public async Task DisposeAfterPartialEnumeration()
{
// ARRANGE
var testDisposable = new TestDisposable();
var enumerator = new AsyncEnumerator <int>(async yield =>
{
using (testDisposable)
{
await yield.ReturnAsync(1);
await yield.ReturnAsync(2);
await yield.ReturnAsync(3);
}
});
// ACT
await enumerator.MoveNextAsync();
enumerator.Dispose();
// ASSERT
Assert.IsTrue(testDisposable.HasDisposed);
}
public async Task DisposeByGCAfterPartialEnumeration()
{
// ARRANGE
var testDisposable = new TestDisposable();
var enumerator = new AsyncEnumerator <int>(async yield =>
{
using (testDisposable)
{
await yield.ReturnAsync(1);
await yield.ReturnAsync(2);
await yield.ReturnAsync(3);
}
});
// ACT
// Do partial enumeration.
await enumerator.MoveNextAsync();
// Instead of calling enumerator.Dispose(), do garbage collection.
enumerator = null;
GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced, blocking: true);
// Give some time to other thread that does the disposal of the enumerator.
// (see finalizer of the AsyncEnumerator for details)
await Task.Delay(16);
// ASSERT
Assert.IsTrue(testDisposable.HasDisposed);
}
public async Task YieldBreak()
{
// ARRANGE
var asyncEnumerationCanceledExceptionRaised = false;
var enumerator = new AsyncEnumerator <int>(async yield =>
{
try
{
yield.Break();
}
catch (AsyncEnumerationCanceledException)
{
asyncEnumerationCanceledExceptionRaised = true;
}
await yield.ReturnAsync(1);
});
// ACT
var result = await enumerator.MoveNextAsync();
await Task.Yield();
// ASSERT
Assert.IsFalse(result, "MoveNextAsync must return False due to Yield.Break");
Assert.IsTrue(asyncEnumerationCanceledExceptionRaised, "Yield.Break must throw AsyncEnumerationCanceledException so the enumerator body can perform finalization");
}
public async Task RaceConditionOnEndOfEnumeration()
{
var enumerator = new AsyncEnumerator <int>(async yield =>
{
await Task.Run(async() =>
{
await yield.ReturnAsync(1);
});
});
var moveResult1 = await enumerator.MoveNextAsync();
var moveResult2 = await enumerator.MoveNextAsync();
var moveResult3 = await enumerator.MoveNextAsync();
Assert.IsTrue(moveResult1);
Assert.IsFalse(moveResult2);
Assert.IsFalse(moveResult3);
}
public void CancelEnumeration()
{
var cts = new CancellationTokenSource();
var enumerator = new AsyncEnumerator <int>(yield =>
{
cts.Cancel();
yield.CancellationToken.ThrowIfCancellationRequested();
return(Task.FromResult(0));
});
Assert.ThrowsAsync <OperationCanceledException>(() => enumerator.MoveNextAsync(cts.Token));
}
public async Task EnumerationMustEndAfterDispose()
{
// ARRANGE
var enumerator = new AsyncEnumerator <int>(async yield =>
{
await yield.ReturnAsync(1);
await yield.ReturnAsync(2);
});
await enumerator.MoveNextAsync();
// ACT
enumerator.Dispose();
bool moveNextResult = await enumerator.MoveNextAsync();
int currentElement = enumerator.Current;
// ASSERT
Assert.IsFalse(moveNextResult, "MoveNextAsync must return False after Dispose");
Assert.AreEqual(1, currentElement, "Current must not change after Dispose");
}
public async Task MeasureEnumerationTime()
{
var iterations = 1000000;
var enumerator = new AsyncEnumerator <int>(async yield =>
{
for (int i = 0; i < iterations; i++)
{
await yield.ReturnAsync(1);
}
});
var sw = Stopwatch.StartNew();
int sum = 0;
while (await enumerator.MoveNextAsync())
{
sum += enumerator.Current;
}
var time = sw.Elapsed;
Console.WriteLine($"Time taken: {time}, Sum: {sum}");
sw = Stopwatch.StartNew();
sum = 0;
foreach (var number in EnumerateNumbers())
{
sum += number;
}
time = sw.Elapsed;
Console.WriteLine($"Time taken: {time}, Sum: {sum}");
sw = Stopwatch.StartNew();
sum = 0;
int _lock = 0;
for (int i = 0; i < iterations; i++)
{
Interlocked.CompareExchange(ref _lock, 1, 0);
var tcs = new TaskCompletionSource <int>();
tcs.TrySetResult(1);
sum += await tcs.Task;
//await Task.Yield();
//await Task.Yield();
Interlocked.Exchange(ref _lock, 0);
}
time = sw.Elapsed;
Console.WriteLine($"Time taken: {time}, Sum: {sum}");
sw = Stopwatch.StartNew();
sum = 0;
var t = Task.FromResult(1);
for (int i = 0; i < iterations; i++)
{
sum += await t;
}
time = sw.Elapsed;
Console.WriteLine($"Time taken: {time}, Sum: {sum}");
}