Online PHP editor | perf for ebQoq

@ 2024-11-28T13:08:42Z

<?php

function isLongerThanCT(string $input, int $targetLength): bool
{
	$amount = PHP_INT_SIZE === 8 ? 63 : 31;
    $len = strlen($input); // use mb_strlen($input, '8bit'); on older PHP
    $res = (($targetLength - $len) >> $amount) & 1;
    /*
     * It's worth taking a moment to explain what the hell the line above is doing.
	 * 
     * ($targetLength - $len) will return a negative value if $targetLength is larger than $len.
     *
     * By two's complement, negative values when shifted 31 or 63 places to the right will have a lower
     * bit set. We then use a bit mask of `1` and the bitwise `&` operator on the result of the bitshift.
     *
     * End result? It's the same as if we did the following, except constant-time:
     * $res = (int) ($len > $targetLength);
     */
    return (bool) ($res);
}

$long = str_repeat('A', 72);
var_dump(
  isLongerThanCT($long, 71),
  isLongerThanCT($long, 72),
  isLongerThanCT($long, 73)
);

Here you find the average performance (time & memory) of each version. A grayed out version indicates it didn't complete successfully (based on exit-code).

Version	System time (s)	User time (s)	Memory (MiB)
8.4.2	0.012	0.009	21.31
8.4.1	0.016	0.006	19.72
8.3.15	0.018	0.000	17.09
8.3.14	0.038	0.008	16.43
8.3.13	0.030	0.011	16.25
8.3.12	0.032	0.008	16.55
8.3.11	0.033	0.007	16.82
8.3.10	0.044	0.003	16.27
8.3.9	0.033	0.013	16.63
8.3.8	0.027	0.003	16.45
8.3.7	0.022	0.011	16.33
8.3.6	0.030	0.015	16.43
8.3.5	0.038	0.007	16.77
8.3.4	0.039	0.000	17.40
8.3.3	0.030	0.006	17.43
8.3.2	0.032	0.004	17.39
8.3.1	0.030	0.006	17.54
8.3.0	0.017	0.003	17.53
8.2.27	0.011	0.007	16.77
8.2.26	0.024	0.008	16.76
8.2.25	0.017	0.017	16.55
8.2.24	0.026	0.006	16.50
8.2.23	0.022	0.013	16.53
8.2.22	0.023	0.013	16.76
8.2.21	0.032	0.008	16.00
8.2.20	0.018	0.018	16.82
8.2.19	0.024	0.015	16.43
8.2.18	0.021	0.012	16.64
8.2.17	0.026	0.016	17.95
8.2.16	0.027	0.010	17.54
8.2.15	0.022	0.019	17.55
8.2.14	0.038	0.003	17.46
8.2.13	0.031	0.006	17.51
8.2.12	0.033	0.000	17.34
8.2.11	0.024	0.003	17.67
8.2.10	0.019	0.000	17.57
8.2.9	0.018	0.003	17.44
8.2.8	0.015	0.004	17.51
8.2.7	0.034	0.006	17.64
8.2.6	0.035	0.006	17.29
8.2.5	0.032	0.008	17.52
8.2.4	0.028	0.006	17.61
8.2.3	0.027	0.003	17.57
8.2.2	0.032	0.006	17.45
8.2.1	0.023	0.013	17.35
8.2.0	0.024	0.012	17.48

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