6c278b6d7e
* Removed spaces around array index * Removed double spaces or added spaces to begin or end of function calls, method signature, conditions or foreachs * Added braces to one-line ifs * Changed multi line conditions to one line conditions * Realigned some arrays Change-Id: Ia04d2a99d663b07101013c2d53b3b2e872fd9cc3
69 lines
2.1 KiB
PHP
69 lines
2.1 KiB
PHP
<?php
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class ArrayUtils {
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/**
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* Sort the given array in a pseudo-random order which depends only on the
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* given key and each element value. This is typically used for load
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* balancing between servers each with a local cache.
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*
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* Keys are preserved. The input array is modified in place.
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*
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* Note: Benchmarking on PHP 5.3 and 5.4 indicates that for small
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* strings, md5() is only 10% slower than hash('joaat',...) etc.,
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* since the function call overhead dominates. So there's not much
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* justification for breaking compatibility with installations
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* compiled with ./configure --disable-hash.
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*
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* @param $array The array to sort
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* @param $key The string key
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* @param $separator A separator used to delimit the array elements and the
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* key. This can be chosen to provide backwards compatibility with
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* various consistent hash implementations that existed before this
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* function was introduced.
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*/
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public static function consistentHashSort( &$array, $key, $separator = "\000" ) {
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$hashes = array();
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foreach ( $array as $elt ) {
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$hashes[$elt] = md5( $elt . $separator . $key );
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}
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uasort( $array, function ( $a, $b ) use ( $hashes ) {
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return strcmp( $hashes[$a], $hashes[$b] );
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} );
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}
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/**
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* Given an array of non-normalised probabilities, this function will select
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* an element and return the appropriate key
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*
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* @param $weights array
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*
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* @return bool|int|string
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*/
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public static function pickRandom( $weights ) {
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if ( !is_array( $weights ) || count( $weights ) == 0 ) {
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return false;
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}
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$sum = array_sum( $weights );
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if ( $sum == 0 ) {
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# No loads on any of them
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# In previous versions, this triggered an unweighted random selection,
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# but this feature has been removed as of April 2006 to allow for strict
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# separation of query groups.
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return false;
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}
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$max = mt_getrandmax();
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$rand = mt_rand( 0, $max ) / $max * $sum;
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$sum = 0;
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foreach ( $weights as $i => $w ) {
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$sum += $w;
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# Do not return keys if they have 0 weight.
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# Note that the "all 0 weight" case is handed above
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if ( $w > 0 && $sum >= $rand ) {
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break;
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}
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}
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return $i;
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}
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}
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