Etc.nprocessors

static VALUE
etc_nprocessors(VALUE obj)
{
    long ret;

#if !defined(_WIN32)

#if defined(HAVE_SCHED_GETAFFINITY) && defined(CPU_ALLOC)
    int ncpus;

    ncpus = etc_nprocessors_affin();
    if (ncpus != -1) {
        return INT2NUM(ncpus);
    }
    /* fallback to _SC_NPROCESSORS_ONLN */
#endif

    errno = 0;
    ret = sysconf(_SC_NPROCESSORS_ONLN);
    if (ret == -1) {
        rb_sys_fail("sysconf(_SC_NPROCESSORS_ONLN)");
    }
#else
# ifndef ALL_PROCESSOR_GROUPS
#   define ALL_PROCESSOR_GROUPS 0xffff
# endif
    /* GetSystemInfo() counts the current processor group only, and mingw-w64 declares GetActiveProcessorCount() only for _WIN32_WINNT >= 0x0601 */
    typedef DWORD (WINAPI *GetActiveProcessorCount_t)(WORD);
    GetActiveProcessorCount_t pGetActiveProcessorCount =
        (GetActiveProcessorCount_t)GetProcAddress(GetModuleHandleW(L"kernel32.dll"), "GetActiveProcessorCount");
    DWORD n = 0;

    if (pGetActiveProcessorCount) {
        n = pGetActiveProcessorCount(ALL_PROCESSOR_GROUPS);
    }
    if (n == 0) {
        SYSTEM_INFO si;
        GetSystemInfo(&si);
        n = si.dwNumberOfProcessors;
    }
    ret = (long)n;
#endif
    return LONG2NUM(ret);
}