grpc: implementation of PreparedMsg API

grpc: implementation of PreparedMsg API

preloader.go

@@ -0,0 +1,66 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package grpc
+
+import (
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+// PreparedMsg is responsible for creating a Marshalled and Compressed object
+type PreparedMsg struct {
+	// Struct for preparing msg before sending them
+	encodedData []byte
+	hdr         []byte
+	payload     []byte
+}
+
+// Encode is responsible for preprocessing the data using relevant information
+// from the stream's Context
+// TODO(prannayk) : if something changes then mark prepared msg as old
+// Encode : marshal and compresses data based on stream context
+// Returns error in case of error
+func (p *PreparedMsg) Encode(s Stream, msg interface{}) error {
+	ctx := s.Context()
+	rpcInfo, ok := rpcInfoFromContext(ctx)
+	if !ok {
+		return status.Errorf(codes.Internal, "grpc: unable to get rpcInfo")
+	}
+
+	// check if the context has the relevant information to prepareMsg
+	if rpcInfo.preloaderInfo == nil {
+		return status.Errorf(codes.Internal, "grpc: rpcInfo.preloaderInfo is nil")
+	}
+	if rpcInfo.preloaderInfo.codec == nil {
+		return status.Errorf(codes.Internal, "grpc: rpcInfo.preloaderInfo.codec is nil")
+	}
+
+	// prepare the msg
+	data, err := encode(rpcInfo.preloaderInfo.codec, msg)
+	if err != nil {
+		return err
+	}
+	p.encodedData = data
+	compData, err := compress(data, rpcInfo.preloaderInfo.cp, rpcInfo.preloaderInfo.comp)
+	if err != nil {
+		return err
+	}
+	p.hdr, p.payload = msgHeader(data, compData)
+	return nil
+}