1 files changed, 69 insertions, 0 deletions
diff --git a/includes/ArrayUtils.php b/includes/ArrayUtils.php
new file mode 100644
index 00000000..0b74f06a
--- /dev/null
+++ b/includes/ArrayUtils.php
@@ -0,0 +1,69 @@
+<?php
+
+class ArrayUtils {
+	/**
+	 * Sort the given array in a pseudo-random order which depends only on the
+	 * given key and each element value. This is typically used for load
+	 * balancing between servers each with a local cache.
+	 *
+	 * Keys are preserved. The input array is modified in place.
+	 *
+	 * Note: Benchmarking on PHP 5.3 and 5.4 indicates that for small
+	 * strings, md5() is only 10% slower than hash('joaat',...) etc.,
+	 * since the function call overhead dominates. So there's not much
+	 * justification for breaking compatibility with installations
+	 * compiled with ./configure --disable-hash.
+	 *
+	 * @param $array The array to sort
+	 * @param $key The string key
+	 * @param $separator A separator used to delimit the array elements and the
+	 *     key. This can be chosen to provide backwards compatibility with
+	 *     various consistent hash implementations that existed before this
+	 *     function was introduced.
+	 */
+	public static function consistentHashSort( &$array, $key, $separator = "\000" ) {
+		$hashes = array();
+		foreach ( $array as $elt ) {
+			$hashes[$elt] = md5( $elt . $separator . $key );
+		}
+		uasort( $array, function ( $a, $b ) use ( $hashes ) {
+			return strcmp( $hashes[$a], $hashes[$b] );
+		} );
+	}
+
+	/**
+	 * Given an array of non-normalised probabilities, this function will select
+	 * an element and return the appropriate key
+	 *
+	 * @param $weights array
+	 *
+	 * @return bool|int|string
+	 */
+	public static function pickRandom( $weights ){
+		if ( !is_array( $weights ) || count( $weights ) == 0 ) {
+			return false;
+		}
+
+		$sum = array_sum( $weights );
+		if ( $sum == 0 ) {
+			# No loads on any of them
+			# In previous versions, this triggered an unweighted random selection,
+			# but this feature has been removed as of April 2006 to allow for strict
+			# separation of query groups.
+			return false;
+		}
+		$max = mt_getrandmax();
+		$rand = mt_rand( 0, $max ) / $max * $sum;
+
+		$sum = 0;
+		foreach ( $weights as $i => $w ) {
+			$sum += $w;
+			# Do not return keys if they have 0 weight.
+			# Note that the "all 0 weight" case is handed above
+			if ( $w > 0 && $sum >= $rand ) {
+				break;
+			}
+		}
+		return $i;
+	}
+}