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See the Extras section of this article.
"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman
"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne
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Hi all,
I'm working with some date formating, with local and UTC time format. At the end I've print the result to the console as follows.
cout << stLocal.wMonth << "/" << stLocal.wDay << "/" << stLocal.wYear << " " << stLocal.wHour << ":" << stLocal.wMinute << "\n";
This line of code works fine, but seems this is too dull when passing this time. Actually I want to pass that value as a string(as a single value) and try the following.
ostringstream os;
os << stLocal.wMonth << "/" << stLocal.wDay << "/" << stLocal.wYear << " " << stLocal.wHour << ":" << stLocal.wMinute << "\t";
cout << os;
The thing here the output is just a number, 0012FA3C for all values.
What's wrong with my code.
I appreciate your help all the time...
Eranga 
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please reduce the second <pre> by adding line returns in it, because you're breaking the page formatting !
BTW, have you tried to debug the code ? you could check that it's only the cout << os line that is not working properly, but that the os object contanis the correct string in it...
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Oki, I think cout << os; gives the pointer value. So I need to get the string from os, like this.
cout << os.str();
Gives the correct value. Is my conclusion is correct.
I appreciate your help all the time...
Eranga
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[added]
OMG you beat me on time! 
[/added]
Eranga Thennakoon wrote: cout << os;//0012FA3C
You're merely asking cout to print the address of the ostringstream object.
You've to do instead:
cout << os.str();
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
[my articles]
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Yep, that's what I've try pal.
I appreciate your help all the time...
Eranga
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Is it memory safe to use SendMessage(PostMessage) to pass parameters between threads?
There are two threads A and B;
// thread A want to send some message to thread B
code sample about thread A:
{<br />
char sz[] = "Hello, CodeProject";<br />
BOOL b = TRUE;<br />
SendMessage(hWnd, WM_SOMEMESSAGE, (WPARAM)sz, (LPRARM)b);<br />
}<br />
Can I write code like this in thread B to retriecve the message?
{<br />
MSG msg<br />
GetMessage(&msg, hWnd, 0, 0);<br />
char* p = (char*)(msg.wParam)<br />
BOOL b = (BOOL)(msg.lParam)<br />
cout<<p<<endl;
}
Thank you for your reply.
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Neither technique is thread safe: in both cases, sz is local to your function and will be destroyed when the function terminates. It means that in the other thread, dependings of how the threads were processed, you may access memory that has been freed.
That's what is called a 'race condition'. It depends how the two threads were processed and sometimes it will work fine and other times, it will fail.
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Cedric Moonen wrote: sz is local to your function and will be destroyed when the function terminates.
Thank you Cédric Moonen
So , if I want to use SendMessage(PostMessage) to send some more information than WPARAM and LPRAM, I should use new operator to allocate memory on the heap, and after GetMessage returned use delete to free memory?
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Yes, in that case it is safe (even if it is not beautifull  ).
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not beautiful? 
Is there some beautiful ways to send large objects between threads? How about Memory-mapped files? I think it is not beautiful too. Because after you copy some information in the memory-mapped file, you still need to tell the other thread to retrieve the information.
Thank you!
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When I said not beautifull, it is mainly because in that case your second thread will need a message loop so it is not applicable in all cases. If you have already a message loop in your second thread then it is fine.
There are, I think, better solutions but it all depends of what you want to achieve. What I do in general is having a class ta wraps the threading functionality (have a member function that will be called from the thread) and then if I need to 'exchange' information, I'll do that through class members and I use events to notify the other thread and eventually critical sections to protect the access to the shared resources.
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Cedric Moonen wrote: If you have already a message loop in your second thread then it is fine.
Yes ,one of the thread is a window thread, and the other is a worker thread, after the worker thread finishes it's working, it will Send(Post) a message with a large block of memory to the window thread.
Thank you Cédric Moonen
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Roughly speaking, usually processes need some technique to exchange data, while threads, by nature, already share data. What I mean is that you just don't need to pass messages to you thread but a bit refactoring to your design.
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
[my articles]
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Thank you!
I'll think twice before coding.
A Chinese VC++ programmer
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zengkun100 wrote: A Chinese VC++ programmer
Greetings to China.
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
[my articles]
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This isnt safe, a better word for it is dangerous. You better work with integer/enum values to singalize the state (for instance String IDs) or a global object which stores the information.
Greetings from Germany
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To achieve 1 to 1 voice communication over LAN and record the voice for storing, i think of doing:
1) use winsock to establish client server connection
2) use DirectSound api:
-at client(A) side, capture sound in buffer
-modify the sound quality
-compress the sound to mp3 or wma file using ACM and store it
beside storing, after compression i send the buffer to server(B) side and playback it so that A talk to B and B can hear it.
-and B also going above procedure to A.
-Full-duplex used allow simultaneous capture and playback.-
Question:
1) I think of using DirectShow api also but how i know my pc hv it or not? I just see DirectSound.
2) Is my step stated will work to allow voice communication over LAN and store the voice? Please point out what i miss or how should it going.
3) I see the RTC(real-time communication) api also and seem like more good, should it be better choice? Is it support the recording also?
4) I should build it as win32 application?
If out there hv any source code sample with no additional feature just basic 1 to 1 voice communication over LAN and can record voice for storing pls post up here. I want it for understanding purpose. Thnks.
modified on Monday, January 14, 2008 12:55:16 AM
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Member 4542272 wrote: 1) I think of using DirectShow api also but how i know my pc hv it or not? I just see DirectSound.
You shouldn't need DirectShow. DirectSound would be sufficient.
DirectSound (and DirectShow) are part of DirectX, which comes with
Windows XP+ and is installable on previous Windows versions.
Member 4542272 wrote: 2) Is my step stated will work to allow voice communication over LAN and store the voice? Please point out what i miss or how should it going.
Yes it will work. MP3 is not a good format for real-time voice
communication but using ACM there's a couple codecs included with
Windows that work fine.
Member 4542272 wrote: 3) I see the RTC(real-time communication) api also and seem like more good, should it be better choice? Is it support the recording also?
RTC is a protocol. It can be used for the networking portion but
you'll need to handle capturing, compressing, uncompressing, and
rendering the audio samples.
Member 4542272 wrote: 4) I should build it as win32 application?
If you want your app to run on Windows, then yes, that's a good choice.
Mark
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://www.codeproject.com/script/Forums/Images/coffee.gif)
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how can I Returns a pointer to the start of the given scanline in the bitmap’s data-bits in BYTE *
Trioum
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Can you more specific?
Are you reading from file?
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yes I am reading from the file filename.bmp
Trioum
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So you can just move the file pointer to there.
The starting of image data is specified in the BITMAPFILEHEADER's bfOffBits member.
You can use Seek API if you are using CFile (MFC), or use SetFilePointer if you are using SDK.
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I tried but failed
can you send me the pieace of code in sdk please please
Trioum
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And what was your code?
If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.
[my articles]
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