timezone_transitions_get is very slow

[blar]

timezone_transitions_get is very slow, because php_format_date in add_nominal with the default value ZEND_LONG_MIN took very long to iterate from ZEND_LONG_MIN to ZEND_LONG_MAX on 64 bit systems. No transitions exists at this time before the timestamp -2147483648 (INT32_MIN).

With this patch:

Default Value
Duration: 0.000201

Timestamp for 1970-01-01 00:00:00
Duration: 0.000092

Timestamp for 0001-01-01 00:00:00
Duration: 0.000087

PHP 7.1.6:

Default Value
Duration: 0.045996

Timestamp for 1970-01-01 00:00:00
Duration: 0.000082

Timestamp for 0001-01-01 00:00:00
Duration: 0.000097

Benchmark

function measure_duration(callable $callback) {
    $start = microtime(true);
    call_user_func($callback);
    $duration = microtime(true) - $start;
    printf("Duration: %s\n\n", number_format($duration, 6));
}

$timezone = new DateTimeZone('Europe/Berlin');

measure_duration(function() use($timezone) {
    printf("Default Value\n");
    $timezone->getTransitions();
});

measure_duration(function() use($timezone) {
    $timestamp = 0;
    printf("Timestamp for %s\n", date('Y-m-d H:i:s', $timestamp));
    $timezone->getTransitions($timestamp);
});

measure_duration(function() use($timezone) {
    $timestamp = -62135596800;
    printf("Timestamp for %s\n", date('Y-m-d H:i:s', $timestamp));
    $timezone->getTransitions($timestamp);
});

https://3v4l.org/MhkR8

[KalleZ]

cc @derickr

[derickr]

This patch fixes a symptom, and not a cause. The real problem lies in timelib:

https://github.com/derickr/timelib/blob/master/unixtime2tm.c#L77-L81

should really do the same as:

https://github.com/derickr/timelib/blob/master/unixtime2tm.c#L52-L55

So I am closing this pull request, and I've added an issue on timelib:

derickr/timelib#18

[derickr]

BTW, I'd be more than welcome to accept a patch for timelib if you wish to make one.