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