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not insane yet! wrote: what's the use of this in a code of programs?
i'm just asking because it was used in the code of magic square..
Your question is not clear!
Are you asking about this keyword?
this pointer is a pointer that is accessible within member functions (that are not static) of a class. It denotes the object for which the member function was called.
Nibu thomas
Software Developer
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this is legal only in a member function, and is a pointer to the object that the method is being called on.
You don't see it a whole lot in C++, however for some reason in C#, it seems to be the convention to use this. when accessing member variables.
--Mike--
Visual C++ MVP 
LINKS~! Ericahist | NEW!! PimpFish | CP SearchBar v3.0 | C++ Forum FAQ
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 what is the use of #include<vecto>? thanks
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The #include directive tells the preprocessor to treat the contents of a specified file as if those contents had appeared in the source program at the point where the directive appears. You can organize constant and macro definitions into include files and then use #include directives to add these definitions to any source file. Include files are also useful for incorporating declarations of external variables and complex data types. You need to define and name the types only once in an include file created for that purpose.
Look here[^] for more details.
Nibu thomas
Software Developer
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Add in previous msg
The main advantage of #include is you can use one code in many programe without copying every time.
Regards,
Divyang Mithaiwala
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hi everyone
I have a problem in this code. I have to write a program that reverses a given file that is it will start reading the first half of the file, and continue to read the second half and replacing it with the reversed first half. It will end the operation by going to the beginning of the file and filling the first half with the reversed second half
I am having problem with reversing the second half and filling it in the first half's position (the second part of the question)
following is what i have done till now
any help would be greatly appreciated!!
thanks for your time!
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
int main(){
int fh;
long pos; /* Position of file pointer */
char buffer[10];
char *d = new char[10];
char buffer1[10];
int a,b,end,middle,i,j,p,count,m;
fh = open("abf.txt", O_RDONLY,0);
/* Seek the beginning of the file: */
pos = lseek( fh, 0L, 0);
if( pos == -1L )
perror( "_lseek to beginning failed" );
else
printf( "Position for beginning of file seek = %ld\n", pos );
end = lseek( fh, 0L, 2 ); /*end of the file*/
if( end == -1L )
perror( "_lseek to end position failed" );
else
printf( "Position for end position seek = %ld\n", end );
middle = end/2;
printf("middle of the file is:%d\n",middle);
for(i=0;i
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Can you not read the input file into a buffer, reverse the buffer (e.g., strrev()), and then write it to the output file?
"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain
"There is no death, only a change of worlds." - Native American Proverb
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here's the problem......at any given time only half of the file can be in memory and the other part in buffer, the buffer already has the first half, all it has to do is overwrite it with the reversed second half but instead the pgm is just overwriting it with the second half not the reversed second half
Thanks!
char buffer[10];
char *d = new char[10];
fh = open("abf.txt", O_RDONLY,0); /* Seek the beginning of the file: */
pos = lseek( fh, 0L, 0);
end = lseek( fh, 0L, 2 ); /*end of the file*/
middle = end/2;
printf("middle of the file is:%d\n",middle);
for(i=0;i {
p=lseek(fh,0L,0);
read(fh,buffer,middle);
printf("character read iin buffer is %c\n", buffer[i]);
}
count=lseek(fh,middle,0);
printf("buffer's characters are %c,%c,%c\n",buffer[0],buffer[1],buffer[2]);
i=2,j=0;
for(j=0;j
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ashira khera wrote: ...only half of the file can be in memory and the other part in buffer...
Huh? Where else could the buffer reside if not in memory?
While it obviously wouldn't be the most efficient, how about using two variables: one to start at the beginning of the file, and the other to start at the end of the file? Read a character into each, swap them, write them back to disk, advance the two variables until they meet in the middle.
