封装多线程处理大量数据操作

们需要解决WaitAny和取得异步执行的返回值的问题。地球人都知道Thread和ThreadPool接受的委托都是没有返回值的。要想取的返回值，我们就得自己动手了，我们需要构造一个AsyncContext类，由这个类来保存异步执行的状态以并存储返回值。

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Collections; 
using System.Threading; 
using System.Diagnostics; 
  
namespace AppUtility 
{ 
 public delegate object DoGetObjTask(object state); 
    public static class AsyncHelper 
    { 
        /// <summary> 
        /// 执行多线程操作任务 
        /// </summary> 
        /// <param name="dataCollection">多线程操作的数据集合</param> 
        /// <param name="threadCn">分多少个线程来做</param> 
        /// <param name="processItemMethod">处理数据集合中单个数据使用的处理方法</param> 
        public static void DoAsync(IList dataCollection, int threadCn, WaitCallback processItemMethod) 
        { 
            DoAsync(dataCollection, threadCn, processItemMethod, true); 
        } 
  
  
        /// <summary> 
        /// 执行多线程操作任务 
        /// </summary> 
        /// <param name="dataCollection">多线程操作的数据集合</param> 
        /// <param name="threadCn">分多少个线程来做</param> 
        /// <param name="processItemMethod">处理数据集合中单个数据使用的处理方法</param> 
        /// <param name="needWaitAll">是否需要等待所有线程执行完毕才返回，为true时会等待所有线程执行完毕，否则则是在有一个线程执行完毕就返回</param> 
        public static void DoAsync(IList dataCollection, int threadCn, DoGetObjTask processItemMethod, bool needWaitAll, out Hashtable processResult) 
        { 
            DoAsyncPrivate(dataCollection, threadCn, null, processItemMethod, needWaitAll, true, out processResult); 
        } 
  
        /// <summary> 
        /// 执行多线程操作任务 
        /// </summary> 
        /// <param name="dataCollection">多线程操作的数据集合</param> 
        /// <param name="threadCn">分多少个线程来做</param> 
        /// <param name="processItemMethod">处理数据集合中单个数据使用的处理方法</param> 
        /// <param name="needWaitAll">是否需要等待所有线程执行完毕才返回，为true时会等待所有线程执行完毕，否则则是在有一个线程执行完毕就返回</param> 
        public static void DoAsync(IList dataCollection, int threadCn, DoGetObjTask processItemMethod, out Hashtable processResult) 
        { 
            DoAsyncPrivate(dataCollection, threadCn, null, processItemMethod, true, true, out processResult); 
        } 
  
        /// <summary> 
        /// 执行多线程操作任务 
        /// </summary> 
        /// <param name="dataCollection">多线程操作的数据集合</param> 
        /// <param name="threadCn">分多少个线程来做</param> 
        /// <param name="processItemMethod">处理数据集合中单个数据使用的处理方法</param> 
        /// <param name="needWaitAll">是否需要等待所有线程执行完毕才返回，为true时会等待所有线程执行完毕，否则则是在有一个线程执行完毕就返回</param> 
        public static void DoAsync(IList dataCollection, int threadCn, WaitCallback processItemMethod, bool needWaitAll) 
        { 
            Hashtable hash; 
            DoAsyncPrivate(dataCollection, threadCn, processItemMethod, null, needWaitAll, false, out hash); 
        } 
  
        private static void DoAsyncPrivate(IList dataCollection, int threadCn, WaitCallback processItemMethod, DoGetObjTask getObjMethod, bool needWaitAll, bool hasReturnValue, out Hashtable processResult) 
        { 
            if (dataCollection == null) throw new ArgumentNullException("dataCollection"); 
  
            if (threadCn >= 64 || threadCn < 2) 
            { 
                throw new ArgumentOutOfRangeException("threadCn", "threadCn 参数必须在2和64之间"); 
            } 
  
            if (threadCn > dataCollection.Count) threadCn = dataCollection.Count; 
  
            IList[] colls = new ArrayList[threadCn]; 
  
