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"Batch" overloads using an array pool
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This is a squashed merge of PR #856 that supersedes #833.

Co-authored-by: Stuart Turner <[email protected]>
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@atifaziz @viceroypenguin
atifaziz and viceroypenguin authored Nov 13, 2022
1 parent c6ca90d commit ba487dd
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Showing 5 changed files with 669 additions and 14 deletions.
272 changes: 261 additions & 11 deletions MoreLinq.Test/BatchTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,18 +23,12 @@ namespace MoreLinq.Test
[TestFixture]
public class BatchTest
{
[Test]
public void BatchZeroSize()
{
AssertThrowsArgument.OutOfRangeException("size",() =>
new object[0].Batch(0));
}

[Test]
public void BatchNegativeSize()
[TestCase(0)]
[TestCase(-1)]
public void BatchBadSize(int size)
{
AssertThrowsArgument.OutOfRangeException("size",() =>
new object[0].Batch(-1));
AssertThrowsArgument.OutOfRangeException("size", () =>
new object[0].Batch(size));
}

[Test]
Expand Down Expand Up @@ -141,3 +135,259 @@ public void BatchEmptySource(SourceKind kind)
}
}
}

#if NETCOREAPP3_1_OR_GREATER

namespace MoreLinq.Test
{
using System;
using System.Buffers;
using System.Collections.Generic;
using MoreLinq.Experimental;
using NUnit.Framework;

[TestFixture]
public class BatchPoolTest
{
[TestCase(0)]
[TestCase(-1)]
public void BatchBadSize(int size)
{
AssertThrowsArgument.OutOfRangeException("size", () =>
new object[0].Batch(size, ArrayPool<object>.Shared,
BreakingFunc.Of<ICurrentBuffer<object>, IEnumerable<object>>(),
BreakingFunc.Of<IEnumerable<object>, object>()));
}

[Test]
public void BatchEvenlyDivisibleSequence()
{
using var input = TestingSequence.Of(1, 2, 3, 4, 5, 6, 7, 8, 9);
using var pool = new TestArrayPool<int>();

var result = input.Batch(3, pool, Enumerable.ToArray);

using var reader = result.Read();
reader.Read().AssertSequenceEqual(1, 2, 3);
reader.Read().AssertSequenceEqual(4, 5, 6);
reader.Read().AssertSequenceEqual(7, 8, 9);
reader.ReadEnd();
}

[Test]
public void BatchUnevenlyDivisibleSequence()
{
using var input = TestingSequence.Of(1, 2, 3, 4, 5, 6, 7, 8, 9);
using var pool = new TestArrayPool<int>();

var result = input.Batch(4, pool, Enumerable.ToArray);

using var reader = result.Read();
reader.Read().AssertSequenceEqual(1, 2, 3, 4);
reader.Read().AssertSequenceEqual(5, 6, 7, 8);
reader.Read().AssertSequenceEqual(9);
reader.ReadEnd();
}

[Test]
public void BatchIsLazy()
{
var input = new BreakingSequence<object>();
_ = input.Batch(1, ArrayPool<object>.Shared,
BreakingFunc.Of<ICurrentBuffer<object>, IEnumerable<object>>(),
BreakingFunc.Of<IEnumerable<object>, object>());
}

[TestCase(SourceKind.BreakingList , 0)]
[TestCase(SourceKind.BreakingReadOnlyList, 0)]
[TestCase(SourceKind.BreakingList , 1)]
[TestCase(SourceKind.BreakingReadOnlyList, 1)]
[TestCase(SourceKind.BreakingList , 2)]
[TestCase(SourceKind.BreakingReadOnlyList, 2)]
public void BatchCollectionSmallerThanSize(SourceKind kind, int oversize)
{
var xs = new[] { 1, 2, 3, 4, 5 };
using var pool = new TestArrayPool<int>();

var result = xs.ToSourceKind(kind)
.Batch(xs.Length + oversize, pool, Enumerable.ToArray);

using var reader = result.Read();
reader.Read().AssertSequenceEqual(1, 2, 3, 4, 5);
reader.ReadEnd();
}

[Test]
public void BatchReadOnlyCollectionSmallerThanSize()
{
var collection = ReadOnlyCollection.From(1, 2, 3, 4, 5);
using var pool = new TestArrayPool<int>();

var result = collection.Batch(collection.Count * 2, pool,
Enumerable.ToArray);

using var reader = result.Read();
reader.Read().AssertSequenceEqual(1, 2, 3, 4, 5);
reader.ReadEnd();
}

