public static IAsyncEnumerable<TSource> Finally<TSource>(this IAsyncEnumerable<TSource> source, Func<Task> finallyAction)
{
if (source == null)
throw Error.ArgumentNull(nameof(source));
if (finallyAction == null)
throw Error.ArgumentNull(nameof(finallyAction));
#if USE_ASYNC_ITERATOR
return AsyncEnumerable.Create(Core);
async IAsyncEnumerator<TSource> Core(CancellationToken cancellationToken)
{
try
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
yield return item;
}
}
finally
{
await finallyAction().ConfigureAwait(false);
}
}
#else
return new FinallyAsyncIteratorWithTask<TSource>(source, finallyAction);
#endif
}
public static IAsyncEnumerable <TSource> Expand <TSource>(this IAsyncEnumerable <TSource> source, Func <TSource, CancellationToken, ValueTask <IAsyncEnumerable <TSource> > > selector)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
if (selector == null)
{
throw Error.ArgumentNull(nameof(selector));
}
#if USE_ASYNC_ITERATOR
return(AsyncEnumerable.Create(Core));
async IAsyncEnumerator <TSource> Core(CancellationToken cancellationToken)
{
var queue = new Queue <IAsyncEnumerable <TSource> >();
queue.Enqueue(source);
while (queue.Count > 0)
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(queue.Dequeue(), cancellationToken).ConfigureAwait(false))
{
queue.Enqueue(await selector(item, cancellationToken).ConfigureAwait(false));
yield return(item);
}
}
}
#else
return(new ExpandAsyncIteratorWithTaskAndCancellation <TSource>(source, selector));
#endif
}
public static IAsyncEnumerable <TResult> Select <TSource, TResult>(this IAsyncEnumerable <TSource> source, Func <TSource, int, TResult> selector)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
if (selector == null)
{
throw Error.ArgumentNull(nameof(selector));
}
#if USE_ASYNC_ITERATOR
return(Create(Core));
async IAsyncEnumerator <TResult> Core(CancellationToken cancellationToken)
{
var index = -1;
await foreach (var element in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
checked
{
index++;
}
yield return(selector(element, index));
}
}
#else
return(new SelectEnumerableWithIndexAsyncIterator <TSource, TResult>(source, selector));
#endif
}
public override async ValueTask <List <TSource> > ToListAsync(CancellationToken cancellationToken)
{
var count = await GetCountAsync(onlyIfCheap : true, cancellationToken).ConfigureAwait(false);
var list = count == -1 ? new List <TSource>() : new List <TSource>(count);
for (var n = _prepended; n != null; n = n.Linked)
{
list.Add(n.Item);
}
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, cancellationToken).ConfigureAwait(false))
{
list.Add(item);
}
if (_appended != null)
{
using (var en2 = _appended.GetEnumerator(_appendCount))
{
while (en2.MoveNext())
{
list.Add(en2.Current);
}
}
}
return(list);
}
static async Task Core(IAsyncEnumerable <TSource> _source, Action <TSource> _action, CancellationToken _cancellationToken)
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, _cancellationToken).ConfigureAwait(false))
{
_action(item);
}
}
public override async ValueTask <List <TSource> > ToListAsync(CancellationToken cancellationToken)
{
var count = await GetCountAsync(onlyIfCheap : true, cancellationToken).ConfigureAwait(false);
cancellationToken.ThrowIfCancellationRequested();
var list = count == -1 ? new List <TSource>() : new List <TSource>(count);
if (!_appending)
{
list.Add(_item);
}
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, cancellationToken).ConfigureAwait(false))
{
list.Add(item);
}
if (_appending)
{
list.Add(_item);
}
return(list);
}
public static IAsyncEnumerable <TAccumulate> Scan <TSource, TAccumulate>(this IAsyncEnumerable <TSource> source, TAccumulate seed, Func <TAccumulate, TSource, TAccumulate> accumulator)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
if (accumulator == null)
{
throw Error.ArgumentNull(nameof(accumulator));
}
#if USE_ASYNC_ITERATOR
return(AsyncEnumerable.Create(Core));
async IAsyncEnumerator <TAccumulate> Core(CancellationToken cancellationToken)
{
var res = seed;
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
res = accumulator(res, item);
yield return(res);
}
}
#else
return(new ScanAsyncEnumerable <TSource, TAccumulate>(source, seed, accumulator));
#endif
}
public static IAsyncEnumerable <TSource> Where <TSource>(this IAsyncEnumerable <TSource> source, Func <TSource, int, bool> predicate)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
