php - 位掩码到数组

Question

我需要从位掩码获取所有工作日。是否有分解位掩码的功能？
例如:

const MONDAY    = 1 << 0; // 1
const TUESSAY   = 1 << 1; // 2
const WEDNESDAY = 1 << 2; // 4
const THURSSAY  = 1 << 3; // 8
const FRIDAY    = 1 << 4; // 16
const SATURDAY  = 1 << 5; // 32
const SUNDAY    = 1 << 6; // 64

function bitmaskToArray(int $bitmask): array
{
    //...
}

$wednesdayAndMonday = WEDNESDAY | MONDAY;

var_dump(bitmaskToArray($wednesdayAndMonday));

我看到了一种解决方案，但我相信它不是最好的:

const WEEKDAYS = [
    MONDAY,
    TUESSAY,
    WEDNESDAY,
    THURSDAY,
    FRIDAY,
    SATURDAY,
    SUNDAY,
];

function bitmaskToArray(int $bitmask): array
{
    $result = [];
    foreach (WEEKDAYS as $weekday) {
        if ($bitmask & $weekday) {
            $result []= $weekday;
        }
    }
    
    return $result;
}

Answer 1

您可以遍历位数并计算循环中的位移。

function bitmaskToArray(int $bitmask, int $maxbits): array
{
    $result = [];
    for ($thisbit = 1; $i < (1 < $maxbits); $thisbit <<= 1) {
        if ($bitmask & $thisbit) {
            $result[] = $thisbit;
        }
    }
    
    return $result;
}

然后您可以调用 bitmaskToArray($wednesdayAndMonday, count(WEEKDAYS))