是否有任何与QUOT;标准＆QUOT; htonl样的功能在C ++ 64位整数？

问题描述

我工作的memcache的协议，该协议，在某些点上，使用64位整数的实现。这些数据必须存储在网络字节顺序。

我希望有一些 uint64_t中htonll（uint64_t中值）函数来完成的改变，但不幸的是，如果它存在，我怎么也找不到它。

所以，我有1个或2个问题：

• 是否有任何的移动（在Windows，Linux，AIX）标准功能做到这一点？
• 如果没有这样的功能，你会如何实现它？

我心里有一个基本的实现，但我不知道如何检查的字节顺序在编译时使code便携。所以，你的帮助是非常欢迎在这里;）

感谢你。

---

下面是最终的解决方案我写的，感谢布赖恩的解决方案。

  uint64_t中htonll（uint64_t中值）
{
    //答案是42
    静态const int的NUM = 42;

    //检查字节顺序
    如果（* reinter pret_cast＆LT;为const char *＆GT;（试验＃）== NUM​​）
    {
        常量uint32_t的high_part = htonl（的static_cast＆LT; uint32_t的＆GT;（值GT;＆GT; 32））;
        常量uint32_t的low_part = htonl（的static_cast＆LT; uint32_t的＆GT;（值放大器; 0xFFFFFFFFLL））;

        回报（的static_cast＆LT; uint64_t中＆GT;（low_part）＆LT;＆LT; 32）| high_part;
    } 其他
    {
        返回值;
    }
}
 

解决方案

您可能正在寻找 bswap_64 我认为这是支持pretty的多随处可见，但我不会T称它为标准。

您可以轻松地创建带有值为1的int，铸造你的廉政局的地址作为的char *检查字节序和检查的第一个字节的值。

例如：

  INT NUM = 42;
如果（*（字符*）试验＃== 42）
{
   //小端
}
其他
{
   //大端
}
 

知道了这一点，你也可以做一个简单的函数，它的交换。

---

您也可以随时使用升压其中包含端宏哪些是可移植的跨平台。

I'm working on an implementation of the memcache protocol which, at some points, uses 64 bits integer values. These values must be stored in "network byte order".

I wish there was some uint64_t htonll(uint64_t value) function to do the change, but unfortunately, if it exist, I couldn't find it.

So I have 1 or 2 questions:

• Is there any portable (Windows, Linux, AIX) standard function to do this ?
• If there is no such function, how would you implement it ?

I have in mind a basic implementation but I don't know how to check the endianness at compile-time to make the code portable. So your help is more than welcome here ;)

Thank you.

---

Here is the final solution I wrote, thanks to Brian's solution.

uint64_t htonll(uint64_t value)
{
    // The answer is 42
    static const int num = 42;

    // Check the endianness
    if (*reinterpret_cast<const char*>(&num) == num)
    {
        const uint32_t high_part = htonl(static_cast<uint32_t>(value >> 32));
        const uint32_t low_part = htonl(static_cast<uint32_t>(value & 0xFFFFFFFFLL));

        return (static_cast<uint64_t>(low_part) << 32) | high_part;
    } else
    {
        return value;
    }
}

解决方案

You are probably looking for bswap_64 I think it is supported pretty much everywhere but I wouldn't call it standard.

You can easily check the endianness by creating an int with a value of 1, casting your int's address as a char* and checking the value of the first byte.

For example:

int num = 42;
if(*(char *)&num == 42)
{
   //Little Endian
}
else
{
   //Big Endian
}

Knowing this you could also make a simple function that does the swapping.

---

You could also always use boost which contains endian macros which are portable cross platform.

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