wince.c

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	   link it dynamically */
	if( hToolHelp32 == NULL )
		{
		/* Obtain the module handle of the kernel to retrieve the addresses
		   of the ToolHelp32 functions */
		if( ( hToolHelp32 = LoadLibrary( TEXT( "Toolhelp.dll" ) ) ) == NULL )
			{
			/* There's no ToolHelp32 available, now we're in a bit of a
			   bind.  Try for at least a fast poll */
			fastPoll();
			return;
			}

		/* Now get pointers to the functions */
		pCreateToolhelp32Snapshot = ( CREATESNAPSHOT ) GetProcAddress( hToolHelp32, TEXT( "CreateToolhelp32Snapshot" ) );
		pCloseToolhelp32Snapshot = ( CLOSESNAPSHOT ) GetProcAddress( hToolHelp32, TEXT( "CloseToolhelp32Snapshot" ) );
		pModule32First = ( MODULEWALK ) GetProcAddress( hToolHelp32, TEXT( "Module32First" ) );
		pModule32Next = ( MODULEWALK ) GetProcAddress( hToolHelp32, TEXT( "Module32Next" ) );
		pProcess32First = ( PROCESSWALK ) GetProcAddress( hToolHelp32, TEXT( "Process32First" ) );
		pProcess32Next = ( PROCESSWALK ) GetProcAddress( hToolHelp32, TEXT( "Process32Next" ) );
		pThread32First = ( THREADWALK ) GetProcAddress( hToolHelp32, TEXT( "Thread32First" ) );
		pThread32Next = ( THREADWALK ) GetProcAddress( hToolHelp32, TEXT( "Thread32Next" ) );
		pHeap32ListFirst = ( HEAPLISTWALK ) GetProcAddress( hToolHelp32, TEXT( "Heap32ListFirst" ) );
		pHeap32ListNext = ( HEAPLISTWALK ) GetProcAddress( hToolHelp32, TEXT( "Heap32ListNext" ) );
		pHeap32First = ( HEAPFIRST ) GetProcAddress( hToolHelp32, TEXT( "Heap32First" ) );
		pHeap32Next = ( HEAPNEXT ) GetProcAddress( hToolHelp32, TEXT( "Heap32Next" ) );

		/* Make sure we got valid pointers for every Toolhelp32 function */
		if( pModule32First == NULL || pModule32Next == NULL || \
			pProcess32First == NULL || pProcess32Next == NULL || \
			pThread32First == NULL || pThread32Next == NULL || \
			pHeap32ListFirst == NULL || pHeap32ListNext == NULL || \
			pHeap32First == NULL || pHeap32Next == NULL || \
			pCreateToolhelp32Snapshot == NULL )
			{
			/* Mark the main function as unavailable in case for future
			   reference */
			pCreateToolhelp32Snapshot = NULL;
			return;
			}
		}
	if( krnlIsExiting() )
		return;

	initRandomData( randomState, buffer, BIG_RANDOM_BUFSIZE );

	/* Take a snapshot of everything we can get to that's currently in the
	   system */
	hSnapshot = pCreateToolhelp32Snapshot( TH32CS_SNAPALL, 0 );
	if( !hSnapshot )
		return;

	/* Walk through the local heap.  We have to be careful to not spend
	   excessive amounts of time on this if we're linked into a large
	   application with a great many heaps and/or heap blocks, since the
	   heap-traversal functions are rather slow.  Fortunately this is
	   quite rare under WinCE since it implies a large/long-running server
	   app, which we're unlikely to run into.

	   Ideally in order to prevent excessive delays we'd count the number
	   of heaps and ensure that no_heaps * no_heap_blocks doesn't exceed
	   some maximum value, however this requires two passes of (slow) heap
	   traversal rather than one, which doesn't help the situation much.
	   To provide at least some protection, we limit the total number of
	   heaps and heap entries traversed, although this leads to slightly
	   suboptimal performance if we have a small number of deep heaps
	   rather than the current large number of shallow heaps.

