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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.
// See the LICENSE file in the project root for more information.
using Xunit;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;
namespace System.SpanTests
{
public static partial class SpanTests
{
[Fact]
public static void IndexOverflow()
{
//
// Although Span constrains indexes to 0..2Gb, it does not similarly constrain index * sizeof(T).
// Make sure that internal offset calculcations handle the >2Gb case properly.
//
unsafe
{
byte* pMemory;
try
{
pMemory = (byte*)Marshal.AllocHGlobal((IntPtr)ThreeGiB);
}
catch (Exception)
{
return; // It's not implausible to believe that a 3gb allocation will fail - if so, skip this test to avoid unnecessary test flakiness.
}
try
{
Span<Guid> span = new Span<Guid>(pMemory, GuidThreeGiBLimit);
int bigIndex = checked(GuidTwoGiBLimit + 1);
uint byteOffset = checked((uint)bigIndex * (uint)sizeof(Guid));
Assert.True(byteOffset > (uint)int.MaxValue); // Make sure byteOffset actually overflows 2Gb, or this test is pointless.
ref Guid expected = ref Unsafe.AsRef<Guid>(((byte*)pMemory) + byteOffset);
Assert.True(Unsafe.AreSame<Guid>(ref expected, ref span.GetItem(bigIndex)));
Span<Guid> slice = span.Slice(bigIndex);
Assert.True(Unsafe.AreSame<Guid>(ref expected, ref slice.DangerousGetPinnableReference()));
slice = span.Slice(bigIndex, 1);
Assert.True(Unsafe.AreSame<Guid>(ref expected, ref slice.DangerousGetPinnableReference()));
}
finally
{
Marshal.FreeHGlobal((IntPtr)pMemory);
}
}
}
private const long ThreeGiB = 3L * 1024L * 1024L * 1024L;
private const long TwoGiB = 2L * 1024L * 1024L * 1024L;
private const long OneGiB = 1L * 1024L * 1024L * 1024L;
private static readonly int GuidThreeGiBLimit = (int)(ThreeGiB / Unsafe.SizeOf<Guid>()); // sizeof(Guid) requires unsafe keyword and I don't want to mark the entire class unsafe.
private static readonly int GuidTwoGiBLimit = (int)(TwoGiB / Unsafe.SizeOf<Guid>());
private static readonly int GuidOneGiBLimit = (int)(OneGiB / Unsafe.SizeOf<Guid>());
}
}
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