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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you 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 io.netty.channel.nio;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.channel.Channel;
import io.netty.channel.ChannelConfig;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelMetadata;
import io.netty.channel.ChannelOutboundBuffer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.FileRegion;
import io.netty.channel.RecvByteBufAllocator;
import io.netty.channel.internal.ChannelUtils;
import io.netty.channel.socket.ChannelInputShutdownEvent;
import io.netty.channel.socket.ChannelInputShutdownReadComplete;
import io.netty.channel.socket.SocketChannelConfig;
import io.netty.util.internal.StringUtil;

import java.io.IOException;
import java.nio.channels.SelectableChannel;
import java.nio.channels.SelectionKey;

import static io.netty.channel.internal.ChannelUtils.WRITE_STATUS_SNDBUF_FULL;

/**
 * {@link AbstractNioChannel} base class for {@link Channel}s that operate on bytes.
 */
public abstract class AbstractNioByteChannel extends AbstractNioChannel {
    private static final ChannelMetadata METADATA = new ChannelMetadata(false, 16);
    private static final String EXPECTED_TYPES =
            " (expected: " + StringUtil.simpleClassName(ByteBuf.class) + ", " +
            StringUtil.simpleClassName(FileRegion.class) + ')';

    private final Runnable flushTask = new Runnable() {
        @Override
        public void run() {
            // Calling flush0 directly to ensure we not try to flush messages that were added via write(...) in the
            // meantime.
            ((AbstractNioUnsafe) unsafe()).flush0();
        }
    };
    private boolean inputClosedSeenErrorOnRead;

    /**
     * Create a new instance
     *
     * @param parent            the parent {@link Channel} by which this instance was created. May be {@code null}
     * @param ch                the underlying {@link SelectableChannel} on which it operates
     */
    protected AbstractNioByteChannel(Channel parent, SelectableChannel ch) {
        super(parent, ch, SelectionKey.OP_READ);
    }

    /**
     * Shutdown the input side of the channel.
     */
    protected abstract ChannelFuture shutdownInput();

    protected boolean isInputShutdown0() {
        return false;
    }

    @Override
    protected AbstractNioUnsafe newUnsafe() {
        return new NioByteUnsafe();
    }

    @Override
    public ChannelMetadata metadata() {
        return METADATA;
    }

    final boolean shouldBreakReadReady(ChannelConfig config) {
        return isInputShutdown0() && (inputClosedSeenErrorOnRead || !isAllowHalfClosure(config));
    }

    private static boolean isAllowHalfClosure(ChannelConfig config) {
        return config instanceof SocketChannelConfig &&
                ((SocketChannelConfig) config).isAllowHalfClosure();
    }

    protected class NioByteUnsafe extends AbstractNioUnsafe {

        private void closeOnRead(ChannelPipeline pipeline) {
            if (!isInputShutdown0()) {
                if (isAllowHalfClosure(config())) {
                    shutdownInput();
                    pipeline.fireUserEventTriggered(ChannelInputShutdownEvent.INSTANCE);
                } else {
                    close(voidPromise());
                }
            } else {
                inputClosedSeenErrorOnRead = true;
                pipeline.fireUserEventTriggered(ChannelInputShutdownReadComplete.INSTANCE);
            }
        }

        private void handleReadException(ChannelPipeline pipeline, ByteBuf byteBuf, Throwable cause, boolean close,
                RecvByteBufAllocator.Handle allocHandle) {
            if (byteBuf != null) {
                if (byteBuf.isReadable()) {
                    readPending = false;
                    pipeline.fireChannelRead(byteBuf);
                } else {
                    byteBuf.release();
                }
            }
            allocHandle.readComplete();
            pipeline.fireChannelReadComplete();
            pipeline.fireExceptionCaught(cause);
            if (close || cause instanceof IOException) {
                closeOnRead(pipeline);
            }
        }

        @Override
        public final void read() {
            final ChannelConfig config = config();
            if (shouldBreakReadReady(config)) {
                clearReadPending();
                return;
            }
            final ChannelPipeline pipeline = pipeline();
            final ByteBufAllocator allocator = config.getAllocator();
            final RecvByteBufAllocator.Handle allocHandle = recvBufAllocHandle();
            allocHandle.reset(config);

            ByteBuf byteBuf = null;
            boolean close = false;
            try {
                do {
                    byteBuf = allocHandle.allocate(allocator);
                    allocHandle.lastBytesRead(doReadBytes(byteBuf));
                    if (allocHandle.lastBytesRead() <= 0) {
                        // nothing was read. release the buffer.
                        byteBuf.release();
                        byteBuf = null;
                        close = allocHandle.lastBytesRead() < 0;
                        if (close) {
                            // There is nothing left to read as we received an EOF.
                            readPending = false;
                        }
                        break;
                    }

                    allocHandle.incMessagesRead(1);
                    readPending = false;
                    pipeline.fireChannelRead(byteBuf);
                    byteBuf = null;
                } while (allocHandle.continueReading());

                allocHandle.readComplete();
                pipeline.fireChannelReadComplete();

                if (close) {
                    closeOnRead(pipeline);
                }
            } catch (Throwable t) {
                handleReadException(pipeline, byteBuf, t, close, allocHandle);
            } finally {
                // Check if there is a readPending which was not processed yet.
                // This could be for two reasons:
                // * The user called Channel.read() or ChannelHandlerContext.read() in channelRead(...) method
                // * The user called Channel.read() or ChannelHandlerContext.read() in channelReadComplete(...) method
                //
                // See https://github.com/netty/netty/issues/2254
                if (!readPending && !config.isAutoRead()) {
                    removeReadOp();
                }
            }
        }
    }