            DataWithStateList dataWithStates = new DataWithStateList(); 
            AutoResetEvent[] evts = new AutoResetEvent[threadCn]; 
  
            for (int i = 0; i < threadCn; i++) 
            { 
                colls[i] = new ArrayList(); 
                evts[i] = new AutoResetEvent(false); 
            } 
  
            for (int i = 0; i < dataCollection.Count; i++) 
            { 
                object obj = dataCollection[i]; 
                int threadIndex = i % threadCn; 
                colls[threadIndex].Add(obj); 
                dataWithStates.Add(new DataWithState(obj, ProcessState.WaitForProcess)); 
            } 
  
            AsyncContext context = AsyncContext.GetContext(threadCn, dataWithStates, needWaitAll, hasReturnValue, processItemMethod, getObjMethod); 
  
            for (int i = 0; i < threadCn; i++) 
            { 
                ThreadPool.QueueUserWorkItem(DoPrivate, new object[] {  
                    colls[i],context,evts[i] 
                }); 
            } 
  
            if (needWaitAll) 
            { 
                WaitHandle.WaitAll(evts); 
            } 
            else
            { 
                WaitHandle.WaitAny(evts); 
                context.SetBreakSignal(); 
            } 
            processResult = context.ProcessResult; 
        } 
  
        private class AsyncContext 
        { 
            static public AsyncContext GetContext( 
                int threadCn, 
                DataWithStateList dataWithStates, 
                bool needWaitAll, 
                bool hasReturnValue, 
                WaitCallback processItemMethod, 
                DoGetObjTask hasReturnValueMethod 
                ) 
            { 
                AsyncContext context = new AsyncContext(); 
                context.ThreadCount = threadCn; 
                context.DataWithStates = dataWithStates; 
                context.NeedWaitAll = needWaitAll; 
                if (hasReturnValue) 
                { 
                    Hashtable processResult = Hashtable.Synchronized(new Hashtable()); 
                    context.ProcessResult = processResult; 
                    context.HasReturnValueMethod = hasReturnValueMethod; 
                } 
                else
                { 
                    context.VoidMethod = processItemMethod; 
                } 
                context.HasReturnValue = hasReturnValue; 
                return context; 
            } 
  
            internal int ThreadCount; 
  
            internal DataWithStateList DataWithStates; 
  
            internal bool NeedWaitAll; 
  
            internal bool HasReturnValue; 
  
            internal WaitCallback VoidMethod; 
  
            internal DoGetObjTask HasReturnValueMethod; 
  
            private bool _breakSignal; 
  
            private Hashtable _processResult; 
  
            internal Hashtable ProcessResult 
            { 
                get { return _processResult; } 
                set { _processResult = value; } 
            } 
  
            internal void SetReturnValue(object obj, object result) 
            { 
                lock (_processResult.SyncRoot) 
                { 
                    _processResult[obj] = result; 
                } 
            } 
  
            internal void SetBreakSignal() 
            { 
                if (NeedWaitAll) throw new NotSupportedException("设定为NeedWaitAll时不可设置BreakSignal"); 
  
                _breakSignal = true; 
            } 
  
            internal bool NeedBreak 
            { 
                get
                { 
                    return !NeedWaitAll && _breakSignal; 
                } 
            } 
  
            internal void Exec(object obj) 
            { 
                if (HasReturnValue) 
                { 
                    SetReturnValue(obj, HasReturnValueMethod(obj)); 
                } 
                else
                { 
                    VoidMethod(obj); 
                } 
                DataWithStates.SetState(obj, ProcessState.Processed); 
            } 
        } 
  
        private enum ProcessState : byte
        { 
            WaitForProcess = 0, 
            Processing = 1, 
            Processed = 2 
        } 
  
        private class DataWithStateList : List<DataWithState> 
        { 
            public void SetState(object obj, ProcessState state) 
            { 
                lock (((ICollection)this).SyncRoot) 
                { 
                    DataWithState dws = this.Find(delegate(DataWithState i) { return Object.Equals(i.Data, obj); }); 
  