if (predicate == null)
{
throw Error.ArgumentNull(nameof(predicate));
}
#if USE_ASYNC_ITERATOR
return(Create(Core));
async IAsyncEnumerator <TSource> Core(CancellationToken cancellationToken)
{
var index = -1;
await foreach (var element in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
checked
{
index++;
}
if (predicate(element, index))
{
yield return(element);
}
}
}
#else
return(new WhereEnumerableWithIndexAsyncIterator <TSource>(source, predicate));
#endif
}
public static IAsyncEnumerable <TSource> Using <TSource, TResource>(Func <CancellationToken, Task <TResource> > resourceFactory, Func <TResource, CancellationToken, ValueTask <IAsyncEnumerable <TSource> > > enumerableFactory) where TResource : IDisposable
{
if (resourceFactory == null)
{
throw Error.ArgumentNull(nameof(resourceFactory));
}
if (enumerableFactory == null)
{
throw Error.ArgumentNull(nameof(enumerableFactory));
}
#if USE_ASYNC_ITERATOR
return(AsyncEnumerable.Create(Core));
async IAsyncEnumerator <TSource> Core(CancellationToken cancellationToken)
{
using (var resource = await resourceFactory(cancellationToken).ConfigureAwait(false))
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation((await enumerableFactory(resource, cancellationToken).ConfigureAwait(false)), cancellationToken).ConfigureAwait(false))
{
yield return(item);
}
}
}
#else
return(new UsingAsyncIteratorWithTaskAndCancellation <TSource, TResource>(resourceFactory, enumerableFactory));
#endif
}
public static IAsyncEnumerable <TSource> Repeat <TSource>(this IAsyncEnumerable <TSource> source, int count)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
if (count < 0)
{
throw Error.ArgumentOutOfRange(nameof(count));
}
#if USE_ASYNC_ITERATOR
return(AsyncEnumerable.Create(Core));
async IAsyncEnumerator <TSource> Core(CancellationToken cancellationToken)
{
for (var i = 0; i < count; i++)
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
yield return(item);
}
}
}
#else
return(new RepeatSequenceAsyncIterator <TSource>(source, count));
#endif
}
public static async ValueTask AddRangeAsync <T>(this List <T> list, IAsyncEnumerable <T> collection, CancellationToken cancellationToken)
{
if (collection is IEnumerable <T> enumerable)
{
list.AddRange(enumerable);
return;
}
if (collection is IAsyncIListProvider <T> listProvider)
{
var count = await listProvider.GetCountAsync(onlyIfCheap : true, cancellationToken).ConfigureAwait(false);
if (count == 0)
{
return;
}
if (count > 0)
{
var newCount = list.Count + count;
if (list.Capacity < newCount)
{
list.Capacity = newCount;
}
}
}
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(collection, cancellationToken).ConfigureAwait(false))
{
list.Add(item);
}
}
// NB: This is a non-standard LINQ operator, because we don't have a non-generic IAsyncEnumerable.
// We're keeping it to enable `from T x in xs` binding in C#.
public static IAsyncEnumerable <TResult> Cast <TResult>(this IAsyncEnumerable <object> source)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
if (source is IAsyncEnumerable <TResult> typedSource)
{
return(typedSource);
}
#if USE_ASYNC_ITERATOR
return(Create(Core));
async IAsyncEnumerator <TResult> Core(CancellationToken cancellationToken)
{
await foreach (var obj in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
yield return((TResult)obj);
}
}
#else
return(new CastAsyncIterator <TResult>(source));
#endif
}
public static IAsyncEnumerable <TSource> Intersect <TSource>(this IAsyncEnumerable <TSource> first, IAsyncEnumerable <TSource> second, IEqualityComparer <TSource> comparer)
{
if (first == null)
{
throw Error.ArgumentNull(nameof(first));
}
if (second == null)
{
throw Error.ArgumentNull(nameof(second));
}
#if USE_ASYNC_ITERATOR
return(Create(Core));
async IAsyncEnumerator <TSource> Core(CancellationToken cancellationToken)
{
var set = new Set <TSource>(comparer);
await foreach (var element in AsyncEnumerableExtensions.WithCancellation(second, cancellationToken).ConfigureAwait(false))
{
set.Add(element);
}
await foreach (var element in AsyncEnumerableExtensions.WithCancellation(first, cancellationToken).ConfigureAwait(false))
{
if (set.Remove(element))
{
yield return(element);
}
}
}
#else
return(new IntersectAsyncIterator <TSource>(first, second, comparer));
#endif
}
