访问结构成员，如果他们是一个单一的阵列？ [英] Access struct members as if they are a single array?

问题描述

我有两种结构，具有能够计算出一个沉吟平均值，像这样的简化版本：

I have two structures, with values that should compute a pondered average, like this simplified version:

typedef struct
{
  int v_move, v_read, v_suck, v_flush, v_nop, v_call;
} values;

typedef struct
{
  int qtt_move, qtt_read, qtt_suck, qtd_flush, qtd_nop, qtt_call;
} quantities;

然后我用它们来计算：

And then I use them to calculate:

average = v_move*qtt_move + v_read*qtt_read + v_suck*qtt_suck + v_flush*qtd_flush + v_nop*qtd_nop + v_call*qtt_call;

每一个现在，他们我需要包括另一个变量。现在，比如说，我需要包括 v_clean 和 qtt_clean 。我不能改变结构数组：

Every now and them I need to include another variable. Now, for instance, I need to include v_clean and qtt_clean. I can't change the structures to arrays:

typedef struct
{
    int v[6];
} values;
typedef struct
{
    int qtt[6];
} quantities;

这将简化了很多我的工作，但他们需要的变量名是明确的API的一部分。

That would simplify a lot my work, but they are part of an API that need the variable names to be clear.

所以，我正在寻找一种方式来访问结构的成员，也许使用的sizeof（），这样我就可以把它们作为一个数组，但仍保持API不变。这是保证所有值都 INT ，但我不能保证一个企业的大小 INT 。

So, I'm looking for a way to access the members of that structures, maybe using sizeof(), so I can treat them as an array, but still keep the API unchangeable. It is guaranteed that all values are int, but I can't guarantee the size of an int.

写的问题来到我的脑海......一个联盟能胜任这项工作？是否有另一种聪明的方式来使自动化添加另一个成员的任务是什么？

Writing the question came to my mind... Can a union do the job? Is there another clever way to automatize the task of adding another member?

谢谢，
贝乔

推荐答案

如果所有成员保证是类型 INT 您可以使用指针来诠释并加一

If all members a guaranteed to be of type int you can use a pointer to int and increment it:

int *value = &(values.v_move);
int *quantity = &(quantities.qtt_move);
int i;
average = 0;
// although it should work, a good practice many times IMHO is to add a null as the last member in struct and change the condition to quantity[i] != null.
for (i = 0; i < sizeof(quantities) / sizeof(*quantity); i++)
    average += values[i] * quantity[i];

（由于成员在一个结构的顺序是保证所申报）

(Since the order of members in a struct is guaranteed to be as declared)

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