Merge pull request #18 from rameel/memorymarshal-view-extensions

MemoryMarshal for unsafe/unchecked StringView/ArrayView creation

Author: rameel

Ramstack.Structures.Tests/InteropServices/MemoryMarshalTests.cs

@@ -0,0 +1,47 @@
+namespace Ramstack.InteropServices;
+
+[TestFixture]
+public class MemoryMarshalTests
+{
+    [Test]
+    public void CreateStringView()
+    {
+        Assert.That(
+            MemoryMarshal.CreateStringView("Hello, World!", 7).ToString(),
+            Is.EqualTo("World!"));
+
+        Assert.That(
+            MemoryMarshal.CreateStringView("Hello, World!", 7).Length,
+            Is.EqualTo(6));
+
+        Assert.That(
+            MemoryMarshal.CreateStringView("Hello, World!", 0, 5).ToString(),
+            Is.EqualTo("Hello"));
+
+        Assert.That(
+            MemoryMarshal.CreateStringView("Hello, World!", 0, 5).Length,
+            Is.EqualTo(5));
+    }
+
+    [Test]
+    public void CreateArrayView()
+    {
+        var array = "Hello, World!".ToArray();
+
+        Assert.That(
+            MemoryMarshal.CreateArrayView(array, 7).AsSpan().ToString(),
+            Is.EqualTo("World!"));
+
+        Assert.That(
+            MemoryMarshal.CreateArrayView(array, 7).Length,
+            Is.EqualTo(6));
+
+        Assert.That(
+            MemoryMarshal.CreateArrayView(array, 0, 5).AsSpan().ToString(),
+            Is.EqualTo("Hello"));
+
+        Assert.That(
+            MemoryMarshal.CreateArrayView(array, 0, 5).Length,
+            Is.EqualTo(5));
+    }
+}

Ramstack.Structures/Collections/ArrayViewExtensions.cs

@@ -34,7 +34,7 @@ public static ArrayView<T> AsView<T>(this T[]? value, int index) =>
     /// starting at a specified position for a specified number of elements.
     /// </summary>
     /// <typeparam name="T">The type of elements in the array.</typeparam>
-    /// <param name="value">The array to create a view over. Can be null.</param>
+    /// <param name="value">The array to create a view over.</param>
     /// <param name="index">The zero-based starting position of the view in the array.</param>
     /// <param name="count">The number of elements to include in the view.</param>
     /// <returns>

