Re: Proper use of code

Neil Butterworth <>
Wed, 4 Feb 2009 06:39:27 CST
On Feb 4, 6:40 am, joshturner1967 <> wrote:

On Feb 3, 1:10 am, joshturner1967 <> wrote:

I gather I can do the following

[code snipped]

First off does this look better or am I off track. If I am off track
could you tell me where and show me what I should be doing?

Definitely on track. You may want to look at the following code which
is a solution to your problem (as I understand it) using fairly
idiomatic C++:

#include <string>
#include <iostream>
#include <sstream>
#include <cstdlib>
using namespace std;

// handy function to turn any streamable type into a string
template <typename T> string ToString( const T & t ) {
     ostringstream os;
     os << t;
     return os.str();

// build filename from base, random number and mimetype extension
string MakeFileName( const string & base, const string & mime ) {

     string filename = base; // always try to initialse

     // find the position of the last slash & extract type
     // if there isn't one, use whole mime type
     string::size_type pos = mime.find_last_of( "/" );
     string ext = pos == string::npos ? mime : mime.substr( pos +
1 );

     // get string rep of a random number
     string rnum = ToString( rand() );

     // build the rest of the filename
     // note we can use += as well as append()
     filename += rnum;
     filename += ".";
     filename += ext;

     return filename;

// test it
int main() {
     cout << MakeFileName( "myfile", "text/xml" ) << endl;
     return 0;

Note that in in te above thre are no fixed sized buffers and no
possibilities of buffer overruns.

Secondly I would like to be able to update filename as well char
**filename from qfilename but using this new method I am confussed and
I dont want to switch between c and c++ and want to learn it

Assuming filename points to something, and assuming you are using
malloc/free in the rest of the code then:

// uncompiled & untested
string f = MakeFileName( "myfile", "text/xml" );
* filename = malloc( sizeof(char) * f.size() + 1 );
strcpy( * filename, f.c_str() );

The string member function c_str() gives you a C-style null-terminated

Neil Butterworth

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