| package bson |
| |
| import ( |
| "bytes" |
| "encoding/binary" |
| "fmt" |
| "io" |
| ) |
| |
| const ( |
| // MinDocumentSize is the size of the smallest possible valid BSON document: |
| // an int32 size header + 0x00 (end of document). |
| MinDocumentSize = 5 |
| |
| // MaxDocumentSize is the largest possible size for a BSON document allowed by MongoDB, |
| // that is, 16 MiB (see https://docs.mongodb.com/manual/reference/limits/). |
| MaxDocumentSize = 16777216 |
| ) |
| |
| // ErrInvalidDocumentSize is an error returned when a BSON document's header |
| // contains a size smaller than MinDocumentSize or greater than MaxDocumentSize. |
| type ErrInvalidDocumentSize struct { |
| DocumentSize int32 |
| } |
| |
| func (e ErrInvalidDocumentSize) Error() string { |
| return fmt.Sprintf("invalid document size %d", e.DocumentSize) |
| } |
| |
| // A Decoder reads and decodes BSON values from an input stream. |
| type Decoder struct { |
| source io.Reader |
| } |
| |
| // NewDecoder returns a new Decoder that reads from source. |
| // It does not add any extra buffering, and may not read data from source beyond the BSON values requested. |
| func NewDecoder(source io.Reader) *Decoder { |
| return &Decoder{source: source} |
| } |
| |
| // Decode reads the next BSON-encoded value from its input and stores it in the value pointed to by v. |
| // See the documentation for Unmarshal for details about the conversion of BSON into a Go value. |
| func (dec *Decoder) Decode(v interface{}) (err error) { |
| // BSON documents start with their size as a *signed* int32. |
| var docSize int32 |
| if err = binary.Read(dec.source, binary.LittleEndian, &docSize); err != nil { |
| return |
| } |
| |
| if docSize < MinDocumentSize || docSize > MaxDocumentSize { |
| return ErrInvalidDocumentSize{DocumentSize: docSize} |
| } |
| |
| docBuffer := bytes.NewBuffer(make([]byte, 0, docSize)) |
| if err = binary.Write(docBuffer, binary.LittleEndian, docSize); err != nil { |
| return |
| } |
| |
| // docSize is the *full* document's size (including the 4-byte size header, |
| // which has already been read). |
| if _, err = io.CopyN(docBuffer, dec.source, int64(docSize-4)); err != nil { |
| return |
| } |
| |
| // Let Unmarshal handle the rest. |
| defer handleErr(&err) |
| return Unmarshal(docBuffer.Bytes(), v) |
| } |
| |
| // An Encoder encodes and writes BSON values to an output stream. |
| type Encoder struct { |
| target io.Writer |
| } |
| |
| // NewEncoder returns a new Encoder that writes to target. |
| func NewEncoder(target io.Writer) *Encoder { |
| return &Encoder{target: target} |
| } |
| |
| // Encode encodes v to BSON, and if successful writes it to the Encoder's output stream. |
| // See the documentation for Marshal for details about the conversion of Go values to BSON. |
| func (enc *Encoder) Encode(v interface{}) error { |
| data, err := Marshal(v) |
| if err != nil { |
| return err |
| } |
| |
| _, err = enc.target.Write(data) |
| return err |
| } |