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|
--TEST--
Random: Randomizer: getBytesFromString(): Fast Path Masking
--FILE--
<?php
use Random\Engine\Test\TestWrapperEngine;
use Random\Engine\Xoshiro256StarStar;
use Random\Randomizer;
require __DIR__ . "/../../engines.inc";
$allBytes = implode('', array_map(
fn ($byte) => chr($byte),
range(0x00, 0xff)
));
// Xoshiro256** is the fastest engine available.
$xoshiro = new Xoshiro256StarStar();
var_dump(strlen($allBytes));
echo PHP_EOL;
// Fast path: Inputs less than or equal to 256.
for ($i = 1; $i <= strlen($allBytes); $i *= 2) {
echo "{$i}:", PHP_EOL;
$wrapper = new TestWrapperEngine($xoshiro);
$r = new Randomizer($wrapper);
$result = $r->getBytesFromString(substr($allBytes, 0, $i), 20000);
// Xoshiro256** is a 64 Bit engine and thus generates 8 bytes at once.
// For powers of two we expect no rejections and thus exactly
// 20000/8 = 2500 calls to the engine.
var_dump($wrapper->getCount());
$count = [];
for ($j = 0; $j < strlen($result); $j++) {
$b = $result[$j];
$count[ord($b)] ??= 0;
$count[ord($b)]++;
}
// We also expect that each possible value appears at least once, if
// not is is very likely that some bits were erroneously masked away.
var_dump(count($count));
echo PHP_EOL;
}
// Test lengths that are one more than the powers of two. For these
// the maximum offset will be a power of two and thus a minimal number
// of bits will be set in the offset.
for ($i = 1; ($i + 1) <= strlen($allBytes); $i *= 2) {
$oneMore = $i + 1;
echo "{$oneMore}:", PHP_EOL;
$wrapper = new TestWrapperEngine($xoshiro);
$r = new Randomizer($wrapper);
$result = $r->getBytesFromString(substr($allBytes, 0, $oneMore), 20000);
$count = [];
for ($j = 0; $j < strlen($result); $j++) {
$b = $result[$j];
$count[ord($b)] ??= 0;
$count[ord($b)]++;
}
// We expect that each possible value appears at least once, if
// not is is very likely that some bits were erroneously masked away.
var_dump(count($count));
echo PHP_EOL;
}
echo "Slow Path:", PHP_EOL;
$wrapper = new TestWrapperEngine($xoshiro);
$r = new Randomizer($wrapper);
$result = $r->getBytesFromString($allBytes . $allBytes, 20000);
// In the slow path we expect one call per byte, i.e. 20000
var_dump($wrapper->getCount());
$count = [];
for ($j = 0; $j < strlen($result); $j++) {
$b = $result[$j];
$count[ord($b)] ??= 0;
$count[ord($b)]++;
}
// We also expect that each possible value appears at least once, if
// not is is very likely that some bits were erroneously masked away.
var_dump(count($count));
?>
--EXPECT--
int(256)
1:
int(2500)
int(1)
2:
int(2500)
int(2)
4:
int(2500)
int(4)
8:
int(2500)
int(8)
16:
int(2500)
int(16)
32:
int(2500)
int(32)
64:
int(2500)
int(64)
128:
int(2500)
int(128)
256:
int(2500)
int(256)
2:
int(2)
3:
int(3)
5:
int(5)
9:
int(9)
17:
int(17)
33:
int(33)
65:
int(65)
129:
int(129)
Slow Path:
int(20000)
int(256)
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