                    if (dws != null) 
                    { 
                        dws.State = state; 
                    } 
                } 
            } 
  
            public ProcessState GetState(object obj) 
            { 
                lock (((ICollection)this).SyncRoot) 
                { 
                    DataWithState dws = this.Find(delegate(DataWithState i) { return Object.Equals(i.Data, obj); }); 
                    return dws.State; 
                } 
            } 
  
            private int GetCount(ProcessState state) 
            { 
                List<DataWithState> datas = this.FindAll(delegate(DataWithState i) { return i.State == state; }); 
                if (datas == null) return 0; 
                return datas.Count; 
            } 
  
            public int WaitForDataCount 
            { 
                get
                { 
                    return GetCount(ProcessState.WaitForProcess); 
                } 
            } 
  
            internal object GetWaitForObject() 
            { 
                lock (((ICollection)this).SyncRoot) 
                { 
                    DataWithState dws = this.Find(delegate(DataWithState i) { return i.State == ProcessState.WaitForProcess; }); 
                    if (dws == null) return null; 
                    dws.State = ProcessState.Processing; 
                    return dws.Data; 
                } 
            } 
  
            internal bool IsWaitForData(object obj, bool setState) 
            { 
                lock (((ICollection)this).SyncRoot) 
                { 
                    DataWithState dws = this.Find(delegate(DataWithState i) { return i.State == ProcessState.WaitForProcess; }); 
  
                    if (setState && dws != null) dws.State = ProcessState.Processing; 
  
                    return dws != null; 
                } 
            } 
        } 
  
        private class DataWithState 
        { 
            public readonly object Data; 
            public ProcessState State; 
  
            public DataWithState(object data, ProcessState state) 
            { 
                Data = data; 
                State = state; 
            } 
        } 
  
        private static int _threadNo = 0; 
  
        private static void DoPrivate(object state) 
        { 
            object[] objs = state as object[]; 
  
            IList datas = objs[0] as IList; 
            AsyncContext context = objs[1] as AsyncContext; 
            AutoResetEvent evt = objs[2] as AutoResetEvent; 
  
            DataWithStateList objStates = context.DataWithStates; 
  
#if DEBUG 
            Thread.CurrentThread.Name = "Thread " + _threadNo; 
  
            Interlocked.Increment(ref _threadNo); 
            string threadName = Thread.CurrentThread.Name + "[" + Thread.CurrentThread.ManagedThreadId + "]"; 
            Trace.WriteLine("线程ID:" + threadName); 
#endif 
            if (datas != null) 
            { 
                for (int i = 0; i < datas.Count; i++) 
                { 
                    if (context.NeedBreak) 
                    { 
#if DEBUG 
                        Trace.WriteLine("线程" + threadName + "未执行完跳出"); 
#endif 
                        break; 
                    } 
                    object obj = datas[i]; 
                    if (objStates.IsWaitForData(obj, true)) 
                    { 
                        if (context.NeedBreak) 
                        { 
#if DEBUG 
                            Trace.WriteLine("线程" + threadName + "未执行完跳出"); 
#endif 
                            break; 
                        } 
  
                        context.Exec(obj); 
  
#if DEBUG 
                        Trace.WriteLine(string.Format("线程{0}处理{1}", threadName, obj)); 
#endif 
                    } 
                } 
            } 
  
            if (context.NeedWaitAll) 
            { 
                //如果执行完当前进程的数据，还要查看剩下多少没有做，如果还剩下超过ThreadCount个没有做 
                while (objStates.WaitForDataCount > context.ThreadCount) 
                { 
                    if (context.NeedBreak) break; 
  
                    object obj = objStates.GetWaitForObject(); 
                    if (obj != null && objStates.IsWaitForData(obj, false)) 
                    { 
                        if (context.NeedBreak) 
                        { 
#if DEBUG 
                            Trace.WriteLine("线程" + threadName + "未执行完跳出"); 
#endif 
                            break; 
                        } 
  
                        context.Exec(obj); 
  
