I have a Windows app that simply runs in the background and watches constantly for data appearing on stdin by means of a separate thread. It does this because it is a Chrome native messaging host and that's how it is expected to communicate with the browser extension (as is clarified in this SO question by RobW). It seems to run fine although imo it uses too much of the cpu when there is no activity. When the browser extension sends bytes on stdin to my app it has to be discovered and processed immediately, and because the processing is intensive an increased demand for cpu usage is understandable, but seems it should not use much when there is no activity.
Disclaimer: I would not call myself an experienced Windows developer.
I am using _beginThreadEx() to launch the function that reads constantly from stdin. The thread is created in InitInstance() like so:
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
HWND hWnd;
int nStdInDescriptor = _fileno(stdin);
hStdIn = (HANDLE) _get_osfhandle(nStdInDescriptor);
OutputDebugStringA("starting message processing thread function");
hReadInputThread = (HANDLE)_beginthreadex(0, 0, &threadfunc_processMessages, &i, 0, 0);
hWnd = CreateWindowEx(WS_EX_TOOLWINDOW, szWindowClass, szTitle, WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);
if (!hWnd && !hReadInputThread)
{
return FALSE;
}
hMainWnd = hWnd;
return TRUE;
}
and
unsigned int __stdcall threadfunc_processMessages(void* data)
{
char buffer_temp[STDIN_BUF_SIZE];
buffer_main = NULL;
DWORD dwNumBytesRead;
DWORD dwNumBytesToRead = STDIN_BUF_SIZE;
while (1) {
if (ReadFile(hStdIn, buffer_temp, dwNumBytesToRead, &dwNumBytesRead, NULL)) {
OutputDebugStringA( "Found some bytes on stdin" );
// byte processing code here. it always processes normally
}
}
return 0;
}
Task Manager shows cpu usage around 49%. I assumed _beginThreadEx() would run in the background, yet still be responsive since it needs to pounce on any data that shows up on stdin. Any help is appreciated.
Related
When you launch a Windows desktop application, the system changes the arrow to one with an animated busy spinner (presumably from IDI_ARROW to IDI_APPSTARTING). Once the application presents a window, the cursor is restored to indicate that it's ready for input.
With my own Win32 applications, the spinner continues for several (5?) seconds, even though the main window is fully rendered and ready for interaction. It was my understanding that the spinner vanishes once the just-launched program started pumping messages. More specifically, I thought it used the same criteria as WaitForInputIdle.
Since Windows 10, however, some applications, including ones I've written, appear to be stuck with the busy cursor for the duration of the timeout—even beyond the moment that the application becomes responsive to mouse and keyboard input.
What should I do in my programs to let the system know that initialization is complete and the spinner is no longer needed?
UPDATE: The problem occurs only when launching the application from the keyboard (like a CMD prompt, the Run window, or using the keyboard to launch the process in the debugger in Visual Studio). If you double-click the program with the mouse, the spinner vanishes quickly, as expected.
UPDATE 2: Given that others cannot repro, my best guess is that there's a buggy driver involved. Thanks to everyone who helped brainstorm in the comments.
Self-contained repro below.
#include <Windows.h>
LRESULT OnPaint(HWND hwnd, UINT, WPARAM, LPARAM) {
PAINTSTRUCT ps;
::BeginPaint(hwnd, &ps);
RECT rc;
::GetClientRect(hwnd, &rc);
::DrawTextW(ps.hdc, L"Hello, World", -1, &rc,
DT_SINGLELINE | DT_CENTER | DT_VCENTER | DT_NOPREFIX);
::EndPaint(hwnd, &ps);
return 0;
}
LRESULT MyWindowProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) {
switch (msg) {
case WM_DESTROY: ::PostQuitMessage(0); break;
case WM_PAINT: return OnPaint(hwnd, msg, wp, lp);
}
return ::DefWindowProcW(hwnd, msg, wp, lp);
}
int WinMain(HINSTANCE hinst, HINSTANCE, LPSTR, int nShowCmd) {
WNDCLASSW wc = {0};
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = MyWindowProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hinst;
wc.hIcon = NULL;
wc.hCursor = ::LoadCursorW(NULL, IDC_ARROW);
wc.hbrBackground = ::GetSysColorBrush(COLOR_WINDOW);
wc.lpszMenuName = nullptr;
wc.lpszClassName = L"My Very Own Window Class";
const ATOM atomClass = ::RegisterClassW(&wc);
if (atomClass == 0) return ::GetLastError();
// Ugly cast for WinAPI's legacy type punning.
