3 * Copyright 2017 gRPC authors.
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
9 * http://www.apache.org/licenses/LICENSE-2.0
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
19 // Package encoding defines the interface for the compressor and codec, and
20 // functions to register and retrieve compressors and codecs.
22 // This package is EXPERIMENTAL.
30 // Identity specifies the optional encoding for uncompressed streams.
31 // It is intended for grpc internal use only.
32 const Identity = "identity"
34 // Compressor is used for compressing and decompressing when sending or
35 // receiving messages.
36 type Compressor interface {
37 // Compress writes the data written to wc to w after compressing it. If an
38 // error occurs while initializing the compressor, that error is returned
40 Compress(w io.Writer) (io.WriteCloser, error)
41 // Decompress reads data from r, decompresses it, and provides the
42 // uncompressed data via the returned io.Reader. If an error occurs while
43 // initializing the decompressor, that error is returned instead.
44 Decompress(r io.Reader) (io.Reader, error)
45 // Name is the name of the compression codec and is used to set the content
46 // coding header. The result must be static; the result cannot change
51 var registeredCompressor = make(map[string]Compressor)
53 // RegisterCompressor registers the compressor with gRPC by its name. It can
54 // be activated when sending an RPC via grpc.UseCompressor(). It will be
55 // automatically accessed when receiving a message based on the content coding
56 // header. Servers also use it to send a response with the same encoding as
59 // NOTE: this function must only be called during initialization time (i.e. in
60 // an init() function), and is not thread-safe. If multiple Compressors are
61 // registered with the same name, the one registered last will take effect.
62 func RegisterCompressor(c Compressor) {
63 registeredCompressor[c.Name()] = c
66 // GetCompressor returns Compressor for the given compressor name.
67 func GetCompressor(name string) Compressor {
68 return registeredCompressor[name]
71 // Codec defines the interface gRPC uses to encode and decode messages. Note
72 // that implementations of this interface must be thread safe; a Codec's
73 // methods can be called from concurrent goroutines.
74 type Codec interface {
75 // Marshal returns the wire format of v.
76 Marshal(v interface{}) ([]byte, error)
77 // Unmarshal parses the wire format into v.
78 Unmarshal(data []byte, v interface{}) error
79 // Name returns the name of the Codec implementation. The returned string
80 // will be used as part of content type in transmission. The result must be
81 // static; the result cannot change between calls.
85 var registeredCodecs = make(map[string]Codec)
87 // RegisterCodec registers the provided Codec for use with all gRPC clients and
90 // The Codec will be stored and looked up by result of its Name() method, which
91 // should match the content-subtype of the encoding handled by the Codec. This
92 // is case-insensitive, and is stored and looked up as lowercase. If the
93 // result of calling Name() is an empty string, RegisterCodec will panic. See
95 // https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
98 // NOTE: this function must only be called during initialization time (i.e. in
99 // an init() function), and is not thread-safe. If multiple Compressors are
100 // registered with the same name, the one registered last will take effect.
101 func RegisterCodec(codec Codec) {
103 panic("cannot register a nil Codec")
105 contentSubtype := strings.ToLower(codec.Name())
106 if contentSubtype == "" {
107 panic("cannot register Codec with empty string result for String()")
109 registeredCodecs[contentSubtype] = codec
112 // GetCodec gets a registered Codec by content-subtype, or nil if no Codec is
113 // registered for the content-subtype.
115 // The content-subtype is expected to be lowercase.
116 func GetCodec(contentSubtype string) Codec {
117 return registeredCodecs[contentSubtype]