阅读Darwin源码的时候看到这个方法，感觉挺有用处，且考虑了多种平台下的实现方式，直接贴代码，以后说不定会用到~

单一种平台下的实现方法可能很容易，但是把这些个系统都收集在一起，在一个函数中实现还是极好的

UInt32  OS::GetNumProcessors()
{
#if (__Win32__)
    SYSTEM_INFO theSystemInfo;
    ::GetSystemInfo(&theSystemInfo);
    
    return (UInt32)theSystemInfo.dwNumberOfProcessors;
#endif

#if (__MacOSX__ || __FreeBSD__)
    int numCPUs = 1;
    size_t len = sizeof(numCPUs);
	int mib[2];
    mib[0] = CTL_HW;
    mib[1] = HW_NCPU;
    (void) ::sysctl(mib,2,&numCPUs,&len,NULL,0);
    if (numCPUs < 1) 
        numCPUs = 1;
    return (UInt32) numCPUs;
#endif

#if(__linux__ || __linuxppc__)
    
    char cpuBuffer[8192] = "";
    StrPtrLen cpuInfoBuf(cpuBuffer, sizeof(cpuBuffer));
    FILE    *cpuFile = ::fopen( "/proc/cpuinfo", "r" );
    if (cpuFile)
    {   cpuInfoBuf.Len = ::fread(cpuInfoBuf.Ptr, sizeof(char),  cpuInfoBuf.Len, cpuFile);
        ::fclose(cpuFile);
    }
    
    StringParser cpuInfoFileParser(&cpuInfoBuf);
    StrPtrLen line;
    StrPtrLen word;
    UInt32 numCPUs = 0;
    
    while( cpuInfoFileParser.GetDataRemaining() != 0 ) 
    {
        cpuInfoFileParser.GetThruEOL(&line);    // Read each line   
        StringParser lineParser(&line);
        lineParser.ConsumeWhitespace();         //skip over leading whitespace

        if (lineParser.GetDataRemaining() == 0) // must be an empty line
            continue;

        lineParser.ConsumeUntilWhitespace(&word);
               
        if ( word.Equal("processor") ) // found a processor as first word in line
        {   numCPUs ++; 
        }
    }
    
    if (numCPUs == 0)
        numCPUs = 1;
        
    return numCPUs;
#endif

#if(__solaris__)
{
    UInt32 numCPUs = 0;
    char linebuff[512] = "";
    StrPtrLen line(linebuff, sizeof(linebuff));
    StrPtrLen word;

    FILE *p = ::popen("uname -X","r");
    while((::fgets(linebuff, sizeof(linebuff -1), p)) > 0)
    {
        StringParser lineParser(&line);
        lineParser.ConsumeWhitespace(); //skip over leading whitespace

        if (lineParser.GetDataRemaining() == 0) // must be an empty line
            continue;

        lineParser.ConsumeUntilWhitespace(&word);

        if ( word.Equal("NumCPU")) // found a tag as first word in line
        {
            lineParser.GetThru(NULL,'=');
            lineParser.ConsumeWhitespace();  //skip over leading whitespace
            lineParser.ConsumeUntilWhitespace(&word); //read the number of cpus
            if (word.Len > 0)
                ::sscanf(word.Ptr, "%"_U32BITARG_"", &numCPUs);

            break;
        }
    }
    if (numCPUs == 0)
        numCPUs = 1;
        
    ::pclose(p);
    
	return numCPUs;
}
#endif

#if(__sgi__) 
    UInt32 numCPUs = 0;

    numCPUs = sysconf(_SC_NPROC_ONLN);
	
	return numCPUs;
#endif		


    return 1;
}

Darwin获取系统处理器数量的方法