const LPCWSTR wndclass =
reinterpret_cast<LPCWSTR>(static_cast<UINT_PTR>(atomClass));
const HWND hwnd =
::CreateWindowW(wndclass, L"Test", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL,
NULL, hinst, nullptr);
if (hwnd == NULL) return ::GetLastError();
::ShowWindow(hwnd, nShowCmd);
MSG msg = {0};
while (::GetMessageW(&msg, NULL, 0, 0) > 0) {
::TranslateMessage(&msg);
::DispatchMessageW(&msg);
}
return (msg.message == WM_QUIT) ? static_cast<int>(msg.wParam) : 1;
}
What should I do in my programs to let the system know that initialization is complete and the spinner is no longer needed?
There seems to be agreement that the spinner should vanish once the application has started pumping messages and has no pending input events queue.
The fact that's not working in all cases for me is likely a local issue, like a buggy driver spamming the input queue (which somehow never make it to window messages). There's not much point in hashing that out here on SO, so I'm putting up this community wiki answer and moving on.
I'm working in Windows 10 and I am trying to write a C++ program that intercepts all touch screen input, however some input is still getting through.
My code calls RegisterPointerInputTarget with PT_TOUCH to intercept touch input. This mostly seems to work, however the results are inconsistent. As a test I have added code that uses SendInput to move the mouse slowly to the right whenever touch input is detected. With my program running I can, for example, open up MS Paint and touch the screen. So long as I hold my finger still on the cursor moves slowly to the right as expected. The moment I move my finger however, the cursor snaps to the position under my finger, just as it would if my program were not running at all.
To give another example, if I try the same thing in visual studio, again the cursor moves slowly to the right until I move my finger at which point the cursor follows my fingers' movement but slowly, lagging be behind it with a significant delay.
The code to set up my window looks like this;
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
hInst = hInstance; // Store instance handle in our global variable
static const char* class_name = "DUMMY_CLASS";
WNDCLASSEX wx = {};
wx.cbSize = sizeof(WNDCLASSEX);
wx.lpfnWndProc = WndProc; // function which will handle messages
wx.hInstance = hInst;
wx.lpszClassName = class_name;
HWND hWnd = 0;
if (RegisterClassEx(&wx)) {
hWnd = CreateWindowEx(0, class_name, "dummy_name", 0, 0, 0, 0, 0, HWND_MESSAGE, NULL, NULL, NULL);
}
if (!hWnd)
{
return FALSE;
}
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
if (RegisterTouchWindow(hWnd, 0) &&
RegisterPointerInputTarget(hWnd, PT_TOUCH))
{
...
and my message handling code looks like this;
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_TOUCH:
{
INPUT Inputs[1] = { 0 };
Inputs[0].type = INPUT_MOUSE;
Inputs[0].mi.dx = 1;
Inputs[0].mi.dy = 0;
Inputs[0].mi.dwFlags = MOUSEEVENTF_MOVE;
SendInput(1, Inputs, sizeof(INPUT));
Ideally this test code would simply move the cursor for any touch input. Any help in fixing or just understanding this would be greatly appreciated!
I have made some progress with this but have hit other, related, problems I will ask about in a separate question. I will add a comment here when that question is live. The key to sorting out this initial issue however was to make sure I am returning 0, without calling DefWindowProc from all WM_POINTERENTER, WM_POINTERLEAVE, WM_POINTERUP, WM_POINTERDOWN, WM_POINTERUPDATE and WM_TOUCH messages, and to put my SendInput call into the code processing the WM_UPDATE message.
I recently tried to write a code to check if a thread in Windows is alive or not. I searched this forum and found discussions like: How to check if a process or thread is alive or not given their IDs in C++?.
I understand I can use OpenThread API. However it doesn't seem to work in my code as follows.
DWORD WINAPI myThread( LPVOID lpParam )
{
cout<<"child thread"<<endl;
return 0;
}
int main(void)
{
DWORD lTldID = 0;
HANDLE lTldHD = CreateThread(NULL, 0, myThread, 0, 0, &lTldID);
WaitForSingleObject(lTldHD, INFINITE);
HANDLE lHD = OpenThread(0x0040, FALSE, lTldID);
return 1;
}
I expect that the HANDLE lHD should be NULL since the thread 'myThread' should have finished at the time of calling OpenThread(). However, I always got NOT NULL values like 0x00000068. I don't know why this happened. Any idea?
Thanks,
Xiaomo
BOOL WINAPI GetExitCodeThread(
_In_ HANDLE hThread,
_Out_ LPDWORD lpExitCode
);
This function returns immediately. If the specified thread has not terminated and the function succeeds, the status returned is STILL_ACTIVE.
