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Description

Determine approximate backtrack count when running PCRE.

Usage

$int = benchmark_pcre_backtracking( $pattern, $subject, $strategy );

Parameters

$pattern

( mixed ) required –

$subject

( mixed ) required –

$strategy

( mixed ) required –

Returns

int The backtrack count.

Source

File name: wordpress-develop-tests/phpunit/includes/utils.php
Lines:

function benchmark_pcre_backtracking( $pattern, $subject, $strategy ) {
  $saved_config = ini_get( 'pcre.backtrack_limit' );

  // Attempt to prevent PHP crashes. Adjust lower when needed.
  $limit = 1000000;

  // Start with small numbers, so if a crash is encountered at higher numbers we can still debug the problem.
  for ( $i = 4; $i <= $limit; $i *= 2 ) {

    ini_set( 'pcre.backtrack_limit', $i );

    switch ( $strategy ) {
      case 'split':
        preg_split( $pattern, $subject );
        break;
      case 'match':
        preg_match( $pattern, $subject );
        break;
      case 'match_all':
        $matches = array();
        preg_match_all( $pattern, $subject, $matches );
        break;
    }

    ini_set( 'pcre.backtrack_limit', $saved_config );

    switch ( preg_last_error() ) {
      case PREG_NO_ERROR:
        return $i;
      case PREG_BACKTRACK_LIMIT_ERROR:
        break;
      case PREG_RECURSION_LIMIT_ERROR:
        trigger_error( 'PCRE recursion limit encountered before backtrack limit.' );
        return;
      case PREG_BAD_UTF8_ERROR:
        trigger_error( 'UTF-8 error during PCRE benchmark.' );
        return;
      case PREG_INTERNAL_ERROR:
        trigger_error( 'Internal error during PCRE benchmark.' );
        return;
      default:
        trigger_error( 'Unexpected error during PCRE benchmark.' );
        return;
    }
  }

  return $i;
}
 

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