private static void MapOneByOne <TSource, TResult>(
IList <TSource> source,
TResult[] resultArray,
Func <TSource, Task <TResult> > method,
TaskCompletionSource <TResult[]> tcs,
SendReceiveCounter counter)
{
var index = counter.IncrementSent() - 1L;
if (index >= source.Count)
{
return;
}
var t1 = method(source[(int)index]);
t1.ContinueWith(t =>
{
if (t.Exception != null)
{
tcs.TrySetException(t.Exception.InnerException);
return;
}
var received = counter.IncrementReceived();
resultArray[index] = t.Result;
if (received == source.Count)
{
tcs.TrySetResult(resultArray);
return;
}
MapOneByOne(source, resultArray, method, tcs, counter);
}, TaskContinuationOptions.ExecuteSynchronously);
}
/// <summary>
/// Executes an asynchronous method n number of times, limiting the amount of operations in parallel without
/// blocking.
/// </summary>
/// <param name="times">The amount of times to execute the async operation.</param>
/// <param name="limit">The maximum amount of executions in parallel</param>
/// <param name="method">The method to execute to obtain the asynchronous operation.</param>
/// <returns>
/// A Task that is completed when all Tasks are completed or is faulted when any of the Tasks
/// transition to Faulted state.
/// </returns>
public static Task Times(long times, int limit, Func <long, Task> method)
{
var counter = new SendReceiveCounter();
var tcs = new TaskCompletionSource <bool>();
if (limit > times)
{
limit = (int)times;
}
for (var i = 0; i < limit; i++)
{
ExecuteOnceAndContinue(times, method, tcs, counter);
}
return(tcs.Task);
}
/// <summary>
/// Asynchronously projects each element of a sequence into a new form, limiting the amount of operations
/// in parallel without blocking.
/// </summary>
/// <param name="source">An immutable sequence of values to invoke a async transform function on.</param>
/// <param name="limit">The maximum amount of async transformations in parallel.</param>
/// <param name="method">A transform function to apply to each element.</param>
/// <returns>The transformed elements</returns>
public static Task <TResult[]> Map <TSource, TResult>(
IList <TSource> source, int limit, Func <TSource, Task <TResult> > method)
{
var counter = new SendReceiveCounter();
var resultArray = new TResult[source.Count];
var tcs = new TaskCompletionSource <TResult[]>();
if (limit > source.Count)
{
limit = source.Count;
}
for (var i = 0; i < limit; i++)
{
MapOneByOne(source, resultArray, method, tcs, counter);
}
return(tcs.Task);
}
private static void ExecuteOnceAndContinue(long times, Func <long, Task> method, TaskCompletionSource <bool> tcs, SendReceiveCounter counter)
{
var index = counter.IncrementSent() - 1L;
if (index >= times)
{
return;
}
var t1 = method(index);
t1.ContinueWith(t =>
{
if (t.Exception != null)
{
tcs.TrySetException(t.Exception.InnerException);
return;
}
var received = counter.IncrementReceived();
if (received == times)
{
tcs.TrySetResult(true);
return;
}
ExecuteOnceAndContinue(times, method, tcs, counter);
}, TaskContinuationOptions.ExecuteSynchronously);
}
