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package proxy
import (
"fmt"
"google.golang.org/grpc/encoding"
grpcproto "google.golang.org/grpc/encoding/proto"
"google.golang.org/protobuf/proto"
)
// NewCodec returns a proxying encoding.Codec with the default protobuf codec as parent.
//
// See CodecWithParent.
func NewCodec() encoding.Codec {
return CodecWithParent(protoCodec{})
}
// CodecWithParent returns a proxying encoding.Codec with a user provided codec as parent.
//
// This codec is *crucial* to the functioning of the proxy. It allows the proxy server to be oblivious
// to the schema of the forwarded messages. It basically treats a gRPC message frame as raw bytes.
// However, if the server handler, or the client caller are not proxy-internal functions it will fall back
// to trying to decode the message using a fallback codec.
func CodecWithParent(fallback encoding.Codec) encoding.Codec {
return rawCodec{fallback}
}
type rawCodec struct {
parentCodec encoding.Codec
}
type frame struct {
payload []byte
}
func (c rawCodec) Marshal(v interface{}) ([]byte, error) {
out, ok := v.(*frame)
if !ok {
return c.parentCodec.Marshal(v)
}
return out.payload, nil
}
func (c rawCodec) Unmarshal(data []byte, v interface{}) error {
dst, ok := v.(*frame)
if !ok {
return c.parentCodec.Unmarshal(data, v)
}
dst.payload = data
return nil
}
func (c rawCodec) Name() string {
return fmt.Sprintf("proxy>%s", c.parentCodec.Name())
}
// protoCodec is a Codec implementation with protobuf. It is the default rawCodec for gRPC.
type protoCodec struct{}
func (protoCodec) Marshal(v interface{}) ([]byte, error) {
return proto.Marshal(v.(proto.Message))
}
func (protoCodec) Unmarshal(data []byte, v interface{}) error {
return proto.Unmarshal(data, v.(proto.Message))
}
func (protoCodec) Name() string {
return grpcproto.Name
}
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