com.lmax.disruptor.util.Util Maven / Gradle / Ivy
/*
* Copyright 2011 LMAX Ltd.
*
* 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.
*/
package com.lmax.disruptor.util;
import java.lang.reflect.Field;
import java.security.AccessController;
import java.security.PrivilegedExceptionAction;
import com.lmax.disruptor.EventProcessor;
import com.lmax.disruptor.Sequence;
import sun.misc.Unsafe;
/**
* Set of common functions used by the Disruptor
*/
public final class Util
{
/**
* Calculate the next power of 2, greater than or equal to x.
* From Hacker's Delight, Chapter 3, Harry S. Warren Jr.
*
* @param x Value to round up
* @return The next power of 2 from x inclusive
*/
public static int ceilingNextPowerOfTwo(final int x)
{
return 1 << (32 - Integer.numberOfLeadingZeros(x - 1));
}
/**
* Get the minimum sequence from an array of {@link com.lmax.disruptor.Sequence}s.
*
* @param sequences to compare.
* @return the minimum sequence found or Long.MAX_VALUE if the array is empty.
*/
public static long getMinimumSequence(final Sequence[] sequences)
{
return getMinimumSequence(sequences, Long.MAX_VALUE);
}
/**
* Get the minimum sequence from an array of {@link com.lmax.disruptor.Sequence}s.
*
* @param sequences to compare.
* @param minimum an initial default minimum. If the array is empty this value will be
* returned.
* @return the smaller of minimum sequence value found in {@code sequences} and {@code minimum};
* {@code minimum} if {@code sequences} is empty
*/
public static long getMinimumSequence(final Sequence[] sequences, long minimum)
{
for (int i = 0, n = sequences.length; i < n; i++)
{
long value = sequences[i].get();
minimum = Math.min(minimum, value);
}
return minimum;
}
/**
* Get an array of {@link Sequence}s for the passed {@link EventProcessor}s
*
* @param processors for which to get the sequences
* @return the array of {@link Sequence}s
*/
public static Sequence[] getSequencesFor(final EventProcessor... processors)
{
Sequence[] sequences = new Sequence[processors.length];
for (int i = 0; i < sequences.length; i++)
{
sequences[i] = processors[i].getSequence();
}
return sequences;
}
private static final Unsafe THE_UNSAFE;
static
{
try
{
final PrivilegedExceptionAction action = new PrivilegedExceptionAction()
{
public Unsafe run() throws Exception
{
Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
theUnsafe.setAccessible(true);
return (Unsafe) theUnsafe.get(null);
}
};
THE_UNSAFE = AccessController.doPrivileged(action);
}
catch (Exception e)
{
throw new RuntimeException("Unable to load unsafe", e);
}
}
/**
* Get a handle on the Unsafe instance, used for accessing low-level concurrency
* and memory constructs.
*
* @return The Unsafe
*/
public static Unsafe getUnsafe()
{
return THE_UNSAFE;
}
/**
* Calculate the log base 2 of the supplied integer, essentially reports the location
* of the highest bit.
*
* @param i Value to calculate log2 for.
* @return The log2 value
*/
public static int log2(int i)
{
int r = 0;
while ((i >>= 1) != 0)
{
++r;
}
return r;
}
}