|
// 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>Correlates the elements of two sequences based on matching keys.</summary>
/// <param name="outer">The first sequence to join.</param>
/// <param name="inner">The sequence to join to the first sequence.</param>
/// <param name="outerKeySelector">A function to extract the join key from each element of the first sequence.</param>
/// <param name="innerKeySelector">A function to extract the join key from each element of the second sequence.</param>
/// <param name="resultSelector">A function to create a result element from two matching elements.</param>
/// <param name="comparer">An <see cref="IEqualityComparer{T}"/> to use to hash and compare keys.</param>
/// <typeparam name="TOuter">The type of the elements of the first sequence.</typeparam>
/// <typeparam name="TInner">The type of the elements of the second sequence.</typeparam>
/// <typeparam name="TKey">The type of the keys returned by the key selector functions.</typeparam>
/// <typeparam name="TResult">The type of the result elements.</typeparam>
/// <returns>An <see cref="IAsyncEnumerable{T}" /> that has elements of type <typeparamref name="TResult" /> that are obtained by performing a right outer join on two sequences.</returns>
/// <exception cref="ArgumentNullException"><paramref name="outer" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="inner" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="outerKeySelector" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="innerKeySelector" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector" /> is <see langword="null" />.</exception>
public static IAsyncEnumerable<TResult> RightJoin<TOuter, TInner, TKey, TResult>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
Func<TOuter?, TInner, TResult> resultSelector,
IEqualityComparer<TKey>? comparer = null)
{
ArgumentNullException.ThrowIfNull(outer);
ArgumentNullException.ThrowIfNull(inner);
ArgumentNullException.ThrowIfNull(outerKeySelector);
ArgumentNullException.ThrowIfNull(innerKeySelector);
ArgumentNullException.ThrowIfNull(resultSelector);
return
inner.IsKnownEmpty() ? Empty<TResult>() :
Impl(outer, inner, outerKeySelector, innerKeySelector, resultSelector, comparer, default);
static async IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
Func<TOuter?, TInner, TResult> resultSelector,
IEqualityComparer<TKey>? comparer,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await using IAsyncEnumerator<TInner> e = inner.GetAsyncEnumerator(cancellationToken);
if (await e.MoveNextAsync())
{
AsyncLookup<TKey, TOuter> outerLookup = await AsyncLookup<TKey, TOuter>.CreateForJoinAsync(outer, outerKeySelector, comparer, cancellationToken);
do
{
TInner item = e.Current;
Grouping<TKey, TOuter>? g = outerLookup.GetGrouping(innerKeySelector(item), create: false);
if (g is null)
{
yield return resultSelector(default, item);
}
else
{
int count = g._count;
TOuter[] elements = g._elements;
for (int i = 0; i != count; ++i)
{
yield return resultSelector(elements[i], item);
}
}
}
while (await e.MoveNextAsync());
}
}
}
/// <summary>Correlates the elements of two sequences based on matching keys.</summary>
/// <param name="outer">The first sequence to join.</param>
/// <param name="inner">The sequence to join to the first sequence.</param>
/// <param name="outerKeySelector">A function to extract the join key from each element of the first sequence.</param>
/// <param name="innerKeySelector">A function to extract the join key from each element of the second sequence.</param>
/// <param name="resultSelector">A function to create a result element from two matching elements.</param>
/// <param name="comparer">An <see cref="IEqualityComparer{T}"/> to use to hash and compare keys.</param>
/// <typeparam name="TOuter">The type of the elements of the first sequence.</typeparam>
/// <typeparam name="TInner">The type of the elements of the second sequence.</typeparam>
/// <typeparam name="TKey">The type of the keys returned by the key selector functions.</typeparam>
/// <typeparam name="TResult">The type of the result elements.</typeparam>
/// <returns>An <see cref="IAsyncEnumerable{T}" /> that has elements of type <typeparamref name="TResult" /> that are obtained by performing a right outer join on two sequences.</returns>
/// <exception cref="ArgumentNullException"><paramref name="outer" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="inner" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="outerKeySelector" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="innerKeySelector" /> is <see langword="null" />.</exception>
/// <exception cref="ArgumentNullException"><paramref name="resultSelector" /> is <see langword="null" />.</exception>
public static IAsyncEnumerable<TResult> RightJoin<TOuter, TInner, TKey, TResult>(
this IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
Func<TOuter?, TInner, CancellationToken, ValueTask<TResult>> resultSelector,
IEqualityComparer<TKey>? comparer = null)
{
ArgumentNullException.ThrowIfNull(outer);
ArgumentNullException.ThrowIfNull(inner);
ArgumentNullException.ThrowIfNull(outerKeySelector);
ArgumentNullException.ThrowIfNull(innerKeySelector);
ArgumentNullException.ThrowIfNull(resultSelector);
return
inner.IsKnownEmpty() ? Empty<TResult>() :
Impl(outer, inner, outerKeySelector, innerKeySelector, resultSelector, comparer, default);
static async IAsyncEnumerable<TResult> Impl(
IAsyncEnumerable<TOuter> outer,
IAsyncEnumerable<TInner> inner,
Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
Func<TOuter?, TInner, CancellationToken, ValueTask<TResult>> resultSelector,
IEqualityComparer<TKey>? comparer,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
await using IAsyncEnumerator<TInner> e = inner.GetAsyncEnumerator(cancellationToken);
if (await e.MoveNextAsync())
{
AsyncLookup<TKey, TOuter> outerLookup = await AsyncLookup<TKey, TOuter>.CreateForJoinAsync(outer, outerKeySelector, comparer, cancellationToken);
do
{
TInner item = e.Current;
Grouping<TKey, TOuter>? g = outerLookup.GetGrouping(await innerKeySelector(item, cancellationToken), create: false);
if (g is null)
{
yield return await resultSelector(default, item, cancellationToken);
}
else
{
int count = g._count;
TOuter[] elements = g._elements;
for (int i = 0; i != count; ++i)
{
yield return await resultSelector(elements[i], item, cancellationToken);
}
}
}
while (await e.MoveNextAsync());
}
}
}
}
}
|