php计算网段内所有IP，分配子网段

由于最近业务需要，写了个获取网段内所有IP的函数，以及分配可用子网段的函数

/**
 * 根据网段获取计算所有IP
 * @param string $segment 网段 '139.217.0.1/24'
 * @return array IP列表 ['139.217.0.1','139.217.0.2'……]
 */
function getIpBySegment($segment)
{
    $segmentInfo = explode("/", $segment);//['139.217.0.1',24]
    $beginIpArray = explode(".", $segmentInfo[0]);//[139,217,0,1]
    $mask = intval($segmentInfo['1']);//24
    $endIp = array();
    foreach ($beginIpArray as $ipKey => $item) {
        $beginFlag = 8 * ($ipKey);//0   8   16  24
        $endFlag = 8 * ($ipKey + 1);//8   16  24  32
        $decbinItem = str_pad(decbin($item), 8, "0", STR_PAD_LEFT);
        $endIp[] = $mask >= $endFlag ? $item : ($mask > $beginFlag ? bindec(str_pad(substr($decbinItem, 0, $mask - $beginFlag), 8, "1", STR_PAD_RIGHT)) : ($ipKey <= 2 ? pow(2, 8) - 1 : pow(2, 8) - 1));
    }
    $ipArray = array();
    for ($beginIp[0] = $beginIpArray[0]; $beginIp[0] <= $endIp[0]; $beginIp[0]++) {
        for ($beginIp[1] = $beginIpArray[1]; $beginIp[1] <= $endIp[1]; $beginIp[1]++) {
            for ($beginIp[2] = $beginIpArray[2]; $beginIp[2] <= $endIp[2]; $beginIp[2]++) {
                for ($beginIp[3] = $beginIpArray[3]; $beginIp[3] <= $endIp[3]; $beginIp[3]++) {
                    $ipArray[] = implode(".", $beginIp);
                }
            }
        }
    }
    return $ipArray;
}

/**
 * 在指定网段中分配子网段
 * @param string $segment 指定网段
 * @param int $ipNum 需要的IP数
 * @param array $usedIpArray 不可用（已经使用）的IP，默认为空数组
 * @return bool|string 成功则返回分配的网段
 */
function allocateSegment($segment, $ipNum, $usedIpArray = [])
{
    $usedIpArray = empty($usedIpArray) ? [] : array_flip($usedIpArray);
    //计算需要多少个IP
    $i = 0;
    $ipCount = pow(2, $i);
    while ($ipCount < $ipNum) {
        $i++;
        $ipCount = pow(2, $i);
    }
    $newMask = 32 - $i;
    //大网段的开始和结束IP
    $segmentInfo = explode("/", $segment);//['139.217.0.1',24]
    $beginIpArray = explode(".", $segmentInfo[0]);//[139,217,0,1]
    $mask = intval($segmentInfo['1']);//24
    if ($newMask < $mask) {
        return false;
    }
    $endIp = array();
    $step = [];
    foreach ($beginIpArray as $ipKey => $item) {
        $beginFlag = 8 * ($ipKey);//0   8   16  24
        $endFlag = 8 * ($ipKey + 1);//8   16  24  32
        $step[$ipKey] = $newMask > $endFlag ? 1 : ($endFlag - $newMask < 8 ? pow(2, $endFlag - $newMask) : pow(2, 8));
        $decbinItem = str_pad(decbin($item), 8, "0", STR_PAD_LEFT);
        $endIp[] = $mask >= $endFlag ? $item : ($mask > $beginFlag ? bindec(str_pad(substr($decbinItem, 0, $mask - $beginFlag), 8, "1", STR_PAD_RIGHT)) : ($ipKey <= 2 ? pow(2, 8) - 1 : pow(2, 8) - 1));
    }
    //遍历生成网段
    for ($beginIp[0] = $beginIpArray[0]; $beginIp[0] <= $endIp[0]; $beginIp[0] += $step[0]) {
        for ($beginIp[1] = $beginIpArray[1]; $beginIp[1] <= $endIp[1]; $beginIp[1] += $step[1]) {
            for ($beginIp[2] = $beginIpArray[2]; $beginIp[2] <= $endIp[2]; $beginIp[2] += $step[2]) {
                for ($beginIp[3] = $beginIpArray[3]; $beginIp[3] <= $endIp[3]; $beginIp[3] += $step[3]) {
                    $newSegment = implode('.', $beginIp) . '/' . $newMask;
                    //获取该网段所有的IP
                    $ipArray = getIpBySegment($newSegment);
                    $canUse = true;
                    //判断该网段是否可用
                    if (!empty($usedIpArray)) {
                        foreach ($ipArray as $ip) {
                            if (isset($usedIpArray[$ip])) {
                                $canUse = false;
                                break;
                            }
                        }
                    }
                    if ($canUse) {
                        return $newSegment;
                    }
                }
            }
        }
    }
    return false;
}