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Help, Im trying to implement my own strcpy

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Re: Help, Im trying to implement my own strcpy

#11

Dec 2nd, 2008

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Originally Posted by StuXYZ

can I just add, you need to remember to add a
*dest=0; line after the while. You will need something similar in any of the other posts.

No with Arkm's algorithm you don't because it will also copy the null terminator.

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Re: Help, Im trying to implement my own strcpy

#12

Dec 2nd, 2008

Regrettably, it's not ArkM's algorithm. It's K&R code.
Thank you, Ancient Dragon: this code is OK, it copies null byte

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Re: Help, Im trying to implement my own strcpy

#13

Dec 2nd, 2008

What about Buffer Overflow?

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Re: Help, Im trying to implement my own strcpy

#14

Dec 2nd, 2008

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Originally Posted by Laiq Ahmed

What about Buffer Overflow?

Look at the requirements: if you forgot strcpy specification I can recall, try to search the target size there

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Re: Help, Im trying to implement my own strcpy

#15

Dec 2nd, 2008

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Originally Posted by Laiq Ahmed

What about Buffer Overflow?

That is a problem with all standard C functions. If you use one of the new Microsoft compilers, Microsoft declared them depreciated and wants us to use the _s functions, such as strcpy_s(), which has an additional destination buffer size parameter. But even that could cause buffer overflow if the calling function passed the wrong buffer size. There is no 100% bullet-proof method in C to prevent buffer overflow. But if you follow the rules and bother to actually read the function's requirements then you can minimize the buffer overflow problem.

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wow this thing is rolling!!

#16

Dec 2nd, 2008

I modified the program it looks like this but no doubt theres something wrong as it wont output anything I await your wisdom guys

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <cstring>
using std::cin;
using std::cout;
 
void StrCpy(char * Dest , char* Src )
{
 int i;
 char *tmp = new char[strlen(Src)+1];
 for(i = 0 ; *Src!='\0' ; Src++)
    tmp[i]=*Src;
 tmp[i]='\0'; 
 Dest = tmp; 
 for(int i= 0 ; tmp[i]!='\0' ; i++)
   cout << tmp[i];
}
 
void main()
{  
 
char *string1;
char * string2 = "EL";
 
 
StrCpy(string1, string2);
 // while(*string1)
 //   cout << *string1++; 
}
#include <iostream>
#include <cstring>
using std::cin;
using std::cout;

void StrCpy(char * Dest , char* Src )
{
 int i;
 char *tmp = new char[strlen(Src)+1];
 for(i = 0 ; *Src!='\0' ; Src++)
    tmp[i]=*Src;
 tmp[i]='\0'; 
 Dest = tmp; 
 for(int i= 0 ; tmp[i]!='\0' ; i++)
   cout << tmp[i];
}

void main()
{  

char *string1;
char * string2 = "EL";


StrCpy(string1, string2);
 // while(*string1)
 //   cout << *string1++; 
}

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Re: Help, Im trying to implement my own strcpy

#17

Dec 2nd, 2008

Your version doesn't work because the first parameter Dest needs to be passed by pointer, not by value

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <cstring>
using std::cin;
using std::cout;
 
void StrCpy(char ** Dest , char* Src )
{
 int i;
 char *tmp = new char[strlen(Src)+1];
 for(i = 0 ; *Src!='\0' ; Src++)
    tmp[i]=*Src;
 tmp[i]='\0'; 
 *Dest = tmp; 
 for(int i= 0 ; tmp[i]!='\0' ; i++)
   cout << tmp[i];
}
 
void main()
{  
 
char *string1 = 0;
char * string2 = "EL";
 
 
StrCpy( &string1, string2);
 // while(*string1)
 //   cout << *string1++; 
}
#include <iostream>
#include <cstring>
using std::cin;
using std::cout;

void StrCpy(char ** Dest , char* Src )
{
 int i;
 char *tmp = new char[strlen(Src)+1];
 for(i = 0 ; *Src!='\0' ; Src++)
    tmp[i]=*Src;
 tmp[i]='\0'; 
 *Dest = tmp; 
 for(int i= 0 ; tmp[i]!='\0' ; i++)
   cout << tmp[i];
}

void main()
{  

char *string1 = 0;
char * string2 = "EL";


StrCpy( &string1, string2);
 // while(*string1)
 //   cout << *string1++; 
}

Last edited by Ancient Dragon; Dec 2nd, 2008 at 10:55 pm.

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Re: Help, Im trying to implement my own strcpy

#18

Dec 2nd, 2008

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
for(i = 0 ; *Src!='\0' ; Src++)
    tmp[i]=*Src;
for(i = 0 ; *Src!='\0' ; Src++)
    tmp[i]=*Src;