如何在VB.net中实现数组的哈希函数

问题描述：

C＃中用于从数组创建哈希值的经典函数看起来像这样或类似：

The classic function in C# to create a hash value from an array looks like this or similar:

public int GetHashCode(T[] array)
    {
        unchecked
        {
            if (array == null)
            {
                return 0;
            }
            int hash = 17;
            foreach (T item in array)
            {
                hash = hash * 31 + item.GetHashCode;
            }
            return hash;
        }
    }

但是由于未选中在VB.Net中不可用，因此当溢出时我会很快收到异常。

我以为我可以使用位移来解决它，但是在VB中它只有算术而不是圆形所以每一个被移出的位都会被丢弃。

虽然我无法相信这在VB中从未解决过，但我的google foo让我失望。

获取哈希值的标准解决方案是什么？ VB中的数组？

But since unchecked is not available in VB.Net I will quickly get an exception when it overflows.
I thought I could solve it using bitshifting, but in VB its only arithmetic and not circular so every bit that is shifted out is dropped.

And while I can't believe this has never been solved in VB my google foo is failing me.

What is the standard solution for getting a hash value for an array in VB?

答

你难道不能将哈希声明为 Int64 并清除上半部分需要？

Couldn't you just declare hash as Int64 and clear the upper part when needed?

为了将来参考，这就是我的解决方案的样子：

For future reference, this is how my solution looks like:

Public Overrides Function GetHashCode() As Integer
     Dim hash As Int64 = 19
     For Each Item As T In Me
         hash = hash * 31 + Item.GetHashCode
         hash = ((hash << 32) >> 32) + hash >> 32
     Next
     hash = ((hash << 32) >> 32)
     Return CInt(hash)
 End Function

有一些改善性能的空间，溢出只需要每6次迭代处理一次，例如

There is some room for improving performance, the overflow only needs to be handled every 6 iterations for example

如何在VB.net中实现数组的哈希函数

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