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ArcanistHgServerChannel.php
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ArcanistHgServerChannel.php
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<?php
/**
* Channel to a Mercurial "cmdserver" server. Messages sent to the server
* look like this:
*
* runcommand\n
* 8 # Length, as a 4-byte unsigned long.
* log\0
* -l\0
* 5
*
* In PHP, the format of these messages is an array of arguments:
*
* array(
* 'runcommand',
* 'log',
* '-l',
* '5',
* );
*
* The server replies with messages that look like this:
*
* o
* 1234 # Length, as a 4-byte unsigned long.
* <data: 1234 bytes>
*
* The first character in a message from the server is the "channel". Mercurial
* channels have nothing to do with Phutil channels; they are more similar to
* stdout/stderr. Mercurial has four primary channels:
*
* 'o'utput, like stdout
* 'e'rror, like stderr
* 'r'esult, like return codes
* 'd'ebug, like an external log file
*
* In PHP, the format of these messages is a pair, with the channel and then
* the data:
*
* array('o', '<data...>');
*
* In general, we send "runcommand" requests, and the server responds with
* a series of messages on the "output" channel and then a single response
* on the "result" channel to indicate that output is complete.
*
* @task protocol Protocol Implementation
*/
final class ArcanistHgServerChannel extends PhutilProtocolChannel {
const MODE_CHANNEL = 'channel';
const MODE_LENGTH = 'length';
const MODE_BLOCK = 'block';
private $mode = self::MODE_CHANNEL;
private $byteLengthOfNextChunk = 1;
private $buf = '';
/* -( Protocol Implementation )-------------------------------------------- */
/**
* Encode a message for transmission to the server. The message should be
* formatted as an array, like this:
*
* array(
* 'runcommand',
* 'log',
* '-l',
* '5',
* );
*
*
* We will return the cmdserver version of this:
*
* runcommand\n
* 8 # Length, as a 4-byte unsigned long.
* log\0
* -l\0
* 5
*
* @param list<string> List of command arguments.
* @return string Encoded string for transmission to the server.
*
* @task protocol
*/
protected function encodeMessage($argv) {
if (!is_array($argv)) {
throw new Exception("Message to Mercurial server should be an array.");
}
$command = head($argv);
$args = array_slice($argv, 1);
$args = implode("\0", $args);
$len = strlen($args);
$len = pack('N', $len);
return "{$command}\n{$len}{$args}";
}
/**
* Decode a message received from the server. The message looks like this:
*
* o
* 1234 # Length, as a 4-byte unsigned long.
* <data: 1234 bytes>
*
* ...where 'o' is the "channel" the message is being sent over.
*
* We decode into a pair in PHP, which looks like this:
*
* array('o', '<data...>');
*
* @param string Bytes from the server.
* @return list<pair<string,string>> Zero or more complete messages.
*
* @task protocol
*/
protected function decodeStream($data) {
$this->buf .= $data;
// We always know how long the next chunk is, so this parser is fairly
// easy to implement.
$messages = array();
while ($this->byteLengthOfNextChunk <= strlen($this->buf)) {
$chunk = substr($this->buf, 0, $this->byteLengthOfNextChunk);
$this->buf = substr($this->buf, $this->byteLengthOfNextChunk);
switch ($this->mode) {
case self::MODE_CHANNEL:
// We've received the channel name, one of 'o', 'e', 'r' or 'd' for
// 'output', 'error', 'result' or 'debug' respectively. This is a
// single byte long. Next, we'll expect a length.
$this->channel = $chunk;
$this->byteLengthOfNextChunk = 4;
$this->mode = self::MODE_LENGTH;
break;
case self::MODE_LENGTH:
// We've received the length of the data, as a 4-byte big-endian
// unsigned integer. Next, we'll expect the data itself.
$this->byteLengthOfNextChunk = head(unpack('N', $chunk));
$this->mode = self::MODE_BLOCK;
break;
case self::MODE_BLOCK:
// We've received the data itself, which is a block of bytes of the
// given length. We produce a message from the channel and the data
// and return it. Next, we expect another channel name.
$message = array($this->channel, $chunk);
$this->byteLengthOfNextChunk = 1;
$this->mode = self::MODE_CHANNEL;
$this->channel = null;
$messages[] = $message;
break;
}
}
// Return zero or more messages, which might look something like this:
//
// array(
// array('o', '<...>'),
// array('o', '<...>'),
// array('r', '<...>'),
// );
return $messages;
}
}

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