#include <windows.h>
#include <cstdlib>
#include <random>

using namespace std;

size_t const BLOCK_SIZE = 4096;
size_t const NUM_BLOCKS = ((size_t)1024 * 1024 * 1024 / BLOCK_SIZE);
size_t const FILE_SIZE  = NUM_BLOCKS * BLOCK_SIZE;

DWORD WINAPI ReaderThread( LPVOID lpvThreadParam );

int main()
{
    HANDLE     hFile;
    OVERLAPPED ol;
    BYTE       abBlock[BLOCK_SIZE];
    int const  THREADS = 500;

    if( (hFile = CreateFile( TEXT("testfile"), GENERIC_READ | GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_FLAG_NO_BUFFERING | FILE_FLAG_OVERLAPPED, NULL )) == INVALID_HANDLE_VALUE )
        return EXIT_FAILURE;

    ol.Offset = FILE_SIZE - BLOCK_SIZE;
    ol.OffsetHigh = 0;
    if( (ol.hEvent = CreateEvent( NULL, FALSE, FALSE, NULL )) == NULL ||
        !WriteFile( hFile, abBlock, BLOCK_SIZE, NULL, &ol ) && GetLastError() != ERROR_IO_PENDING )
        return EXIT_FAILURE;

    for( int thread = 0; thread < THREADS; thread++ )
        CreateThread( NULL, 0, ReaderThread, hFile, 0, NULL );

    Sleep( INFINITE );

    return EXIT_SUCCESS;
}

DWORD WINAPI ReaderThread( LPVOID lpvThreadParam )
{
    HANDLE                          hFile = (HANDLE)lpvThreadParam;
    random_device                   rd;
    mt19937                         mt( rd() );
    uniform_int_distribution<DWORD> uid( 0, FILE_SIZE - BLOCK_SIZE );
    HANDLE                          hEvent;

    if( (hEvent = CreateEvent( NULL, FALSE, FALSE, NULL )) == NULL )
        ExitProcess( EXIT_FAILURE );

    for( ; ; )
    {
        OVERLAPPED ol;
        BYTE       abBlock[BLOCK_SIZE];

        ol.Offset     = uid( mt ) & (DWORD)-(LONG)BLOCK_SIZE;
        ol.OffsetHigh = 0;
        ol.hEvent     = hEvent;
        if( !ReadFile( hFile, abBlock, BLOCK_SIZE, NULL, &ol ) && GetLastError() != ERROR_IO_PENDING ||
            WaitForSingleObject( hEvent, INFINITE ) != WAIT_OBJECT_0 )
            ExitProcess( EXIT_FAILURE );
    }
}