Scott Baker | 2d89798 | 2019-09-24 11:50:08 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * |
| 3 | * Copyright 2017 gRPC authors. |
| 4 | * |
| 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 |
| 8 | * |
| 9 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 10 | * |
| 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. |
| 16 | * |
| 17 | */ |
| 18 | |
| 19 | // Package encoding defines the interface for the compressor and codec, and |
| 20 | // functions to register and retrieve compressors and codecs. |
| 21 | // |
| 22 | // This package is EXPERIMENTAL. |
| 23 | package encoding |
| 24 | |
| 25 | import ( |
| 26 | "io" |
| 27 | "strings" |
| 28 | ) |
| 29 | |
| 30 | // Identity specifies the optional encoding for uncompressed streams. |
| 31 | // It is intended for grpc internal use only. |
| 32 | const Identity = "identity" |
| 33 | |
| 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 |
| 39 | // instead. |
| 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 |
| 47 | // between calls. |
| 48 | Name() string |
| 49 | } |
| 50 | |
| 51 | var registeredCompressor = make(map[string]Compressor) |
| 52 | |
| 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 |
| 57 | // the request. |
| 58 | // |
| 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 |
| 64 | } |
| 65 | |
| 66 | // GetCompressor returns Compressor for the given compressor name. |
| 67 | func GetCompressor(name string) Compressor { |
| 68 | return registeredCompressor[name] |
| 69 | } |
| 70 | |
| 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. |
| 82 | Name() string |
| 83 | } |
| 84 | |
| 85 | var registeredCodecs = make(map[string]Codec) |
| 86 | |
| 87 | // RegisterCodec registers the provided Codec for use with all gRPC clients and |
| 88 | // servers. |
| 89 | // |
| 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 |
| 94 | // Content-Type on |
| 95 | // https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for |
| 96 | // more details. |
| 97 | // |
| 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) { |
| 102 | if codec == nil { |
| 103 | panic("cannot register a nil Codec") |
| 104 | } |
| 105 | contentSubtype := strings.ToLower(codec.Name()) |
| 106 | if contentSubtype == "" { |
| 107 | panic("cannot register Codec with empty string result for String()") |
| 108 | } |
| 109 | registeredCodecs[contentSubtype] = codec |
| 110 | } |
| 111 | |
| 112 | // GetCodec gets a registered Codec by content-subtype, or nil if no Codec is |
| 113 | // registered for the content-subtype. |
| 114 | // |
| 115 | // The content-subtype is expected to be lowercase. |
| 116 | func GetCodec(contentSubtype string) Codec { |
| 117 | return registeredCodecs[contentSubtype] |
| 118 | } |