C / C++ / MFC

Matthew Faithfull3-Jul-07 6:18

Matthew Faithfull

3-Jul-07 6:18

Strictly speaking you can't do what you've asked about in ordinary C++. Only using .NET reflection, but the chances are that the set of types is not really 'unknown' at compile time it's just that you don't want to have to write much or any new code when you change that set?
If that's true you have a chance. Consider using templates e.g.

<br />
template< typename Ti, typename To ><br />
Convert( Ti* pIn, To* pOut )<br />
{<br />
//Conversion code would go here but it's going to have to make<br />
//some assumptions about the types in order to work<br />
//which means it won't work with just anything :(<br />
}<br />

In the end you'll probably have to provide lots of type specific template overrides like

<br />
Convert( double* pIn, char* pOut )<br />
{<br />
//a call to printf may occur somewhere in here :omg:<br />
}<br />

which is not much better than where you started out.
If you've hit this problem and most of us have D'Oh! | :doh:

then you probably need to go back and look at your design with a 'what is this really try to achieve' hat on Smile | :)

Nothing is exactly what it seems but everything with seems can be unpicked.

led mike3-Jul-07 6:22

3-Jul-07 6:22

Is there some reason a template function won't work?

Nuxser3-Jul-07 15:59

Nuxser

3-Jul-07 15:59

Must admit that I am not sure if I understood your problem. But according to I interpreted,

when you talk about converting types, you imply the concept of "casting" (Casting one data type to be another). With respect to your given pseudocode, I guess you want the type pointed by "out" to be treated as type "in" so that the assignment can work nicely. Thus you want to cast the type pointed by "out" to be as type pointed by "in".

If that understanding is true ...

You need to delve in to understanding how "type casting" works in C++. A nice tutorial -

http://www.cplusplus.com/doc/tutorial/typecasting.html

I like it as they quickly goes into how type casting with classes/structs and pointer to those needs to be carefull than for basic types.

Also for completeness, even in the case of template, it will eventually boils down to type casting as soon as the type is provided for the templates. So if you have defined two template types being them as type independent, during the runtime they are associated with provided types, hence the game boils down to type conversion between those two types.

So understanding the "type casting" will enlighten you about how to do it and if done will it be meaning full.

And for the conclusion, you will see that even though it is not a runtime error some casting will not be meaningfull or result in an wanted manner. There is no such freedom as converting ANY type to ANY type. Its not meaningfully possible (such as converting a student info class to a integer number).

Hope it can help.

Regards

get Distinguished Email id from GAL

Nuxser3-Jul-07 16:17

Nuxser

3-Jul-07 16:17

Just in case I wan't clear about it - I agree with Matthew Faithfull.

And interestingly enough, quick Googling shows that there seems to be few implementation of Reflection in C++.

http://www.extreme.indiana.edu/reflcpp/

Hey, Its C++, It can do everything ... Wink | ;)

Ganesh_T3-Jul-07 5:47

Ganesh_T

3-Jul-07 5:47

I am developing an app which will fetch addresses from the GAL. I need the email address of the users. I get those in the exchnage format (Electronic mail format)

for eg. /c=US/a=att/p=Microsoft/o=Finance/ou=Purchasing/s=Furthur/g=Joe

and need those in

I am using Exchange SDk to fetch the contacts from GAL.

for e.g : xyz@fgh.com

"A winner is not one who never fails...but the one who never quits"

Thread syncronization Win32

Alex Cutovoi3-Jul-07 5:26

3-Jul-07 5:26

Hi for all

I've created a program that triggers some threads.
I don't get to use the syncronization. Some threads are triggered before others.

I created a class called ResourceObject. This is a simple class with a boolean value and a CRITICAL_SECTION value:

<br />
ResourceObject::ResourceObject()<br />
{<br />
   m_bLocked = false;<br />
   InitializeCriticalSection(&m_ResourceSection);<br />
}<br />
ResourceObject::~ResourceObject()<br />
{<br />
   DeleteCriticalSection(&m_ResourceSection);<br />
}<br />
<br />
void ResourceObject::LockResource(unsigned int uiTimeToSleep)<br />
{<br />
   EnterCriticalSection(&m_ResourceSection);<br />
      m_bLocked = true;<br />
	  Sleep(uiTimeToSleep);<br />
   LeaveCriticalSection(&m_ResourceSection);<br />
}<br />
<br />
void ResourceObject::ReleaseResource()<br />
{<br />
   EnterCriticalSection(&m_ResourceSection);<br />
      if(m_bLocked)m_bLocked = false;<br />
   LeaveCriticalSection(&m_ResourceSection);<br />
}<br />

