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// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.io;
import java.nio.channels.WritableByteChannel;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Stack;
import java.util.LinkedList;
import java.util.Iterator;
import java.nio.ByteBuffer;
/**
* @author Bjørn Borud
*/
public class GrowableBufferOutputStream extends OutputStream {
private ByteBuffer lastBuffer;
private ByteBuffer directBuffer;
private LinkedList<ByteBuffer> bufferList = new LinkedList<>();
private Stack<ByteBuffer> recycledBuffers = new Stack<>();
private int bufferSize;
private int maxBuffers;
public GrowableBufferOutputStream(int bufferSize, int maxBuffers) {
this.bufferSize = bufferSize;
this.maxBuffers = maxBuffers;
lastBuffer = ByteBuffer.allocate(bufferSize);
directBuffer = ByteBuffer.allocateDirect(bufferSize);
}
@Override
public void write(byte[] cbuf, int off, int len) throws IOException {
if (lastBuffer.remaining() >= len) {
lastBuffer.put(cbuf, off, len);
return;
}
int residue = len;
while (residue > 0) {
int newOffset = len - residue;
int toWrite = Math.min(lastBuffer.remaining(), residue);
lastBuffer.put(cbuf, newOffset, toWrite);
residue -= toWrite;
if (residue != 0) {
extend();
}
}
}
@Override
public void write(byte[] b) throws IOException {
write(b,0,b.length);
}
@Override
public String toString() {
return "GrowableBufferOutputStream, writable size " + writableSize()
+ " bytes, " + numWritableBuffers() + " buffers, last buffer"
+ " position " + lastBuffer.position() + ", last buffer limit "
+ lastBuffer.limit();
}
public void write(int b) {
if (lastBuffer.remaining() == 0) {
extend();
}
lastBuffer.put((byte) b);
}
@Override
public void flush() {
// if the last buffer is untouched we do not need to do anything; if
// it has been touched we call extend(), which enqueues the buffer
// and allocates or recycles a buffer for us
if (lastBuffer.position() > 0) {
extend();
}
}
@Override
public void close() {
flush();
}
public int channelWrite(WritableByteChannel channel) throws IOException {
ByteBuffer buffer;
int totalWritten = 0;
while (!bufferList.isEmpty()) {
buffer = bufferList.getFirst();
int written = 0;
synchronized (directBuffer) {
directBuffer.clear();
directBuffer.put(buffer);
directBuffer.flip();
written = channel.write(directBuffer);
int left = directBuffer.remaining();
if (left > 0) {
int oldpos = buffer.position();
buffer.position(oldpos - left);
}
totalWritten += written;
}
// if we've completed writing this buffer we can dispose of it
if (buffer.remaining() == 0) {
bufferList.removeFirst();
recycleBuffer(buffer);
}
// if we didn't write any bytes we terminate
if (written == 0) {
break;
}
}
return totalWritten;
}
public int numWritableBuffers() {
return bufferList.size();
}
public void clear() {
flush();
bufferList.clear();
}
public void clearCache() {
recycledBuffers.clear();
}
public void clearAll() {
clear();
clearCache();
}
public int writableSize() {
Iterator<ByteBuffer> it = bufferList.iterator();
int size = 0;
while (it.hasNext()) {
size += (it.next()).remaining();
}
return size;
}
public ByteBuffer[] getWritableBuffers() {
flush();
ByteBuffer[] result = new ByteBuffer[numWritableBuffers()];
return bufferList.toArray(result);
}
private void extend() {
enqueueBuffer(lastBuffer);
if (recycledBuffers.empty()) {
lastBuffer = ByteBuffer.allocate(bufferSize);
} else {
lastBuffer = recycledBuffers.pop();
lastBuffer.clear();
}
}
private void enqueueBuffer(ByteBuffer buffer) {
buffer.flip();
bufferList.addLast(buffer);
}
private void recycleBuffer(ByteBuffer buffer) {
if (recycledBuffers.size() >= maxBuffers) {
return;
}
recycledBuffers.push(buffer);
}
}
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