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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Threading;
using System.Threading.Tasks;
namespace System.Linq
{
public static partial class AsyncEnumerable
{
/// <summary>Returns the number of elements in a sequence.</summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">A sequence that contains elements to be counted.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
/// <returns>The number of elements in the input sequence.</returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="OverflowException">The number of elements in source is larger than <see cref="int.MaxValue"/> (via the returned task).</exception>
public static ValueTask<int> CountAsync<TSource>(
this IAsyncEnumerable<TSource> source,
CancellationToken cancellationToken = default)
{
ThrowHelper.ThrowIfNull(source);
return Impl(source, cancellationToken);
static async ValueTask<int> Impl(
IAsyncEnumerable<TSource> source,
CancellationToken cancellationToken = default)
{
IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);
try
{
int count = 0;
while (await e.MoveNextAsync().ConfigureAwait(false))
{
checked { count++; }
}
return count;
}
finally
{
await e.DisposeAsync().ConfigureAwait(false);
}
}
}
/// <summary>Returns the number of elements in a sequence satisfy a condition.</summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">A sequence that contains elements to be tested and counted.</param>
/// <param name="predicate">A function to test each element for a condition.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
/// <returns>The number of elements in the input sequence that satisfy the condition in the predicate function.</returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="OverflowException">The number of elements that satisfy the condition is larger than <see cref="int.MaxValue"/> (via the returned task).</exception>
public static ValueTask<int> CountAsync<TSource>(
this IAsyncEnumerable<TSource> source,
Func<TSource, bool> predicate,
CancellationToken cancellationToken = default)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(predicate);
return Impl(source.WithCancellation(cancellationToken).ConfigureAwait(false), predicate);
static async ValueTask<int> Impl(
ConfiguredCancelableAsyncEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
int count = 0;
await foreach (TSource element in source)
{
if (predicate(element))
{
checked { count++; }
}
}
return count;
}
}
/// <summary>Returns the number of elements in a sequence satisfy a condition.</summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">A sequence that contains elements to be tested and counted.</param>
/// <param name="predicate">A function to test each element for a condition.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
/// <returns>The number of elements in the input sequence that satisfy the condition in the predicate function.</returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
/// <exception cref="OverflowException">The number of elements that satisfy the condition is larger than <see cref="int.MaxValue"/> (via the returned task).</exception>
public static ValueTask<int> CountAsync<TSource>(
this IAsyncEnumerable<TSource> source,
Func<TSource, CancellationToken, ValueTask<bool>> predicate,
CancellationToken cancellationToken = default)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(predicate);
return Impl(source, predicate, cancellationToken);
static async ValueTask<int> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, CancellationToken, ValueTask<bool>> predicate,
CancellationToken cancellationToken = default)
{
int count = 0;
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
if (await predicate(element, cancellationToken).ConfigureAwait(false))
{
checked { count++; }
}
}
return count;
}
}
/// <summary>Returns the number of elements in a sequence satisfy a condition.</summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">A sequence that contains elements to be tested and counted.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
/// <returns>The number of elements in the input sequence that satisfy the condition in the predicate function.</returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
public static ValueTask<long> LongCountAsync<TSource>(
this IAsyncEnumerable<TSource> source,
CancellationToken cancellationToken = default)
{
ThrowHelper.ThrowIfNull(source);
return Impl(source, cancellationToken);
static async ValueTask<long> Impl(
IAsyncEnumerable<TSource> source,
CancellationToken cancellationToken = default)
{
IAsyncEnumerator<TSource> e = source.GetAsyncEnumerator(cancellationToken);
try
{
long count = 0;
while (await e.MoveNextAsync().ConfigureAwait(false))
{
count++;
}
return count;
}
finally
{
await e.DisposeAsync().ConfigureAwait(false);
}
}
}
/// <summary>Returns the number of elements in a sequence satisfy a condition.</summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">A sequence that contains elements to be tested and counted.</param>
/// <param name="predicate">A function to test each element for a condition.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
/// <returns>The number of elements in the input sequence that satisfy the condition in the predicate function.</returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
public static ValueTask<long> LongCountAsync<TSource>(
this IAsyncEnumerable<TSource> source,
Func<TSource, bool> predicate,
CancellationToken cancellationToken = default)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(predicate);
return Impl(source.WithCancellation(cancellationToken).ConfigureAwait(false), predicate);
static async ValueTask<long> Impl(
ConfiguredCancelableAsyncEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
long count = 0;
await foreach (TSource element in source)
{
if (predicate(element))
{
count++;
}
}
return count;
}
}
/// <summary>Returns the number of elements in a sequence satisfy a condition.</summary>
/// <typeparam name="TSource">The type of the elements of source.</typeparam>
/// <param name="source">A sequence that contains elements to be tested and counted.</param>
/// <param name="predicate">A function to test each element for a condition.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
/// <returns>The number of elements in the input sequence that satisfy the condition in the predicate function.</returns>
/// <exception cref="ArgumentNullException"><paramref name="source"/> is <see langword="null"/>.</exception>
public static ValueTask<long> LongCountAsync<TSource>(
this IAsyncEnumerable<TSource> source,
Func<TSource, CancellationToken, ValueTask<bool>> predicate,
CancellationToken cancellationToken = default)
{
ThrowHelper.ThrowIfNull(source);
ThrowHelper.ThrowIfNull(predicate);
return Impl(source, predicate, cancellationToken);
static async ValueTask<long> Impl(
IAsyncEnumerable<TSource> source,
Func<TSource, CancellationToken, ValueTask<bool>> predicate,
CancellationToken cancellationToken = default)
{
long count = 0;
await foreach (TSource element in source.WithCancellation(cancellationToken).ConfigureAwait(false))
{
if (await predicate(element, cancellationToken).ConfigureAwait(false))
{
count++;
}
}
return count;
}
}
}
}
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