com.gh.bmd.jrt.runner.LocalQueue Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of jroutine Show documentation
Show all versions of jroutine Show documentation
Parallel programming on the go
/*
* 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.gh.bmd.jrt.runner;
import com.gh.bmd.jrt.common.InvocationInterruptedException;
import com.gh.bmd.jrt.time.TimeDuration;
import java.util.concurrent.TimeUnit;
import javax.annotation.Nonnull;
import static com.gh.bmd.jrt.time.TimeDuration.fromUnit;
import static com.gh.bmd.jrt.time.TimeDuration.nanos;
/**
* Class maintaining a queue of executions which is local to the calling thread.
*
* The implementation ensures that recursive executions are broken into commands handled inside a
* consuming loop, running in the same thread.
*
* Created by davide on 9/18/14.
*/
class LocalQueue {
private static final int INITIAL_CAPACITY = 10;
private static final ThreadLocal sQueue = new ThreadLocal() {
@Override
protected LocalQueue initialValue() {
return new LocalQueue();
}
};
private TimeDuration[] mDelays;
private long[] mExecutionTimeNs;
private Execution[] mExecutions;
private int mFirst;
private boolean mIsRunning;
private int mLast;
/**
* Constructor.
*/
private LocalQueue() {
mExecutionTimeNs = new long[INITIAL_CAPACITY];
mExecutions = new Execution[INITIAL_CAPACITY];
mDelays = new TimeDuration[INITIAL_CAPACITY];
}
/**
* Runs the specified execution.
*
* @param execution the execution.
* @param delay the execution delay.
* @param timeUnit the delay time unit.
*/
public static void run(@Nonnull final Execution execution, final long delay,
@Nonnull final TimeUnit timeUnit) {
sQueue.get().addExecution(execution, delay, timeUnit);
}
private static void resizeArray(@Nonnull final T[] src, @Nonnull final T[] dst,
final int first) {
final int remainder = src.length - first;
System.arraycopy(src, 0, dst, 0, first);
System.arraycopy(src, first, dst, dst.length - remainder, remainder);
}
private static void resizeArray(@Nonnull final long[] src, @Nonnull final long[] dst,
final int first) {
final int remainder = src.length - first;
System.arraycopy(src, 0, dst, 0, first);
System.arraycopy(src, first, dst, dst.length - remainder, remainder);
}
private void add(@Nonnull final Execution execution, @Nonnull final TimeDuration delay) {
final int i = mLast;
mExecutionTimeNs[i] = System.nanoTime();
mExecutions[i] = execution;
mDelays[i] = delay;
final int newLast;
if ((i >= (mExecutions.length - 1)) || (i == Integer.MAX_VALUE)) {
newLast = 0;
} else {
newLast = i + 1;
}
if (mFirst == newLast) {
ensureCapacity(mExecutions.length + 1);
}
mLast = newLast;
}
private void addExecution(@Nonnull final Execution execution, final long delay,
@Nonnull final TimeUnit timeUnit) {
add(execution, fromUnit(delay, timeUnit));
if (!mIsRunning) {
run();
}
}
private void ensureCapacity(final int capacity) {
final int size = mExecutions.length;
if (capacity <= size) {
return;
}
int newSize = size;
while (newSize < capacity) {
newSize = newSize << 1;
if (newSize < size) {
throw new OutOfMemoryError();
}
}
final int first = mFirst;
final int last = mLast;
final long[] newExecutionTimeNs = new long[newSize];
resizeArray(mExecutionTimeNs, newExecutionTimeNs, first);
final Execution[] newExecutions = new Execution[newSize];
resizeArray(mExecutions, newExecutions, first);
final TimeDuration[] newDelays = new TimeDuration[newSize];
resizeArray(mDelays, newDelays, first);
mExecutionTimeNs = newExecutionTimeNs;
mExecutions = newExecutions;
mDelays = newDelays;
final int shift = newSize - size;
mFirst = first + shift;
mLast = (last < first) ? last : last + shift;
}
private void run() {
mIsRunning = true;
try {
while (mFirst != mLast) {
final int i = mFirst;
final int last = mLast;
final long[] executionTimeNs = mExecutionTimeNs;
final Execution[] executions = mExecutions;
final TimeDuration[] delays = mDelays;
long timeNs = executionTimeNs[i];
Execution execution = executions[i];
TimeDuration delay = delays[i];
final long currentTimeNs = System.nanoTime();
long delayNs = timeNs - currentTimeNs + delay.toNanos();
if (delayNs > 0) {
final int length = executions.length;
long minDelay = delayNs;
int s = i;
int j = i + 1;
if (j >= length) {
j = 0;
}
while (j != last) {
final long nextDelayNs =
executionTimeNs[j] - currentTimeNs + delays[j].toNanos();
if (nextDelayNs <= 0) {
s = j;
break;
}
if (nextDelayNs < minDelay) {
minDelay = nextDelayNs;
s = j;
}
if (++j >= length) {
j = 0;
}
}
if (s != i) {
timeNs = executionTimeNs[s];
execution = executions[s];
delay = delays[s];
executionTimeNs[s] = executionTimeNs[i];
executions[s] = executions[i];
delays[s] = delays[i];
}
delayNs = timeNs - System.nanoTime() + delay.toNanos();
}
if (delayNs > 0) {
try {
nanos(delayNs).sleepAtLeast();
} catch (final InterruptedException e) {
throw new InvocationInterruptedException(e);
}
}
try {
// This call could be re-entrant
execution.run();
} catch (final InvocationInterruptedException e) {
throw e;
} catch (final Throwable ignored) {
}
// Note that the field values may have changed here
final int n = mFirst;
mExecutions[n] = null;
mDelays[n] = null;
final int newFirst = mFirst + 1;
if (newFirst >= mExecutions.length) {
mFirst = 0;
} else {
mFirst = newFirst;
}
}
} finally {
mIsRunning = false;
}
}
}