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This is a pipe-like class written in standard c.Read() and Write()can critically access the inner data section.When there is no data to be read,Read() will block and wait for Write() to write some data to the pipe.Only when
it reads datas does Read() return.
The inner data section are block structures using new operator to calloc units.
/*--------------------------------------------------------
* Pipe.h: interface for the CPipe class.
*
* 2003 DJ Express Studio All rights reserved
*------------------------------------------------------*/
#ifndef _PIPE_H_
#define _PIPE_H_
/* CRITICAL_SECTION was defined in winbase.h
* possibly not compatible with stdafx.h */
#include <Winbase.h>
#define BL_ERROR -1
#define BL_OK 0
struct Block
{
PBYTE pData;
int data_len;
Block* next;
Block* pre;
};
class CPipe
{
private:
CRITICAL_SECTION cs;
HANDLE hEvent;
Block* pBuffer;
Block* pHead;
Block* pTail;
int pointer;
int nBlocks;
public:
void CPipe::EmptyPipe();
int Write(BYTE* buf, int len, int* write);
int Read(BYTE* buf, int len, int* read);
bool IsEmpty();
CPipe()
{
pHead=NULL;
pTail=NULL;
nBlocks=0;
pointer=0;
InitializeCriticalSection(&cs);
hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);
};
virtual ~CPipe()
{
CloseHandle(hEvent);
DeleteCriticalSection (&cs);
};
};
#endif
/*---------------------------------------------------
* Pipe.cpp: implementation of the CPipe class.
*
* 2003 DJ Express Studio All rights reserved
*-------------------------------------------------*/
#include "Pipe.h"
int CPipe::Write(BYTE* buf,int len,int* write)
{
Block* pTem;
if(!buf || len <=0 )
goto error;
pTem=NULL;
if(!(pTem=new Block))
goto error;
if(!(pTem->pData=new BYTE[len]))
goto error;
else
{
/* lock the pipe */
EnterCriticalSection(&cs);
pTem->data_len=len;
memcpy(pTem->pData,buf,len);
nBlocks++;
pTem->pre=NULL;
if(pHead==NULL)
pTail=pTem;
else pHead->pre=pTem;
pHead=pTem;
/* unlock the pipe */
LeaveCriticalSection(&cs);
}
*write=len;
SetEvent(hEvent);
return BL_OK;
error:
*write=0;
return BL_ERROR;
}
int CPipe::Read(BYTE* buf,int len,int* read)
{
int total;
Block* tem;
if(!buf || len <= 0 )
goto error;
if( nBlocks <= 0 )
{
WaitForSingleObject(hEvent,INFINITE);
ResetEvent(hEvent);
}
/* lock the pipe */
EnterCriticalSection(&cs);
if(len < pTail->data_len )
{
pointer = len;
memcpy(buf,pTail->pData,len);
*read = len;
}
else
{
total=0;
tem=NULL;
while(len-total)
{
if(len-total >= pTail->data_len )
{
memcpy(buf+total,pTail->pData,pTail->data_len);
total += pTail->data_len;
tem = pTail;
pTail=pTail->pre;
pointer = 0;
delete []tem->pData;
delete tem;
}
else
{
memcpy(buf+total,pTail->pData,len-total);
total = len;
pointer = len - total;
break;
}
if(--nBlocks <= 0)
{
pTail=NULL;
pHead=NULL;
break;
}
}
*read = total;
}
/* unlock the pipe */
LeaveCriticalSection(&cs);
return BL_OK;
error:
*read=0;
return BL_ERROR;
}
bool CPipe::IsEmpty()
{
return nBlocks > 0 ? false : true ;
}
void CPipe::EmptyPipe()
{
Block* tem;
if(nBlocks <= 0)
return;
/* lock the pipe */
EnterCriticalSection(&cs);
while(nBlocks--)
{
tem=pTail;
pTail=pTail->pre;
delete []tem->pData;
delete tem;
tem=NULL;
}
pHead=pTail=NULL;
/* unlock the pipe */
LeaveCriticalSection(&cs);
}
/*---------------------------------------------------------*/
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hi,
i have a program written that reads a flat text tab separated file using ODBC ,the database
contains various number and text columns.Using VC++ classwizard, i created my CRecordset derived class and the type of member-variables corresponding to the text columns is CString .My problem is that i am able to connect and open the database and fetch all the records i want by fetching the recordsets in loop, but i couldn't read all but first text columns and when i try to read them ,it gives exception.All other columns of type number are read correctly for all records.Surprisingly the first text column field is also read correctly but the subsequent fields are not.
