code.grnet.gr Git - pithos-ms-client/blob - trunk/Pithos.Core/TaskExtensions.cs

   1 using System;
   2 using System.Collections.Generic;
   3 using System.Diagnostics.Contracts;
   4 using System.Linq;
   5 using System.Text;
   6 using System.Threading;
   7 using System.Threading.Tasks;
   8
   9 namespace Pithos.Core
  10 {
  11     static class TaskExtensions
  12     {
  13         public static Task<T2> Then<T1, T2>(this Task<T1> first, Func<T1, Task<T2>> next)
  14         {
  15             if (first == null)
  16                 throw new ArgumentNullException("first");
  17             if (next == null)
  18                 throw new ArgumentNullException("next");
  19             Contract.EndContractBlock();
  20             return Then(first, next, CancellationToken.None);
  21         }
  22
  23         public static Task Then<T1>(this Task<T1> first, Func<T1, Task> next)
  24         {
  25             if (first == null)
  26                 throw new ArgumentNullException("first");
  27             if (next == null)
  28                 throw new ArgumentNullException("next");
  29             Contract.EndContractBlock();
  30             return Then(first, next, CancellationToken.None);
  31         }
  32
  33         public static Task<T2> Then<T1, T2>(this Task<T1> first, Func<T1, Task<T2>> next, CancellationToken cancellationToken)
  34         {
  35             if (first == null)
  36                 throw new ArgumentNullException("first");
  37             if (next == null)
  38                 throw new ArgumentNullException("next");
  39             Contract.EndContractBlock();
  40             Contract.Assume(TaskScheduler.Current!=null);
  41
  42             var tcs = new TaskCompletionSource<T2>();
  43             first.ContinueWith(delegate
  44             {
  45                 if (first.IsFaulted) tcs.TrySetException(first.Exception.InnerExceptions);
  46                 else if (first.IsCanceled) tcs.TrySetCanceled();
  47                 else
  48                 {
  49                     try
  50                     {
  51                         var t = next(first.Result);
  52                         if (t == null) tcs.TrySetCanceled();
  53                         else t.ContinueWith(delegate
  54                         {
  55                             if (t.IsFaulted) tcs.TrySetException(t.Exception.InnerExceptions);
  56                             else if (t.IsCanceled) tcs.TrySetCanceled();
  57                             else tcs.TrySetResult(t.Result);
  58                         }, TaskContinuationOptions.ExecuteSynchronously);
  59                     }
  60                     catch (Exception exc) { tcs.TrySetException(exc); }
  61                 }
  62             }, cancellationToken, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Current);
  63             return tcs.Task;
  64         }
  65
  66         public static Task Then<T1>(this Task<T1> first, Func<T1, Task> next, CancellationToken cancellationToken)
  67         {
  68             if (first == null)
  69                 throw new ArgumentNullException("first");
  70             if (next == null)
  71                 throw new ArgumentNullException("next");
  72             Contract.EndContractBlock();
  73             Contract.Assume(TaskScheduler.Current != null);
  74
  75             var tcs = new TaskCompletionSource<object>();
  76             first.ContinueWith(delegate
  77             {
  78                 if (first.IsFaulted) tcs.TrySetException(first.Exception.InnerExceptions);
  79                 else if (first.IsCanceled) tcs.TrySetCanceled();
  80                 else
  81                 {
  82                     try
  83                     {
  84                         var t = next(first.Result);
  85                         if (t == null) tcs.TrySetCanceled();
  86                         else t.ContinueWith(delegate
  87                         {
  88                             if (t.IsFaulted) tcs.TrySetException(t.Exception.InnerExceptions);
  89                             else if (t.IsCanceled) tcs.TrySetCanceled();
  90                             else tcs.TrySetResult(null);
  91                         }, TaskContinuationOptions.ExecuteSynchronously);
  92                     }
  93                     catch (Exception exc) { tcs.TrySetException(exc); }
  94                 }
  95             }, cancellationToken, TaskContinuationOptions.ExecuteSynchronously, TaskScheduler.Current);
  96             return tcs.Task;
  97         }
  98
  99
 100
 101         public static void ReportExceptions(this Task task,Action<AggregateException> OnError,Action OnSuccess )
 102         {
 103             if (!task.IsCompleted) throw new InvalidOperationException("The task has not completed.");
 104             if (task.IsFaulted)
 105                 task.Exception.Handle(exc=>
 106                                           {
 107                                               OnError(task.Exception);
 108                                               return true;
 109                                           });
 110             else
 111             {
 112                 OnSuccess();
 113             }
 114         }
 115
 116     }
 117 }