X-Git-Url: https://scripts.mit.edu/gitweb/autoinstallsdev/mediawiki.git/blobdiff_plain/19e297c21b10b1b8a3acad5e73fc71dcb35db44a..6932310fd58ebef145fa01eb76edf7150284d8ea:/vendor/wikimedia/cdb/src/Util.php

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+<?php
+
+namespace Cdb;
+
+/**
+ * This is a port of D.J. Bernstein's CDB to PHP. It's based on the copy that
+ * appears in PHP 5.3. Changes are:
+ *    * Error returns replaced with exceptions
+ *    * Exception thrown if sizes or offsets are between 2GB and 4GB
+ *    * Some variables renamed
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+
+/**
+ * Common functions for readers and writers
+ */
+class Util {
+	/**
+	 * Take a modulo of a signed integer as if it were an unsigned integer.
+	 * $b must be less than 0x40000000 and greater than 0
+	 *
+	 * @param int $a
+	 * @param int $b
+	 *
+	 * @return int
+	 */
+	public static function unsignedMod( $a, $b ) {
+		if ( $a & 0x80000000 ) {
+			$m = ( $a & 0x7fffffff ) % $b + 2 * ( 0x40000000 % $b );
+
+			return $m % $b;
+		} else {
+			return $a % $b;
+		}
+	}
+
+	/**
+	 * Shift a signed integer right as if it were unsigned
+	 * @param int $a
+	 * @param int $b
+	 * @return int
+	 */
+	public static function unsignedShiftRight( $a, $b ) {
+		if ( $b == 0 ) {
+			return $a;
+		}
+		if ( $a & 0x80000000 ) {
+			return ( ( $a & 0x7fffffff ) >> $b ) | ( 0x40000000 >> ( $b - 1 ) );
+		} else {
+			return $a >> $b;
+		}
+	}
+
+	/**
+	 * The CDB hash function.
+	 *
+	 * @param string $s
+	 *
+	 * @return int
+	 */
+	public static function hash( $s ) {
+		$h = 5381;
+		$len = strlen( $s );
+		for ( $i = 0; $i < $len; $i++ ) {
+			$h5 = ( $h << 5 ) & 0xffffffff;
+			// Do a 32-bit sum
+			// Inlined here for speed
+			$sum = ( $h & 0x3fffffff ) + ( $h5 & 0x3fffffff );
+			$h =
+				(
+					( $sum & 0x40000000 ? 1 : 0 )
+					+ ( $h & 0x80000000 ? 2 : 0 )
+					+ ( $h & 0x40000000 ? 1 : 0 )
+					+ ( $h5 & 0x80000000 ? 2 : 0 )
+					+ ( $h5 & 0x40000000 ? 1 : 0 )
+				) << 30
+				| ( $sum & 0x3fffffff );
+			$h ^= ord( $s[$i] );
+			$h &= 0xffffffff;
+		}
+
+		return $h;
+	}
+}