CODEWITHSUNDEEP
c++winapidlltime
user1978386
user1978386

Reputation: 257

Linking failure. How to use 'NtQuerySystemTime' windows function?

I try this simple code to calculate HDD write speed in my application:

#include <winternl.h>

...
float speed;
double divident;
PLARGE_INTEGER systime0, systime1;
LONGLONG elapsed_time;
...

write_flag = true ;

NtQuerySystemTime(systime0) ;

f_out->write(out_buffer0, chunk_len0);
f_out->write(out_buffer1, chunk_len1);

NtQuerySystemTime(systime1);

elapsed_time = systime1->QuadPart - systime0->QuadPart;

write_flag = false ;

divident = static_cast<double>(chunk_len0 + chunk_len1) / 1.048576 ;  // 1.024 * 1.024 = 1.048576; divident yield value 1000000 times greater then value in MB
divident *= 10 ;  // I want 'speed' to be in MB/s
speed = divident / static_cast<double>(elapsed_time) ;
...

but it fails to link.

On MSDN, the NtQuerySystemTime documentation says there is no associated import library and that I must use the LoadLibrary() and GetProcAddress() functions to dynamically link to Ntdll.dll. But I don't understand how to use those functions. Can someone please provide a code example of how to use those functions?

Upvotes: 1

Views: 1388

Answers (2)

Jame
Jame

Reputation: 11

#include <stdio.h>
#include <windows.h>

typedef  NTSYSAPI (CALLBACK *LPNTQUERYSYSTEMTIME)(PLARGE_INTEGER);

void main(void)
{
    PLARGE_INTEGER  SystemTime;
    SystemTime = (PLARGE_INTEGER) malloc(sizeof(LARGE_INTEGER));

    HMODULE hNtDll = GetModuleHandleA("ntdll");

    LPNTQUERYSYSTEMTIME fnNtQuerySystemTime = (LPNTQUERYSYSTEMTIME)GetProcAddress(hNtDll, "NtQuerySystemTime");

    if(fnNtQuerySystemTime){

        printf("found NtQuerySystemTime function at ntdll.dll address:%p\n",fnNtQuerySystemTime);
        fnNtQuerySystemTime(SystemTime);
        printf("%llx\n", SystemTime->QuadPart);

    }

    free(SystemTime);
}

Upvotes: 1

typ1232
typ1232

Reputation: 5607

This is how you would be able to use this function.

HMODULE hNtDll = GetModuleHandleA("ntdll");
NTSTATUS (WINAPI *NtQuerySystemTime)(PLARGE_INTEGER) = 
    (NTSTATUS (WINAPI*)(PLARGE_INTEGER))GetProcAddress(hNtDll, "NtQuerySystemTime");

Upvotes: 1

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