Another idea is something like:
void main( void )
{
char szBuffer[] = "ABCDEFGHIJKLMNOPQRS";
char *psTemp;
int x,
y;
psTemp = new char[strlen(szBuffer) / 2];
for (x = 0; x < 10; x++)
psTemp[x] = szBuffer[x];
for (y = 0, x = strlen(szBuffer) - 1; x >= strlen(szBuffer) / 2; x--, y++)
{
char c = szBuffer[x];
szBuffer[x] = psTemp[y];
psTemp[y] = c;
}
for (x = 0; x < strlen(szBuffer) / 2; x++)
szBuffer[x] = psTemp[x];
}
"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain
"There is no death, only a change of worlds." - Native American Proverb
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I have a dialog-based MFC application. I create a prop sheet, add some pages to it, and display it. Everything works fine at first, but if I move focus away from the dialog (like alt-tabbing to another window or clicking on another window), if I try to view my application again it hangs. However, it will ONLY hang if I interact with the prop sheet (tab control) window. I play around all I want with dialog controls that aren't in the prop sheet or its prop pages, but the minute I touch anything having to do with the prop sheet, the dialog will hang in the manner I just described.
Some other random things I've noticed:
1) If I do anything with the prop sheet (even something as simple as switch tabs), then move focus back to the main dialog by clicking one of the non-propsheet controls, the program will still hang when it gets focus back.
2) The program works perfectly fine while as long as it has focus. It's just when I switch to another window and then return that it hangs.
3) If I hit break in VC++6 while the program is hung, 99% of the time the message that my window is attempting to handle is WM_ACTIVATE (surprise surprise).
Here's my main dialog's OnInitDialog function:
<br />
m_PropSheet = new CPropertySheet("Project Manager");<br />
<br />
m_ThreadProperties = new ThreadPropertiesPage;<br />
m_PropSheet->AddPage(m_ThreadProperties);<br />
<br />
m_TestSpec = new TestSpecificationPage;<br />
m_PropSheet->AddPage(m_TestSpec);<br />
<br />
m_MapProts = new MapPrototypes;<br />
m_PropSheet->AddPage(m_MapProts);<br />
<br />
m_PersistPage = new PersistPage;<br />
m_PropSheet->AddPage(m_PersistPage);<br />
<br />
m_ProjViewPage = new ProjectViewPage;<br />
m_PropSheet->AddPage(m_ProjViewPage);<br />
m_ProjViewPage->SetPMDlg(this);<br />
<br />
m_PropSheet->Create(this,WS_CHILD,NULL);<br />
<br />
m_PropSheet->SetWindowPos(NULL,10,27, 750,300,NULL); <br />
m_PropSheet->ShowWindow(TRUE);<br />
Nothin' much there.
Thanks much for your help.
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Well, I've found that the dialog WILL in fact refresh itself if there's something new to display. For instance, if I'm debugging in visual studio, and I insert a breakpoint before a statement that does something to one of the controls in a property page (like,say, add a string to a listbox), the dialog refreshes itself without any problems. But if I'm debugging and I look at my source code and then try to look back at the window, I get the hang I was talking about before.
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Hello. My name is Vegas and I am in dire need for help in a college programming class I have called File Structures in C++. I am having alot of trouble with this class and need it to graduate this semester. I was looking for a tutor in the Bay Area in California. I will pay per hour or per session. THanks alot for your time.
please email me at totyt4wrds@yahoo.com
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I have not lived there for years, but if you post a code snippit here and what you do not understand, then someone may explane it to you.
Peaple here will not do your home work for you, but given a piece of code and an explination of what you do not understand, they will usualy give you an answer.
Good luck!
INTP
Every thing is relative...
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I will say right up front that I am very new to C++. What I am trying to do is to take a year that is input and make two new variables out of that year. One variable being the century information and the other variable being the year information. For instance, the year 1999 would produce two variables...one that was equal to 19 and the other would be equal to 99. Any thoughts on how to declare/initiat these two new variables would be greatly appreciated.
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Using integers the century is the entered date divided by one hundred, and the year is the entered date minus the century times one hundred. The algorithm is the same no matter what programming language is used.
You may be right
I may be crazy
-- Billy Joel --
Within you lies the power for good - Use it!
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Thanks for the help guys. I guess I got it so stuck in my mind that there was a function to do this that I never stopped long enough to actually think of a mathmatical way to do it.
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Hi! Can anyone tell me what are the advantages in using a .dll instead of a .lib file containing exactly the same functions defintions? For example if I statically link myLib.lib and load-time link myDll.dll (using myDll.lib), they both load when my client executable does... So why is it better to use dlls? Thanks in advance!