In another class I have this struct that have a pointer to a ResourceObject

<br />
typedef struct LineText<br />
{<br />
   FloatText * Line;<br />
   bool bShow;<br />
   float fTimeWait;<br />
   ResourceObject * resource;<br />
}TextLine;<br />

In the same class I have the following codes:
- the first is how I create a thread;

<br />
	  idThread[m_iLineCount] = CreateThread(NULL, 0, Helper::TextThread, (void*)&Lines[m_iLineCount], CREATE_SUSPENDED, NULL);<br />

- the second is the thread:

<br />
DWORD WINAPI Helper::TextThread(void * vData)<br />
{<br />
   LineText * temp = (LineText *)vData;<br />
   temp->resource->LockResource(2000);<br />
   temp->bShow = true;<br />
   temp->resource->ReleaseResource();<br />
   return 0;<br />
}<br />

- the third is when I Resume the threads and show some text;

<br />
void Helper::ShowImages()<br />
{<br />
   for(int i = 0 ; i < m_iLineCount ; i++)<br />
   {<br />
      ResumeThread(idThread[i]);<br />
      if(Lines[i].bShow)Lines[i].Line->PrintText();<br />
   }<br />
}<br />

The threads must have to follow the sequence in that they are resumed, but they don't. Even the first thread is started with the resource, it is not the first to show the text.
Anyone can help me to solve this problem?

Thanks

Matthew Faithfull3-Jul-07 6:08

Matthew Faithfull

3-Jul-07 6:08

If you want multiple threads to pass through a single function in predetermined order you're going to need a master thread to manage them and each one will have to wait to be signalled. I would add an Event to your one-per-thread structure, have each worker wait on its event and then have the main thread signal each event and wait for it to be reset by the signalled thread before singalling the next one. Have the worker reset its event after it has executed your controlled function. I can't see why you'd want to do this as it seems to negate any real benefit of threading but it's your project Smile | :)

Nothing is exactly what it seems but everything with seems can be unpicked.

led mike3-Jul-07 6:19

3-Jul-07 6:19

Not sure I understand, you want to use multiple threads to perform sequential operations? Confused | :confused:

Alex Cutovoi3-Jul-07 6:46

3-Jul-07 6:46

More or less.

Like you've seen in my code, I have a thread that receives a structure. I have about 10 structures that have different values of text. And I need to show these texts in some moment. At the moment I need to show these values sequentially, but in any other time I would need to show these texts in any other sequence. Just like that, I create the ResourceObject class. I have a pointer to an object of this type in my structs. The first started thread access this object and the others wait.
I called the threads sequentially thinking that the calling order have been respected, with one thread at time access the resource and release it.

led mike3-Jul-07 8:26

3-Jul-07 8:26

Alex Cutovoi wrote:
More or less.

What? You don't know? How are we supposed to help you if you can't specify exactly what your requirements are.

Alex Cutovoi wrote:
I need to show these texts in some moment.

I have no idea what that means. I am not familiar with "Moment Based Processing".

Look the bottom line is that trying to use multiple threads to execute sequential operations is like putting a square peg in a round hole. It doesn't seem your approach is the appropriate solution to your problem, whatever that is.

Alex Cutovoi5-Jul-07 6:53

5-Jul-07 6:53

Look, I'll explain better.

What I really want is the threads access the resource in the order that they started. What that is not occur at the moment.
Example, I have 4 thread(thread1, thread2, thread3, thread4).
If I start the threads in a sequence like thread4, thread2, thread1, thread3, the threads must access the resource in this sequence. Even with the CriticalSection, this is not occur. The threads access the resource in an arbitrary order. The only thing that works is that the resource is accessed for one thread at a time.
I've tried to put a mutex to guarantee this type of access but I didn't get the expected results.
This is EXACTLY what I want.

led mike5-Jul-07 7:17

5-Jul-07 7:17

Alex Cutovoi wrote:
Look, I'll explain better.

Alex Cutovoi wrote:
This is EXACTLY what I want.

No that is not an explanation of the "requirements". What "you want" has nothing to do with what "the requirements" are. Do you have requirements for sequential operations? Yes or no? If yes then threads are not an appropriate solution even if you "want" to use threads.

Note: You should never "want" to use threads. They should be used as a last resort, only to satisfy specific requirements.

Alex Cutovoi5-Jul-07 11:29