While debugging ,when i see the value of these string member-variables of the recordset ,it says CXX0033:ERROR: error in OMF type information.
Can anybody give some suggestions.
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Simply wait. Be sure that if someone has a solution, it will post it here. But do not be too insistant, this usually is the best way to get no answer. 
~RaGE();
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Hi,
In a dialog based application, i have a AfxBeginThread function
to write some data to make a multi-session CD.
between the first session and the second session i need the thread wait a some seconds until the lead-out of first session be written.
Anyone can point me which wait function is useful for this purpose? For example,
Sleep(100); or
WaitForSingleObject(pThread->m_hThread, 100)
or others.
Thanks in advance!
chen
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If you just want to wait a number of seconds, use Sleep
If you want to wait on an event that is triggered from another thread, use CreateEvent and then WaitForSingleObject.
If you want to wait on another thread to finnish use WaitForSingleObject(pThread->m_hThread, INFINITE)
Magnus
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If you just want to pause for a while, use Sleep().
Your second suggestion is for waiting for the thread object to be signalled, which it is when the thread completes execution (i.e. returns from the thread function, or calls ExitThread). In the code you've written, the call to WaitForSingleObject will return WAIT_OBJECT_0 if the thread exits before the 100ms delay is up, or WAIT_TIMEOUT if the 100ms delay expires first.
Typically you would only wait for a thread if that thread is doing something blocking that you don't want to run on the current thread. I haven't found a way, for example, of setting a timeout value for the InternetConnect function, so I launch another thread whose sole job is calling InternetConnect, then I wait on the thread handle for the desired timeout period. If the thread isn't signalled within the timeout, I assume it's going to fail and shut down the WinInet session.
Normally you'd never wait on your own thread handle, unless you're trying to use a function that requires a wait handle, but you actually want different behaviour. For example, I've needed to be able to call GetMessage with a timeout, but no such function exists. I had to call MsgWaitForMultipleObjects, but that requires at least one wait handle.
I would question whether you should be waiting: it's not really an exact science - you'll get some situations where your wait isn't long enough, due to race conditions. Is there no way to find out when the first session has been written?
--
Mike Dimmick
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Hi, Magnus and Mike,
Thanks for reply.
I have try to the following to methods in the loop
for(session=1; session<=2; session++)
{
....
....
here a command will tell the cd-driver, the first session data finished
and then the driver write the leadout datd (now i need the thread do nothing until the leadout finished) ...
Method_1 or Method_2
}
Method_1:
while(ts->m_CD.test_unit_ready() != 1) //unit not ready
Sleep(100);
Method_2:
while(ses != 2)
{
if(WAIT_OBJECT_0 == WaitForSingleObject(ts->pThread->m_hThread, 100))
{
ResetEvent(ts->pThread->m_hThread);
}
if(ts->m_CD.test_unit_ready() == 1)
{
SetEvent(ts->pThread->m_hThread);
break;
}
}
It seems both method cannot work.
any ideas?
chen
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Why cant Method_1 work?
If you cant tell the CD to call you back when its finnished, then you will have to do polling.
Magnus
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Hi,
I have to develop some software wich will use the command line for input, after that the GUI will be shown with the information provided in the command line already displayed (in textBoxes etc.).
Can someone tell me how to do this?
Thank you in advance
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Derive your own class from CCommandLineInfo. THen override ParseParam to parse the command line arguments. In your applications InitInstance write
// Parse command line for standard shell commands, DDE, file open
CYourCommandLineInfo cmdInfo;
ParseCommandLine(cmdInfo);
After that, you have the information in member variables of cmdInfo that you must have created. Or perhaps within ParseParam you could have stored the information wherever you want..
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If you are using MFC, check out the CCommandLineInfo class, or CWinApp::m_lpCmdLine. Otherwise, the command-line arguments come to you in the third parameter of WinMain(), or the second parameter of main().