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.lib, pros:
* Easier distribution - less files
* Quality ensurance - you get what you've linked
* You can't (easily) intercept function calls between exe and library
* Fast load time - no need for the loader to do extra passes
.lib, cons:
* Exe is bloated
* Not shareable between programs
* Cannot contain resources (I think... :~)
.dll, pros:
* Keeps exe size down
* Easier bug fix management - just fix the dll and replace it
* May be shared between different programs
.dll, cons:
* If several DLLs exist on the system - which one is loaded?
* Easy to intercept by malicious software - it's easy to put a fake layer between exe and dll
* Increases load time for program, as the loader has to do more work
Those are a few points that comes to mind.
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What can I say Sigvardsson is right, but he should have included that you may need to include some DLLs in the install software. Ocassionaly some one asks why their progam works on one machine and not anouther, the answer is usualy because they did not include the required DLL in the install program. If you want your users to be able to just copy the EXE and have it run, then you need to staticaly link the libraries (.libs) with the program. If you know that all the DLLs are standard (on all systems) then you do not need to staticaly link them.
The main advantage of using a DLL is that if there is a problem with it, it is their problem. The main disadvantage of using a DLL is that a problem in an updated version may affect any program depending on it. Of course the same thing applies to ActiveX controls, which are just a specalised version of a DLL.
INTP
Every thing is relative...
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Depending on how they are linked, DLLs can cause problems with such things as memory allocations. When a DLL is linked to CRTL statically, then it will use a different heap than your program. Or if the DLL is linked dynamically to a different version of CRTL then there will be problems.
Also, DLLs actually increase blot for most programs instead of decrease it. When working with LIB files, compiliation modules that are not required will not be linked into the EXE. However, with a DLL, if you EXE only needs a small portion of the code in the DLL, then the DLL version will be larger.
If you aren't having to modify the DLL a lot, using a DLL will improve link times since the code in the DLL won't need to be relinked everytime you rebuild the EXE.
If you have more than one EXE that uses the code, then in the long run, a DLL might reduce the total distribution since since each EXE doesn't contain a copy of the same code.
With many CPP classes, they will fail to operate properly if they are defined in a DLL and used in the EXE. Often the problem is with global variables that aren't properly exported and thus any code in the EXE will access the wrong global variable. With was a problem with the VC6 version of std::map.
There are more issues, but that I what I could think of off the top of my head.
Tim Smith
I'm going to patent thought. I have yet to see any prior art.
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I have an openGL window within an MFC dialog. I've connected to MSAccess as my DB where i pick coordinates which i use to draw GL_LINES and GL_QUADS.
I've checked out my code and it seems to be working correctly but nothing shows on the GLWindow. Wne i hardcode values ... it shows sometimes and other times it doesn't. Might anyone know what i'm doing wrong here?
Any help would be highly appreciated...
My code for connecting and drawing is as follows:
<br />
<br />
<br />
HRESULT hr;<br />
CoInitialize(NULL);<br />
<br />
try{<br />
hr = cnSURMPtr2.CreateInstance(__uuidof(ADODB::Connection));<br />
if (FAILED(hr))<br />
{<br />
throw _com_error(hr);<br />
}<br />
<br />
