[SL.Core] Throw better exceptions from MemoryAllocators

src/SixLabors.Core/Memory/ArrayPoolMemoryAllocator.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.Buffers;
 using System.Runtime.CompilerServices;
 
@@ -91,8 +92,15 @@ namespace SixLabors.Memory
         /// <inheritdoc />
         public override IMemoryOwner<T> Allocate<T>(int length, AllocationOptions options = AllocationOptions.None)
         {
+            Guard.MustBeGreaterThanOrEqualTo(length, 0, nameof(length));
             int itemSizeBytes = Unsafe.SizeOf<T>();
             int bufferSizeInBytes = length * itemSizeBytes;
+            if (bufferSizeInBytes < 0)
+            {
+                throw new ArgumentOutOfRangeException(
+                    nameof(length),
+                    $"{nameof(ArrayPoolMemoryAllocator)} can not allocate {length} elements of {typeof(T).Name}.");
+            }
 
             ArrayPool<byte> pool = this.GetArrayPool(bufferSizeInBytes);
             byte[] byteArray = pool.Rent(bufferSizeInBytes);
@@ -109,6 +117,9 @@ namespace SixLabors.Memory
         /// <inheritdoc />
         public override IManagedByteBuffer AllocateManagedByteBuffer(int length, AllocationOptions options = AllocationOptions.None)
         {
+            Guard.MustBeGreaterThanOrEqualTo(length, 0, nameof(length));
+            Guard.MustBeLessThan(length, int.MaxValue, nameof(length));
+
             ArrayPool<byte> pool = this.GetArrayPool(length);
             byte[] byteArray = pool.Rent(length);
 

src/SixLabors.Core/Memory/SimpleGcMemoryAllocator.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
 using System.Buffers;
 using SixLabors.Memory.Internals;
 
@@ -14,12 +15,18 @@ namespace SixLabors.Memory
         /// <inheritdoc />
         public override IMemoryOwner<T> Allocate<T>(int length, AllocationOptions options = AllocationOptions.None)
         {
+            Guard.MustBeGreaterThanOrEqualTo(length, 0, nameof(length));
+            Guard.MustBeLessThan(length, int.MaxValue, nameof(length));
+
             return new BasicArrayBuffer<T>(new T[length]);
         }
 
         /// <inheritdoc />
         public override IManagedByteBuffer AllocateManagedByteBuffer(int length, AllocationOptions options = AllocationOptions.None)
         {
+            Guard.MustBeGreaterThanOrEqualTo(length, 0, nameof(length));
+            Guard.MustBeLessThan(length, int.MaxValue, nameof(length));
+
             return new BasicByteBuffer(new byte[length]);
         }
     }

tests/SixLabors.Core.Tests/Memory/ArrayPoolMemoryManagerTests.cs → tests/SixLabors.Core.Tests/Memory/ArrayPoolMemoryAllocatorTests.cs

@@ -12,7 +12,7 @@ using Xunit;
 
 namespace SixLabors.Memory.Tests
 {
-    public class ArrayPoolMemoryManagerTests
+    public class ArrayPoolMemoryAllocatorTests
     {
         private const int MaxPooledBufferSizeInBytes = 2048;
 
@@ -231,9 +231,29 @@ namespace SixLabors.Memory.Tests
             private uint dummy;
         }
 
-        [StructLayout(LayoutKind.Explicit, Size = MaxPooledBufferSizeInBytes / 5)]
+        private const int SizeOfLargeStruct = MaxPooledBufferSizeInBytes / 5;
+
+        [StructLayout(LayoutKind.Explicit, Size = SizeOfLargeStruct)]
         private struct LargeStruct
         {
         }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData((int.MaxValue / SizeOfLargeStruct) + 1)]
+        public void AllocateIncorrectAmount_ThrowsCorrect_ArgumentOutOfRangeException(int length)
+        {
+            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => this.MemoryAllocator.Allocate<LargeStruct>(length));
+            Assert.Equal("length", ex.ParamName);
+        }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(int.MaxValue)]
+        public void AllocateManagedByteBuffer_IncorrectAmount_ThrowsCorrect_ArgumentOutOfRangeException(int length)
+        {
+            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => this.MemoryAllocator.AllocateManagedByteBuffer(length));
+            Assert.Equal("length", ex.ParamName);
+        }
     }
 }

tests/SixLabors.Core.Tests/Memory/SimpleGcMemoryAllocatorTests.cs

@@ -0,0 +1,45 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Runtime.InteropServices;
+using Xunit;
+
+namespace SixLabors.Memory.Tests
+{
+    public class SimpleGcMemoryAllocatorTests
+    {
+        public class BufferTests : BufferTestSuite
+        {
+            public BufferTests()
+                : base(new SimpleGcMemoryAllocator())
+            {
+            }
+        }
+
+        protected SimpleGcMemoryAllocator MemoryAllocator { get; } = new SimpleGcMemoryAllocator();
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(int.MaxValue)]
+        public void Allocate_IncorrectAmount_ThrowsCorrect_ArgumentOutOfRangeException(int length)
+        {
+            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => this.MemoryAllocator.Allocate<BigStruct>( length));
+            Assert.Equal("length", ex.ParamName);
+        }
+
+        [Theory]
+        [InlineData(-1)]
+        [InlineData(int.MaxValue)]
+        public void AllocateManagedByteBuffer_IncorrectAmount_ThrowsCorrect_ArgumentOutOfRangeException(int length)
+        {
+            var ex = Assert.Throws<ArgumentOutOfRangeException>(() => this.MemoryAllocator.AllocateManagedByteBuffer(length));
+            Assert.Equal("length", ex.ParamName);
+        }
+
+        [StructLayout(LayoutKind.Explicit, Size = 512)]
+        private struct BigStruct
+        {
+        }
+    }
+}

tests/SixLabors.Core.Tests/Memory/SimpleGcMemoryManagerTests.cs

@@ -1,16 +0,0 @@
-// Copyright (c) Six Labors and contributors.
-// Licensed under the Apache License, Version 2.0.
-
-namespace SixLabors.Memory.Tests
-{
-    public class SimpleGcMemoryManagerTests
-    {
-        public class BufferTests : BufferTestSuite
-        {
-            public BufferTests()
-                : base(new SimpleGcMemoryAllocator())
-            {
-            }
-        }
-    }
-}