ProxyCache.java
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package com.danikula.videocache;
import java.util.concurrent.atomic.AtomicInteger;
import static com.danikula.videocache.Preconditions.checkNotNull;
/**
* Proxy for {@link Source} with caching support ({@link Cache}).
* <p/>
* Can be used only for sources with persistent data (that doesn't change with time).
* Method {@link #read(byte[], long, int)} will be blocked while fetching data from source.
* Useful for streaming something with caching e.g. streaming video/audio etc.
*
* @author Alexey Danilov (danikula@gmail.com).
*/
class ProxyCache {
private static final int MAX_READ_SOURCE_ATTEMPTS = 1;
private final Source source;
private final Cache cache;
private final Object wc = new Object();
private final Object stopLock = new Object();
private final AtomicInteger readSourceErrorsCount;
private volatile Thread sourceReaderThread;
private volatile boolean stopped;
private volatile int percentsAvailable = -1;
public ProxyCache(Source source, Cache cache) {
this.source = checkNotNull(source);
this.cache = checkNotNull(cache);
this.readSourceErrorsCount = new AtomicInteger();
}
public int read(byte[] buffer, long offset, int length) throws ProxyCacheException {
ProxyCacheUtils.assertBuffer(buffer, offset, length);
while (!cache.isCompleted() && cache.available() < (offset + length) && !stopped) {
readSourceAsync();
waitForSourceData();
checkReadSourceErrorsCount();
}
int read = cache.read(buffer, offset, length);
if (cache.isCompleted() && percentsAvailable != 100) {
percentsAvailable = 100;
onCachePercentsAvailableChanged(100);
}
return read;
}
private void checkReadSourceErrorsCount() throws ProxyCacheException {
int errorsCount = readSourceErrorsCount.get();
if (errorsCount >= MAX_READ_SOURCE_ATTEMPTS) {
readSourceErrorsCount.set(0);
throw new ProxyCacheException("Error reading source " + errorsCount + " times");
}
}
public void shutdown() {
synchronized (stopLock) {
Logger.debug("Shutdown proxy for " + source);
try {
stopped = true;
if (sourceReaderThread != null) {
sourceReaderThread.interrupt();
}
cache.close();
} catch (ProxyCacheException e) {
onError(e);
}
}
}
private synchronized void readSourceAsync() throws ProxyCacheException {
boolean readingInProgress = sourceReaderThread != null && sourceReaderThread.getState() != Thread.State.TERMINATED;
if (!stopped && !cache.isCompleted() && !readingInProgress) {
sourceReaderThread = new Thread(new SourceReaderRunnable(), "Source reader for " + source);
sourceReaderThread.start();
}
}
private void waitForSourceData() throws ProxyCacheException {
synchronized (wc) {
try {
wc.wait(1000);
} catch (InterruptedException e) {
throw new ProxyCacheException("Waiting source data is interrupted!", e);
}
}
}
private void notifyNewCacheDataAvailable(long cacheAvailable, long sourceAvailable) {
onCacheAvailable(cacheAvailable, sourceAvailable);
synchronized (wc) {
wc.notifyAll();
}
}
protected void onCacheAvailable(long cacheAvailable, long sourceLength) {
boolean zeroLengthSource = sourceLength == 0;
int percents = zeroLengthSource ? 100 : (int) ((float) cacheAvailable / sourceLength * 100);
boolean percentsChanged = percents != percentsAvailable;
boolean sourceLengthKnown = sourceLength >= 0;
if (sourceLengthKnown && percentsChanged) {
onCachePercentsAvailableChanged(percents);
}
percentsAvailable = percents;
}
protected void onCachePercentsAvailableChanged(int percentsAvailable) {
}
private void readSource() {
long sourceAvailable = -1;
long offset = 0;
try {
offset = cache.available();
source.open(offset);
sourceAvailable = source.length();
byte[] buffer = new byte[ProxyCacheUtils.DEFAULT_BUFFER_SIZE];
int readBytes;
while ((readBytes = source.read(buffer)) != -1) {
synchronized (stopLock) {
if (isStopped()) {
return;
}
cache.append(buffer, readBytes);
}
offset += readBytes;
notifyNewCacheDataAvailable(offset, sourceAvailable);
}
tryComplete();
onSourceRead();
} catch (Throwable e) {
readSourceErrorsCount.incrementAndGet();
onError(e);
} finally {
closeSource();
notifyNewCacheDataAvailable(offset, sourceAvailable);
}
}
private void onSourceRead() {
// guaranteed notify listeners after source read and cache completed
percentsAvailable = 100;
onCachePercentsAvailableChanged(percentsAvailable);
}
private void tryComplete() throws ProxyCacheException {
synchronized (stopLock) {
if (!isStopped() && cache.available() == source.length()) {
cache.complete();
}
}
}
private boolean isStopped() {
return Thread.currentThread().isInterrupted() || stopped;
}
private void closeSource() {
try {
source.close();
} catch (ProxyCacheException e) {
onError(new ProxyCacheException("Error closing source " + source, e));
}
}
protected final void onError(final Throwable e) {
boolean interruption = e instanceof InterruptedProxyCacheException;
if (interruption) {
Logger.debug("ProxyCache is interrupted");
} else {
Logger.error("ProxyCache error");
}
}
private class SourceReaderRunnable implements Runnable {
@Override
public void run() {
readSource();
}
}
}