C++获取特定进程CPU使用率的实现代码

#include <Windows.h>  
//原理：调用GetProcessTimes()，并与上次调用得到的结果相减，即得到某段时间内CPU的使用时间 
//C++ 获取特定进程规定CPU使用率 原文：http://blog.csdn.net/liuqx97bb/article/details/52058657 
class CPUusage {  
private: 
  typedef long long     int64_t; 
  typedef unsigned long long uint64_t; 
  HANDLE _hProcess;  
  int _processor;  //cpu数量  
  int64_t _last_time;     //上一次的时间  
  int64_t _last_system_time;  
 
 
  // 时间转换  
  uint64_t file_time_2_utc(const FILETIME* ftime); 
 
  // 获得CPU的核数  
  int get_processor_number(); 
 
  //初始化 
  void init() 
  { 
    _last_system_time = 0; 
    _last_time = 0; 
    _hProcess = 0; 
  } 
 
  //关闭进程句柄 
  void clear() 
  { 
    if (_hProcess) { 
      CloseHandle(_hProcess); 
      _hProcess = 0; 
    } 
  } 
 
public: 
  CPUusage(DWORD ProcessID) {  
    init();  
    _processor = get_processor_number(); 
    setpid(ProcessID); 
  } 
  CPUusage() { init(); _processor = get_processor_number(); } 
  ~CPUusage() { clear(); } 
 
  //返回值为进程句柄，可判断OpenProcess是否成功 
  HANDLE setpid(DWORD ProcessID) {  
    clear();  //如果之前监视过另一个进程，就先关闭它的句柄 
    init();  
    return _hProcess= OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, false, ProcessID);  
  } 
 
  //-1 即为失败或进程已退出； 如果成功，首次调用会返回-2（中途用setpid更改了PID后首次调用也会返回-2） 
  float get_cpu_usage();  
};

float CPUusage::get_cpu_usage() 
{ 
 
  FILETIME now; 
  FILETIME creation_time; 
  FILETIME exit_time; 
  FILETIME kernel_time; 
  FILETIME user_time; 
  int64_t system_time; 
  int64_t time; 
  int64_t system_time_delta; 
  int64_t time_delta; 
 
  DWORD exitcode; 
 
  float cpu = -1; 
 
  if (!_hProcess) return -1; 
 
  GetSystemTimeAsFileTime(&now); 
 
  //判断进程是否已经退出 
  GetExitCodeProcess(_hProcess, &exitcode);  
  if (exitcode != STILL_ACTIVE) { 
    clear(); 
    return -1; 
  } 
 
  //计算占用CPU的百分比 
  if (!GetProcessTimes(_hProcess, &creation_time, &exit_time, &kernel_time, &user_time)) 
  { 
    clear(); 
    return -1; 
  } 
  system_time = (file_time_2_utc(&kernel_time) + file_time_2_utc(&user_time)) 
    / _processor; 
  time = file_time_2_utc(&now); 
 
  //判断是否为首次计算 
  if ((_last_system_time == 0) || (_last_time == 0)) 
  { 
    _last_system_time = system_time; 
    _last_time = time; 
    return -2; 
  } 
 
  system_time_delta = system_time - _last_system_time; 
  time_delta = time - _last_time; 
 
  if (time_delta == 0) { 
    return -1; 
  } 
 
  cpu = (float)system_time_delta * 100 / (float)time_delta; 
  _last_system_time = system_time; 
  _last_time = time; 
  return cpu; 
} 
 
CPUusage::uint64_t CPUusage::file_time_2_utc(const FILETIME* ftime) 
{ 
  LARGE_INTEGER li; 
 
  li.LowPart = ftime->dwLowDateTime; 
  li.HighPart = ftime->dwHighDateTime; 
  return li.QuadPart; 
} 
 
int CPUusage::get_processor_number() 
{ 
  SYSTEM_INFO info; 
  GetSystemInfo(&info); 
  return info.dwNumberOfProcessors; 
}

#include "CPUusage.h" 
int _tmain(int argc, _TCHAR* argv[]) 
{ 
 
  CPUusage usg(12316); 
  for (int i = 0; i < 10; i++) 
  { 
    float cpu = usg.get_cpu_usage(); 
    printf("Taskmgr.exe: %.2f%%\n", cpu); 
    Sleep(500); 
  } 
 
  usg.setpid(11084); 
  for (int i = 0; i < 10; i++) 
  { 
    float cpu = usg.get_cpu_usage(); 
    printf("devenv.exe: %.2f%%\n", cpu); 
    Sleep(1000); 
  } 
   
  return 0; 
}