/// <summary>
/// Helper method to invoke constructor of <see cref="WrappingEnumerationStartInfo{T}"/> without explicitly specifying generic type arguments.
/// </summary>
/// <typeparam name="T">The type of items being enumerated.</typeparam>
/// <param name="waitForNext">The callback that will be used by <see cref="IAsyncEnumerator{T}.WaitForNextAsync"/>.</param>
/// <param name="tryGetNext">The callback that will be used by <see cref="IAsyncEnumerator{T}.TryGetNext"/>.</param>
/// <param name="dispose">The optional callback that will be used by <see cref="IAsyncDisposable.DisposeAsync"/>.</param>
/// <returns>A new instance of <see cref="WrappingEnumerationStartInfo{T}"/>.</returns>
/// <exception cref="ArgumentNullException">If either of <paramref name="waitForNext"/> or <paramref name="tryGetNext"/> is <c>null</c>.</exception>
/// <seealso cref="WrappingEnumerationStartInfo{T}"/>
public static WrappingEnumerationStartInfo <T> CreateWrappingStartInfo <T>(
WaitForNextDelegate waitForNext,
TryGetNextDelegate <T> tryGetNext,
EnumerationEndedDelegate dispose
)
{
return(new WrappingEnumerationStartInfo <T>(waitForNext, tryGetNext, dispose));
}
/// <summary>
/// Creates a new instance of <see cref="WrappingEnumerationStartInfo{T}"/>.
/// </summary>
/// <param name="waitForNext">The callback that will be used by <see cref="IAsyncEnumerator{T}.WaitForNextAsync"/>.</param>
/// <param name="tryGetNext">The callback that will be used by <see cref="IAsyncEnumerator{T}.TryGetNext"/>.</param>
/// <param name="dispose">The optional callback that will be used by <see cref="IAsyncDisposable.DisposeAsync"/>.</param>
/// <exception cref="ArgumentNullException">If either of <paramref name="waitForNext"/> or <paramref name="tryGetNext"/> is <c>null</c>.</exception>
public WrappingEnumerationStartInfo(
WaitForNextDelegate waitForNext,
TryGetNextDelegate <T> tryGetNext,
EnumerationEndedDelegate dispose
)
{
this.WaitForNext = waitForNext;
this.TryGetNext = tryGetNext;
this.Dispose = dispose;
}
internal static void InitVars <T>(
WaitForNextDelegate waitForNext,
TryGetNextDelegate <T> tryGetNext,
EnumerationEndedDelegate dispose,
out WaitForNextDelegate fieldWaitForNext,
out TryGetNextDelegate <T> fieldTryGetNext,
out EnumerationEndedDelegate fieldDispose
)
{
fieldWaitForNext = ArgumentValidator.ValidateNotNull(nameof(waitForNext), waitForNext);
fieldTryGetNext = ArgumentValidator.ValidateNotNull(nameof(tryGetNext), tryGetNext);
fieldDispose = dispose ?? (() => TaskUtils.CompletedTask);
}
/// <summary>
/// Helper method to create <see cref="WrappingEnumerationStartInfo{T}"/> which will return <c>true</c> only once for its <see cref="IAsyncEnumerator{T}.WaitForNextAsync"/> method, and the rest of the items are returned via <see cref="IAsyncEnumerator{T}.TryGetNext(out Boolean)"/> method.
/// </summary>
/// <typeparam name="T">The type of items being enumerated.</typeparam>
/// <param name="tryGetNext">The callback to get next item.</param>
/// <param name="dispose">The optional disposing callback.</param>
/// <returns></returns>
public static WrappingEnumerationStartInfo <T> CreateSynchronousWrappingStartInfo <T>(
TryGetNextDelegate <T> tryGetNext,
EnumerationEndedDelegate dispose = null
)
{
const Int32 INITIAL = 0;
const Int32 STARTED = 1;
var state = INITIAL;
return(CreateWrappingStartInfo(
() =>
{
return TaskUtils.TaskFromBoolean(Interlocked.CompareExchange(ref state, STARTED, INITIAL) == INITIAL);
},
tryGetNext,
dispose
));
}