I have a com server that is started in the following way:
extern "C" int WINAPI _tWinMain(HINSTANCE hInstance,
HINSTANCE /*hPrevInstance*/, LPTSTR lpCmdLine, int /*nShowCmd*/)
{
lpCmdLine = GetCommandLine(); //this line necessary for _ATL_MIN_CRT
#if _WIN32_WINNT >= 0x0400 & defined(_ATL_FREE_THREADED)
HRESULT hRes = CoInitializeEx(NULL, COINIT_MULTITHREADED);
#else
HRESULT hRes = CoInitialize(NULL);
#endif
_ASSERTE(SUCCEEDED(hRes));
_Module.Init(ObjectMap, hInstance, &LIBID_EXACTACONSOLIDATIONLib);
_Module.dwThreadID = GetCurrentThreadId();
TCHAR szTokens[] = _T("-/");
int nRet = 0;
BOOL bRun = TRUE;
LPCTSTR lpszToken = FindOneOf(lpCmdLine, szTokens);
while (lpszToken != NULL)
{
if (lstrcmpi(lpszToken, _T("UnregServer"))==0)
{
_Module.UpdateRegistryFromResource(IDR_ExactaConsolidation, FALSE);
nRet = _Module.UnregisterServer(TRUE);
bRun = FALSE;
break;
}
if (lstrcmpi(lpszToken, _T("RegServer"))==0)
{
_Module.UpdateRegistryFromResource(IDR_ExactaConsolidation, TRUE);
nRet = _Module.RegisterServer(TRUE);
bRun = FALSE;
break;
}
lpszToken = FindOneOf(lpszToken, szTokens);
}
if (bRun)
{
_Module.StartMonitor();
#if _WIN32_WINNT >= 0x0400 & defined(_ATL_FREE_THREADED)
hRes = _Module.RegisterClassObjects(CLSCTX_LOCAL_SERVER,
REGCLS_MULTIPLEUSE | REGCLS_SUSPENDED);
_ASSERTE(SUCCEEDED(hRes));
hRes = CoResumeClassObjects();
#else
hRes = _Module.RegisterClassObjects(CLSCTX_LOCAL_SERVER,
REGCLS_MULTIPLEUSE);
#endif
_ASSERTE(SUCCEEDED(hRes));
MSG msg;
while (GetMessage(&msg, 0, 0, 0))
DispatchMessage(&msg);
_Module.RevokeClassObjects();
Sleep(dwPause); //wait for any threads to finish
}
}
My question is if multiple clients are connected to this COM Server does it process the requests (function calls to the com object that the com server is hosting) in a synchronous fashion?
The reason I ask is because of the following scenario:
Client A and Client B both connect to Com Server C. They both issue a request and this request involves using the COM Object to retrieve the next item (order in my case) from the database. No two clients should be allowed to have the same item so what basically happens is each item is marked as taken when it's retrieved from the database and returned to the client.
Is it sufficient in the scenario above to mark the item in the database as taken without worrying about race conditions if it's 2 clients connecting to the same COM server? If the requests are processed synchronously I would think this would be ok to just mark the item as taken.
This depends on whether the thread registering (or, rather, creating) the class objects is a Single Threaded Apartment or Multi-Threaded Apartment. See the MSDN article on the threading modes. If you initialized COM with CoInitialize(NULL) or CoInitializeEx(NULL, COINIT_APARTMENTTHREADED), you're in a STA; if you used CoInitializeEx(NULL, COINIT_MULTITHREADED) or CoInitializeEx(NULL, 0), you're in a MTA.
If you're in a MTA, COM will make multiple calls to your objects at the same time from a thread pool. In a STA, only one call will be made at a time. If you just want to avoid races, using a STA can be a reasonable approach; keep in mind that this will create a performance bottleneck, however, so for very high volume servers, or servers where requests may take a while, using a MTA with your own synchronization logic may be preferable.
Is it possible to use overlapped I/O with an anonymous pipe? CreatePipe() does not have any way of specifying FILE_FLAG_OVERLAPPED, so I assume ReadFile() will block, even if I supply an OVERLAPPED-structure.
Here is an implementation for an anonymous pipe function with the possibility to specify FILE_FLAG_OVERLAPPED:
/******************************************************************************\
* This is a part of the Microsoft Source Code Samples.
* Copyright 1995 - 1997 Microsoft Corporation.
* All rights reserved.
* This source code is only intended as a supplement to
* Microsoft Development Tools and/or WinHelp documentation.
