mirror of
https://github.com/genuinetools/reg.git
synced 2024-08-22 14:40:22 -04:00
8e5eba8735
Signed-off-by: Jess Frazelle <acidburn@microsoft.com>
69 lines
2.4 KiB
Markdown
69 lines
2.4 KiB
Markdown
# Custom types
|
|
|
|
Custom types is a gogo protobuf extensions that allows for using a custom
|
|
struct type to decorate the underlying structure of the protocol message.
|
|
|
|
# How to use
|
|
|
|
## Defining the protobuf message
|
|
|
|
```proto
|
|
message CustomType {
|
|
optional ProtoType Field = 1 [(gogoproto.customtype) = "T"];
|
|
}
|
|
|
|
message ProtoType {
|
|
optional string Field = 1;
|
|
}
|
|
```
|
|
|
|
or alternatively you can declare the field type in the protocol message to be
|
|
`bytes`:
|
|
|
|
```proto
|
|
message BytesCustomType {
|
|
optional bytes Field = 1 [(gogoproto.customtype) = "T"];
|
|
}
|
|
```
|
|
|
|
The downside of using `bytes` is that it makes it harder to generate protobuf
|
|
code in other languages. In either case, it is the user responsibility to
|
|
ensure that the custom type marshals and unmarshals to the expected wire
|
|
format. That is, in the first example, gogo protobuf will not attempt to ensure
|
|
that the wire format of `ProtoType` and `T` are wire compatible.
|
|
|
|
## Custom type method signatures
|
|
|
|
The custom type must define the following methods with the given
|
|
signatures. Assuming the custom type is called `T`:
|
|
|
|
```go
|
|
func (t T) Marshal() ([]byte, error) {}
|
|
func (t *T) MarshalTo(data []byte) (n int, err error) {}
|
|
func (t *T) Unmarshal(data []byte) error {}
|
|
|
|
func (t T) MarshalJSON() ([]byte, error) {}
|
|
func (t *T) UnmarshalJSON(data []byte) error {}
|
|
|
|
// only required if the compare option is set
|
|
func (t T) Compare(other T) int {}
|
|
// only required if the equal option is set
|
|
func (t T) Equal(other T) bool {}
|
|
// only required if populate option is set
|
|
func NewPopulatedT(r randyThetest) *T {}
|
|
```
|
|
|
|
Check [t.go](test/t.go) for a full example
|
|
|
|
# Warnings and issues
|
|
|
|
`Warning about customtype: It is your responsibility to test all cases of your marshaling, unmarshaling and size methods implemented for your custom type.`
|
|
|
|
Issues with customtype include:
|
|
* <a href="https://github.com/gogo/protobuf/issues/199">A Bytes method is not allowed.<a/>
|
|
* <a href="https://github.com/gogo/protobuf/issues/132">Defining a customtype as a fake proto message is broken.</a>
|
|
* <a href="https://github.com/gogo/protobuf/issues/147">proto.Clone is broken.</a>
|
|
* <a href="https://github.com/gogo/protobuf/issues/125">Using a proto message as a customtype is not allowed.</a>
|
|
* <a href="https://github.com/gogo/protobuf/issues/200">cusomtype of type map can not UnmarshalText</a>
|
|
* <a href="https://github.com/gogo/protobuf/issues/201">customtype of type struct cannot jsonpb unmarshal</a>
|