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90b71af Mar 3, 2018
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@atifaziz @jskeet @JohannesRudolph
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#region License and Terms
// MoreLINQ - Extensions to LINQ to Objects
// Copyright (c) 2009 Atif Aziz. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#endregion
namespace MoreLinq
{
using System;
using System.Collections.Generic;
static partial class MoreEnumerable
{
/// <summary>
/// Batches the source sequence into sized buckets.
/// </summary>
/// <typeparam name="TSource">Type of elements in <paramref name="source"/> sequence.</typeparam>
/// <param name="source">The source sequence.</param>
/// <param name="size">Size of buckets.</param>
/// <returns>A sequence of equally sized buckets containing elements of the source collection.</returns>
/// <remarks>
/// This operator uses deferred execution and streams its results (buckets and bucket content).
/// </remarks>
public static IEnumerable<IEnumerable<TSource>> Batch<TSource>(this IEnumerable<TSource> source, int size)
{
return Batch(source, size, x => x);
}
/// <summary>
/// Batches the source sequence into sized buckets and applies a projection to each bucket.
/// </summary>
/// <typeparam name="TSource">Type of elements in <paramref name="source"/> sequence.</typeparam>
/// <typeparam name="TResult">Type of result returned by <paramref name="resultSelector"/>.</typeparam>
/// <param name="source">The source sequence.</param>
/// <param name="size">Size of buckets.</param>
/// <param name="resultSelector">The projection to apply to each bucket.</param>
/// <returns>A sequence of projections on equally sized buckets containing elements of the source collection.</returns>
/// <remarks>
/// This operator uses deferred execution and streams its results (buckets and bucket content).
/// </remarks>
public static IEnumerable<TResult> Batch<TSource, TResult>(this IEnumerable<TSource> source, int size,
Func<IEnumerable<TSource>, TResult> resultSelector)
{
if (source == null) throw new ArgumentNullException(nameof(source));
if (size <= 0) throw new ArgumentOutOfRangeException(nameof(size));
if (resultSelector == null) throw new ArgumentNullException(nameof(resultSelector));
return _(); IEnumerable<TResult> _()
{
TSource[] bucket = null;
var count = 0;
foreach (var item in source)
{
if (bucket == null)
{
bucket = new TSource[size];
}
bucket[count++] = item;
// The bucket is fully buffered before it's yielded
if (count != size)
{
continue;
}
yield return resultSelector(bucket);
bucket = null;
count = 0;
}
// Return the last bucket with all remaining elements
if (bucket != null && count > 0)
{
Array.Resize(ref bucket, count);
yield return resultSelector(bucket);
}
}
}
}
}