mirror of
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119 lines
4.5 KiB
Go
119 lines
4.5 KiB
Go
/*
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*
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* Copyright 2017 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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// Package encoding defines the interface for the compressor and codec, and
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// functions to register and retrieve compressors and codecs.
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//
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// This package is EXPERIMENTAL.
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package encoding
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import (
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"io"
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"strings"
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)
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// Identity specifies the optional encoding for uncompressed streams.
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// It is intended for grpc internal use only.
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const Identity = "identity"
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// Compressor is used for compressing and decompressing when sending or
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// receiving messages.
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type Compressor interface {
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// Compress writes the data written to wc to w after compressing it. If an
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// error occurs while initializing the compressor, that error is returned
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// instead.
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Compress(w io.Writer) (io.WriteCloser, error)
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// Decompress reads data from r, decompresses it, and provides the
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// uncompressed data via the returned io.Reader. If an error occurs while
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// initializing the decompressor, that error is returned instead.
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Decompress(r io.Reader) (io.Reader, error)
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// Name is the name of the compression codec and is used to set the content
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// coding header. The result must be static; the result cannot change
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// between calls.
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Name() string
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}
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var registeredCompressor = make(map[string]Compressor)
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// RegisterCompressor registers the compressor with gRPC by its name. It can
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// be activated when sending an RPC via grpc.UseCompressor(). It will be
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// automatically accessed when receiving a message based on the content coding
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// header. Servers also use it to send a response with the same encoding as
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// the request.
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//
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// NOTE: this function must only be called during initialization time (i.e. in
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// an init() function), and is not thread-safe. If multiple Compressors are
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// registered with the same name, the one registered last will take effect.
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func RegisterCompressor(c Compressor) {
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registeredCompressor[c.Name()] = c
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}
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// GetCompressor returns Compressor for the given compressor name.
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func GetCompressor(name string) Compressor {
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return registeredCompressor[name]
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}
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// Codec defines the interface gRPC uses to encode and decode messages. Note
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// that implementations of this interface must be thread safe; a Codec's
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// methods can be called from concurrent goroutines.
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type Codec interface {
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// Marshal returns the wire format of v.
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Marshal(v interface{}) ([]byte, error)
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// Unmarshal parses the wire format into v.
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Unmarshal(data []byte, v interface{}) error
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// Name returns the name of the Codec implementation. The returned string
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// will be used as part of content type in transmission. The result must be
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// static; the result cannot change between calls.
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Name() string
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}
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var registeredCodecs = make(map[string]Codec)
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// RegisterCodec registers the provided Codec for use with all gRPC clients and
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// servers.
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//
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// The Codec will be stored and looked up by result of its Name() method, which
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// should match the content-subtype of the encoding handled by the Codec. This
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// is case-insensitive, and is stored and looked up as lowercase. If the
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// result of calling Name() is an empty string, RegisterCodec will panic. See
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// Content-Type on
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// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
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// more details.
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//
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// NOTE: this function must only be called during initialization time (i.e. in
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// an init() function), and is not thread-safe. If multiple Compressors are
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// registered with the same name, the one registered last will take effect.
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func RegisterCodec(codec Codec) {
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if codec == nil {
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panic("cannot register a nil Codec")
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}
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if codec.Name() == "" {
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panic("cannot register Codec with empty string result for Name()")
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}
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contentSubtype := strings.ToLower(codec.Name())
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registeredCodecs[contentSubtype] = codec
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}
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// GetCodec gets a registered Codec by content-subtype, or nil if no Codec is
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// registered for the content-subtype.
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//
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// The content-subtype is expected to be lowercase.
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func GetCodec(contentSubtype string) Codec {
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return registeredCodecs[contentSubtype]
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}
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