refactor(mask): simplify MaskUtil::getDataMaskBit implementation

[vlakoff]

Several simplifications in the MaskUtil::getDataMaskBit implementation, the most significant ones being:

• replacing BitUtils::unsignedRightShift with straightforward integer division
• using a PHP match expression

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.81%. Comparing base (3feed0e) to head (b07cd58).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #226      +/-   ##
============================================
- Coverage     71.95%   71.81%   -0.14%     
+ Complexity      996      995       -1     
============================================
  Files            49       49              
  Lines          3170     3151      -19     
============================================
- Hits           2281     2263      -18     
+ Misses          889      888       -1     

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[vlakoff]

About replacing BitUtils::unsignedRightShift with straightforward integer division:

Quick benchmark code - unsignedRightShift method call vs integer division

class BitUtils {
    public static function unsignedRightShift(int $a, int $b): int
    {
        return (
            $a >= 0
            ? $a >> $b
            : (($a & 0x7fffffff) >> $b) | (0x40000000 >> ($b - 1))
        );
    }
}

function bench(callable $fn, int $iterations = 1_000_000): string {
    $start = microtime(true);
    $sum = 0;

    for ($i = 0; $i < $iterations; ++$i) {
        $y = ($i & 0xFFFF) - 32768; // includes negatives
        $sum += $fn($y);
    }

    return number_format(microtime(true) - $start, 3);
}

$timeStaticMethod = bench(function($y) {
    return BitUtils::unsignedRightShift($y, 1);
});

$timeInline = bench(function($y) {
    return ($y >= 0)
        ? ($y >> 1)
        : (($y & 0x7fffffff) >> 1) | 0x40000000;
});

$timeOptimized = bench(function($y) {
    return ($y >> 1) & 0x7fffffff;
});

$timeDivision = bench(function($y) {
    return (int) ($y / 2);
});

$timeIntdiv = bench(function($y) {
    return intdiv($y, 2);
});

echo "Static method shift:      {$timeStaticMethod} sec\n";
echo "Inline unsigned shift:    {$timeInline} sec\n";
echo "Optimized unsigned shift: {$timeOptimized} sec\n";
echo "Integer division:         {$timeDivision} sec\n";
echo "intdiv():                 {$timeIntdiv} sec\n";

Results:

== https://onlinephp.io/ - 1M iterations ==

PHP 8.2.29:
Static method shift:      0.295 sec
Inline unsigned shift:    0.100 sec
Optimized unsigned shift: 0.167 sec
Integer division:         0.137 sec
intdiv():                 0.212 sec

PHP 8.3.21:
Static method shift:      0.183 sec
Inline unsigned shift:    0.217 sec
Optimized unsigned shift: 0.188 sec
Integer division:         0.199 sec
intdiv():                 0.137 sec

PHP 8.4.10:
Static method shift:      0.216 sec
Inline unsigned shift:    0.162 sec
Optimized unsigned shift: 0.108 sec
Integer division:         0.203 sec
intdiv():                 0.201 sec

== local - 5M iterations ==

PHP 8.5.4:
Static method shift:      0.396 sec
Inline unsigned shift:    0.261 sec
Optimized unsigned shift: 0.229 sec
Integer division:         0.261 sec
intdiv():                 0.278 sec

intdiv() is the cleanest method, and as a bonus it is marginally faster than calling BitUtils::unsignedRightShift.

[DASPRiD]

I assume other places which use unsignedRightShift cannot be modified the same way?

[vlakoff]

This simplification only works when the value being shifted is guaranteed to be non‑negative.

For non‑negative inputs, unsignedRightShift($x, n) behaves the same as an arithmetic operation like intdiv($x, 2**n).

But if the input can be negative, logical right shift and arithmetic right shift diverge, so those cases can’t be simplified in the same straightforward way.

[Copilot]

Pull request overview

Refactors MaskUtil::getDataMaskBit() to simplify mask-bit computation logic in the QR encoder, replacing the prior switch/bitwise implementation with a match expression and integer division.

Changes:

• Replaced switch-based mask selection with a PHP match expression.
• Removed dependency on BitUtils::unsignedRightShift() in favor of intdiv().
• Dropped InvalidArgumentException handling/documentation for invalid mask patterns.

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[DASPRiD]

thanks!