[TestCase(SourceKind.Sequence)]
[TestCase(SourceKind.BreakingList)]
[TestCase(SourceKind.BreakingReadOnlyList)]
[TestCase(SourceKind.BreakingReadOnlyCollection)]
[TestCase(SourceKind.BreakingCollection)]
public void BatchEmptySource(SourceKind kind)
{
using var pool = new TestArrayPool<int>();

var result = Enumerable.Empty<int>()
.ToSourceKind(kind)
.Batch(100, pool, Enumerable.ToArray);

Assert.That(result, Is.Empty);
}

[Test]
public void BatchFilterBucket()
{
const int scale = 2;
var input = TestingSequence.Of(1, 2, 3, 4, 5, 6, 7, 8, 9);
using var pool = new TestArrayPool<int>();

var result = input.Batch(3, pool,
current => from n in current
where n % 2 == 0
select n * scale,
Enumerable.ToArray);

using var reader = result.Read();
reader.Read().AssertSequenceEqual(2 * scale);
reader.Read().AssertSequenceEqual(4 * scale, 6 * scale);
reader.Read().AssertSequenceEqual(8 * scale);
reader.ReadEnd();
}

[Test]
public void BatchSumBucket()
{
var input = TestingSequence.Of(1, 2, 3, 4, 5, 6, 7, 8, 9);
using var pool = new TestArrayPool<int>();

var result = input.Batch(3, pool, Enumerable.Sum);

using var reader = result.Read();
Assert.That(reader.Read(), Is.EqualTo(1 + 2 + 3));
Assert.That(reader.Read(), Is.EqualTo(4 + 5 + 6));
Assert.That(reader.Read(), Is.EqualTo(7 + 8 + 9));
reader.ReadEnd();
}

/// <remarks>
/// This test does not exercise the intended usage!
/// </remarks>

[Test]
public void BatchUpdatesCurrentListInPlace()
{
var input = TestingSequence.Of(1, 2, 3, 4, 5, 6, 7, 8, 9);
using var pool = new TestArrayPool<int>();

var result = input.Batch(4, pool, current => current, current => (ICurrentBuffer<int>)current);

using var reader = result.Read();
var current = reader.Read();
current.AssertSequenceEqual(1, 2, 3, 4);
_ = reader.Read();
current.AssertSequenceEqual(5, 6, 7, 8);
_ = reader.Read();
current.AssertSequenceEqual(9);

reader.ReadEnd();

Assert.That(current, Is.Empty);
}

[Test]
public void BatchCallsBucketSelectorBeforeIteratingSource()
{
var iterations = 0;
IEnumerable<int> Source()
{
iterations++;
yield break;
}

var input = Source();
using var pool = new TestArrayPool<int>();
var initIterations = -1;

var result = input.Batch(4, pool,
current =>
{
initIterations = iterations;
return current;
},
_ => 0);

using var enumerator = result.GetEnumerator();
Assert.That(enumerator.MoveNext(), Is.False);
Assert.That(initIterations, Is.Zero);
}

[Test]
public void BatchBucketSelectorCurrentList()
{
var input = TestingSequence.Of(1, 2, 3, 4, 5, 6, 7, 8, 9);
using var pool = new TestArrayPool<int>();
int[] bucketSelectorItems = null;

var result = input.Batch(4, pool, current => bucketSelectorItems = current.ToArray(), _ => 0);

using var reader = result.Read();
_ = reader.Read();
Assert.That(bucketSelectorItems, Is.Not.Null);
Assert.That(bucketSelectorItems, Is.Empty);
}

/// <summary>
/// An <see cref="ArrayPool{T}"/> implementation for testing purposes that holds only
/// one array in the pool and ensures that it is returned when the pool is disposed.
/// </summary>

sealed class TestArrayPool<T> : ArrayPool<T>, IDisposable
{
T[] _pooledArray;
T[] _rentedArray;

public override T[] Rent(int minimumLength)
{
if (_pooledArray is null && _rentedArray is null)
_pooledArray = new T[minimumLength * 2];

if (_pooledArray is null)
throw new InvalidOperationException("The pool is exhausted.");

(_pooledArray, _rentedArray) = (null, _pooledArray);

return _rentedArray;
}

public override void Return(T[] array, bool clearArray = false)
{
if (_rentedArray is null)
throw new InvalidOperationException("Cannot return when nothing has been rented from this pool.");

if (array != _rentedArray)
throw new InvalidOperationException("Cannot return what has not been rented from this pool.");

_pooledArray = array;
_rentedArray = null;
}

public void Dispose() =>
Assert.That(_rentedArray, Is.Null);
}
}
}

#endif // NETCOREAPP3_1_OR_GREATER
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