internal static IAsyncEnumerable <TSource> TakeWhileAwaitCore <TSource>(this IAsyncEnumerable <TSource> source, Func <TSource, ValueTask <bool> > predicate)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
if (predicate == null)
{
throw Error.ArgumentNull(nameof(predicate));
}
#if USE_ASYNC_ITERATOR
return(Create(Core));
async IAsyncEnumerator <TSource> Core(CancellationToken cancellationToken)
{
await foreach (var element in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
if (!await predicate(element).ConfigureAwait(false))
{
break;
}
yield return(element);
}
}
#else
return(new TakeWhileAsyncIteratorWithTask <TSource>(source, predicate));
#endif
}
static async ValueTask <List <TSource> > Core(IAsyncEnumerable <TSource> _source, CancellationToken _cancellationToken)
{
var list = new List <TSource>();
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, _cancellationToken).ConfigureAwait(false))
{
list.Add(item);
}
return(list);
}
static async ValueTask <HashSet <TSource> > Core(IAsyncEnumerable <TSource> _source, IEqualityComparer <TSource> _comparer, CancellationToken _cancellationToken)
{
var set = new HashSet <TSource>(_comparer);
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, _cancellationToken).ConfigureAwait(false))
{
set.Add(item);
}
return(set);
}
static async ValueTask <bool> Core(IAsyncEnumerable <TSource> _source, TSource _value, CancellationToken _cancellationToken)
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, _cancellationToken).ConfigureAwait(false))
{
if (EqualityComparer <TSource> .Default.Equals(item, _value))
{
return(true);
}
}
return(false);
}
static async ValueTask <bool> Core(IAsyncEnumerable <TSource> _source, Func <TSource, bool> _predicate, CancellationToken _cancellationToken)
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, _cancellationToken).ConfigureAwait(false))
{
if (!_predicate(item))
{
return(false);
}
}
return(true);
}
static async ValueTask <Dictionary <TKey, TSource> > Core(IAsyncEnumerable <TSource> _source, Func <TSource, TKey> _keySelector, IEqualityComparer <TKey> _comparer, CancellationToken _cancellationToken)
{
var d = new Dictionary <TKey, TSource>(_comparer);
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, _cancellationToken).ConfigureAwait(false))
{
var key = _keySelector(item);
d.Add(key, item);
}
return(d);
}
public static IAsyncEnumerable <IList <TSource> > Buffer <TSource>(this IAsyncEnumerable <TSource> source, int count, int skip)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
if (count <= 0)
{
throw Error.ArgumentOutOfRange(nameof(count));
}
if (skip <= 0)
{
throw Error.ArgumentOutOfRange(nameof(skip));
}
#if USE_ASYNC_ITERATOR
return(AsyncEnumerable.Create(Core));
async IAsyncEnumerator <IList <TSource> > Core(CancellationToken cancellationToken)
{
var buffers = new Queue <IList <TSource> >();
var index = 0;
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
if (index++ % skip == 0)
{
buffers.Enqueue(new List <TSource>(count));
}
foreach (var buffer in buffers)
{
buffer.Add(item);
}
if (buffers.Count > 0 && buffers.Peek().Count == count)
{
yield return(buffers.Dequeue());
}
}
while (buffers.Count > 0)
{
yield return(buffers.Dequeue());
}
}
#else
return(new BufferAsyncIterator <TSource>(source, count, skip));
#endif
}
static async ValueTask <int> Core(IAsyncEnumerable <int> _source, CancellationToken _cancellationToken)
{
var sum = 0;
await foreach (int value in AsyncEnumerableExtensions.WithCancellation(_source, _cancellationToken).ConfigureAwait(false))
{
checked
{
sum += value;
}
}
return(sum);
}
static async ValueTask <int> Core(IAsyncEnumerable <TSource> _source, CancellationToken _cancellationToken)
{
var count = 0;
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, _cancellationToken).ConfigureAwait(false))
{
checked
{
count++;
}
}
return(count);
}
public override async ValueTask <TSource[]> ToArrayAsync(CancellationToken cancellationToken)
{
var count = await GetCountAsync(onlyIfCheap : true, cancellationToken).ConfigureAwait(false);
if (count == -1)
{
return(await AsyncEnumerableHelpers.ToArray(this, cancellationToken).ConfigureAwait(false));
}
cancellationToken.ThrowIfCancellationRequested();
var array = new TSource[count];
int index;
if (_appending)
{
index = 0;
}
else
{
array[0] = _item;
index = 1;
}
if (_source is ICollection <TSource> sourceCollection)
{
sourceCollection.CopyTo(array, index);
}
else
