73 | } |
| 74 | |
| 75 | // NewEncoder returns a new Encoder that writes to target. |
| 76 | func NewEncoder(target io.Writer) *Encoder { |
| 77 | return &Encoder{target: target} |
| 78 | } |
| 79 | |
| 80 | // Encode encodes v to BSON, and if successful writes it to the Encoder's output stream. |
| 81 | // See the documentation for Marshal for details about the conversion of Go values to BSON. |
| 82 | func (enc *Encoder) Encode(v interface{}) error { |
| 83 | data, err := Marshal(v) |
| 84 | if err != nil { |
| 85 | return err |
| 86 | } |
| 87 | |
| 88 | _, err = enc.target.Write(data) |
| 89 | return err |
| 90 | } |