www.pudn.com > snmp.rar > uptime.c

/*++ 
 
Copyright (c) 1992-1997  Microsoft Corporation 
 
Module Name: 
 
    uptime.c 
 
Abstract: 
 
    Contains routines to calculate sysUpTime. 
 
        SnmpSvcInitUptime 
        SnmpSvcGetUptime 
 
Environment: 
 
    User Mode - Win32 
 
Revision History: 
 
--*/ 
 
/////////////////////////////////////////////////////////////////////////////// 
//                                                                           // 
// Include files                                                             // 
//                                                                           // 
/////////////////////////////////////////////////////////////////////////////// 
 
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#include  
 
 
/////////////////////////////////////////////////////////////////////////////// 
//                                                                           // 
// Global Variables                                                          // 
//                                                                           // 
/////////////////////////////////////////////////////////////////////////////// 
 
DWORD g_dwUpTimeReference = 0; 
LONGLONG g_llUpTimeReference = 0; 
extern PFNNTQUERYSYSTEMINFORMATION g_pfnNtQuerySystemInformation; 
extern PFNRTLEXTENDEDLARGEINTEGERDIVIDE g_pfnRtlExtendedLargeIntegerDivide; 
 
 
/////////////////////////////////////////////////////////////////////////////// 
//                                                                           // 
// Private Definitions                                                       // 
//                                                                           // 
/////////////////////////////////////////////////////////////////////////////// 
 
#define INVALID_UPTIME  0xFFFFFFFF 
 
 
/////////////////////////////////////////////////////////////////////////////// 
//                                                                           // 
// Private Procedures                                                        // 
//                                                                           // 
/////////////////////////////////////////////////////////////////////////////// 
 
DWORD 
SNMP_FUNC_TYPE  
SnmpSvcInitUptime( 
    ) 
 
/*++ 
 
Routine Description: 
 
    Initializes sysUpTime reference for SNMP process. 
 
Arguments: 
 
    None. 
 
Return Values: 
 
    Returns sysUpTime reference to pass to subagents.  
 
--*/ 
 
{ 
    // obtain reference the lame outdated way 
    DWORD g_dwUpTimeReference = GetCurrentTime(); 
 
    // check to see if new method is available 
    if (g_pfnNtQuerySystemInformation != NULL) { 
         
        NTSTATUS NtStatus; 
        SYSTEM_TIMEOFDAY_INFORMATION TimeOfDay; 
 
        // query time in spiffy new precise manner         
        NtStatus = (*g_pfnNtQuerySystemInformation)( 
                        SystemTimeOfDayInformation, 
                        &TimeOfDay, 
                        sizeof(SYSTEM_TIMEOFDAY_INFORMATION), 
                        NULL 
                        ); 
         
        // validate return code 
        if (NT_SUCCESS(NtStatus)) { 
 
            // initialize higher precision startup time          
            g_llUpTimeReference = TimeOfDay.CurrentTime.QuadPart; 
        } 
    } 
 
    // 
    // The algorithm for subagents to calculate sysUpTime 
    // is based on GetCurrentTime() which returns the time  
    // in milliseconds and therefore wraps every 49.71 days. 
    // RFC1213 specifies that sysUpTime is to be returned in 
    // centaseconds but we cannot break existing subagents. 
    // The old value is returned to the master agent here  
    // but newer subagents should use SnmpUtilGetUpTime. 
    // 
 
    return g_dwUpTimeReference; 
}  
 
 
/////////////////////////////////////////////////////////////////////////////// 
//                                                                           // 
// Public Procedures                                                         // 
//                                                                           // 
/////////////////////////////////////////////////////////////////////////////// 
 
DWORD 
SNMP_FUNC_TYPE 
SnmpSvcGetUptime( 
    ) 
 
/*++ 
 
Routine Description: 
 
    Retrieves sysUpTime for SNMP process. 
 
Arguments: 
 
    None. 
 
Return Values: 
 
    Returns sysUpTime value for use by subagents.  
 
--*/ 
 
{ 
    DWORD dwUpTime = INVALID_UPTIME; 
 
    // check to see if new method is available 
    if ((g_pfnNtQuerySystemInformation != NULL) && 
        (g_pfnRtlExtendedLargeIntegerDivide != NULL) && 
        (g_llUpTimeReference != 0)) { 
         
        NTSTATUS NtStatus; 
        SYSTEM_TIMEOFDAY_INFORMATION TimeOfDay; 
 
        // query time in spiffy new precise manner         
        NtStatus = (*g_pfnNtQuerySystemInformation)( 
                        SystemTimeOfDayInformation, 
                        &TimeOfDay, 
                        sizeof(SYSTEM_TIMEOFDAY_INFORMATION), 
                        NULL 
                        ); 
         
        // validate return code 
        if (NT_SUCCESS(NtStatus)) { 
 
            LARGE_INTEGER liUpTime; 
            LARGE_INTEGER liUpTimeInCentaseconds; 
 
            // calculate difference from reference 
            liUpTime.QuadPart = TimeOfDay.CurrentTime.QuadPart -  
                                                    g_llUpTimeReference; 
                                     
            // convert 100ns units (10^-7) into centasecond units (10^-2) 
            liUpTimeInCentaseconds = (*g_pfnRtlExtendedLargeIntegerDivide)( 
                                            liUpTime, 
                                            100000, 
                                            NULL 
                                            ); 
 
            // convert large integer to dword value 
            dwUpTime = (DWORD)(LONGLONG)liUpTimeInCentaseconds.QuadPart; 
        } 
     
    } else if (g_dwUpTimeReference != 0) { 
 
        // calculate difference from reference 
        dwUpTime = (GetCurrentTime() - g_dwUpTimeReference) / 10; 
    } 
 
    return dwUpTime; 
}