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libphutil/src/channel/PhutilExecChannel.php
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PhutilExecChannel.php
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<?php
/*
* Copyright 2012 Facebook, Inc.
*
* 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.
*/
/**
* Channel on an underlying @{class:ExecFuture}. For a description of channels,
* see @{class:PhutilChannel}.
*
* For example, you can open a channel on `nc` like this:
*
* $future = new ExecFuture('nc example.com 80');
* $channel = new PhutilExecChannel($future);
*
* $channel->write("GET / HTTP/1.0\n\n");
* while (true) {
* echo $channel->read();
*
* PhutilChannel::waitForAny(array($channel));
* if (!$channel->update()) {
* // Break out of the loop when the channel closes.
* break;
* }
* }
*
* This script makes an HTTP request to "example.com". This example is heavily
* contrived. In most cases, @{class:ExecFuture} and other futures constructs
* offer a much easier way to solve problems which involve system commands, and
* @{class:HTTPFuture} and other HTTP constructs offer a much easier way to
* solve problems which involve HTTP.
*
* @{class:PhutilExecChannel} is generally useful only when a program acts like
* a server but performs I/O on stdin/stdout, and you need to act like a client
* or interact with the program at the same time as you manage traditional
* socket connections. Examples are Mercurial operating in "cmdserve" mode, git
* operating in "receive-pack" mode, etc. It is unlikely that any reasonble
* use of this class is concise enough to make a short example out of, so you
* get a contrived one instead.
*
* See also @{class:PhutilSocketChannel}, for a similar channel that uses
* sockets for I/O.
*
* Since @{class:ExecFuture} already supports buffered I/O and socket selection,
* the implementation of this class is fairly straightforward.
*
* @task construct Construction
*
* @group channel
*/
final class PhutilExecChannel extends PhutilChannel {
private $future;
/* -( Construction )------------------------------------------------------- */
/**
* Construct an exec channel from a @{class:ExecFuture}. The future should
* **NOT** have been started yet (e.g., with `isReady()` or `start()`),
* because @{class:ExecFuture} closes stdin by default when futures start.
* If stdin has been closed, you will be unable to write on the channel.
*
* @param ExecFuture Future to use as an underlying I/O source.
* @task construct
*/
public function __construct(ExecFuture $future) {
// Make an empty write to keep the stdin pipe open. By default, futures
// close this pipe when they start.
$future->write('', $keep_pipe = true);
// Start the future so that reads and writes work immediately.
$future->isReady();
$this->future = $future;
}
public function __destruct() {
if (!$this->future->isReady()) {
$this->future->resolveKill();
}
}
public function update() {
$this->future->isReady();
return parent::update();
}
public function isOpen() {
return !$this->future->isReady();
}
protected function readBytes() {
list($stdout, $stderr) = $this->future->read();
$this->future->discardBuffers();
if (strlen($stderr)) {
throw new Exception("Unexpected output to stderr on Exec channel.");
}
return $stdout;
}
public function write($bytes) {
$this->future->write($bytes, $keep_pipe = true);
}
protected function writeBytes($bytes) {
throw new Exception("ExecFuture can not write bytes directly!");
}
protected function getReadSockets() {
return $this->future->getReadSockets();
}
protected function getWriteSockets() {
return $this->future->getWriteSockets();
}
}
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