MFC, Problem with WM

Problem with WM_COPYDATA

Author	Message
Dan #1 / 6	Problem with WM_COPYDATA Hi All, Trying to communication from a worker thread to a UI thread using WM_COPYDATA. The following is the code in the worker thread: TypeDef Void* Foo; int Count = 32; CopyDataStruct cds; Foo test = new Foo[32]; { I fill in the Foo array here Quote: } cds.cbData = sizeof(Foo); cds.lpData = test; cds.dwData = Count; Use SendMessage to send the message here. In the OnCopyData method in the receiving thread is the following code: Foo test2 = (Foo*)pCopyDataStruct->lpdata; If I increment through <test2> to retreive the values I have sent the first value is correct but everything else is garbage. Where am I going wrong? Is this a limitation on WM_COPYDATA? What others ways could I get the same information in the array across without using multiple messages? Thanks, Dan Pearce
Mon, 02 Jun 2003 13:19:16 GMT

Thomas Moone #2 / 6	Problem with WM_COPYDATA One apparent problem is that cdw.cbData is set to 4 (sizeof(Foo)) when it should be set to 32 (Count). You have effectively told WM_COPYDATA that you only want to transfer 4 bytes of data. Keep in mind that the data is copied from one address space to another. The pointer you have provided (lpData) is not passed across. Rather that data pointed to by lpData is copied to the receiving application's address space. The amount of data copied is determined by cbData. The dwData member is typically used to transfer a small amount of data, fo example a "hint" of what type of data is being passed in lpData. TFM3 Note: Spam-resistant e-mail address Quote: > Hi All, > Trying to communication from a worker thread to a UI thread using > WM_COPYDATA. The following is the code in the worker thread: > TypeDef Void* Foo; > int Count = 32; > CopyDataStruct cds; > Foo test = new Foo[32]; > { > I fill in the Foo array here > } > cds.cbData = sizeof(Foo); > cds.lpData = test; > cds.dwData = Count; > Use SendMessage to send the message here. > In the OnCopyData method in the receiving thread is the following code: > Foo test2 = (Foo*)pCopyDataStruct->lpdata; > If I increment through <test2> to retreive the values I have sent the first > value is correct but everything else is garbage. Where am I going wrong? > Is this a limitation on WM_COPYDATA? What others ways could I get the same > information in the array across without using multiple messages? > Thanks, > Dan Pearce
Mon, 02 Jun 2003 13:48:40 GMT

Don Grasberge #3 / 6	Problem with WM_COPYDATA If the worker thread and UI thread are in the same process, there is no reason to use WM_COPYDATA at all. Inside a process, you can use WM_APP + x (or a registered message) and pass a pointer in WPARAM or LPARAM. Quote: >Hi All, >Trying to communication from a worker thread to a UI thread using >WM_COPYDATA. The following is the code in the worker thread: >TypeDef Void* Foo; >int Count = 32; >CopyDataStruct cds; >Foo test = new Foo[32]; >{ >I fill in the Foo array here >} >cds.cbData = sizeof(Foo); >cds.lpData = test; >cds.dwData = Count; >Use SendMessage to send the message here. >In the OnCopyData method in the receiving thread is the following code: >Foo test2 = (Foo*)pCopyDataStruct->lpdata; >If I increment through <test2> to retreive the values I have sent the first >value is correct but everything else is garbage. Where am I going wrong? >Is this a limitation on WM_COPYDATA? What others ways could I get the same >information in the array across without using multiple messages? >Thanks, >Dan Pearce Don Grasberger (remove --- from address to e-mail)
Mon, 02 Jun 2003 22:43:30 GMT

Bob Moor #4 / 6	Problem with WM_COPYDATA Quote: >If the worker thread and UI thread are in the same process, there is >no reason to use WM_COPYDATA at all. Inside a process, you can use >WM_APP + x (or a registered message) and pass a pointer in WPARAM or >LPARAM. He'd still have to wrap a critical section around any access though, if using a shared area. -- Bob Moore [WinSDK MVP] http://www.mooremvp.freeserve.co.uk/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Do not reply via email unless specifically requested to do so. Unsolicited email is NOT welcome and will go unanswered. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tue, 03 Jun 2003 06:14:00 GMT

Don Grasberge #5 / 6	Problem with WM_COPYDATA On Thu, 14 Dec 2000 22:14:00 +0000, Bob Moore Quote: >>If the worker thread and UI thread are in the same process, there is >>no reason to use WM_COPYDATA at all. Inside a process, you can use >>WM_APP + x (or a registered message) and pass a pointer in WPARAM or >>LPARAM. >He'd still have to wrap a critical section around any access though, >if using a shared area. Well, not really. SendMessage() won't return until the UI thread has processed the message, so there's no synchronization issues with the thread sending the message. If there are more than those 2 threads accessing the object, then something like a CS will be necessary. Of course, if Dan wants to use PostMessage(), more complexities arise concerning the lifetime of the pointed to object as well as synchronization. Don Grasberger (remove --- from address to e-mail)
Tue, 03 Jun 2003 22:24:22 GMT

Bob Moor #6 / 6	Problem with WM_COPYDATA Quote: >SendMessage() won't return until the UI thread has >processed the message, so there's no synchronization issues with the >thread sending the message Duh. Must engage brain before posting. Sorry. -- Bob Moore [WinSDK MVP] http://www.mooremvp.freeserve.co.uk/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Do not reply via email unless specifically requested to do so. Unsolicited email is NOT welcome and will go unanswered. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Wed, 04 Jun 2003 07:13:40 GMT

Page 1 of 1

[ 6 post ]