这个reinterpret_cast是如何工作的？ （将 C++ 移植到 Java）
我有一些 C++ 代码正在尝试移植到 Java，如下所示：
struct foostruct {
unsigned char aa : 3;
bool ab : 1;
unsigned char ba : 3;
bool bb : 1;
};
static void foo(const unsigned char* buffer, int length)
{
const unsigned char *end = buffer + length;
while (buffer < end)
{
const foostruct bar = *(reinterpret_cast<const foostruct*>(buffer++));
//read some values from struct and act accordingly
}
}
reinterpret_cast 正在做什么？
I have some C++ code I'm trying to port to Java, that looks like this:
struct foostruct {
unsigned char aa : 3;
bool ab : 1;
unsigned char ba : 3;
bool bb : 1;
};
static void foo(const unsigned char* buffer, int length)
{
const unsigned char *end = buffer + length;
while (buffer < end)
{
const foostruct bar = *(reinterpret_cast<const foostruct*>(buffer++));
//read some values from struct and act accordingly
}
}
What is the reinterpret_cast doing?
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评论（3）
它基本上是说当前指针表示的 8 位应该被解释为“foostruct”。
在我看来，最好写成如下：
我认为那时所做的事情要明显得多。我认为您可能会发现通过这种方式移植到 Java 也更容易......
its basically saying the 8 bits represented at the current pointer should be interpreted as a "foostruct".
In my opinion it would be better written as follows:
I think it is far more obvious what is being done then. I think you may well find it easier to port to Java this way too ...
它执行经典 C 风格
(const foostruct *)buffer在最坏的情况下会执行的操作：告诉 C++ 忽略所有安全性，并且您确实知道自己在做什么。在这种情况下，缓冲区实际上由 foostruct 组成，而这些结构又是覆盖在单个 8 位字符上的位字段。本质上，您可以在 Java 中执行相同的操作，只需获取字节并自行执行移位和掩码操作即可。It does what a classic C-style
(const foostruct *)bufferwould do at worst: tells C++ to ignore all safety and that you really know what you are doing. In this case, that thebufferactually consists offoostructs, which in turn are bit fields overlain on single 8 bit characters. Essentially, you can do the same in Java by just getting the bytes and doing the shift and mask operations yourself.你有一个指向 unsigned char 的指针吗？现在想象一下，指针指向的位被视为 foostruct 类型的对象。这就是 reinterpret_cast 所做的 - 它将位模式重新解释为另一种类型的内存表示......
you have a pointer to unsigned char right? Now imagine that the bits pointed to by the pointer are treated as though it were an object of type foostruct. That's what reinterpret_cast does - it reinterprets the bit pattern to be a memory representation of another type...