| // Package bsoncodec provides a system for encoding values to BSON representations and decoding |
| // values from BSON representations. This package considers both binary BSON and ExtendedJSON as |
| // BSON representations. The types in this package enable a flexible system for handling this |
| // encoding and decoding. |
| // |
| // The codec system is composed of two parts: |
| // |
| // 1) ValueEncoders and ValueDecoders that handle encoding and decoding Go values to and from BSON |
| // representations. |
| // |
| // 2) A Registry that holds these ValueEncoders and ValueDecoders and provides methods for |
| // retrieving them. |
| // |
| // ValueEncoders and ValueDecoders |
| // |
| // The ValueEncoder interface is implemented by types that can encode a provided Go type to BSON. |
| // The value to encode is provided as a reflect.Value and a bsonrw.ValueWriter is used within the |
| // EncodeValue method to actually create the BSON representation. For convenience, ValueEncoderFunc |
| // is provided to allow use of a function with the correct signature as a ValueEncoder. An |
| // EncodeContext instance is provided to allow implementations to lookup further ValueEncoders and |
| // to provide configuration information. |
| // |
| // The ValueDecoder interface is the inverse of the ValueEncoder. Implementations should ensure that |
| // the value they receive is settable. Similar to ValueEncoderFunc, ValueDecoderFunc is provided to |
| // allow the use of a function with the correct signature as a ValueDecoder. A DecodeContext |
| // instance is provided and serves similar functionality to the EncodeContext. |
| // |
| // Registry and RegistryBuilder |
| // |
| // A Registry is an immutable store for ValueEncoders, ValueDecoders, and a type map. For looking up |
| // ValueEncoders and Decoders the Registry first attempts to find a ValueEncoder or ValueDecoder for |
| // the type provided; if one cannot be found it then checks to see if a registered ValueEncoder or |
| // ValueDecoder exists for an interface the type implements. Finally, the reflect.Kind of the type |
| // is used to lookup a default ValueEncoder or ValueDecoder for that kind. If no ValueEncoder or |
| // ValueDecoder can be found, an error is returned. |
| // |
| // The Registry also holds a type map. This allows users to retrieve the Go type that should be used |
| // when decoding a BSON value into an empty interface. This is primarily only used for the empty |
| // interface ValueDecoder. |
| // |
| // A RegistryBuilder is used to construct a Registry. The Register methods are used to associate |
| // either a reflect.Type or a reflect.Kind with a ValueEncoder or ValueDecoder. A RegistryBuilder |
| // returned from NewRegistryBuilder contains no registered ValueEncoders nor ValueDecoders and |
| // contains an empty type map. |
| // |
| // The RegisterTypeMapEntry method handles associating a BSON type with a Go type. For example, if |
| // you want to decode BSON int64 and int32 values into Go int instances, you would do the following: |
| // |
| // var regbuilder *RegistryBuilder = ... intType := reflect.TypeOf(int(0)) |
| // regbuilder.RegisterTypeMapEntry(bsontype.Int64, intType).RegisterTypeMapEntry(bsontype.Int32, |
| // intType) |
| // |
| // DefaultValueEncoders and DefaultValueDecoders |
| // |
| // The DefaultValueEncoders and DefaultValueDecoders types provide a full set of ValueEncoders and |
| // ValueDecoders for handling a wide range of Go types, including all of the types within the |
| // primitive package. To make registering these codecs easier, a helper method on each type is |
| // provided. For the DefaultValueEncoders type the method is called RegisterDefaultEncoders and for |
| // the DefaultValueDecoders type the method is called RegisterDefaultDecoders, this method also |
| // handles registering type map entries for each BSON type. |
| package bsoncodec |