cubefs
130 строк · 4.9 Кб
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// Experimental
23//
24// Notice: This package is EXPERIMENTAL and may be changed or removed in a
25// later release.
26package encoding
27
28import (
29"io"
30"strings"
31)
32
33// Identity specifies the optional encoding for uncompressed streams.
34// It is intended for grpc internal use only.
35const Identity = "identity"
36
37// Compressor is used for compressing and decompressing when sending or
38// receiving messages.
39type Compressor interface {
40// Compress writes the data written to wc to w after compressing it. If an
41// error occurs while initializing the compressor, that error is returned
42// instead.
43Compress(w io.Writer) (io.WriteCloser, error)
44// Decompress reads data from r, decompresses it, and provides the
45// uncompressed data via the returned io.Reader. If an error occurs while
46// initializing the decompressor, that error is returned instead.
47Decompress(r io.Reader) (io.Reader, error)
48// Name is the name of the compression codec and is used to set the content
49// coding header. The result must be static; the result cannot change
50// between calls.
51Name() string
52// If a Compressor implements
53// DecompressedSize(compressedBytes []byte) int, gRPC will call it
54// to determine the size of the buffer allocated for the result of decompression.
55// Return -1 to indicate unknown size.
56//
57// Experimental
58//
59// Notice: This API is EXPERIMENTAL and may be changed or removed in a
60// later release.
61}
62
63var registeredCompressor = make(map[string]Compressor)
64
65// RegisterCompressor registers the compressor with gRPC by its name. It can
66// be activated when sending an RPC via grpc.UseCompressor(). It will be
67// automatically accessed when receiving a message based on the content coding
68// header. Servers also use it to send a response with the same encoding as
69// the request.
70//
71// NOTE: this function must only be called during initialization time (i.e. in
72// an init() function), and is not thread-safe. If multiple Compressors are
73// registered with the same name, the one registered last will take effect.
74func RegisterCompressor(c Compressor) {
75registeredCompressor[c.Name()] = c
76}
77
78// GetCompressor returns Compressor for the given compressor name.
79func GetCompressor(name string) Compressor {
80return registeredCompressor[name]
81}
82
83// Codec defines the interface gRPC uses to encode and decode messages. Note
84// that implementations of this interface must be thread safe; a Codec's
85// methods can be called from concurrent goroutines.
86type Codec interface {
87// Marshal returns the wire format of v.
88Marshal(v interface{}) ([]byte, error)
89// Unmarshal parses the wire format into v.
90Unmarshal(data []byte, v interface{}) error
91// Name returns the name of the Codec implementation. The returned string
92// will be used as part of content type in transmission. The result must be
93// static; the result cannot change between calls.
94Name() string
95}
96
97var registeredCodecs = make(map[string]Codec)
98
99// RegisterCodec registers the provided Codec for use with all gRPC clients and
100// servers.
101//
102// The Codec will be stored and looked up by result of its Name() method, which
103// should match the content-subtype of the encoding handled by the Codec. This
104// is case-insensitive, and is stored and looked up as lowercase. If the
105// result of calling Name() is an empty string, RegisterCodec will panic. See
106// Content-Type on
107// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
108// more details.
109//
110// NOTE: this function must only be called during initialization time (i.e. in
111// an init() function), and is not thread-safe. If multiple Compressors are
112// registered with the same name, the one registered last will take effect.
113func RegisterCodec(codec Codec) {
114if codec == nil {
115panic("cannot register a nil Codec")
116}
117if codec.Name() == "" {
118panic("cannot register Codec with empty string result for Name()")
119}
120contentSubtype := strings.ToLower(codec.Name())
121registeredCodecs[contentSubtype] = codec
122}
123
124// GetCodec gets a registered Codec by content-subtype, or nil if no Codec is
125// registered for the content-subtype.
126//
127// The content-subtype is expected to be lowercase.
128func GetCodec(contentSubtype string) Codec {
129return registeredCodecs[contentSubtype]
130}
131