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, cancellationToken).ConfigureAwait(false))
{
array[index] = item;
++index;
}
}
if (_appending)
{
array[array.Length - 1] = _item;
}
return(array);
}
private async Task <Set <TSource> > FillSetAsync(CancellationToken cancellationToken)
{
cancellationToken.ThrowIfCancellationRequested();
var set = new Set <TSource>(_comparer);
for (var index = 0; ; ++index)
{
var enumerable = GetEnumerable(index);
if (enumerable == null)
{
return(set);
}
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(enumerable, cancellationToken).ConfigureAwait(false))
{
set.Add(item);
}
}
}
public static IAsyncEnumerable <TSource> Defer <TSource>(Func <CancellationToken, Task <IAsyncEnumerable <TSource> > > factory)
{
if (factory == null)
{
throw Error.ArgumentNull(nameof(factory));
}
#if USE_ASYNC_ITERATOR
return(AsyncEnumerable.Create(Core));
async IAsyncEnumerator <TSource> Core(CancellationToken cancellationToken)
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation((await factory(cancellationToken).ConfigureAwait(false)), cancellationToken).ConfigureAwait(false))
{
yield return(item);
}
}
#else
return(new AsyncDeferIteratorWithCancellation <TSource>(factory));
#endif
}
public override async ValueTask <TSource[]> ToArrayAsync(CancellationToken cancellationToken)
{
var count = await GetCountAsync(onlyIfCheap : true, cancellationToken).ConfigureAwait(false);
if (count == -1)
{
return(await AsyncEnumerableHelpers.ToArray(this, cancellationToken).ConfigureAwait(false));
}
var array = new TSource[count];
var index = 0;
for (var n = _prepended; n != null; n = n.Linked)
{
array[index] = n.Item;
++index;
}
if (_source is ICollection <TSource> sourceCollection)
{
sourceCollection.CopyTo(array, index);
}
else
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, cancellationToken).ConfigureAwait(false))
{
array[index] = item;
++index;
}
}
index = array.Length;
for (var n = _appended; n != null; n = n.Linked)
{
--index;
array[index] = n.Item;
}
return(array);
}
public static IAsyncEnumerable <TSource> IgnoreElements <TSource>(this IAsyncEnumerable <TSource> source)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
#if USE_ASYNC_ITERATOR
return(AsyncEnumerable.Create(Core));
async IAsyncEnumerator <TSource> Core(CancellationToken cancellationToken)
{
await foreach (var _ in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
}
yield break;
}
#else
return(new IgnoreElementsAsyncIterator <TSource>(source));
#endif
}
public static IAsyncEnumerable <IList <TSource> > Buffer <TSource>(this IAsyncEnumerable <TSource> source, int count)
{
if (source == null)
{
throw Error.ArgumentNull(nameof(source));
}
if (count <= 0)
{
throw Error.ArgumentOutOfRange(nameof(count));
}
#if USE_ASYNC_ITERATOR
return(AsyncEnumerable.Create(Core));
async IAsyncEnumerator <IList <TSource> > Core(CancellationToken cancellationToken)
{
var buffer = new List <TSource>(count);
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
buffer.Add(item);
if (buffer.Count == count)
{
yield return(buffer);
buffer = new List <TSource>(count);
}
}
if (buffer.Count > 0)
{
yield return(buffer);
}
}
#else
return(new BufferAsyncIterator <TSource>(source, count, count));
#endif
}
public async ValueTask <List <TSource> > ToListAsync(CancellationToken cancellationToken)
{
cancellationToken.ThrowIfCancellationRequested();
var list = new List <TSource>();
for (var i = 0; ; i++)
{
var source = GetAsyncEnumerable(i);
if (source == null)
{
break;
}
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(source, cancellationToken).ConfigureAwait(false))
{
list.Add(item);
}
}
return(list);
}
static async ValueTask <TSource> Core(IAsyncEnumerable <TSource> _source, int _index, CancellationToken _cancellationToken)
{
if (_source is IAsyncPartition <TSource> p)
{
var first = await p.TryGetElementAtAsync(_index, _cancellationToken).ConfigureAwait(false);
if (first.HasValue)
{
return(first.Value);
}
}
else
{
if (_source is IList <TSource> list)
{
return(list[_index]);
}
if (_index >= 0)
{
await foreach (var item in AsyncEnumerableExtensions.WithCancellation(_source, _cancellationToken).ConfigureAwait(false))
{
if (_index == 0)
{
return(item);
}
_index--;
}
}
}
// NB: Even though index is captured, no closure is created.
// The nameof expression is lowered to a literal prior to creating closures.
throw Error.ArgumentOutOfRange(nameof(index));
}