如何分配16字节对齐的内存? [英] How to allocate memory with a 16 byte alignment?

问题描述

我使用Marshal.GlobalHAlloc分配内存.如文档所述:此方法从Kernel32.dll中公开Win32 LocalAlloc函数.". GlobalAlloc的文档说它将对齐8个字节，但是LocalAlloc没有说任何关于align的内容.

I use Marshal.GlobalHAlloc to allocate memory. As documentation says: "This method exposes the Win32 LocalAlloc function from Kernel32.dll.". GlobalAlloc's documentation says it will be 8 byte aligned but LocalAlloc don't say anything about align.

例如，我想分配1024个字节并确保它与16对齐.当我分配1024 + 16个字节然后检查指针％16时，它可以工作吗?如果结果为0，则表示内存已对齐；当结果不为0时，我只是增加指针以符合我的期望.问题是我不知道，如果我有对齐的指针，它真的在物理内存中对齐了吗?

For example I want to allocate 1024 bytes and ensure it is aligned by 16. Will it work when I allocate 1024+16 bytes then I check pointer % 16? If result is 0 it means memory is aligned, when it is not 0, I just increment pointer to fit my expectations. The problem is I don't know, if I have aligned pointer it is really aligned in physical memory?

推荐答案

所有Windows堆分配器按8对齐.您可以通过过度分配和调整指针来解决此问题，如下所示:

All Windows heap allocators align by 8. You can fix that by over-allocating and adjusting the pointer, like this:

    var rawptr = Marshal.AllocHGlobal(size + 8);
    var aligned = new IntPtr(16 * (((long)rawptr + 15) / 16));
    // Use aligned
    //...
    Marshal.FreeHGlobal(rawptr);

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