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Are these statements equivalent?
char *TextString
char TextString[]
Both declarations work with my program, but I'm not sure which is correct. Basically, I want to pass a string as a parameter, but when I define the function I don't really know the size of the string.
Thank You.
CBerg
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Functionally there are the same excluding some obscure rules. Maybe one of the uber C++ people here will know.
One thing is that char *TextString says a pointer to a character where char TextString [] actually does imply an array.
Tim Smith
I'm going to patent thought. I have yet to see any prior art.
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Specifically,
I am printing out text strings to my Display Window using DirectX. Basically I am storing a float variable into a text string:
char fpsString[] = "Fps: 0000.000000";
float fps;
fps = FrameCnt / TimeElapsed;
sprintf(fpsString, "Fps: %f \0", fps);
m_Font.Render(fpsString, 0, 0, g_Width, g_Height, DT_TOP | DT_RIGHT, 0xff000000);
that function is defined as...
void CDXFont::Render( char *TextString, int Xpos, int Ypos, int Width, int Height, DWORD Format, D3DCOLOR Color )
{
//
// Render the Font
//
Font->DrawText(
0,
TextString,
-1, // size of string or -1 indicates null terminating string
&Rect, // rectangle text is to be formatted to in windows coords
Format, // where to draw in viewport
Color); // Color of text.
}
Don't worry about the DirectX and COM stuff, but I am wondering the proper way to go about printing a string which is a float number. This number might be really big or even negative at times, so that is why my parameter is a pointer. Am doing this the wrong way? I also want to format this number so that it is only about 2 or 3 decimal precision instead of 6. How would I be able to do this in C++?
Thank You,
CBerg
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The biggest problem in your code is that sprintf() may overflow the boundaries of fpsString if fps is large. You should use proper C++ strings instead of legacy C character arrays, e.g.
std::ostringstream fpsString;
fpsString << "Fps: " << fps;
m_font.Render(fpsString.str().c_str(), 0, 0, g_height, DT_TOP | DT_RIGHT, 0xff000000);
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OH GOD NO!!!
std::ostringstream is slower than a dead man glued to the sidewalk.
Tim Smith
I'm going to patent thought. I have yet to see any prior art.
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See my other post. Using stringstream just to avoid the buffer overrun issue can cause performance problems. snprintf was created just for this problem.
A while back someone had a problem with std::hash being very slow. It was discovered that he was generating his keys with stringstream. Once he switched over to something with less overhead, it was MUCH faster.
Don't get me wrong, stringstream is great. However in this case it is like using a 767 airliner for cropdusting.
Tim Smith
I'm going to patent thought. I have yet to see any prior art.
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Thank You everybody.
I would like to mention that it appears snprintf() is limited to Unix. I am using Visual C++ .NET and I had to call _snprintf() for this to work.
I still had to be sure that my string declaration was fairly large to accomodate the whole number.
char fpsString[22];
But, I could easily change decimal precision using the _snprintf().
I'm not sure about the speed issue, but if someone else could confirm that would be nice.
CBerg
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Woops, I forgot about that...
(Which is another reason to use stringstream due to badly designed C routines.)
Tim Smith
I'm going to patent thought. I have yet to see any prior art.
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char fpsString [80];
float fps;
fps = FrameCnt / TimeElapsed;
snprintf(fpsString, 80, "Fps: %f \0", fps);
1. Trying to sprintf to a string like you were doing might cause problems on some platforms.
2. As someone pointed out, the sprintf might overflow the buffer. snprintf works great to avoid this problem without using STL which has its share of problems.
Tim Smith
I'm going to patent thought. I have yet to see any prior art.
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See here.
"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)
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first,in "afx.h" include "afxdb.h"
second declare global variable "CDatabase db;" and define "CString os="ODBC;DSN=MyDb;UID="user";PWD="mypassword";"in view
third,when i write"db.open(NULL,FALSE,FALSE,os);the result of compiling show there are 4 error.
why?
how to connect access database in vc++6.0?(the data source of ODBC done already)
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You create a ODBC connection. Example: Name is MyDb.
The function is:
db.Open("MyDb");
If has User Name, Password:
db.Open("MyDb", FALSE, FALSE, "ODBC;UID=UserName;PWD=MyPassword");
Not use the char " in UserName And Password string
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i did it in the way recommended by you,first ,set the odbc
second in my view declare CDatabase db;at the same time #iclude "afxdb.h"in afx.h,but when i write db.open("student")(student is my odbc data source),
after running ,telling me 4 error.
i am ambarrassed!
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CString sDsn;
CString sFile = "e:\\DAS.mdb"; //path to database
// You must change above path if it's different
// Build ODBC connection string
sDsn.Format("ODBC;DRIVER={%s};DSN='';DBQ = %s",sDriver,sFile);
TRY
{CDatabase ComboDatabase;
// Open the database
ComboDatabase.Open(NULL,false,false,sDsn);
// Build the SQL statement
SqlCommand = "DELETE FROM BandSetting "
"WHERE BANDNAME = '" + m_Store + "'" ;
ComboDatabase.ExecuteSQL(SqlCommand);
// Close the database
ComboDatabase.Close();
}
CATCH(CDBException, e)
{
// If a database exception occured, show error msg
AfxMessageBox("Database error: "+e->m_strError);
}
END_CATCH;
}
#include "afxdb.h"
#include "odbcinst.h" include these 2 as header files
this shd worl perfectlt fine.. cos it worked well for me =)
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Anonymous wrote:
...after running ,telling me 4 error.
And those errors are?
"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)
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Since you are using ODBC, and have created a working DSN, why not just let ClassWizard create a CRecordset-derived class for you. It's much easier than the path you are currently taking. Once the class has been created, it's very easy to create and use an instance of it:
CDatabase db;
CMyRecordset rs(&db);
rs.Open();
rs.MoveFirst();
while (! rs.IsEOF())
rs.MoveNext();
rs.Close();
"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)
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Hi,
I had used Visual C++ AppWizard to create a database using Microsoft's Access but when I copied the whole program into other PC, I could run it.
Listed below is the error message I received.
Error Message - Unable to Locate DLL
The dynamic link library MFC42D.DLL cound not be found in the specified path...
How to I solve this problems?
Need Help
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You find all the DLL file in CD ROM of Visual C++ or Microsoft Access. And then, copy them to C:\Windows\System.
Example: MFC42D.DLL Show on the Error Message
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Hi,
The "Unable to Locate DLL" error is gone but I'm getting another error of "Data source name not found and no default driver specified".
Please Help..
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I'm just guessing here, but this is an ODBC application, and your second machine doesn't have an ODBC source configured, or you have hardcoded the path to your database and it doesn't exist in the same location on the second machine.
Tim is right; it's illegal to redistribute the debug DLLs that Microsoft supply as part of Visual C++, as you will then be in breach of your license agreement.
Steve S
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Ok, I know this is a bit anal, but...
You can not legally redistribute any of the debug libraries. If you are actually trying to distribute this program, then build it in release mode.
Tim Smith
I'm going to patent thought. I have yet to see any prior art.
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siew hoon wrote:
The dynamic link library MFC42D.DLL cound not be found in the specified path...
You need to compile the application in release mode before distributing it. The only machines that will have the debug versions of the MFC libraries (e.g., MFC42D.DLL) are those with Visual Studio installed. Otherwise, distributing the debug versions of the MFC libraries is against the rules!
"The pointy end goes in the other man." - Antonio Banderas (Zorro, 1998)
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