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<?php |
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/** |
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* Wait loop that reaches a condition or times out. |
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* |
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* This program is free software; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License as published by |
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* the Free Software Foundation; either version 2 of the License, or |
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* (at your option) any later version. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License along |
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* with this program; if not, write to the Free Software Foundation, Inc., |
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
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* http://www.gnu.org/copyleft/gpl.html |
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* |
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* @file |
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* @author Aaron Schulz |
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*/ |
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/** |
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* Wait loop that reaches a condition or times out |
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* @since 1.28 |
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*/ |
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class WaitConditionLoop { |
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/** @var callable */ |
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private $condition; |
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/** @var callable[] */ |
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private $busyCallbacks = []; |
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/** @var float Seconds */ |
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private $timeout; |
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/** @var float Seconds */ |
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private $lastWaitTime; |
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const CONDITION_REACHED = 1; |
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const CONDITION_CONTINUE = 0; // evaluates as falsey |
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const CONDITION_TIMED_OUT = -1; |
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const CONDITION_ABORTED = -2; |
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/** |
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* @param callable $condition Callback that returns a WaitConditionLoop::CONDITION_ constant |
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* @param float $timeout Timeout in seconds |
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* @param array &$busyCallbacks List of callbacks to do useful work (by reference) |
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*/ |
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public function __construct( callable $condition, $timeout = 5.0, &$busyCallbacks = [] ) { |
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$this->condition = $condition; |
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$this->timeout = $timeout; |
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$this->busyCallbacks =& $busyCallbacks; |
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} |
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/** |
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* Invoke the loop and continue until either: |
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* - a) The condition callback does not return either CONDITION_CONTINUE or true |
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* - b) The timeout is reached |
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* This a condition callback can return true (stop) or false (continue) for convenience. |
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* In such cases, the halting result of "true" will be converted to CONDITION_REACHED. |
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* |
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* Exceptions in callbacks will be caught and the callback will be swapped with |
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* one that simply rethrows that exception back to the caller when invoked. |
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* |
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* @return integer WaitConditionLoop::CONDITION_* constant |
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* @throws Exception Any error from the condition callback |
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*/ |
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public function invoke() { |
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$elapsed = 0.0; // seconds |
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$sleepUs = 0; // microseconds to sleep each time |
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$lastCheck = false; |
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$finalResult = self::CONDITION_TIMED_OUT; |
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do { |
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$checkStartTime = $this->getWallTime(); |
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// Check if the condition is met yet |
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$realStart = $this->getWallTime(); |
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$cpuStart = $this->getCpuTime(); |
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$checkResult = call_user_func( $this->condition ); |
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$cpu = $this->getCpuTime() - $cpuStart; |
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$real = $this->getWallTime() - $realStart; |
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// Exit if the condition is reached |
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if ( (int)$checkResult !== self::CONDITION_CONTINUE ) { |
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$finalResult = is_int( $checkResult ) ? $checkResult : self::CONDITION_REACHED; |
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break; |
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} elseif ( $lastCheck ) { |
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break; // timeout |
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} |
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// Detect if condition callback seems to block or if justs burns CPU |
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$conditionUsesInterrupts = ( $real > 0.100 && $cpu <= $real * .03 ); |
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if ( !$this->popAndRunBusyCallback() && !$conditionUsesInterrupts ) { |
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// 10 queries = 10(10+100)/2 ms = 550ms, 14 queries = 1050ms |
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$sleepUs = min( $sleepUs + 10 * 1e3, 1e6 ); // stop incrementing at ~1s |
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$this->usleep( $sleepUs ); |
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} |
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$checkEndTime = $this->getWallTime(); |
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// The max() protects against the clock getting set back |
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$elapsed += max( $checkEndTime - $checkStartTime, 0.010 ); |
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// Do not let slow callbacks timeout without checking the condition one more time |
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$lastCheck = ( $elapsed >= $this->timeout ); |
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} while ( true ); |
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$this->lastWaitTime = $elapsed; |
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return $finalResult; |
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} |
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/** |
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* @return float Seconds |
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*/ |
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public function getLastWaitTime() { |
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return $this->lastWaitTime; |
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} |
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/** |
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* @param integer $microseconds |
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*/ |
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protected function usleep( $microseconds ) { |
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usleep( $microseconds ); |
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} |
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/** |
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* @return float |
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*/ |
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protected function getWallTime() { |
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return microtime( true ); |
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} |
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/** |
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* @return float Returns 0.0 if not supported (Windows on PHP < 7) |
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*/ |
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protected function getCpuTime() { |
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$time = 0.0; |
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if ( defined( 'HHVM_VERSION' ) && PHP_OS === 'Linux' ) { |
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$ru = getrusage( 2 /* RUSAGE_THREAD */ ); |
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} else { |
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$ru = getrusage( 0 /* RUSAGE_SELF */ ); |
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} |
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if ( $ru ) { |
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$time += $ru['ru_utime.tv_sec'] + $ru['ru_utime.tv_usec'] / 1e6; |
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$time += $ru['ru_stime.tv_sec'] + $ru['ru_stime.tv_usec'] / 1e6; |
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} |
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return $time; |
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} |
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/** |
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* Run one of the callbacks that does work ahead of time for another caller |
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* |
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* @return bool Whether a callback was executed |
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*/ |
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private function popAndRunBusyCallback() { |
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if ( $this->busyCallbacks ) { |
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reset( $this->busyCallbacks ); |
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$key = key( $this->busyCallbacks ); |
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/** @var callable $workCallback */ |
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$workCallback =& $this->busyCallbacks[$key]; |
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try { |
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$workCallback(); |
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} catch ( Exception $e ) { |
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$workCallback = function () use ( $e ) { |
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throw $e; |
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}; |
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} |
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unset( $this->busyCallbacks[$key] ); // consume |
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return true; |
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} |
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return false; |
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} |
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} |
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wikimedia /
mediawiki
