Introduce new Compressor/Decompressor API (#1428)

encoding/encoding.go

@@ -0,0 +1,57 @@
+/*
+ *
+ * Copyright 2017 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 encoding defines the interface for the compressor and the functions
+// to register and get the compossor.
+// This package is EXPERIMENTAL.
+package encoding
+
+import (
+	"io"
+)
+
+var registerCompressor = make(map[string]Compressor)
+
+// Compressor is used for compressing and decompressing when sending or receiving messages.
+type Compressor interface {
+	// Compress writes the data written to wc to w after compressing it.  If an error
+	// occurs while initializing the compressor, that error is returned instead.
+	Compress(w io.Writer) (io.WriteCloser, error)
+	// Decompress reads data from r, decompresses it, and provides the uncompressed data
+	// via the returned io.Reader.  If an error occurs while initializing the decompressor, that error
+	// is returned instead.
+	Decompress(r io.Reader) (io.Reader, error)
+	// Name is the name of the compression codec and is used to set the content coding header.
+	Name() string
+}
+
+// RegisterCompressor registers the compressor with gRPC by its name.  It can be activated when
+// sending an RPC via grpc.UseCompressor().  It will be automatically accessed when receiving a
+// message based on the content coding header.  Servers also use it to send a response with the
+// same encoding as the request.
+//
+// NOTE: this function must only be called during initialization time (i.e. in an init() function).  If
+// multiple Compressors are registered with the same name, the one registered last will take effect.
+func RegisterCompressor(c Compressor) {
+	registerCompressor[c.Name()] = c
+}
+
+// GetCompressor returns Compressor for the given compressor name.
+func GetCompressor(name string) Compressor {
+	return registerCompressor[name]
+}