hr = rsObjectsPtr.CreateInstance(__uuidof(ADODB::Recordset));<br />
if (FAILED(hr))<br />
{<br />
throw _com_error(hr);<br />
}<br />
<br />
cnSURMPtr2->CursorLocation = ADODB::adUseClient;<br />
<br />
_bstr_t dbLocation(L"");<br />
dbLocation = (L".\\SURM.mdb");<br />
<br />
cnSURMPtr2->Open("Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+ dbLocation +";Persist Security Info=False","","",ADODB::adConnectUnspecified);<br />
<br />
rsObjectsPtr->Open("SELECT * from Objects", cnSURMPtr2.GetInterfacePtr(),<br />
ADODB::adOpenDynamic, ADODB::adLockOptimistic, ADODB::adCmdText);<br />
<br />
if(!rsObjectsPtr->ADOEOF){<br />
if(rsObjectsPtr->GetRecordCount()>0){<br />
while (rsObjectsPtr->ADOEOF == false){<br />
_variant_t myCoordinates;<br />
<br />
myCoordinates = rsObjectsPtr->GetCollect(L"Coordinates");<br />
<br />
if(myCoordinates.vt != VT_NULL){<br />
CString myStrCoords;<br />
<br />
myStrCoords = static_cast<char *>(_bstr_t(myCoordinates.bstrVal));<br />
<br />
int myArraySize = (myStrCoords.GetLength()/9);<br />
CString *singleCoord = new CString[myArraySize];<br />
int tokenCounter = 0;<br />
<br />
while(myStrCoords.GetLength()>=9){<br />
singleCoord[tokenCounter] = myStrCoords.Left(9);<br />
myStrCoords.Delete(0,10);<br />
tokenCounter++;<br />
}<br />
<br />
if(tokenCounter<=2){<br />
drawLine((string)singleCoord[0],(string)singleCoord[0]);<br />
}<br />
else{<br />
drawQuad((string)singleCoord[0],(string)singleCoord[1],(string)singleCoord[2],(string)singleCoord[3]);<br />
drawQuad("000001000","000001001","000000001","000000000");<br />
}<br />
}
rsObjectsPtr->MoveNext();<br />
}<br />
if(rsObjectsPtr->BOF){<br />
rsObjectsPtr->MoveFirst();<br />
}<br />
if(rsObjectsPtr->ADOEOF){<br />
rsObjectsPtr->MoveLast();<br />
}<br />
};<br />
}<br />
}<br />
catch(_com_error &e)<br />
{<br />
<br />
AfxMessageBox(static_cast<char *>(e.Description()));<br />
}<br />
catch(...)<br />
{<br />
AfxMessageBox("Unhandled Exception");<br />
};<br />
<br />
<br />
drawQuad("000001000","000001001","000000001","000000000");<br />
<br />
SwapBuffers(dc->m_hDC);<br />
}<br />
<br />
This is the code for drawing the QUAD
<br />
void COpenGLControl::drawQuad(string Coord_A, string Coord_B, string Coord_C, string Coord_D){<br />
<br />
<br />
float myAx = atof(Coord_A.substr(0,3).c_str());<br />
float Ax = (myAx/10);<br />
float myAy = atof(Coord_A.substr(3,3).c_str());<br />
float Ay = (myAy/10);<br />
float myAz = atof(Coord_A.substr(6,3).c_str());<br />
float Az = (myAz/10);<br />
<br />
float myBx = atof(Coord_B.substr(0,3).c_str());<br />
float Bx = (myBx/10);<br />
float myBy = atof(Coord_B.substr(3,3).c_str());<br />
float By = (myBy/10);<br />
float myBz = atof(Coord_B.substr(6,3).c_str());<br />
float Bz = (myBz/10);<br />
<br />
float myCx = atof(Coord_C.substr(0,3).c_str());<br />
float Cx = (myCx/10);<br />
float myCy = atof(Coord_C.substr(3,3).c_str());<br />
float Cy = (myCy/10);<br />
float myCz = atof(Coord_C.substr(6,3).c_str());<br />
float Cz = (myCz/10);<br />
<br />
float myDx = atof(Coord_D.substr(0,3).c_str());<br />
float Dx = (myDx/10);<br />
float myDy = atof(Coord_D.substr(3,3).c_str());<br />
float Dy = (myDy/10);<br />
float myDz = atof(Coord_D.substr(6,3).c_str());<br />
float Dz = (myDz/10);<br />
<br />
glBegin(GL_QUADS);<br />
glColor3f(0.0,1.0,0.0);<br />
<br />
glVertex3f(Ax,Ay,Az);<br />
glVertex3f(Bx,By,Bz);<br />
glVertex3f(Cx,Cy,Cz);<br />
glVertex3f(Dx,Dy,Dz);<br />
glEnd();<br />
}<br />
Thanks in advance...
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The only thing I can think of off the top of my head is the default winding in opengl is counter-clockwise, so you need to draw your quad vertexes in that order, unless you change it to clockwise with glFrontFace(GL_CW).
delete this;
* poof! *
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So I want to enumerate the processes using NtQuerySystemInformation() native api.