* See these sources for detailed information regarding the
* Microsoft samples programs.
\******************************************************************************/
/*++
Copyright (c) 1997 Microsoft Corporation
Module Name:
pipeex.c
Abstract:
CreatePipe-like function that lets one or both handles be overlapped
Author:
Dave Hart Summer 1997
Revision History:
--*/
#include <windows.h>
#include <stdio.h>
static volatile long PipeSerialNumber;
BOOL
APIENTRY
MyCreatePipeEx(
OUT LPHANDLE lpReadPipe,
OUT LPHANDLE lpWritePipe,
IN LPSECURITY_ATTRIBUTES lpPipeAttributes,
IN DWORD nSize,
DWORD dwReadMode,
DWORD dwWriteMode
)
/*++
Routine Description:
The CreatePipeEx API is used to create an anonymous pipe I/O device.
Unlike CreatePipe FILE_FLAG_OVERLAPPED may be specified for one or
both handles.
Two handles to the device are created. One handle is opened for
reading and the other is opened for writing. These handles may be
used in subsequent calls to ReadFile and WriteFile to transmit data
through the pipe.
Arguments:
lpReadPipe - Returns a handle to the read side of the pipe. Data
may be read from the pipe by specifying this handle value in a
subsequent call to ReadFile.
lpWritePipe - Returns a handle to the write side of the pipe. Data
may be written to the pipe by specifying this handle value in a
subsequent call to WriteFile.
lpPipeAttributes - An optional parameter that may be used to specify
the attributes of the new pipe. If the parameter is not
specified, then the pipe is created without a security
descriptor, and the resulting handles are not inherited on
process creation. Otherwise, the optional security attributes
are used on the pipe, and the inherit handles flag effects both
pipe handles.
nSize - Supplies the requested buffer size for the pipe. This is
only a suggestion and is used by the operating system to
calculate an appropriate buffering mechanism. A value of zero
indicates that the system is to choose the default buffering
scheme.
Return Value:
TRUE - The operation was successful.
FALSE/NULL - The operation failed. Extended error status is available
using GetLastError.
--*/
{
HANDLE ReadPipeHandle, WritePipeHandle;
DWORD dwError;
UCHAR PipeNameBuffer[ MAX_PATH ];
//
// Only one valid OpenMode flag - FILE_FLAG_OVERLAPPED
//
if ((dwReadMode | dwWriteMode) & (~FILE_FLAG_OVERLAPPED)) {
SetLastError(ERROR_INVALID_PARAMETER);
return FALSE;
}
//
// Set the default timeout to 120 seconds
//
if (nSize == 0) {
nSize = 4096;
}
sprintf( PipeNameBuffer,
"\\\\.\\Pipe\\RemoteExeAnon.%08x.%08x",
GetCurrentProcessId(),
InterlockedIncrement(&PipeSerialNumber)
);
ReadPipeHandle = CreateNamedPipeA(
PipeNameBuffer,
PIPE_ACCESS_INBOUND | dwReadMode,
PIPE_TYPE_BYTE | PIPE_WAIT,
1, // Number of pipes
nSize, // Out buffer size
nSize, // In buffer size
120 * 1000, // Timeout in ms
lpPipeAttributes
);
if (! ReadPipeHandle) {
return FALSE;
}
WritePipeHandle = CreateFileA(
PipeNameBuffer,
GENERIC_WRITE,
0, // No sharing
lpPipeAttributes,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL | dwWriteMode,
NULL // Template file
);
if (INVALID_HANDLE_VALUE == WritePipeHandle) {
dwError = GetLastError();
CloseHandle( ReadPipeHandle );
SetLastError(dwError);
return FALSE;
}
*lpReadPipe = ReadPipeHandle;
*lpWritePipe = WritePipeHandle;
return( TRUE );
}
No. As explained here, anonymous pipes do not support asynchronous I/O. You need to use a named pipe. There's example code to do this on MSDN here and here.
first of all need understand - what is Anonymous Pipes and what, are exist difference between anonymous and Named Pipes at all.
really exist only single pipe type (implemented by npfs.sys). no any difference, except name, between named and anonymous pipes at all. both is only pipes.
so called anonymous pipes - this is special/random named pipes before win7 and true unnamed pipes begin from win7.
when msdn write that "anonymous pipe is one-way pipe" - this is lie. as any pipe it can be one-way or duplex. when msdn write that "Asynchronous (overlapped) read and write operations are not supported by anonymous pipes." - this is lie. of course pipes support asynchronous io. the name of pipe not affect this.
