在POSIX不符合要求的系统上替代ssize_t [英] Alternative to ssize_t on POSIX-unconformant systems

问题描述

我正在编写一个涉及网络I/O的程序，因此使用send和recv，它们是POSIX函数.它们返回一个ssize_t，它也是POSIX特定的.
包装器看起来像这样的ATM:

I'm writing a program involving network I/O, so send and recv are used, which are POSIX functions. They return a ssize_t, which is POSIX-specific too.
The wrappers look like this ATM:

ssize_t sock_send(int sock, const void* msg, size_t len) {
    return send(sock, msg, len, 0);
}

即使我在当前的实现中严重依赖POSIX，我还是希望使接口与标准紧密结合，因为我计划稍后再编写Windows实现，而POSIX不一定可用(该死，Windows). ！).

Even though I'm heavily depending on POSIX in my current implementation, I want to make the interface stick closely to the standard because I am planning on writing a Windows implementation later, where POSIX isn't necessarily available (dammit, Windows!).

按照C11标准的规定，什么可以很好地替代ssize_t?也许ptrdiff_t?
还是应该以其他方式解决这个问题?

What would be a good substitution for ssize_t as specified by the C11 standard? Perhaps ptrdiff_t?
Or how should I approach this issue otherwise?

推荐答案

如果未定义类型ssize_t，则可以自己定义.它应该是signed类型，其大小与size_t相同.从技术上讲，类型ptrdiff_t不应小于size_t，但可以更大以适应更大的范围.

If the type ssize_t is not defined, you can just define it yourself. It is supposed to be a signed type with the same size as size_t. Technically, the type ptrdiff_t should not be smaller than size_t, but it could be larger to accommodate for the larger range.

这里是一种可移植的定义方式:

Here is a portable way to define it:

#include <limits.h>
#include <stddef.h>

#if SIZE_MAX == UINT_MAX
typedef int ssize_t;        /* common 32 bit case */
#elif SIZE_MAX == ULONG_MAX
typedef long ssize_t;       /* linux 64 bits */
#elif SIZE_MAX == ULLONG_MAX
typedef long long ssize_t;  /* windows 64 bits */
#elif SIZE_MAX == USHRT_MAX
typedef short ssize_t;      /* is this even possible? */
#else
#error platform has exotic SIZE_MAX
#endif

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