I load it from ntdll.dll
i use the process structure below unlike the one documented by microsoft. but i've seen that others use it too.
typedef struct _SYSTEM_PROCESS_INFORMATION
{
DWORD dNext;
DWORD dThreadCount;
DWORD dReserved01;
DWORD dReserved02;
DWORD dReserved03;
DWORD dReserved04;
DWORD dReserved05;
DWORD dReserved06;
QWORD qCreateTime;
QWORD qUserTime;
QWORD qKernelTime;
UNICODE_STRING usName;
DWORD BasePriority;
DWORD dUniqueProcessId;
DWORD dInheritedFromUniqueProcessId;
DWORD dHandleCount;
DWORD dReserved07;
DWORD dReserved08;
VM_COUNTERS VmCounters;
DWORD dCommitCharge;
SYSTEM_THREAD Threads[1];
} SYSTEM_PROCESS_INFORMATION;
the thing is that when I call it I don't get any error code or null pointers but the structure's members are zeros.
the dNext member is not zero but I can't obtain the next pointer for another system_process_information because i get the invalid pointer error when I try this:
if (ProcessInfo->dNext!=0)
ProcessInfo=(SYSTEM_PROCESS_INFORMATION_DEF *)((ULONG *)ProcessInfo+ProcessInfo->dNext);
And I have another question.
How much space should I allocate for the ProcessInfo structure
i only allocate for one structure
SYSTEM_PROCESS_INFORMATION *ProcessInfo=(SYSTEM_PROCESS_INFORMATION *)malloc(sizeof(SYSTEM_PROCESS_INFORMATION));
or I shouldn't allocate at all. I will obtain a pointer to the structure anyway ?
here is the code I use:
HMODULE ntHinst;
ntHinst=LoadLibraryA(NTDLL);
if (ntHinst==NULL)
{
MessageBoxA(GetDesktopWindow(),"Error loading ntdll\nThe program will now end","ERROR",MB_ICONSTOP);
return 0;
}
_NtQuerySystemInformation=(NTQUERYSYSTEMINFORMATION)GetProcAddress(ntHinst,"NtQuerySystemInformation");
if(!_NtQuerySystemInformation)
{
MessageBoxA(GetDesktopWindow(),"Error obtaining function pointer\nThe program will now terminate","ERROR",MB_ICONSTOP);
return 0;
}
SYSTEM_PROCESS_INFORMATION *ProcessInfo=(SYSTEM_PROCESS_INFORMATION *)malloc(sizeof(SYSTEM_PROCESS_INFORMATION);
if (IsBadReadPtr(ProcessInfo,sizeof(SYSTEM_PROCESS_INFORMATION))||IsBadWritePtr(ProcessInfo,sizeof(SYSTEM_PROCESS_INFORMATION)))
return 0;
_NtQuerySystemInformation(SystemProcessInformation ,(PVOID)ProcessInfo,sizeof(SYSTEM_PROCESS_INFORMATION),&ret);
if (ret==0)
{
MessageBoxA(GetDesktopWindow(),"Function Call Failed: NtQuerySystemInformation\nThe program will now terminate","ERROR",MB_ICONSTOP);
return 0;
}
if(ProcessInfo==NULL)
{
MessageBoxA(GetDesktopWindow(),"Function Call Failed: NtQuerySystemInformation\nThe program will now terminate","ERROR",MB_ICONSTOP);
return 0;
}
while(ProcessInfo!=NULL)
{
//RtlUnicodeStringToOemString(usname,&ProcessInfo->usName,TRUE);
//MessageBoxA(0,usname->Buffer,"",MB_OK);
//RtlFreeOemString(usname);
HANDLE hProc;
hProc=OpenProcess(PROCESS_QUERY_INFORMATION,FALSE,ProcessInfo->dUniqueProcessId);
if (hProc!=NULL)
{
HMODULE hmods[300];
DWORD retv;
char fname[1024];
EnumProcessModules(hProc,hmods,sizeof(hmods),&retv);
retv=retv/sizeof(DWORD);
GetModuleFileNameA(*hmods,fname,sizeof(fname));
MessageBoxA(GetDesktopWindow(),fname,"Process Name",MB_OK);
}
else if (ProcessInfo->dNext!=0)
ProcessInfo=(SYSTEM_PROCESS_INFORMATION_DEF *)((ULONG *)ProcessInfo+ProcessInfo->dNext);
else
ProcessInfo=NULL;
if (ProcessInfo->dNext!=0)
ProcessInfo=(SYSTEM_PROCESS_INFORMATION_DEF *)((ULONG *)ProcessInfo+ProcessInfo->dNext);
else
ProcessInfo=NULL;
}
free(ProcessInfo);
So I get no errors durin calling. but I also get a structure full of zero's.
What is the pb ?
gabby
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