C#：一个增强的TcpClient（三）读取

using System;using System.IO;using System.Net.Sockets;using System.Text;using System.Threading;namespace Splash.Net.Sockets{    /// <summary>    /// 异步读状态对象    /// </summary>    internal class AsyncReadStateObject    {        public ManualResetEvent eventDone;        public NetworkStream stream;        public Exception exception;        public Int32 numberOfBytesRead;    }    /// <summary>    /// 实现TcpClient的异步接收    /// </summary>    public partial class TcpClientPlus    {        /// <summary>        /// 设置读超时等待值        /// </summary>        public Int32 ReadTimeout = Timeout.Infinite;        /// <summary>        /// 异步接收        /// </summary>        /// <param name="data">接收到的字节数组</param>        public void Read(out Byte[] data)        {            // 获取网络数据流            NetworkStream netStream = GetStream();            // 用户定义对象            AsyncReadStateObject State = new AsyncReadStateObject            {   // 将事件状态设置为非终止状态，导致线程阻止                eventDone = new ManualResetEvent(false),                stream = netStream,                exception = null,                numberOfBytesRead = -1            };            Byte[] Buffer = new Byte[ReceiveBufferSize];            using (MemoryStream memStream = new MemoryStream(ReceiveBufferSize))            {                Int32 TotalBytes = 0;       // 总共需要接收的字节数                Int32 ReceivedBytes = 0;    // 当前已接收的字节数                while (true)                {                    // 将事件状态设置为非终止状态，导致线程阻止                    State.eventDone.Reset();                    // 异步读取网络数据流                    netStream.BeginRead(Buffer, 0, Buffer.Length, new AsyncCallback(AsyncReadCallback), State);                    // 等待操作完成信号                    if (State.eventDone.WaitOne(ReadTimeout, false))                    {   // 接收到信号                        if (State.exception != null) throw State.exception;                        if (State.numberOfBytesRead == 0)                        {   // 连接已经断开                            throw new SocketException();                        }                        else if (State.numberOfBytesRead > 0)                        {                            if (TotalBytes == 0)                            {   // 提取流头部字节长度信息                                TotalBytes = BitConverter.ToInt32(Buffer, 0);                                // 保存剩余信息                                memStream.Write(Buffer, 4, State.numberOfBytesRead - 4);                            }                            else                            {                                memStream.Write(Buffer, 0, State.numberOfBytesRead);                            }                            ReceivedBytes += State.numberOfBytesRead;                            if (ReceivedBytes >= TotalBytes) break;                        }                    }                    else                    {   // 超时异常                        throw new TimeoutException();                    }                }                // 将流内容写入字节数组                if (String.IsNullOrEmpty(_secretKey))                {                    data = (memStream.Length > 0) ? memStream.ToArray() : null;                }                else                {   // 解密数据                    data = (memStream.Length > 0) ? Decrypt(memStream.ToArray(), 0, TotalBytes - 4) : null;                }                            }        }        /// <summary>        /// 异步接收        /// </summary>        /// <param name="answer">接收到的字符串</param>        /// <param name="codePage">代码页</param>        /// <remarks>        /// 代码页：        ///     936：简体中文GB2312        ///     54936：简体中文GB18030        ///     950：繁体中文BIG5        ///     1252：西欧字符CP1252        ///     65001：UTF-8编码        /// </remarks>        public void Read(out String answer, Int32 codePage = 65001)        {            Byte[] data;            Read(out data);            answer = (data != null) ? Encoding.GetEncoding(codePage).GetString(data) : null;        }        /// <summary>        /// 异步读取回调函数        /// </summary>        /// <param name="ar">异步操作结果</param>        private static void AsyncReadCallback(IAsyncResult ar)        {            AsyncReadStateObject State = ar.AsyncState as AsyncReadStateObject;            try            {   // 异步写入结束                State.numberOfBytesRead = State.stream.EndRead(ar);            }            catch (Exception e)            {   // 异步连接异常                State.exception = e;            }            finally            {   // 将事件状态设置为终止状态，线程继续                State.eventDone.Set();            }        }    }}