Object.GetHashCode() 的默认实现 [英] Default implementation for Object.GetHashCode()

问题描述

GetHashCode() 的默认实现如何工作?它是否足够有效和良好地处理结构、类、数组等?

How does the default implementation for GetHashCode() work? And does it handle structures, classes, arrays, etc. efficiently and well enough?

我正在尝试决定在哪些情况下我应该自己打包，以及在哪些情况下我可以安全地依赖默认实现来做好.如果可能的话，我不想重新发明轮子.

I am trying to decide in what cases I should pack my own and in what cases I can safely rely on the default implementation to do well. I don't want to reinvent the wheel, if at all possible.

推荐答案

namespace System {
    public class Object {
        [MethodImpl(MethodImplOptions.InternalCall)]
        internal static extern int InternalGetHashCode(object obj);

        public virtual int GetHashCode() {
            return InternalGetHashCode(this);
        }
    }
}

InternalGetHashCode 映射到 CLR 中的 ObjectNative::GetHashCode 函数，如下所示:

InternalGetHashCode is mapped to an ObjectNative::GetHashCode function in the CLR, which looks like this:

FCIMPL1(INT32, ObjectNative::GetHashCode, Object* obj) {  
    CONTRACTL  
    {  
        THROWS;  
        DISABLED(GC_NOTRIGGER);  
        INJECT_FAULT(FCThrow(kOutOfMemoryException););  
        MODE_COOPERATIVE;  
        SO_TOLERANT;  
    }  
    CONTRACTL_END;  

    VALIDATEOBJECTREF(obj);  

    DWORD idx = 0;  

    if (obj == 0)  
        return 0;  

    OBJECTREF objRef(obj);  

    HELPER_METHOD_FRAME_BEGIN_RET_1(objRef);        // Set up a frame  

    idx = GetHashCodeEx(OBJECTREFToObject(objRef));  

    HELPER_METHOD_FRAME_END();  

    return idx;  
}  
FCIMPLEND

GetHashCodeEx 的完整实现相当大，因此只需链接到C++ 源代码.

The full implementation of GetHashCodeEx is fairly large, so it's easier to just link to the C++ source code.

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