#if DEBUG 
                        Trace.WriteLine(string.Format("线程{0}执行另一个进程的数据{1}", threadName, obj)); 
#endif 
                    } 
                } 
            } 
  
            evt.Set(); 
        } 
  
  
    } 
} 

使用AsyncHelper类，请看下面的测试代码：

using System; 
using System.Collections.Generic; 
using System.Text; 
using System.Diagnostics; 
using AppUtility; 
using System.IO; 
using System.Collections; 
using System.Threading; 
  
namespace ConsoleApplication2 
{ 
    class Program 
    { 
        static void Main(string[] args) 
        { 
            Stopwatch sw = new Stopwatch(); 
            sw.Start(); 
            /* 
            List<string> testFiles = new List<string>(); 
            for (int i = 0; i < 100; i++) 
            { 
                testFiles.Add("D:\test\async\file_" + i.ToString() + ".log"); 
            } 
            AsyncHelper.DoAsync(testFiles, 10, WriteFile); 
  
            Console.WriteLine("异步写耗时"+sw.ElapsedMilliseconds + "ms"); 
            */
  
            List<string> testFiles = new List<string>(); 
            for (int i = 0; i < 200; i++) 
            { 
                testFiles.Add("D:\test\async\file_" + i.ToString() + ".log"); 
            } 
              
            Hashtable result; 
  
            AsyncHelper.DoAsync(testFiles, 20, WriteFileAndReturnRowCount,false,out result); 
  
            Console.WriteLine("异步写耗时" + sw.ElapsedMilliseconds + "ms"); 
  
            Thread.Sleep(10); 
  
            if (result != null) 
            { 
                foreach (object key in result.Keys) 
                { 
                    Console.WriteLine("{0}={1}",  key,result[key]); 
                } 
  
            } 
  
            sw.Reset(); 
            sw.Start(); 
            for (int i = 0; i < 200; i++) 
            { 
                WriteFile("D:\test\sync\file_" + i.ToString() + ".log"); 
            } 
  
            Console.WriteLine("同步写耗时" + sw.ElapsedMilliseconds + "ms"); 
  
            Console.Read(); 
        } 
  
        static void WriteFile(object objFilePath) 
        { 
            string filePath = (string)objFilePath; 
            string dir = Path.GetDirectoryName(filePath); 
            if (!Directory.Exists(dir)) 
            { 
                Directory.CreateDirectory(dir); 
            } 
  
            //Random r = new Random(DateTime.Now.Minute); 
            int rowCn = 10000; 
            using (StreamWriter writer = new StreamWriter(filePath, false, Encoding.Default)) 
            { 
                for (int i = 0; i < rowCn; i++) writer.WriteLine(Guid.NewGuid()); 
            } 
        } 
  
        static object WriteFileAndReturnRowCount(object objFilePath) 
        { 
            string filePath = (string)objFilePath; 
            string dir = Path.GetDirectoryName(filePath); 
            if (!Directory.Exists(dir)) 
            { 
                Directory.CreateDirectory(dir); 
            } 
  
            //Random r = new Random(DateTime.Now.Minute); 
            int rowCn = 10000; 
            using (StreamWriter writer = new StreamWriter(filePath, false, Encoding.Default)) 
            { 
                for (int i = 0; i < rowCn ; i++) writer.WriteLine(Guid.NewGuid()); 
            } 
            return DateTime.Now.ToLongTimeString(); 
        } 
    } 
}

转自：http://www.cnblogs.com/yukaizhao/archive/2009/12/18/system_threading_threadpool_AsyncHelper_2.html

需求是从一个文件夹中读取N个文件，将N个文件平均分配到10个线程，然后分别读取每个文件里面的内容。经测试，发现在DoPrivate方法里面，每个datas.Count分配是对的，但到objStates.IsWaitForData(obj, true)方法总有不定数量返回false，因此最后没有完全执行，最后数量总少于N，而且不定，降至2个线程也一样，使用这种方法会造成漏数据，因此只能改进DoPrivate方法，去掉objStates.IsWaitForData方法判断。