osu/osu.Game/Audio/SampleInfo.cs
Bartłomiej Dach 15d9147edd Ensure equality member consistency for SampleInfo
The previous implementation of `SampleInfo`'s equality members was not
completely correct in its treatment of the `sampleNames` array. While
`Equals()` compared the values of `sampleNames` using `SequenceEqual()`,
therefore performing a structural check that inspects the contents of
both arrays, `GetHashCode()` used `HashCode.Combine()` directly on the
arrays, therefore operating on reference equality. This could cause the
pooling mechanism of samples to fail, as pointed out in #11079.

To resolve, change the `GetHashCode()` implementation such that it also
considers the contents of the array rather than just the reference to
the array itself. This is achieved by leveraging
`StructuralEqualityComparer`.

Additionally, as a bonus, an array sort was added to the constructor of
`SampleInfo`. This is intended to be a "canonicalisation" processing
step for the array of sample names. Thanks to that sort, two instances
of `SampleInfo` that have the same sample names but permutated will also
turn out to be equal and have the same hash codes, given the
implementation of both equality members. This gives `SampleInfo`
set-like semantics.
2020-12-03 23:25:53 +01:00

42 lines
1.2 KiB
C#

// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
namespace osu.Game.Audio
{
/// <summary>
/// Describes a gameplay sample.
/// </summary>
public class SampleInfo : ISampleInfo, IEquatable<SampleInfo>
{
private readonly string[] sampleNames;
public SampleInfo(params string[] sampleNames)
{
this.sampleNames = sampleNames;
Array.Sort(sampleNames);
}
public IEnumerable<string> LookupNames => sampleNames;
public int Volume { get; } = 100;
public override int GetHashCode()
{
return HashCode.Combine(
StructuralComparisons.StructuralEqualityComparer.GetHashCode(sampleNames),
Volume);
}
public bool Equals(SampleInfo other)
=> other != null && sampleNames.SequenceEqual(other.sampleNames);
public override bool Equals(object obj)
=> obj is SampleInfo other && Equals(other);
}
}