mirror of
https://github.com/kemko/nomad.git
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15fb4c990a
This PR switches the Nomad repository from using govendor to Go modules for managing dependencies. Aspects of the Nomad workflow remain pretty much the same. The usual Makefile targets should continue to work as they always did. The API submodule simply defers to the parent Nomad version on the repository, keeping the semantics of API versioning that currently exists.
103 lines
2.9 KiB
Go
103 lines
2.9 KiB
Go
// Copyright 2017 The Gorilla WebSocket Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package websocket
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import (
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"bytes"
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"net"
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"sync"
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"time"
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)
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// PreparedMessage caches on the wire representations of a message payload.
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// Use PreparedMessage to efficiently send a message payload to multiple
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// connections. PreparedMessage is especially useful when compression is used
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// because the CPU and memory expensive compression operation can be executed
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// once for a given set of compression options.
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type PreparedMessage struct {
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messageType int
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data []byte
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mu sync.Mutex
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frames map[prepareKey]*preparedFrame
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}
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// prepareKey defines a unique set of options to cache prepared frames in PreparedMessage.
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type prepareKey struct {
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isServer bool
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compress bool
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compressionLevel int
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}
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// preparedFrame contains data in wire representation.
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type preparedFrame struct {
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once sync.Once
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data []byte
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}
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// NewPreparedMessage returns an initialized PreparedMessage. You can then send
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// it to connection using WritePreparedMessage method. Valid wire
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// representation will be calculated lazily only once for a set of current
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// connection options.
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func NewPreparedMessage(messageType int, data []byte) (*PreparedMessage, error) {
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pm := &PreparedMessage{
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messageType: messageType,
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frames: make(map[prepareKey]*preparedFrame),
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data: data,
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}
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// Prepare a plain server frame.
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_, frameData, err := pm.frame(prepareKey{isServer: true, compress: false})
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if err != nil {
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return nil, err
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}
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// To protect against caller modifying the data argument, remember the data
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// copied to the plain server frame.
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pm.data = frameData[len(frameData)-len(data):]
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return pm, nil
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}
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func (pm *PreparedMessage) frame(key prepareKey) (int, []byte, error) {
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pm.mu.Lock()
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frame, ok := pm.frames[key]
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if !ok {
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frame = &preparedFrame{}
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pm.frames[key] = frame
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}
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pm.mu.Unlock()
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var err error
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frame.once.Do(func() {
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// Prepare a frame using a 'fake' connection.
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// TODO: Refactor code in conn.go to allow more direct construction of
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// the frame.
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mu := make(chan struct{}, 1)
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mu <- struct{}{}
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var nc prepareConn
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c := &Conn{
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conn: &nc,
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mu: mu,
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isServer: key.isServer,
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compressionLevel: key.compressionLevel,
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enableWriteCompression: true,
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writeBuf: make([]byte, defaultWriteBufferSize+maxFrameHeaderSize),
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}
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if key.compress {
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c.newCompressionWriter = compressNoContextTakeover
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}
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err = c.WriteMessage(pm.messageType, pm.data)
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frame.data = nc.buf.Bytes()
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})
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return pm.messageType, frame.data, err
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}
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type prepareConn struct {
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buf bytes.Buffer
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net.Conn
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}
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func (pc *prepareConn) Write(p []byte) (int, error) { return pc.buf.Write(p) }
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func (pc *prepareConn) SetWriteDeadline(t time.Time) error { return nil }
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