    /**
     * Write objects to the OS.
     * @param in the collection which contains objects to write.
     * @return The value that should be decremented from the write quantum which starts at
     * {@link ChannelConfig#getWriteSpinCount()}. The typical use cases are as follows:
     * 
    *
  • 0 - if no write was attempted. This is appropriate if an empty {@link ByteBuf} (or other empty content) * is encountered
  • *
  • 1 - if a single call to write data was made to the OS
  • *
  • {@link ChannelUtils#WRITE_STATUS_SNDBUF_FULL} - if an attempt to write data was made to the OS, but no * data was accepted
  • *
* @throws Exception if an I/O exception occurs during write. */ protected final int doWrite0(ChannelOutboundBuffer in) throws Exception { Object msg = in.current(); if (msg == null) { // Directly return here so incompleteWrite(...) is not called. return 0; } return doWriteInternal(in, in.current()); } private int doWriteInternal(ChannelOutboundBuffer in, Object msg) throws Exception { if (msg instanceof ByteBuf) { ByteBuf buf = (ByteBuf) msg; if (!buf.isReadable()) { in.remove(); return 0; } final int localFlushedAmount = doWriteBytes(buf); if (localFlushedAmount > 0) { in.progress(localFlushedAmount); if (!buf.isReadable()) { in.remove(); } return 1; } } else if (msg instanceof FileRegion) { FileRegion region = (FileRegion) msg; if (region.transferred() >= region.count()) { in.remove(); return 0; } long localFlushedAmount = doWriteFileRegion(region); if (localFlushedAmount > 0) { in.progress(localFlushedAmount); if (region.transferred() >= region.count()) { in.remove(); } return 1; } } else { // Should not reach here. throw new Error(); } return WRITE_STATUS_SNDBUF_FULL; } @Override protected void doWrite(ChannelOutboundBuffer in) throws Exception { int writeSpinCount = config().getWriteSpinCount(); do { Object msg = in.current(); if (msg == null) { // Wrote all messages. clearOpWrite(); // Directly return here so incompleteWrite(...) is not called. return; } writeSpinCount -= doWriteInternal(in, msg); } while (writeSpinCount > 0); incompleteWrite(writeSpinCount < 0); } @Override protected final Object filterOutboundMessage(Object msg) { if (msg instanceof ByteBuf) { ByteBuf buf = (ByteBuf) msg; if (buf.isDirect()) { return msg; } return newDirectBuffer(buf); } if (msg instanceof FileRegion) { return msg; } throw new UnsupportedOperationException( "unsupported message type: " + StringUtil.simpleClassName(msg) + EXPECTED_TYPES); } protected final void incompleteWrite(boolean setOpWrite) { // Did not write completely. if (setOpWrite) { setOpWrite(); } else { // It is possible that we have set the write OP, woken up by NIO because the socket is writable, and then // use our write quantum. In this case we no longer want to set the write OP because the socket is still // writable (as far as we know). We will find out next time we attempt to write if the socket is writable // and set the write OP if necessary. clearOpWrite(); // Schedule flush again later so other tasks can be picked up in the meantime eventLoop().execute(flushTask); } } /** * Write a {@link FileRegion} * * @param region the {@link FileRegion} from which the bytes should be written * @return amount the amount of written bytes */ protected abstract long doWriteFileRegion(FileRegion region) throws Exception; /** * Read bytes into the given {@link ByteBuf} and return the amount. */ protected abstract int doReadBytes(ByteBuf buf) throws Exception; /** * Write bytes form the given {@link ByteBuf} to the underlying {@link java.nio.channels.Channel}. * @param buf the {@link ByteBuf} from which the bytes should be written * @return amount the amount of written bytes */ protected abstract int doWriteBytes(ByteBuf buf) throws Exception; protected final void setOpWrite() { final SelectionKey key = selectionKey(); // Check first if the key is still valid as it may be canceled as part of the deregistration // from the EventLoop // See https://github.com/netty/netty/issues/2104 if (!key.isValid()) { return; } final int interestOps = key.interestOps(); if ((interestOps & SelectionKey.OP_WRITE) == 0) { key.interestOps(interestOps | SelectionKey.OP_WRITE); } } protected final void clearOpWrite() { final SelectionKey key = selectionKey(); // Check first if the key is still valid as it may be canceled as part of the deregistration // from the EventLoop // See https://github.com/netty/netty/issues/2104 if (!key.isValid()) { return; } final int interestOps = key.interestOps(); if ((interestOps & SelectionKey.OP_WRITE) != 0) { key.interestOps(interestOps & ~SelectionKey.OP_WRITE); } } }




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