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I have a document object with , say an array of 100 integers.
I want to have 2 different displays of this data: 1 textual and
1 graphical.
To my understanding, i have to create 2 views one for each, say
CTextView and CGraphView. It is also obvious that i must have an MDI application.
My question is this:
1. DO i have to have 2 different document templates (say m_pDocTemplate1, m_pDocTemplate2 with the *doc and *frame classes same, but different views)? Or
2. if i have only one document template, how do i connect it with both views?
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giorgos wrote:
DO i have to have 2 different document templates (say m_pDocTemplate1, m_pDocTemplate2 with the *doc and *frame classes same, but different views)?
No. You could, but it's not necessary. If you do this, I think you'll end up with two options in the new document box that pops up when you've got multiple doc types (I'm not sure about this, but I think it's right).
There's a good tutorial on switching between multiple view here[^].
Hope this helps,
Ryan "Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"
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1. So.. you suggest that i have only one document template, associate it with one of the two views (randomly choose one?) and switch views according to needs?
2. The document object supports a linked list of different view objects if i want to iterate between them?
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giorgos wrote:
So.. you suggest that i have only one document template, associate it with one of the two views (randomly choose one?) and switch views according to needs?
Yes. I have done this and it works well. Associate it with the view that you want to appear on startup.
giorgos wrote:
The document object supports a linked list of different view objects if i want to iterate between them?
I'm not sure what you're asking here... Do you want to elaborate a bit?
Ryan "Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"
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In each document object i can use GetFirstViewPosition, and GetNextView functions to iterate between the open views. I wonder, if this will work if i have for example as 1st view a CAView, and as 2nd View a CBView.
But i think that it should work with proper checking for example:
POSITION pos = GetFirstViewPosition();
while (pos != NULL)
{
CView* pView = GetNextView(pos);
if (pView->IsKindOf(RUNTIME_CLASS(CAView))) { ... }
else if (pView->IsKindOf(RUNTIME_CLASS(CBView))){ ... }
}
Thx you veru much for your valuable help!
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Yes, that will work. No problem at all 
Ryan "Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"
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I realize that the following line of code calculates the absolute value of a, but why would you want to do this in a program? 
<br />
<br />
#define ABS(a) ( (a) < 0 ? -(a) : (a) ) <br />
<br />
Thanks, Dave
VC++ 6.0
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There are many reasons to use it. One is finding the distance between two values (not the difference, just the magnitude of the difference), and there are many others. There are lots of mathematical solutions that require finding the absolute value of a number.
Ryan "Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"
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do what? Using this macro, or using ABS?
a) using a macro: for C sources that don't know of templates, this was the only way to define abs once, without having to redefine it for every type you possibly need.
b) calculating ABS:
one is float comparison, due to round off errors, should usually be done with an eps, e.g. fabs(b-a) < eps. If you have an array of samples (both positive and negative), and you want to normalize them (so they fit e.g. into a (-1, +1) range), you need to find the highest absolute value in the samples.
reasons are many...
"Der Geist des Kriegers ist erwacht / Ich hab die Macht" StS
sighist | Agile Programming | doxygen
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I'm still a bit confused on the use of ABS ( ), I'm going to have to read up on it some more. Hopefully it'll become more clear in time.
Thanks guys
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 I'm working on a project which is Single Document-MFC.
I'm learning database(ODBC) programing vith visual C++ 6.0.
I want to enter a numeric value into an EditBox.
Then this value should be stored in *.mdb table as Long Integer.
I chose catagory as value and variable type as long for EditBox from class wizard.
But I could not write any code for it.
please,help me !
emroz
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Emre Zorlu wrote:
But I could not write any code for it.
What do you mean by it? This is the second time you're asking this question. Don't you think you should provide more details?
// Afterall, I realized that even my comment lines have bugs
When one cannot invent, one must at least improve (in bed).-My latest fortune cookie
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At a very high level:
1) Get the text from the edit box
2) Validate it
3) Create a DAO object and connect to your database
4) Call the Recordset's AddNew or Update to insert the data
Which of these actions do you need more help with?
I'm going to live forever or die trying!
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