CANNOT copying char into last address of char* ( string )?

Question

i would like to copy data of char* to another last address of char*

illustration

var1 -> O
var2 -> K

first step

var1 -> OK
var2 -> K

copy var2 to var1

result

var1 -> OK

written code

#include <stdio.h>
#include <string.h>

void timpah(char *dest, char *src, int l_dest, int l_src)
{
    int i = 0;
    while(i < l_dest)
    {
        dest[l_dest+i] = src[l_src+i];
    i++;
    }
}

int main()
{

char res[2024];
res[1] = 0x4f;

char a[] = {0x4b};


timpah(res,a,1,1);

printf("%s [%d]\n",res,strlen(res));
return 0;
}

run

root@xxx:/tmp# gcc -o a a.c
root@xxx:/tmp# ./a
 [0]

question

why my code is not working ? or is there any function had exists already to perform these, but i haven't know it yet ?

thx for any attention

What happens if you print res just after `res[1] = 0x4f;` ? What is in `res[0]`? — Anders Lindahl, May 27 '11 at 07:59
im quite sure its like typos, but when im correcting `res[1] = 0x4f` to `res[0] = 0x4f` and `timpah(res,a,1,1)` to `timpah(res,a,1,2)`, the result still the same.. any solution ? — capede, May 27 '11 at 08:03
What are l_dest and l_src? Are they supposed to be lengths or offsets? — Tom Shaw, May 27 '11 at 08:04
Then why do you use them as offsets in `dest[l_dest+i] = src[l_src+i];` ? — Tom Shaw, May 27 '11 at 08:06

score 4 · Accepted Answer · answered May 27 '11 at 08:01

4

You aren't setting res[0] at any point. If res[0] contains \0 your string ends there. You are probably making things harder than they have to be; you can always use strncpy and strncat.

answered May 27 '11 at 08:01

cnicutar

178,505
25
365
392

score 0 · Answer 2 · answered May 27 '11 at 08:02

0

You probably should have a look at strncat(), strncpy(), etc

answered May 27 '11 at 08:02

ColWhi

1,077
6
16

score 0 · Answer 3 · answered May 27 '11 at 08:13

#include <stdio.h>
#include <string.h>

void timpah(char *dest, char *src, int l_dest, int l_src)
{
    int i = 0;
    while(i < l_dest)
    {
        dest[l_dest+i] = src[l_src+i];
    i++;
    }
}

int main()
{

char res[2024];
res[0] = 0x4f;


char a[] = {0x4b};


timpah(res,a,1,0);

res[2] = '\0';
printf("%s [%d]\n",res,strlen(res));
return 0;
}

CANNOT copying char into last address of char* ( string )?

3 Answers3