before win7 really unnamed pipes even not exist at all. CreatePipe function use Win32Pipes.%08x.%08x format for create name of "Anonymous Pipe".
static LONG PipeSerialNumber;
WCHAR name[64];
swprintf(name, L"\\Device\\NamedPipe\\Win32Pipes.%08x.%08x",
GetCurrentProcessId(), InterlockedIncrement(&PipeSerialNumber));
begin from win7 CreatePipe use another technique (relative file open) for create pipe pair - now it really anonymous.
for example code witch create pipe pair where one pipe is asynchronous and not inheritable. and another pipe is synchronous and inheritable. both pipes is duplex (support both read and write)
ULONG CreatePipeAnonymousPair7(PHANDLE phServerPipe, PHANDLE phClientPipe)
{
HANDLE hNamedPipe;
IO_STATUS_BLOCK iosb;
static UNICODE_STRING NamedPipe = RTL_CONSTANT_STRING(L"\\Device\\NamedPipe\\");
OBJECT_ATTRIBUTES oa = { sizeof(oa), 0, const_cast<PUNICODE_STRING>(&NamedPipe), OBJ_CASE_INSENSITIVE };
NTSTATUS status;
if (0 <= (status = NtOpenFile(&hNamedPipe, SYNCHRONIZE, &oa, &iosb, FILE_SHARE_VALID_FLAGS, 0)))
{
oa.RootDirectory = hNamedPipe;
static LARGE_INTEGER timeout = { 0, MINLONG };
static UNICODE_STRING empty = {};
oa.ObjectName = ∅
if (0 <= (status = ZwCreateNamedPipeFile(phServerPipe,
FILE_READ_ATTRIBUTES|FILE_READ_DATA|
FILE_WRITE_ATTRIBUTES|FILE_WRITE_DATA|
FILE_CREATE_PIPE_INSTANCE,
&oa, &iosb, FILE_SHARE_READ|FILE_SHARE_WRITE,
FILE_CREATE, 0, FILE_PIPE_BYTE_STREAM_TYPE, FILE_PIPE_BYTE_STREAM_MODE,
FILE_PIPE_QUEUE_OPERATION, 1, 0, 0, &timeout)))
{
oa.RootDirectory = *phServerPipe;
oa.Attributes = OBJ_CASE_INSENSITIVE|OBJ_INHERIT;
if (0 > (status = NtOpenFile(phClientPipe, SYNCHRONIZE|FILE_READ_ATTRIBUTES|FILE_READ_DATA|
FILE_WRITE_ATTRIBUTES|FILE_WRITE_DATA, &oa, &iosb,
FILE_SHARE_VALID_FLAGS, FILE_SYNCHRONOUS_IO_NONALERT)))
{
NtClose(oa.RootDirectory);
}
}
NtClose(hNamedPipe);
}
return RtlNtStatusToDosError(status);
}
ULONG CreatePipeAnonymousPair(PHANDLE phServerPipe, PHANDLE phClientPipe)
{
static char flag_supported = -1;
if (flag_supported < 0)
{
ULONG dwMajorVersion, dwMinorVersion;
RtlGetNtVersionNumbers(&dwMajorVersion, &dwMinorVersion, 0);
flag_supported = _WIN32_WINNT_WIN7 <= ((dwMajorVersion << 8)| dwMinorVersion);
}
if (flag_supported)
{
return CreatePipeAnonymousPair7(phServerPipe, phClientPipe);
}
static LONG PipeSerialNumber;
WCHAR name[64];
swprintf(name, L"\\\\?\\pipe\\Win32Pipes.%08x.%08x", GetCurrentProcessId(), InterlockedIncrement(&PipeSerialNumber));
HANDLE hClient, hServer = CreateNamedPipeW(name,
PIPE_ACCESS_DUPLEX|FILE_READ_DATA|FILE_WRITE_DATA|FILE_FLAG_OVERLAPPED,
PIPE_TYPE_BYTE|PIPE_READMODE_BYTE, 1, 0, 0, 0, 0);
if (hServer != INVALID_HANDLE_VALUE)
{
static SECURITY_ATTRIBUTES sa = { sizeof(sa), 0, TRUE };
hClient = CreateFileW(name, FILE_GENERIC_READ|FILE_GENERIC_WRITE,
FILE_SHARE_READ|FILE_SHARE_WRITE, &sa, OPEN_EXISTING, 0, 0);
if (hClient != INVALID_HANDLE_VALUE)
{
*phServerPipe = hServer, *phClientPipe = hClient;
return NOERROR;
}
CloseHandle(hServer);
}
return GetLastError();
}