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/*
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* SONEWS News Server
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* see AUTHORS for the list of contributors
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package org.sonews.daemon;
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import java.nio.ByteBuffer;
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import java.nio.channels.ClosedChannelException;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* Class holding ByteBuffers for SocketChannels/NNTPConnection.
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* Due to the complex nature of AIO/NIO we must properly handle the line
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* buffers for the input and output of the SocketChannels.
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* @author Christian Lins
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* @since sonews/0.5.0
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*/
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public class ChannelLineBuffers
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{
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/**
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* Size of one small buffer;
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* per default this is 512 bytes to fit one standard line.
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*/
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public static final int BUFFER_SIZE = 512;
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private static int maxCachedBuffers = 2048; // Cached buffers maximum
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private static final List<ByteBuffer> freeSmallBuffers = new ArrayList<ByteBuffer>(maxCachedBuffers);
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/**
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* Allocates a predefined number of direct ByteBuffers (allocated via
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* ByteBuffer.allocateDirect()). This method is Thread-safe, but should only
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* called at startup.
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*/
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public static void allocateDirect()
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{
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synchronized (freeSmallBuffers) {
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for (int n = 0; n < maxCachedBuffers; n++) {
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ByteBuffer buffer = ByteBuffer.allocateDirect(BUFFER_SIZE);
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freeSmallBuffers.add(buffer);
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}
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}
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}
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private ByteBuffer inputBuffer = newLineBuffer();
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private List<ByteBuffer> outputBuffers = new ArrayList<ByteBuffer>();
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/**
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* Add the given ByteBuffer to the list of buffers to be send to the client.
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* This method is Thread-safe.
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* @param buffer
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* @throws java.nio.channels.ClosedChannelException If the client channel was
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* already closed.
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*/
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public void addOutputBuffer(ByteBuffer buffer)
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throws ClosedChannelException
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{
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if (outputBuffers == null) {
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throw new ClosedChannelException();
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}
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synchronized (outputBuffers) {
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outputBuffers.add(buffer);
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}
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}
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/**
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* Currently a channel has only one input buffer. This *may* be a bottleneck
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* and should investigated in the future.
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* @param channel
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* @return The input buffer associated with given channel.
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*/
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public ByteBuffer getInputBuffer()
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{
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return inputBuffer;
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}
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/**
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* Returns the current output buffer for writing(!) to SocketChannel.
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* @param channel
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* @return The next input buffer that contains unprocessed data or null
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* if the connection was closed or there are no more unprocessed buffers.
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*/
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public ByteBuffer getOutputBuffer()
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{
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synchronized (outputBuffers) {
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if (outputBuffers == null || outputBuffers.isEmpty()) {
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return null;
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} else {
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ByteBuffer buffer = outputBuffers.get(0);
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if (buffer.remaining() == 0) {
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outputBuffers.remove(0);
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// Add old buffers to the list of free buffers
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recycleBuffer(buffer);
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buffer = getOutputBuffer();
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}
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return buffer;
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}
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}
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}
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/**
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* @return false if there are output buffers pending to be written to the
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* client.
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*/
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boolean isOutputBufferEmpty()
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{
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synchronized (outputBuffers) {
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return outputBuffers.isEmpty();
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}
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}
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/**
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* Goes through the input buffer of the given channel and searches
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* for next line terminator. If a '\n' is found, the bytes up to the
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* line terminator are returned as array of bytes (the line terminator
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* is omitted). If none is found the method returns null.
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* @param channel
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* @return A ByteBuffer wrapping the line.
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*/
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ByteBuffer nextInputLine()
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{
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if (inputBuffer == null) {
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return null;
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}
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synchronized (inputBuffer) {
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ByteBuffer buffer = inputBuffer;
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// Mark the current write position
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int mark = buffer.position();
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// Set position to 0 and limit to current position
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buffer.flip();
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ByteBuffer lineBuffer = newLineBuffer();
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while (buffer.position() < buffer.limit()) {
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byte b = buffer.get();
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if (b == 10) // '\n'
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{
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// The bytes between the buffer's current position and its limit,
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// if any, are copied to the beginning of the buffer. That is, the
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// byte at index p = position() is copied to index zero, the byte at
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// index p + 1 is copied to index one, and so forth until the byte
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// at index limit() - 1 is copied to index n = limit() - 1 - p.
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// The buffer's position is then set to n+1 and its limit is set to
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// its capacity.
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buffer.compact();
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lineBuffer.flip(); // limit to position, position to 0
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return lineBuffer;
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} else {
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lineBuffer.put(b);
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}
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}
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buffer.limit(BUFFER_SIZE);
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buffer.position(mark);
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if (buffer.hasRemaining()) {
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return null;
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} else {
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// In the first 512 was no newline found, so the input is not standard
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// compliant. We return the current buffer as new line and add a space
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// to the beginning of the next line which corrects some overlong header
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// lines.
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inputBuffer = newLineBuffer();
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inputBuffer.put((byte) ' ');
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buffer.flip();
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return buffer;
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}
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}
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}
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/**
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* Returns a at least 512 bytes long ByteBuffer ready for usage.
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* The method first try to reuse an already allocated (cached) buffer but
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* if that fails returns a newly allocated direct buffer.
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* Use recycleBuffer() method when you do not longer use the allocated buffer.
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*/
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static ByteBuffer newLineBuffer()
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{
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ByteBuffer buf = null;
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synchronized (freeSmallBuffers) {
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if (!freeSmallBuffers.isEmpty()) {
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buf = freeSmallBuffers.remove(0);
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}
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}
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if (buf == null) {
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// Allocate a non-direct buffer
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buf = ByteBuffer.allocate(BUFFER_SIZE);
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}
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assert buf.position() == 0;
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assert buf.limit() >= BUFFER_SIZE;
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return buf;
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}
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/**
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* Adds the given buffer to the list of free buffers if it is a valuable
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* direct allocated buffer.
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* @param buffer
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*/
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public static void recycleBuffer(ByteBuffer buffer)
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{
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assert buffer != null;
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if (buffer.isDirect()) {
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assert buffer.capacity() >= BUFFER_SIZE;
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// Add old buffers to the list of free buffers
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synchronized (freeSmallBuffers) {
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buffer.clear(); // Set position to 0 and limit to capacity
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freeSmallBuffers.add(buffer);
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}
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} // if(buffer.isDirect())
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}
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/**
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* Recycles all buffers of this ChannelLineBuffers object.
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*/
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public void recycleBuffers()
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{
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synchronized (inputBuffer) {
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recycleBuffer(inputBuffer);
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this.inputBuffer = null;
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}
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synchronized (outputBuffers) {
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for (ByteBuffer buf : outputBuffers) {
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recycleBuffer(buf);
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}
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outputBuffers = null;
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}
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}
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}
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