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/*
*
* 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 codec, and
// functions to register and retrieve compressors and codecs.
//
// Experimental
//
// Notice: This package is EXPERIMENTAL and may be changed or removed in a
// later release.
package encoding
import (
"io"
"strings"
)
// Identity specifies the optional encoding for uncompressed streams.
// It is intended for grpc internal use only.
const Identity = "identity"
// 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. The result must be static; the result cannot change
// between calls.
Name() string
// If a Compressor implements
// DecompressedSize(compressedBytes []byte) int, gRPC will call it
// to determine the size of the buffer allocated for the result of decompression.
// Return -1 to indicate unknown size.
//
// Experimental
//
// Notice: This API is EXPERIMENTAL and may be changed or removed in a
// later release.
}
var registeredCompressor = make(map[string]Compressor)
// 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), and is not thread-safe. If multiple Compressors are
// registered with the same name, the one registered last will take effect.
func RegisterCompressor(c Compressor) {
registeredCompressor[c.Name()] = c
}
// GetCompressor returns Compressor for the given compressor name.
func GetCompressor(name string) Compressor {
return registeredCompressor[name]
}
// Codec defines the interface gRPC uses to encode and decode messages. Note
// that implementations of this interface must be thread safe; a Codec's
// methods can be called from concurrent goroutines.
type Codec interface {
// Marshal returns the wire format of v.
Marshal(v interface{}) ([]byte, error)
// Unmarshal parses the wire format into v.
Unmarshal(data []byte, v interface{}) error
// Name returns the name of the Codec implementation. The returned string
// will be used as part of content type in transmission. The result must be
// static; the result cannot change between calls.
Name() string
}
var registeredCodecs = make(map[string]Codec)
// RegisterCodec registers the provided Codec for use with all gRPC clients and
// servers.
//
// The Codec will be stored and looked up by result of its Name() method, which
// should match the content-subtype of the encoding handled by the Codec. This
// is case-insensitive, and is stored and looked up as lowercase. If the
// result of calling Name() is an empty string, RegisterCodec will panic. See
// Content-Type on
// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
// more details.
//
// NOTE: this function must only be called during initialization time (i.e. in
// an init() function), and is not thread-safe. If multiple Compressors are
// registered with the same name, the one registered last will take effect.
func RegisterCodec(codec Codec) {
if codec == nil {
panic("cannot register a nil Codec")
}
if codec.Name() == "" {
panic("cannot register Codec with empty string result for Name()")
}
contentSubtype := strings.ToLower(codec.Name())
registeredCodecs[contentSubtype] = codec
}
// GetCodec gets a registered Codec by content-subtype, or nil if no Codec is
// registered for the content-subtype.
//
// The content-subtype is expected to be lowercase.
func GetCodec(contentSubtype string) Codec {
return registeredCodecs[contentSubtype]
}
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