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MemoizedCallable.php
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MemoizedCallable.php
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<?php
/**
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @author Ori Livneh
*/
/**
* APCu-backed function memoization
*
* This class provides memoization for pure functions. A function is pure
* if its result value depends on nothing other than its input parameters
* and if invoking it does not cause any side-effects.
*
* The first invocation of the memoized callable with a particular set of
* arguments will be delegated to the underlying callable. Repeat invocations
* with the same input parameters will be served from APCu.
*
* @par Example:
* @code
* $memoizedStrrev = new MemoizedCallable( 'range' );
* $memoizedStrrev->invoke( 5, 8 ); // result: array( 5, 6, 7, 8 )
* $memoizedStrrev->invokeArgs( array( 5, 8 ) ); // same
* MemoizedCallable::call( 'range', array( 5, 8 ) ); // same
* @endcode
*
* @since 1.27
*/
class MemoizedCallable {
/** @var callable */
private $callable;
/** @var string Unique name of callable; used for cache keys. */
private $callableName;
/** @var int */
private $ttl;
/**
* @param callable $callable Function or method to memoize.
* @param int $ttl TTL in seconds. Defaults to 3600 (1hr). Capped at 86400 (24h).
*/
public function __construct( $callable, $ttl = 3600 ) {
if ( !is_callable( $callable, false, $this->callableName ) ) {
throw new InvalidArgumentException(
'Argument 1 passed to MemoizedCallable::__construct() must ' .
'be an instance of callable; ' . get_debug_type( $callable ) . ' given'
);
}
if ( $this->callableName === 'Closure::__invoke' ) {
throw new InvalidArgumentException( 'Cannot memoize unnamed closure' );
}
$this->callable = $callable;
$this->ttl = min( max( $ttl, 1 ), 86400 );
}
/**
* Fetch the result of a previous invocation.
*
* @param string $key
* @param bool &$success
* @return bool
*/
protected function fetchResult( $key, &$success ) {
$success = false;
if ( function_exists( 'apcu_fetch' ) ) {
return apcu_fetch( $key, $success );
}
return false;
}
/**
* Store the result of an invocation.
*
* @param string $key
* @param mixed $result
*/
protected function storeResult( $key, $result ) {
if ( function_exists( 'apcu_store' ) ) {
apcu_store( $key, $result, $this->ttl );
}
}
/**
* Invoke the memoized function or method.
*
* @throws InvalidArgumentException If parameters list contains non-scalar items.
* @param array $args Parameters for memoized function or method.
* @return mixed The memoized callable's return value.
*/
public function invokeArgs( array $args = [] ) {
foreach ( $args as $arg ) {
if ( $arg !== null && !is_scalar( $arg ) ) {
throw new InvalidArgumentException(
'MemoizedCallable::invoke() called with non-scalar ' .
'argument'
);
}
}
$hash = md5( serialize( $args ) );
$key = __CLASS__ . ':' . $this->callableName . ':' . $hash;
$success = false;
$result = $this->fetchResult( $key, $success );
if ( !$success ) {
$result = ( $this->callable )( ...$args );
$this->storeResult( $key, $result );
}
return $result;
}
/**
* Invoke the memoized function or method.
*
* Like MemoizedCallable::invokeArgs(), but variadic.
*
* @param mixed ...$params Parameters for memoized function or method.
* @return mixed The memoized callable's return value.
*/
public function invoke( ...$params ) {
return $this->invokeArgs( $params );
}
/**
* Shortcut method for creating a MemoizedCallable and invoking it
* with the specified arguments.
*
* @param callable $callable
* @param array $args
* @param int $ttl
* @return mixed
*/
public static function call( $callable, array $args = [], $ttl = 3600 ) {
$instance = new self( $callable, $ttl );
return $instance->invokeArgs( $args );
}
}

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