Timothy Vismor wrote:
> On 11/17/06, Havoc Pennington <[EMAIL PROTECTED]> wrote:
>>
>>
>>
>> Timothy Vismor wrote:
>> >
>> > A common way to guarantee a unique instance of a Windows application
>> > is to use a well known mutex name. A simple example is:
>> >
>>
>> Thanks, that looks pretty good. We'd need to solve one more problem
>> also, which is how to get the address of the existing process... any
>> typical pattern for that? ;-)
>>
>> Havoc
>
>
> Never needed to do that specific operation, but it seems that a simple
> solution could be to use named shared memory. When a process grabs
> the DBus mutex, it could write relevant address information to a well
> known block of named shared memory. When you release the
> mutex, you also release the shared memory block. If a process
> fails to grab the mutex, it could read the required information from
> shared memory.
>
> DURING STARTUP, AFTER YOU CREATE THE MUTEX
>
> SECURITY_ATTRIBUTES sa;
> sa.nLength = sizeof( sa );
> sa.lpSecurityDescriptor = m_pMemSD;
> sa.bInheritHandle = TRUE;
>
> // Create shared virual memory in the page file.
> m_hSharedMem = CreateFileMapping( (HANDLE)0xFFFFFFFF, &sa,
> PAGE_READWRITE,
> ZERO, nBytes, "DBusAddressInfo"
> );
> if( m_hSharedMem == NULL )
> {
> // Unable to allocate shared memory.
> return( FALSE );
> }
>
> // Map shared memory into process address space.
> if( m_hSharedMem != NULL )
> {
> m_pSharedMem = MapViewOfFile( m_hSharedMem, FILE_MAP_WRITE, ZERO,
> ZERO, ZERO );
> if( m_pSharedMem == NULL )
> {
> // Unable to map shared memory.
> ::CloseHandle( m_hSharedMem );
> m_hSharedMem = NULL;
> return( FALSE );
> }
> }
> // Write process information to shared memory.
> ...
>
> DURING SHUTDOWN
>
> if( m_pSharedMem != NULL )
> {
> ::UnmapViewOfFile( m_pSharedMem );
> m_pSharedMem = NULL;
> }
> if( m_hNetDevMem != NULL )
> {
> ::CloseHandle( m_hSharedMem );
> m_hSharedMem = NULL;
> }
>
>
> IF CAN'T GET MUTEX
>
> // Connect to the memory mapped file (actually the paging file).
> m_hSharedMem = OpenFileMapping(FILE_MAP_READ, FALSE, "DBusAddressInfo");
>
> if( m_hSharedMem == NULL )
> {
> // Unable to link to shared memory.
> // Process is no longer running.
> return( FALSE );
> }
>
> // Map shared memory into our address space.
> m_pSharedMem = MapViewOfFile( m_hSharedMem, FILE_MAP_READ,ZERO, ZERO,
> ZERO );
> if( m_pSharedMem == NULL )
> {
> // Unable to map shared memory.
> CloseHandle( m_hSharedMem );
> m_hSharedMem = NULL;
> return( FALSE );
> }
> // Read process info from shared mem
> ....
Great! I'll give it a try.
Peter
