Append Array with Pointer

[Daok]

Hello,
I have a question. I am trying to code a function that will append two array.

Here is the code, all work but the value doesn't return well, why?

#include <iostream>
using namespace std;

void CopyChaineSuite(char *&s1, char *s2);

void main()
{
	char cPrenom1[80] = "Me";
	char cPrenom2[80] = "andYou";
	CopyChaineSuite(cPrenom1, cPrenom2);
	cout << "Prenom #1 : " << cPrenom1 << endl;
	cout << "Prenom #2 : " << cPrenom2 << endl;
}//Fin du main

void CopyChaineSuite(char *&s1, char *s2)
{
	
	char *ptrDebut = new char;
	char *p = ptrDebut;

	while(*s1 != '\0')
		*ptrDebut++ = *s1++;

	while(*s2 != '\0')
		*ptrDebut++ = *s2++;
	*ptrDebut = '\0';

	s1 = p;
}//Fin de CopyChaineSuite

[Daok]

I'm happy to found that is not a easy problem....

[Morphine]

try this:

main() {
char *firstString, *secondString;
firstString = (char *)malloc( 80 ); //or however many bytes you want
secondString = (char *)malloc( 80);

firstString = "something";
secondString = " else";

strcat( firstString, secondString );


/***********
or even
strncat( firstString, secondString, max_bytes_to_append );
**********/

//and then

free( firstString );
free( secondString );

//when you are done with them....

[parksie]

main() {

int main(void) {

[Daok]

The idea with my question was how to make it with pointer without any stuff already done like strcat.

[jim mcnamara]

How about -

char *cat(char *dest,char *src){
      register char *buf,*s;
      for(buf=dest;*buf;buf++);  /* goto end of current array */
      for(s=src;*s;buf++,s++) *buf=*s; /* add characters */
      *buf=0x00; /* null terminate string */
      return dest;

[Daok]

Why register???

[Daok]

void CopyChaineSuite(char *s1, char *s2)
{
	while(*s1 != '\0'){s1++;}
	while(*s2 != '\0'){*s1++ = *s2++;}
	*s1 = '\0';
}//Fin de CopyChaineSuite

This is my code and yours together and it work well.

I have an other question, can I know if it's possible to do s1--... if I want to make a reverser function I will need it right?

[jim mcnamara]

Yes you can go backwards with a pointer. One caveat -
Don't go back before the start of the buffer or you will have some nasty surprises Try something like ptrdiff() below:

char *strrev(char *s){ // reverse a string
     register char *buf,*dest;
     char *tmp;
     if(!*s) return s;
     for(buf=s;*buf;buf++);     
     tmp=calloc(1,ptrdiff(buf,s);
     buf--;
     for(dest=tmp; ptrdiff(buf,s);buf--,dest++) *dest=*buf;
     *dest=0x00;
     cpy(s,tmp);
     return s;
}
void cpy(char *dest,char *src){
      register char *buf, *s;
      for(s=src,buf=dest;*s;buf++,s++)*buf=*s;
      buf=0x00;
      return;
}
int ptrdif(void *a, void *b){
        return (int)a-(int)b;
}

[twanvl]

You can't change what an array that is declared as "char name[size];" points to. I suggest that you use C++ strings:

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

void CopyChaineSuite(char *&s1, char *s2);

int main()
{
	string cPrenom1 = "Me";
	string cPrenom2 = "andYou";
	CopyChaineSuite(cPrenom1, cPrenom2);
	cout << "Prenom #1 : " << cPrenom1 << endl;
	cout << "Prenom #2 : " << cPrenom2 << endl;
        return 0;
}//Fin du main

void CopyChaineSuite(string &s1, const string& s2)
{
        s1 += s2;
}//Fin de CopyChaineSuite

[parksie]

In that case, what's the point of another function call?

[kedaman]

habit of using functions?

[parksie]

Quiet, you

How's Sq?

[kedaman]

hehe

the compiler is still being planned, the language definitions are quite set now i think.

[CornedBee]

char *ptrDebut = new char;

Once I'm away everyone goes blind...


A single character is not enough to hold two complete arrays.