kbe
ccde012e45
Add MarshalCache<T> static class that computes Size, SizeU, TypeRequiresMarshal, IsIntPtr, TypeCode, and RealType once per type in the static constructor. Handles bool (size=1), enums (underlying type), and MarshalAs-attributed fields (TypeRequiresMarshal). 12 new tests covering: blittable sizes, bool size, enum size, struct size, marshal-required flag, IsIntPtr, computed-once caching. All passing.
70 lines
2.4 KiB
C#
70 lines
2.4 KiB
C#
using System.Reflection;
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using System.Runtime.InteropServices;
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namespace WhiteMagic;
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/// <summary>
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/// Computes and caches marshal-related metadata for type <typeparamref name="T"/>
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/// exactly once. <see cref="MemoryBase.Read{T}"/> and <see cref="MemoryBase.Write{T}"/>
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/// branch on these cached flags to decide between blittable <c>Span</c>/<c>MemoryMarshal</c>
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/// paths and the fallback marshal path.
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/// </summary>
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/// <typeparam name="T">The type to cache metadata for.</typeparam>
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public static class MarshalCache<T>
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{
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/// <summary>The unmanaged size of <typeparamref name="T"/> in bytes.</summary>
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public static readonly int Size;
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/// <summary>The unmanaged size of <typeparamref name="T"/> as an unsigned integer.</summary>
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public static readonly uint SizeU;
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/// <summary>
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/// <see langword="true"/> when <typeparamref name="T"/> has at least one field
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/// decorated with <see cref="MarshalAsAttribute"/>, meaning it cannot be copied
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/// via a simple pointer dereference.
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/// </summary>
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public static readonly bool TypeRequiresMarshal;
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/// <summary><see langword="true"/> when <typeparamref name="T"/> is <see cref="IntPtr"/>.</summary>
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public static readonly bool IsIntPtr;
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/// <summary>The underlying type code of <typeparamref name="T"/>.</summary>
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public static readonly TypeCode TypeCode;
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/// <summary>
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/// The effective type that the marshaler uses. For an enum this is the underlying
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/// integer type; for all other types it is <typeparamref name="T"/> itself.
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/// </summary>
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public static readonly Type RealType;
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static MarshalCache()
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{
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TypeCode = Type.GetTypeCode(typeof(T));
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if (typeof(T) == typeof(bool))
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{
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Size = 1;
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RealType = typeof(T);
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}
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else if (typeof(T).IsEnum)
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{
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Type underlying = typeof(T).GetEnumUnderlyingType();
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Size = Marshal.SizeOf(underlying);
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RealType = underlying;
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TypeCode = Type.GetTypeCode(underlying);
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}
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else
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{
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Size = Marshal.SizeOf(typeof(T));
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RealType = typeof(T);
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}
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SizeU = (uint)Size;
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IsIntPtr = RealType == typeof(IntPtr);
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TypeRequiresMarshal =
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RealType.GetFields(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic)
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.Any(f => f.GetCustomAttributes(typeof(MarshalAsAttribute), true).Length != 0);
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}
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}
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