/// <summary>
/// Convenience extension to cheaply have only a single task running an operation, by using a semaphore as a latch.
///
/// It will run <paramref name="operation"/> if the gate allows it to, or <paramref name="duplicated"/> otherwise.
/// </summary>
public static async Task <TResult> DeduplicatedOperationAsync <TResult>(this SemaphoreSlim gate, Func <TimeSpan, int, Task <TResult> > operation, Func <TimeSpan, int, Task <TResult> > duplicated, CancellationToken token = default)
{
Contract.RequiresNotNull(gate);
Contract.RequiresNotNull(operation);
Contract.RequiresNotNull(duplicated);
var sw = Stopwatch.StartNew();
var taken = await gate.WaitAsync(millisecondsTimeout : 0, token);
if (!taken)
{
var currentCount = gate.CurrentCount;
return(await duplicated(sw.Elapsed, currentCount));
}
try
{
var currentCount = gate.CurrentCount;
return(await operation(sw.Elapsed, currentCount));
}
finally
{
gate.Release();
}
}
/// <summary>
/// Convenience extension to allow tracing the time it takes to Wait a semaphore
/// </summary>
public static async Task <TResult> GatedOperationAsync <TResult>(
this SemaphoreSlim gate,
Func <TimeSpan, int, Task <TResult> > operation,
CancellationToken token = default,
TimeSpan?ioGateTimeout = null)
{
Contract.RequiresNotNull(gate);
Contract.RequiresNotNull(operation);
var sw = Stopwatch.StartNew();
var acquired = await gate.WaitAsync(ioGateTimeout ?? Timeout.InfiniteTimeSpan, token);
if (!acquired)
{
throw new TimeoutException($"IO gate timed out after {ioGateTimeout}");
}
try
{
var currentCount = gate.CurrentCount;
return(await operation(sw.Elapsed, currentCount));
}
finally
{
gate.Release();
}
}
/// <summary>
/// Convenience extension to allow tracing the time it takes to Wait a semaphore
/// </summary>
public static async Task <TResult> GatedOperationAsync <TResult>(this SemaphoreSlim gate, Func <TimeSpan, int, Task <TResult> > operation, CancellationToken token = default)
{
Contract.RequiresNotNull(gate);
Contract.RequiresNotNull(operation);
var sw = Stopwatch.StartNew();
await gate.WaitAsync(token);
try
{
var currentCount = gate.CurrentCount;
return(await operation(sw.Elapsed, currentCount));
}
finally
{
gate.Release();
}
}