代码之家 › 专栏 › 技术社区 › Red Riding Hood

使用内存<T>或ArraySegment<T>访问非托管数组?

unmanaged-memory c#

6

Red Riding Hood · 技术社区 · 6 年前

随着 Memory , Span 和 ArraySegment

跨度 基本上实现了我想要的:例如。

unsafe { bytes = new Span<byte>((byte*)ptr + (index * Width), Width);

有没有可能用同样的方法 排列分段 记忆 ? 他们的施工人员只接受 byte[] ,也许有什么办法可以骗C#通过a byte* 而不是 ?

1 回复 | 直到 6 年前

1

20

Marc Gravell 6 年前

是的 Memory<T> ,但你需要创建自己的 MemoryManager<T> . 别担心-这并不像听起来那么可怕- here's one I wrote earlier... :

/// <summary>
/// A MemoryManager over a raw pointer
/// </summary>
/// <remarks>The pointer is assumed to be fully unmanaged, or externally pinned - no attempt will be made to pin this data</remarks>
public sealed unsafe class UnmanagedMemoryManager<T> : MemoryManager<T>
    where T : unmanaged
{
    private readonly T* _pointer;
    private readonly int _length;

    /// <summary>
    /// Create a new UnmanagedMemoryManager instance at the given pointer and size
    /// </summary>
    /// <remarks>It is assumed that the span provided is already unmanaged or externally pinned</remarks>
    public UnmanagedMemoryManager(Span<T> span)
    {
        fixed (T* ptr = &MemoryMarshal.GetReference(span))
        {
            _pointer = ptr;
            _length = span.Length;
        }
    }
    /// <summary>
    /// Create a new UnmanagedMemoryManager instance at the given pointer and size
    /// </summary>
    public UnmanagedMemoryManager(T* pointer, int length)
    {
        if (length < 0) throw new ArgumentOutOfRangeException(nameof(length));
        _pointer = pointer;
        _length = length;
    }
    /// <summary>
    /// Obtains a span that represents the region
    /// </summary>
    public override Span<T> GetSpan() => new Span<T>(_pointer, _length);

    /// <summary>
    /// Provides access to a pointer that represents the data (note: no actual pin occurs)
    /// </summary>
    public override MemoryHandle Pin(int elementIndex = 0)
    {
        if (elementIndex < 0 || elementIndex >= _length)
            throw new ArgumentOutOfRangeException(nameof(elementIndex));
        return new MemoryHandle(_pointer + elementIndex);
    }
    /// <summary>
    /// Has no effect
    /// </summary>
    public override void Unpin() { }

    /// <summary>
    /// Releases all resources associated with this object
    /// </summary>
    protected override void Dispose(bool disposing) { }
}

var mgr = new UnmanagedMemoryManager((byte*)ptr + (index * Width), Width);
Memory<byte> memory = mgr.Memory;

memory 可以存储在堆上。

UnmanagedMemoryManager<byte> 涵盖了 整个的 区域-仅限一次-然后使用 .Slice(...) 上 .Memory

注意:这个实现假设您将在其他地方控制内存的生存期—内存 Dispose() 在这里没有 Marshal 等。