在阵列上工作时应该固定什么？ [英] What should I pin when working on arrays?

问题描述

我正在尝试编写 DynamicMethod 来包装 cpblk IL操作码 。我需要复制字节数组的块，并在x64平台上，这可能是最快的方法。 Array.Copy 和 Buffer.BlockCopy 都可以，但是我想探索所有选项。

I'm trying to write a DynamicMethod to wrap the cpblk IL opcode. I need to copy chunks of byte arrays and on x64 platforms, this is supposedly the fastest way to do it. Array.Copy and Buffer.BlockCopy both work, but I'd like to explore all options.

我的目标是将托管内存从一个字节数组复制到新的托管字节数组。我关心的是如何知道如何正确固定存储位置。我不希望垃圾收集器移动数组并破坏所有内容。到目前为止，它仍然有效，但是我不确定如何测试这是否是GC安全的。

My goal is to copy managed memory from one byte array to a new managed byte array. My concern is how do I know how to correctly "pin" memory location. I don't want the garbage collector to move the arrays and break everything. SO far it works but I'm not sure how to test if this is GC safe.

// copying 'count' bytes from offset 'index' in 'source' to offset 0 in 'target'
// i.e. void _copy(byte[] source, int index, int count, byte[] target)

static Action<byte[], int, int, byte[]> Init()
{
    var dmethod = new DynamicMethod("copy", typeof(void), new[] { typeof(object),typeof(byte[]), typeof(int), typeof(int),typeof(byte[]) },typeof(object), true);
    var il = dmethod.GetILGenerator();

    il.DeclareLocal(typeof(byte).MakeByRefType(), true);
    il.DeclareLocal(typeof(byte).MakeByRefType(), true);
    // pin the source
    il.Emit(OpCodes.Ldarg_1);
    il.Emit(OpCodes.Ldarg_2);
    il.Emit(OpCodes.Ldelema, typeof(byte));
    il.Emit(OpCodes.Stloc_0);
    // pin the target
    il.Emit(OpCodes.Ldarg_S,(byte)4);
    il.Emit(OpCodes.Ldc_I4_0);
    il.Emit(OpCodes.Ldelema, typeof(byte));
    il.Emit(OpCodes.Stloc_1);

    il.Emit(OpCodes.Ldloc_1);
    il.Emit(OpCodes.Ldloc_0);
    // load the length
    il.Emit(OpCodes.Ldarg_3);
    // perform the memcpy
    il.Emit(OpCodes.Unaligned,(byte)1);
    il.Emit(OpCodes.Cpblk);

    il.Emit(OpCodes.Ret);
    return dmethod.CreateDelegate(typeof(Action<byte[], int, int, byte[]>)) as Action<byte[], int, int, byte[]>;
}

推荐答案

我相信您对固定的局部变量是正确的。

I believe that your usage of pinned local variables is correct.

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