[編織訊息架構][netty源碼分析]7 Unsafe 實作類別NioSocketChannelUnsafe職責與實現

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Unsafe 是channel的內部介面， 負責跟socket底層打交道。從書寫跟命名上看是不公開給開發人員使用的，直到最後實現NioSocketChannelUnsafe也沒有公開出去

public interface Channel extends AttributeMap, ChannelOutboundInvoker, Comparable<Channel> {    interface Unsafe {        RecvByteBufAllocator.Handle recvBufAllocHandle();        SocketAddress localAddress();        SocketAddress remoteAddress();        void register(EventLoop eventLoop, ChannelPromise promise);        void bind(SocketAddress localAddress, ChannelPromise promise);        void connect(SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise);        void disconnect(ChannelPromise promise);        void close(ChannelPromise promise);        void closeForcibly();        void deregister(ChannelPromise promise);        void beginRead();        void write(Object msg, ChannelPromise promise);        void flush();        ChannelPromise voidPromise();        ChannelOutboundBuffer outboundBuffer();    }    public interface NioUnsafe extends Unsafe {        SelectableChannel ch();        void finishConnect();        void read();        void forceFlush();    }}

 

NioSocketChannelUnsafe 繼承關係為： NioSocketChannelUnsafe -> NioByteUnsafe -> AbstractNioUnsafe -> AbstractUnsafe

AbstractUnsafe：負責socket 鏈路綁定、接受、關閉，資料fush操作

每個操作大概分四個階段處理

        @Override        public final void bind(final SocketAddress localAddress, final ChannelPromise promise) {            assertEventLoop();            //執行前檢查            if (!promise.setUncancellable() || !ensureOpen(promise)) {                return;            }            boolean wasActive = isActive();            //調用實現            try {                doBind(localAddress);            } catch (Throwable t) {                safeSetFailure(promise, t);                closeIfClosed();                return;            }            //調用業務,通知pipeline            if (!wasActive && isActive()) {                invokeLater(()-> pipeline.fireChannelActive(););            }            //完成階段處理            safeSetSuccess(promise);        }

 

 @Override        public final void flush() {            assertEventLoop();            ChannelOutboundBuffer outboundBuffer = this.outboundBuffer;            if (outboundBuffer == null) {                return;            }            outboundBuffer.addFlush();            flush0();        }        @SuppressWarnings("deprecation")        protected void flush0() {            //剛完成Flush操作            if (inFlush0) {                 return;            }            final ChannelOutboundBuffer outboundBuffer = this.outboundBuffer;            if (outboundBuffer == null || outboundBuffer.isEmpty()) {                return;            }            inFlush0 = true;            //發送資料前鏈路檢查            if (!isActive()) {                try {                    if (isOpen()) {                        //true 通知 handler channelWritabilityChanged方法                        outboundBuffer.failFlushed(FLUSH0_NOT_YET_CONNECTED_EXCEPTION, true);                    } else {                        outboundBuffer.failFlushed(FLUSH0_CLOSED_CHANNEL_EXCEPTION, false);                    }                } finally {                    inFlush0 = false;                }                return;            }            try {                //調用channel實現                doWrite(outboundBuffer);            } catch (Throwable t) {                if (t instanceof IOException && config().isAutoClose()) {                    close(voidPromise(), t, FLUSH0_CLOSED_CHANNEL_EXCEPTION, false);                } else {                    outboundBuffer.failFlushed(t, true);                }            } finally {                inFlush0 = false;            }        }

 

AbstractNioUnsafe：是NioUnsafe介面模板類，簡單的封裝

NioByteUnsafe：主要對NioUnsafe介面 read操作實現

NioSocketChannelUnsafe:只是簡單的封裝，最終公開給內部使用

NioByteUnsafe read方法

      public final void read() {            final ChannelConfig config = config();            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);                    //填充byteBuf 調用channel實現                    int size = doReadBytes(byteBuf);                    //記錄最後讀取長度                    allocHandle.lastBytesRead(size);                    //鏈路關閉，釋放byteBuf                    if (allocHandle.lastBytesRead() <= 0) {                        byteBuf.release();                        byteBuf = null;                        close = allocHandle.lastBytesRead() < 0;                        break;                    }                    //自增訊息讀取處理次數                    allocHandle.incMessagesRead(1);                    //已完成填充byteBuf 調用業務pipeline                    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 {                //如果不是主動read 要完成後要清理read op                if (!readPending && !config.isAutoRead()) {                    removeReadOp();                }            }        }    }

小結：可以看出沒有任何的計算代碼，Unsafe只實現邊界檢查、流程式控制制，具體實現交給上層處理

[編織訊息架構][netty源碼分析]7 Unsafe 實作類別NioSocketChannelUnsafe職責與實現