Adding a string or int to a character array

[Spikey]

Hi,

I have a problem that's (probably) very easy to solve, only I'am more a Java programmer and I couldn't find anything like it on the internet.
My problem is that I have to add a variable (int, string, double) to a character array. I know that it is very easy with Java but I din't find any thing for C/C++.
Everything I found created errors.

Example:
I've added the first 4 lines of the methode "setOffset( int arg1)". "msg" is the char array created at the beginning of the methode it's importend that the size of this array is equal to the size of the hardcoded string + the length of arg1, because it is used in the "viWrite(.....) ".
The char array won't be changed after it's made.

bool Tektronix::setOffset(int arg1){
    char msg[] = "source1:Voltage:Offset " + arg1; //this is the Java way
    status = viWrite(vi, (ViBuf) msg , sizeof(msg), &retCnt);
    if (status < VI_SUCCESS) return false;
        .............
 

ERROR: cannot convert from 'System::String ^' to 'char []'
ERROR: 'char []': illegal sizeof operand

Second problem is that it says illegal sizeof opperand, but I expect that error will disapear if I've solved the first.

Thanks for all the support

GreetZ

Spikey

[sicarie]

I believe you will need string streams. That should help you convert to a string.

[Spikey]

Hi,

I guess it's not that easy... the strcpy I have to use (to convert the string to a char array) is creating a Warning. I can live with that but it's not pretty.
The real problem is that the sstream is creating an error in combination with my errorhandler.

ERROR: error C2362: initialization of 's2' is skipped by 'goto errorHandler'

GreetZ.

[Spikey]

Hi,

I have a few things working now, but I really need to have an array with the exact size of the string.
I was hoping the following code would do the trick, but it ain't

example:

string s1 = "output1?";  // s1.size = 8
char ch1[s1.size()]; // this ain't gonne work, I know!
strcpy (ch1 , s1.c_str());
 

it's essential that afterwards sizeof(ch1) is equal to the number of characters inside, otherwise I can't use the viWrite methode (created by National Instuments).

every possible help is welcome :D

Greetz

Spikey

[weaknessforcats]

string s1 = "output1?"; // s1.size = 8
char ch1[s1.size()]; // this ain't gonne work, I know!
strcpy (ch1 , s1.c_str());

Did you read what Sicarie said in Post #2?? He gave you the answer.
This is C++ and not C of 1972. That is, you don't use the C-string library anymore.

//Java:
char msg[] = "source1:Voltage:Offset " + arg1; //this is the Java way
//C++:
stringstream ss;
ss << "source1:Voltage:Offset " << arg1; 
string msg;
ss >> msg;
 

[Spikey]

Sorry to bother you, but I really NEED a char array like "char msg[]" instead of a string. The only reason I used a string was to add data to a text line, afterwards I really need to convert it to a char array.
The methode viWrite is a methode writen by National Instruments and I only can convert a char array to a ViBuf (see also code of post#1). ViBuf is defined as a char.

in the visatype.h (the source of National Instruments) is the following defined about ViBuf

typedef unsigned char       ViByte;
typedef ViByte      _VI_PTR ViPByte;
typedef ViPByte             ViBuf;
 

So please if some body understand what I am trying to say (what i need) and know a way to solve the problem. please help, but read Post#1 and Post#4 really carefully before you reply and also come with a solution ending with a string!

GreetZ.

[Spikey]

I have found the solution. Sorry for every one I just pissed off.
I only had to use the c_str() methode of a string and I'am sure I did try it yesterday multiple times, but I gues I forgot the "()".

greetz

Spikey