RE: generating sha256 hashes with openssl?
- From: "Sina Bahram" <sbahram@xxxxxxxxx>
- To: <programmingblind@xxxxxxxxxxxxx>
- Date: Sun, 22 Aug 2010 23:39:55 -0400
Why are you not using strncpy?
Take care,
Sina
-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Littlefield, Tyler
Sent: Sunday, August 22, 2010 11:36 PM
To: programmingblind@xxxxxxxxxxxxx
Subject: Re: generating sha256 hashes with openssl?
I seem to have forgotten a line:
While this isn't good coding practice, it's a great example of what I'm
saying...
#include <iostream>
#include <string>
#include <cstring>
int main(void)
{
char* i = new char(10);
memset(i, 0, 10);
strcpy(i, "hello!");
std::string s=i;
delete [] i;
memset(i, 0, 10);
std::cout << s << std::endl;
return 0;
}
In short, we create an array of 10 bytes, fill it with zeros (so the string is
NULL terminated), assign that to a std::string,
delete the array and set the 10 bytes at that address back to zero. If the
std::string held a reference or just the address of that
pointer, we wouldn't see the "hello"
being printed, because the memory where the array was was just filled with
zeros. The fact that it is, tells us that std::string's =
operator does a strcpy, or a similar copy operation.
----- Original Message -----
From: "Littlefield, Tyler" <tyler@xxxxxxxxxxxxx>
To: <programmingblind@xxxxxxxxxxxxx>
Sent: Sunday, August 22, 2010 9:30 PM
Subject: Re: generating sha256 hashes with openssl?
> #include <iostream>
> #include <string>
> #include <cstring>
>
> int main(void)
> {
> char* i = new char(10);
> memset(i, 0, 10);
> strcpy(i, "hello!");
> std::string s=i;
> delete [] i;
> std::cout << s << std::endl;
> return 0;
> }
>
> tyler@tangerine:~$ g++ poc.cpp
> tyler@tangerine:~$ ./a.out
> hello!
> tyler@tangerine:~$
> so... It -is- copying, as I said earlier.
> the std::string manages it's own array, so it can expand and etc. A smart
> pointer won't do any good as it's not used after the strcpy, thus deleting
> it has no affect here.
> Thanks,
> Ty
>
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