Utils.java

/**                                                                                                                                                                                
 * Copyright (c) 2010 Yahoo! Inc. All rights reserved.                                                                                                                             
 *                                                                                                                                                                                 
 * Licensed under the Apache License, Version 2.0 (the "License"); you                                                                                                             
 * may not use this file except in compliance with the License. You                                                                                                                
 * may obtain a copy of the License at                                                                                                                                             
 *                                                                                                                                                                                 
 * http://www.apache.org/licenses/LICENSE-2.0                                                                                                                                      
 *                                                                                                                                                                                 
 * Unless required by applicable law or agreed to in writing, software                                                                                                             
 * distributed under the License is distributed on an "AS IS" BASIS,                                                                                                               
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or                                                                                                                 
 * implied. See the License for the specific language governing                                                                                                                    
 * permissions and limitations under the License. See accompanying                                                                                                                 
 * LICENSE file.                                                                                                                                                                   
 */

package com.couchbase.loadgen;

import java.util.Random;

/**
 * Utility functions.
 */
public class Utils {
	static Random random = new Random();

	/**
	 * Generate a random ASCII string of a given length.
	 */
	public static String ASCIIString(int length) {
		int interval = '~' - ' ' + 1;

		byte[] buf = new byte[length];
		random.nextBytes(buf);
		for (int i = 0; i < length; i++) {
			if (buf[i] < 0) {
				buf[i] = (byte) ((-buf[i] % interval) + ' ');
			} else {
				buf[i] = (byte) ((buf[i] % interval) + ' ');
			}
		}
		return new String(buf);
	}

	/**
	 * Hash an integer value.
	 */
	public static int hash(int val) {
		return FNVhash32(val);
	}

	public static final int FNV_offset_basis_32 = 0x811c9dc5;
	public static final int FNV_prime_32 = 16777619;

	/**
	 * 32 bit FNV hash. Produces more "random" hashes than (say)
	 * String.hashCode().
	 * 
	 * @param val
	 *            The value to hash.
	 * @return The hash value
	 */
	public static int FNVhash32(int val) {
		// from http://en.wikipedia.org/wiki/Fowler_Noll_Vo_hash
		int hashval = FNV_offset_basis_32;

		for (int i = 0; i < 4; i++) {
			int octet = val & 0x00ff;
			val = val >> 8;

			hashval = hashval ^ octet;
			hashval = hashval * FNV_prime_32;
			// hashval = hashval ^ octet;
		}
		return Math.abs(hashval);
	}

	public static final long FNV_offset_basis_64 = 0xCBF29CE484222325L;
	public static final long FNV_prime_64 = 1099511628211L;

	/**
	 * 64 bit FNV hash. Produces more "random" hashes than (say)
	 * String.hashCode().
	 * 
	 * @param val
	 *            The value to hash.
	 * @return The hash value
	 */
	public static long FNVhash64(long val) {
		// from http://en.wikipedia.org/wiki/Fowler_Noll_Vo_hash
		long hashval = FNV_offset_basis_64;

		for (int i = 0; i < 8; i++) {
			long octet = val & 0x00ff;
			val = val >> 8;

			hashval = hashval ^ octet;
			hashval = hashval * FNV_prime_64;
			// hashval = hashval ^ octet;
		}
		return Math.abs(hashval);
	}
}