C / C ++后增加多个 [英] C/C++ Post-increment by more than one

问题描述

我正在从缓冲区读取字节。但有时我正在读的是一个字或更长。

I'm reading bytes from a buffer. But sometimes what I'm reading is a word or longer.

// assume buffer is of type unsigned char *
read_ptr(buffer+(position++))

这很好，但是我如何可以将位置递增2或4？有没有办法我可以得到 + = 运算符后递增，是吗？

That's fine but how can I post-increment position by 2 or 4? There's no way I can get the += operator to post-increment, is there?

原因是，我有一个非常糟糕的表达式，我想评估，同时增加位置变量。

Reason is, I have this big awful expression which I want to evaluate, while at the same time incrementing the position variable.

我想到了我自己的解决方案。我确定它的工作。每个人都会讨厌它，因为这是不是很可读的代码。

I think I came up with my own solution. I'm pretty sure it works. Everyone's gonna hate it though, since this isn't very readable code.

read_ptr(buffer+(position+=4)-4)

然后我会在测试一下之后将它变成一个宏，以确保它做正确的事情。

I will then make this into a macro after testing it a bit to make sure it's doing the right thing.

结论：

不要这样做。这只是一个坏主意，因为这是一种生成不可维护的代码的东西。但是...它确实很容易将任何预递增运算符转换为后递增运算符。

Don't do this. It's just a bad idea because this is the sort of thing that generates unmaintainable code. But... it does turn out to be quite easy to convert any pre-incrementing operator into a post-incrementing one.

推荐答案

好吧，我在编辑中回答了我的问题...基本上我想要的是一个单独的表达式，但是具有增加任意量的副作用。这里有一些宏。

Well, I did answer my question in the edit... Basically what I wanted was a single expression which evaluates to the original value but has a side effect of incrementing by an arbitrary amount. Here are some macros.

#define INC(x,inc) (((x)+=(inc))-(inc))
#define INC2(x) INC(x,2)
#define INC4(x) INC(x,4)
#define INC8(x) INC(x,8)

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