利用未公布API获取CPU使用率

利用ntdll.dll中没有公开的API函数: NtQuerySystemInformation

typedef LONG (WINAPI *PROCNTQSI)(UINT,PVOID,ULONG,PULONG); PROCNTQSI NtQuerySystemInformation;

NtQuerySystemInformation = (PROCNTQSI)GetProcAddress(
                                      GetModuleHandle("ntdll"),
                                     "NtQuerySystemInformation"
                                     );
if (!NtQuerySystemInformation)

{ return; }

// get number of processors in the system
status = NtQuerySystemInformation(SystemBasicInformation,
                          &SysBaseInfo;,sizeof(SysBaseInfo),NULL);
if (status != NO_ERROR)

{ return; } status = NtQuerySystemInformation(SystemTimeInformation, &SysTimeInfo;,sizeof(SysTimeInfo),0); if (status!=NO_ERROR) { return; } // get new CPU’’s idle time status = NtQuerySystemInformation(SystemPerformanceInformation, &SysPerfInfo;,sizeof(SysPerfInfo),NULL); if (status != NO_ERROR) { return; } // if it’’s a first call - skip it if (m_liOldIdleTime.QuadPart != 0) { // CurrentValue = NewValue - OldValue dbIdleTime = Li2Double(SysPerfInfo.liIdleTime) - Li2Double(m_liOldIdleTime); dbSystemTime = Li2Double(SysTimeInfo.liKeSystemTime) - Li2Double(m_liOldSystemTime);

     // CurrentCpuIdle = IdleTime / SystemTime
     dbIdleTime = dbIdleTime / dbSystemTime;

     // CurrentCpuUsage% = 100 - (CurrentCpuIdle * 100) / NumberOfProcessors
     dbIdleTime = 100.0 - dbIdleTime * 100.0 / (double)SysBaseInfo.bKeNumberProcessors + 0.5;

     m_fNewUsges = (UINT)dbIdleTime;
}