C法通过一个结构的成员进行迭代像一个数组？ [英] C method for iterating through a struct's members like an array?

问题描述

让我们说我有一个向量类：

Let's say I have a vector class:

typedef struct vec3_s
{
    float x, y, z;
}
vec3;

不过，我希望能够通过它来遍历无需将其转换为float数组。虽然投在这种情况下是可以接受的，我很好奇，看看是否沿着C的行++类的东西的功能是可行的直C.例如，在C ++中，因为的std ::矢量＆lt; T＆GT; 具有标 [] 操作符重载，我可以通过它的第一个索引到一个函数采取无效* 。

But, I would like to be able to iterate through it without converting it to an array of floats. While a cast is acceptable in this case, I'm curious to see if anything along the lines of C++ like functionality is doable in straight C. For example, in C++, since std::vector< T > has the subscript [] operator overloaded, I can pass the address of its first index to a function taking a void*.

即，

void do_something_with_pointer_to_mem( void* mem )
{
    // do stuff
}

int main( void )
{
    std::vector< float > v;

    // fill v with values here

    // pass to do_something_with_pointer_to_mem

    do_some_with_pointer_to_mem( &v[ 0 ] );

    return;
}

另一个更具体的例子是，当向 glBufferData呼叫（... ）在OpenGL（使用C ++时）由：

Another, more concrete example is when calls to glBufferData(...) are made in OpenGL (when using C++):

glBufferData（GL_ARRAY_BUFFER，sizeof的（somevector），放大器; somevector [0]，GL_STREAM_DRAW）;

那么，是不是可以使用下标操作符来实现用C类似的东西？如果没有，我只好写一个函数（例如，浮动vec3_value_at（无符号整型我）），这将是有意义的只是静态内联它在头文件，它的定义？

So, is it possible to accomplish something similar in C using the subscript operator? If not, and I had to write a function (e.g., float vec3_value_at( unsigned int i )), would it make sense to just static inline it in the header file it's defined in?

推荐答案

如果您所有的结构化字段都是同一类型的，你可以使用一个工会如下：

If all of your structure fields are of the same type, you could use a union as following:

typedef union vec3_u
{
    struct vec3_s {
        float x, y, z;
    };
    float vect3_a[3];
}
vec3;

这样您便可以独立访问到每个X，Y或Z字段或使用vect3_a阵列上进行遍历。这内存或计算，但长期的解决方案成本没有我们可能有点远从C ++类似的解决方案。

This way you could access to each x, y or z field independently or iterate over them using the vect3_a array. This solution cost nothing in term of memory or computation but we may be a bit far from a C++ like solution.

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