	   There is however a second consideration that needs to be taken into
	   account when doing this, which is that the heap-management functions
	   aren't completely thread-safe, so that under (very rare) conditions
	   of heavy allocation/deallocation this can cause problems when calling
	   HeapNext().  By limiting the amount of time that we spend in each
	   heap, we can reduce our exposure somewhat */
	hl32.dwSize = sizeof( HEAPLIST32 );
	if( pHeap32ListFirst( hSnapshot, &hl32 ) )
		do
			{
			HEAPENTRY32 he32;
			int entryCount = 0;

			/* First add the information from the basic Heaplist32
			   structure */
			if( krnlIsExiting() )
				{
				pCloseToolhelp32Snapshot( hSnapshot );
				return;
				}
			addRandomData( randomState, &hl32, sizeof( HEAPLIST32 ) );

			/* Now walk through the heap blocks getting information
			   on each of them */
			he32.dwSize = sizeof( HEAPENTRY32 );
			if( pHeap32First( hSnapshot, &he32, hl32.th32ProcessID, hl32.th32HeapID ) )
				do
					{
					if( krnlIsExiting() )
						{
						pCloseToolhelp32Snapshot( hSnapshot );
						return;
						}
					addRandomData( randomState, &he32,
								   sizeof( HEAPENTRY32 ) );
					}
				while( entryCount++ < 20 && pHeap32Next( hSnapshot, &he32 ) );
			}
		while( listCount++ < 20 && pHeap32ListNext( hSnapshot, &hl32 ) );

	/* Walk through all processes */
	pe32.dwSize = sizeof( PROCESSENTRY32 );
	if( pProcess32First( hSnapshot, &pe32 ) )
		do
			{
			if( krnlIsExiting() )
				{
				pCloseToolhelp32Snapshot( hSnapshot );
				return;
				}
			addRandomData( randomState, &pe32, sizeof( PROCESSENTRY32 ) );
			}
		while( pProcess32Next( hSnapshot, &pe32 ) );

	/* Walk through all threads */
	te32.dwSize = sizeof( THREADENTRY32 );
	if( pThread32First( hSnapshot, &te32 ) )
		do
			{
			if( krnlIsExiting() )
				{
				pCloseToolhelp32Snapshot( hSnapshot );
				return;
				}
			addRandomData( randomState, &te32, sizeof( THREADENTRY32 ) );
			}
	while( pThread32Next( hSnapshot, &te32 ) );

	/* Walk through all modules associated with the process */
	me32.dwSize = sizeof( MODULEENTRY32 );
	if( pModule32First( hSnapshot, &me32 ) )
		do
			{
			if( krnlIsExiting() )
				{
				pCloseToolhelp32Snapshot( hSnapshot );
				return;
				}
			addRandomData( randomState, &me32, sizeof( MODULEENTRY32 ) );
			}
	while( pModule32Next( hSnapshot, &me32 ) );

	/* Clean up the snapshot */
	pCloseToolhelp32Snapshot( hSnapshot );
	if( krnlIsExiting() )
		return;

	/* Flush any remaining data through */
	endRandomData( randomState, 100 );
	}

/* Perform a thread-safe slow poll for Windows CE */

DWORD WINAPI threadSafeSlowPoll( void *dummy )
	{
	UNUSED( dummy );

	slowPollWinCE();
	ExitThread( 0 );
	return( 0 );
	}

/* Perform a generic slow poll.  This starts the OS-specific poll in a
   separate thread */

void slowPoll( void )
	{
	if( krnlIsExiting() )
		return;

	/* Start a threaded slow poll.  If a slow poll is already running, we
	   just return since there isn't much point in running two of them at the
	   same time */
	if( hThread )
		return;
	hThread = CreateThread( NULL, 0, threadSafeSlowPoll, NULL, 0, &threadID );
	assert( hThread );
	}

/* Wait for the randomness gathering to finish.  Anything that requires the
   gatherer process to have completed gathering entropy should call
   waitforRandomCompletion(), which will block until the background process
   completes */

void waitforRandomCompletion( const BOOLEAN force )
	{
	/* If there's not polling thread running, there's nothing to do */
	if( !hThread )
		return;

	/* If this is a forced shutdown, tell the polling thread to exit */
	if( force )
		{
		/* Wait for the polling thread to terminate.  Since this is a forced
		   shutdown, we only wait a fixed amount of time (2s) before we bail
		   out */
		WaitForSingleObject( hThread, 2000 );
		CloseHandle( hThread );
		hThread = NULL;

		return;
		}

	/* Sign the system object over to the polling thread to allow it to
	   update the entropy data */
	krnlRelinquishSystemObject( threadID );

	/* Wait for the polling thread to terminate */
	WaitForSingleObject( hThread, INFINITE );
	CloseHandle( hThread );
	hThread = NULL;

	/* Return the system object to the calling thread */
	krnlReacquireSystemObject();
	}

/* Initialise and clean up any auxiliary randomness-related objects */

void initRandomPolling( void )
	{
	/* Reset the various object handles and status info */
	hToolHelp32 = hThread = NULL;
	}

void endRandomPolling( void )
	{
	assert( hThread == NULL );
	if( hToolHelp32 )
		{
		FreeLibrary( hToolHelp32 );
		hToolHelp32 = NULL;
		}
	}