铸造泛型参数，并从整 [英] Casting generic parameter to and from integer

问题描述

我想写其目的是一起工作的泛型类的内置类型，如字节和 USHORT 。在内部计算，我需要投泛型类型为整数，并返回到泛型类型。我发现方式编译这样的代码，例如：

I want to write generic class which is intended to work with built-in types like byte and ushort. In internal computations I need to cast generic type to integer and back to generic type. I found the way to compile such code, for example:

class Test<T> where T : struct, IConvertible
{
    public static T TestFunction(T x)
    {
        int n = Convert.ToInt32(x);
        T result = (T)Convert.ChangeType(n, typeof(T));
        return result;
    }
}

我觉得用这样的转换可能显著降低性能，如果它们在计算循环使用。有没有更好的办法让这些转换？

I think that using such conversions may significantly reduce performance, if they are used in computation loops. Is there a better way to make these conversions?

推荐答案

INT 来 T 转换是有点棘手。我想你可以在这里使用表达式类。

int to T conversion is a bit tricky. I think you could use Expression class here.

测试< T> 类应该可以看起来像：

Test<T> class should can look like that:

class Test<T> where T : struct, IConvertible
{
    private static Func<int, T> _getInt;

    static Test()
    {
        var param = Expression.Parameter(typeof(int), "x");
        UnaryExpression body = Expression.Convert(param, typeof(T));
        _getInt = Expression.Lambda<Func<int, T>>(body, param).Compile();
    }

    public static T TestFunction(T x)
    {
        int n = Convert.ToInt32(x);
        T result = _getInt(n);
        return result;
    }
}

它准备 _getInt = X = GT; （T）X 并为您在静态构造函数之后使用它，转换 INT 到 T 。

It prepares _getInt = x => (T)x for you in static constructor and uses it later, to convert int to T.

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