string_codec.go

Documentation: go.mongodb.org/mongo-driver/bson/bsoncodec

     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 bsoncodec
     8  
     9  import (
    10  	"fmt"
    11  	"reflect"
    12  
    13  	"go.mongodb.org/mongo-driver/bson/bsonoptions"
    14  	"go.mongodb.org/mongo-driver/bson/bsonrw"
    15  	"go.mongodb.org/mongo-driver/bson/bsontype"
    16  )
    17  
    18  // StringCodec is the Codec used for string values.
    19  //
    20  // Deprecated: StringCodec will not be directly accessible in Go Driver 2.0. To
    21  // override the default string encode and decode behavior, create a new registry
    22  // with [go.mongodb.org/mongo-driver/bson.NewRegistry] and register a new
    23  // encoder and decoder for strings.
    24  //
    25  // For example,
    26  //
    27  //	reg := bson.NewRegistry()
    28  //	reg.RegisterKindEncoder(reflect.String, myStringEncoder)
    29  //	reg.RegisterKindDecoder(reflect.String, myStringDecoder)
    30  type StringCodec struct {
    31  	// DecodeObjectIDAsHex specifies if object IDs should be decoded as their hex representation.
    32  	// If false, a string made from the raw object ID bytes will be used. Defaults to true.
    33  	//
    34  	// Deprecated: Decoding object IDs as raw bytes will not be supported in Go Driver 2.0.
    35  	DecodeObjectIDAsHex bool
    36  }
    37  
    38  var (
    39  	defaultStringCodec = NewStringCodec()
    40  
    41  	// Assert that defaultStringCodec satisfies the typeDecoder interface, which allows it to be
    42  	// used by collection type decoders (e.g. map, slice, etc) to set individual values in a
    43  	// collection.
    44  	_ typeDecoder = defaultStringCodec
    45  )
    46  
    47  // NewStringCodec returns a StringCodec with options opts.
    48  //
    49  // Deprecated: NewStringCodec will not be available in Go Driver 2.0. See
    50  // [StringCodec] for more details.
    51  func NewStringCodec(opts ...*bsonoptions.StringCodecOptions) *StringCodec {
    52  	stringOpt := bsonoptions.MergeStringCodecOptions(opts...)
    53  	return &StringCodec{*stringOpt.DecodeObjectIDAsHex}
    54  }
    55  
    56  // EncodeValue is the ValueEncoder for string types.
    57  func (sc *StringCodec) EncodeValue(_ EncodeContext, vw bsonrw.ValueWriter, val reflect.Value) error {
    58  	if val.Kind() != reflect.String {
    59  		return ValueEncoderError{
    60  			Name:     "StringEncodeValue",
    61  			Kinds:    []reflect.Kind{reflect.String},
    62  			Received: val,
    63  		}
    64  	}
    65  
    66  	return vw.WriteString(val.String())
    67  }
    68  
    69  func (sc *StringCodec) decodeType(_ DecodeContext, vr bsonrw.ValueReader, t reflect.Type) (reflect.Value, error) {
    70  	if t.Kind() != reflect.String {
    71  		return emptyValue, ValueDecoderError{
    72  			Name:     "StringDecodeValue",
    73  			Kinds:    []reflect.Kind{reflect.String},
    74  			Received: reflect.Zero(t),
    75  		}
    76  	}
    77  
    78  	var str string
    79  	var err error
    80  	switch vr.Type() {
    81  	case bsontype.String:
    82  		str, err = vr.ReadString()
    83  		if err != nil {
    84  			return emptyValue, err
    85  		}
    86  	case bsontype.ObjectID:
    87  		oid, err := vr.ReadObjectID()
    88  		if err != nil {
    89  			return emptyValue, err
    90  		}
    91  		if sc.DecodeObjectIDAsHex {
    92  			str = oid.Hex()
    93  		} else {
    94  			// TODO(GODRIVER-2796): Return an error here instead of decoding to a garbled string.
    95  			byteArray := [12]byte(oid)
    96  			str = string(byteArray[:])
    97  		}
    98  	case bsontype.Symbol:
    99  		str, err = vr.ReadSymbol()
   100  		if err != nil {
   101  			return emptyValue, err
   102  		}
   103  	case bsontype.Binary:
   104  		data, subtype, err := vr.ReadBinary()
   105  		if err != nil {
   106  			return emptyValue, err
   107  		}
   108  		if subtype != bsontype.BinaryGeneric && subtype != bsontype.BinaryBinaryOld {
   109  			return emptyValue, decodeBinaryError{subtype: subtype, typeName: "string"}
   110  		}
   111  		str = string(data)
   112  	case bsontype.Null:
   113  		if err = vr.ReadNull(); err != nil {
   114  			return emptyValue, err
   115  		}
   116  	case bsontype.Undefined:
   117  		if err = vr.ReadUndefined(); err != nil {
   118  			return emptyValue, err
   119  		}
   120  	default:
   121  		return emptyValue, fmt.Errorf("cannot decode %v into a string type", vr.Type())
   122  	}
   123  
   124  	return reflect.ValueOf(str), nil
   125  }
   126  
   127  // DecodeValue is the ValueDecoder for string types.
   128  func (sc *StringCodec) DecodeValue(dctx DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
   129  	if !val.CanSet() || val.Kind() != reflect.String {
   130  		return ValueDecoderError{Name: "StringDecodeValue", Kinds: []reflect.Kind{reflect.String}, Received: val}
   131  	}
   132  
   133  	elem, err := sc.decodeType(dctx, vr, val.Type())
   134  	if err != nil {
   135  		return err
   136  	}
   137  
   138  	val.SetString(elem.String())
   139  	return nil
   140  }
   141
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