137 lines
4.2 KiB
Go
137 lines
4.2 KiB
Go
// Copyright (C) MongoDB, Inc. 2017-present.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may
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// not use this file except in compliance with the License. You may obtain
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// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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package bson
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import (
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"errors"
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"fmt"
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"reflect"
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"sync"
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)
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// ErrDecodeToNil is the error returned when trying to decode to a nil value
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var ErrDecodeToNil = errors.New("cannot Decode to nil value")
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// This pool is used to keep the allocations of Decoders down. This is only used for the Marshal*
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// methods and is not consumable from outside of this package. The Decoders retrieved from this pool
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// must have both Reset and SetRegistry called on them.
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var decPool = sync.Pool{
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New: func() interface{} {
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return new(Decoder)
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},
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}
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// A Decoder reads and decodes BSON documents from a stream. It reads from a ValueReader as
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// the source of BSON data.
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type Decoder struct {
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dc DecodeContext
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vr ValueReader
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}
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// NewDecoder returns a new decoder that reads from vr.
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func NewDecoder(vr ValueReader) *Decoder {
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return &Decoder{
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dc: DecodeContext{Registry: defaultRegistry},
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vr: vr,
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}
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}
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// Decode reads the next BSON document from the stream and decodes it into the
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// value pointed to by val.
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//
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// See [Unmarshal] for details about BSON unmarshaling behavior.
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func (d *Decoder) Decode(val interface{}) error {
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if unmarshaler, ok := val.(Unmarshaler); ok {
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// TODO(skriptble): Reuse a []byte here and use the AppendDocumentBytes method.
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buf, err := copyDocumentToBytes(d.vr)
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if err != nil {
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return err
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}
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return unmarshaler.UnmarshalBSON(buf)
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}
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rval := reflect.ValueOf(val)
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switch rval.Kind() {
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case reflect.Ptr:
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if rval.IsNil() {
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return ErrDecodeToNil
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}
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rval = rval.Elem()
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case reflect.Map:
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if rval.IsNil() {
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return ErrDecodeToNil
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}
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default:
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return fmt.Errorf("argument to Decode must be a pointer or a map, but got %v", rval)
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}
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decoder, err := d.dc.LookupDecoder(rval.Type())
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if err != nil {
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return err
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}
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return decoder.DecodeValue(d.dc, d.vr, rval)
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}
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// Reset will reset the state of the decoder, using the same *DecodeContext used in
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// the original construction but using vr for reading.
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func (d *Decoder) Reset(vr ValueReader) {
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d.vr = vr
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}
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// SetRegistry replaces the current registry of the decoder with r.
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func (d *Decoder) SetRegistry(r *Registry) {
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d.dc.Registry = r
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}
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// DefaultDocumentM causes the Decoder to always unmarshal documents into the bson.M type. This
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// behavior is restricted to data typed as "interface{}" or "map[string]interface{}".
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func (d *Decoder) DefaultDocumentM() {
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d.dc.defaultDocumentType = reflect.TypeOf(M{})
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}
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// AllowTruncatingDoubles causes the Decoder to truncate the fractional part of BSON "double" values
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// when attempting to unmarshal them into a Go integer (int, int8, int16, int32, or int64) struct
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// field. The truncation logic does not apply to BSON "decimal128" values.
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func (d *Decoder) AllowTruncatingDoubles() {
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d.dc.truncate = true
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}
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// BinaryAsSlice causes the Decoder to unmarshal BSON binary field values that are the "Generic" or
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// "Old" BSON binary subtype as a Go byte slice instead of a bson.Binary.
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func (d *Decoder) BinaryAsSlice() {
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d.dc.binaryAsSlice = true
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}
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// ObjectIDAsHexString causes the Decoder to decode object IDs to their hex representation.
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func (d *Decoder) ObjectIDAsHexString() {
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d.dc.objectIDAsHexString = true
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}
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// UseJSONStructTags causes the Decoder to fall back to using the "json" struct tag if a "bson"
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// struct tag is not specified.
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func (d *Decoder) UseJSONStructTags() {
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d.dc.useJSONStructTags = true
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}
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// UseLocalTimeZone causes the Decoder to unmarshal time.Time values in the local timezone instead
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// of the UTC timezone.
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func (d *Decoder) UseLocalTimeZone() {
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d.dc.useLocalTimeZone = true
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}
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// ZeroMaps causes the Decoder to delete any existing values from Go maps in the destination value
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// passed to Decode before unmarshaling BSON documents into them.
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func (d *Decoder) ZeroMaps() {
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d.dc.zeroMaps = true
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}
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// ZeroStructs causes the Decoder to delete any existing values from Go structs in the destination
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// value passed to Decode before unmarshaling BSON documents into them.
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func (d *Decoder) ZeroStructs() {
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d.dc.zeroStructs = true
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}
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