class Environment

class Environment {
    
    /**
     * Compares the memory required for an operation to the available memory.
     *
     * @param string $required
     *   The memory required for the operation, expressed as a number of bytes with
     *   optional SI or IEC binary unit prefix (e.g. 2, 3K, 5MB, 10G, 6GiB, 8bytes,
     *   9mbytes).
     * @param $memory_limit
     *   (optional) The memory limit for the operation, expressed as a number of
     *   bytes with optional SI or IEC binary unit prefix (e.g. 2, 3K, 5MB, 10G,
     *   6GiB, 8bytes, 9mbytes). If no value is passed, the current PHP
     *   memory_limit will be used. Defaults to NULL.
     *
     * @return bool
     *   TRUE if there is sufficient memory to allow the operation, or FALSE
     *   otherwise.
     */
    public static function checkMemoryLimit($required, $memory_limit = NULL) {
        if (!isset($memory_limit)) {
            $memory_limit = ini_get('memory_limit');
        }
        // There is sufficient memory if:
        // - No memory limit is set.
        // - The memory limit is set to unlimited (-1).
        // - The memory limit is greater than or equal to the memory required for
        //   the operation.
        return !$memory_limit || $memory_limit == -1 || Bytes::toNumber($memory_limit) >= Bytes::toNumber($required);
    }
    
    /**
     * Attempts to set the PHP maximum execution time.
     *
     * This function is a wrapper around the PHP function set_time_limit(). When
     * called, set_time_limit() restarts the timeout counter from zero. In other
     * words, if the timeout is the default 30 seconds, and 25 seconds into script
     * execution a call such as set_time_limit(20) is made, the script will run
     * for a total of 45 seconds before timing out.
     *
     * If the current time limit is not unlimited it is possible to decrease the
     * total time limit if the sum of the new time limit and the current time
     * spent running the script is inferior to the original time limit. It is
     * inherent to the way set_time_limit() works, it should rather be called with
     * an appropriate value every time you need to allocate a certain amount of
     * time to execute a task than only once at the beginning of the script.
     *
     * Before calling set_time_limit(), we check if this function is available
     * because it could be disabled by the server administrator.
     *
     * @param int $time_limit
     *   An integer time limit in seconds, or 0 for unlimited execution time.
     *
     * @return bool
     *   Whether set_time_limit() was successful or not.
     */
    public static function setTimeLimit($time_limit) {
        if (function_exists('set_time_limit')) {
            $current = ini_get('max_execution_time');
            // Do not set time limit if it is currently unlimited.
            if ($current != 0) {
                return set_time_limit($time_limit);
            }
        }
        return FALSE;
    }
    
    /**
     * Determines the maximum file upload size by querying the PHP settings.
     *
     * @return int
     *   A file size limit in bytes based on the PHP upload_max_filesize and
     *   post_max_size settings.
     */
    public static function getUploadMaxSize() {
        static $max_size = -1;
        if ($max_size < 0) {
            // Start with post_max_size.
            $max_size = Bytes::toNumber(ini_get('post_max_size'));
            // If upload_max_size is less, then reduce. Except if upload_max_size is
            // zero, which indicates no limit.
            $upload_max = Bytes::toNumber(ini_get('upload_max_filesize'));
            if ($upload_max > 0 && $upload_max < $max_size) {
                $max_size = $upload_max;
            }
        }
        return $max_size;
    }

}