byte helper

/**
 * Gets max upload size from post_max_size and upload_max_filesize
 * Returns whichever is smaller
 *
 * @return int
 */
function file_upload_max_size() {
    $max_size = convert_to_bytes(ini_get('post_max_size'));
    $upload_max = convert_to_bytes(ini_get('upload_max_filesize'));
    if ($upload_max > 0 && $upload_max < $max_size) {
        $max_size = $upload_max;
    }
    return $max_size;
}

/**
 * Converts KB (K) through GB (G) to bytes
 *
 * @param string $from
 * @return int bytes
 */
function convert_to_bytes($from) {
    $number = filter_var($from, FILTER_SANITIZE_NUMBER_INT);
    if (empty($number)) {
        return 0;
    }
    $type = strtoupper(str_replace($number, '', $from));
    switch ($type) {
        case "KB":
        case "K":
            $number = $number * 1024;
            break;
        case "MB":
        case "M":
            $number = $number * pow(1024, 2);
            break;
        case "GB":
        case "G":
            $number = $number * pow(1024, 3);
            break;
        default:
            return 0;
    }
    return fix_integer_overflow($number);
}

/**
 * Converts bytes to KB (K) through GB (G)
 *
 * @param int $bytes
 * @param string $type Type to convert to
 *                     KB (K) through GB (G)
 * @return int bytes
 */
function convert_bytes_to_type($bytes, $type = 'MB') {
    $number = filter_var($bytes, FILTER_SANITIZE_NUMBER_INT);
    if (empty($number)) {
        return 0;
    }
    $type = strtoupper(str_replace($number, '', $type));
    switch ($type) {
        case "KB":
        case "K":
            $divisor = 1024;
            break;
        case "MB":
        case "M":
            $divisor = pow(1024, 2);
            break;
        case "GB":
        case "G":
            $divisor = pow(1024, 3);
            break;
        default:
            return 0;
    }
    return $bytes / $divisor;
}

/**
 * Converts bytes into human readable form
 *
 * @param string || File
 * @param int precision round precision
 * @return int rounded bytes in units
 */
function human_readable_bytes($bytes, $precision = 2) {
    $CI = & get_instance();
    $CI->lang->load('number');
    if (is_file($bytes)) {
        $bytes = fix_integer_overflow(filesize($bytes));
    }
    $units = array(
        $CI->lang->line('bytes'),
        $CI->lang->line('kilobyte_abbr'),
        $CI->lang->line('megabyte_abbr'),
        $CI->lang->line('gigabyte_abbr'),
        $CI->lang->line('terabyte_abbr')
    );
    $bytes = max($bytes, 0);
    $pow = floor(($bytes ? log($bytes) : 0) / log(1024));
    $pow = min($pow, count($units) - 1);
    $bytes /= pow(1024, $pow);
    return round($bytes, $precision) . ' ' . $units[$pow];
}

/**
 * Fixes integer overflow
 *
 * @param int $size
 * @return int
 */
function fix_integer_overflow($size) {
    if ($size < 0) {
        $size += 2.0 * (PHP_INT_MAX + 1);
    }
    return $size;
}