Ramstack.Structures/InteropServices/MemoryMarshalExtensions.cs

@@ -0,0 +1,123 @@
+using Ramstack.Collections;
+using Ramstack.Text;
+
+namespace Ramstack.InteropServices;
+
+/// <summary>
+/// Provides extension methods for the <see cref="MemoryMarshal"/> class.
+/// </summary>
+public static class MemoryMarshalExtensions
+{
+    extension(MemoryMarshal)
+    {
+        /// <summary>
+        /// Creates a new <see cref="StringView"/> over a portion of the specified string
+        /// starting at a specified position to the end of the string.
+        /// </summary>
+        /// <param name="value">The string to create a view over.</param>
+        /// <param name="index">The zero-based starting position of the view in the string.</param>
+        /// <returns>
+        /// A <see cref="StringView"/> representing the specified portion of the string.
+        /// </returns>
+        /// <remarks>
+        /// This method should be used with caution as it doesn't perform argument validation.
+        /// The caller is responsible for ensuring:
+        /// <list type="bullet">
+        ///   <item><description><paramref name="value"/> is not null.</description></item>
+        ///   <item><description><paramref name="index"/> is within the bounds of the string.</description></item>
+        /// </list>
+        /// </remarks>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static StringView CreateStringView(string value, int index)
+        {
+            Debug.Assert(value is not null);
+            Debug.Assert(value.AsSpan(index).Length == value.Length - index);
+
+            return new StringView(value, index, value.Length - index, unused: 0);
+        }
+
+        /// <summary>
+        /// Creates a new <see cref="StringView"/> over a portion of the specified string
+        /// starting at a specified position for a specified number of characters.
+        /// </summary>
+        /// <param name="value">The string to create a view over.</param>
+        /// <param name="index">The zero-based starting position of the view in the string.</param>
+        /// <param name="length">The number of characters to include in the view.</param>
+        /// <returns>
+        /// A <see cref="StringView"/> representing the specified portion of the string.
+        /// </returns>
+        /// <remarks>
+        /// This method should be used with caution as it doesn't perform argument validation.
+        /// The caller is responsible for ensuring:
+        /// <list type="bullet">
+        ///   <item><description><paramref name="value"/> is not null.</description></item>
+        ///   <item><description><paramref name="index"/> is within the bounds of the string.</description></item>
+        ///   <item><description><paramref name="length"/> is valid for the specified index.</description></item>
+        /// </list>
+        /// </remarks>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static StringView CreateStringView(string value, int index, int length)
+        {
+            Debug.Assert(value is not null);
+            Debug.Assert(value.AsSpan(index, length).Length == length);
+
+            return new StringView(value, index, length, unused: 0);
+        }
+
+        /// <summary>
+        /// Creates a new <see cref="ArrayView{T}"/> over a portion of the specified array,
+        /// starting at a specified position to the end of the array.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in the array.</typeparam>
+        /// <param name="array">The array to create a view over.</param>
+        /// <param name="index">The zero-based starting position of the view in the array.</param>
+        /// <returns>
+        /// An <see cref="ArrayView{T}"/> representing the specified portion of the array.
+        /// </returns>
+        /// <remarks>
+        /// This method should be used with caution as it doesn't perform argument validation.
+        /// The caller is responsible for ensuring:
+        /// <list type="bullet">
+        ///   <item><description><paramref name="array"/> is not null.</description></item>
+        ///   <item><description><paramref name="index"/> is within the bounds of the array.</description></item>
+        /// </list>
+        /// </remarks>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ArrayView<T> CreateArrayView<T>(T[] array, int index)
+        {
+            Debug.Assert(array is not null);
+            Debug.Assert(array.AsSpan(index).Length == array.Length - index);
+
+            return new ArrayView<T>(array, index, array.Length - index, unused: 0);
+        }
+
+        /// <summary>
+        /// Creates a new <see cref="ArrayView{T}"/> over a portion of the specified array
+        /// starting at a specified position for a specified number of elements.
+        /// </summary>
+        /// <typeparam name="T">The type of elements in the array.</typeparam>
+        /// <param name="array">The array to create a view over.</param>
+        /// <param name="index">The zero-based starting position of the view in the array.</param>
+        /// <param name="length">The number of elements to include in the view.</param>
+        /// <returns>
+        /// An <see cref="ArrayView{T}"/> representing the specified portion of the array.
+        /// </returns>
+        /// <remarks>
+        /// This method should be used with caution as it doesn't perform argument validation.
+        /// The caller is responsible for ensuring:
+        /// <list type="bullet">
+        ///   <item><description><paramref name="array"/> is not null.</description></item>
+        ///   <item><description><paramref name="index"/> is within the bounds of the array.</description></item>
+        ///   <item><description><paramref name="length"/> is valid for the specified index.</description></item>
+        /// </list>
+        /// </remarks>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static ArrayView<T> CreateArrayView<T>(T[] array, int index, int length)
+        {
+            Debug.Assert(array is not null);
+            Debug.Assert(array.AsSpan(index, length).Length == length);
+
+            return new ArrayView<T>(array, index, length, unused: 0);
+        }
+    }
+}

Ramstack.Structures/Text/StringView.cs

@@ -107,7 +107,7 @@ public StringView(string value, int index, int length)
     /// <param name="length">The number of characters to include in the view.</param>
     /// <param name="unused">Unused parameter used only to differentiate between overloads.</param>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private StringView(string value, int index, int length, int unused)
+    internal StringView(string value, int index, int length, int unused)
     {
         _index = index;
         _length = length;