I know that :
atoi() converts a string to an integer in C programming.Code:int atoi ( const char * string );
Is there an equivalent in C++ programming?
Printable View
I know that :
atoi() converts a string to an integer in C programming.Code:int atoi ( const char * string );
Is there an equivalent in C++ programming?
In C++, it is not that easy anymore.
You can make your own atoi, but you have to use stringstreams (it's the standard):
Warning!! I have not tested it.Code:#include <sstream>
int AtoI(char *input){
int temp;
stringstream ssout(*input);
ssout>>temp;
return temp;
}
Why not using atoi() in C++?
I don't know exactly. It's not a good habit to use C standards in a C++ program...
C++ is based on C. atoi() is also standard in C++.
Argue with someone who has more experience...
>Why not using atoi() in C++?
Because it sucks just as badly in C++ as it does in C. :)
> Why not using atoi() in C++?
Because it has no error checking, or overflow checking.
strtol() would be OK I think.
Use stringstream or a lexical cast
http://www.boost.org/libs/conversion/lexical_cast.htm
atoi_s()?
itoa()Quote:
Originally Posted by Prelude
If your buffer's size is at least 12 bytes, there can be no buffer overflow.
atoi()
How can it have any buffer overflow, if it is not doing anything to buffers?
You can only make atoi() or itoa() "fail", if you make a serious bug in your program...
itoa() is non-standard in both C and C++.Quote:
itoa()
If your buffer's size is at least 12 bytes, there can be no buffer overflow.
Where did Prelude mention buffer overflow in this thread?Quote:
atoi()
How can it have any buffer overflow, if it is not doing anything to buffers?
Salem did.Quote:
Originally Posted by laserlight
I am not saying it is a good idea to use itoa() and atoi(), but that you shouldn't have other problems with it, except that you're writing unstandard code.
> itoa() If your buffer's size is at least 12 bytes, there can be no buffer overflow.
itoa is not standard.
> atoi() How can it have any buffer overflow, if it is not doing anything to buffers?
Salem didn't mention buffer overflow, he said overflow checking.
Code:char strnumber[50];
/*... fill the number ... */
int number = atoi(strnumber); // results in undefined behavior
Overflow checking checks for buffer overflow (that means, avoids it), doesn't it?Quote:
Salem didn't mention buffer overflow, he said overflow checking.
No, in this case 'overflow' is with respect to arithmetic, not character buffers.Quote:
Overflow checking checks for buffer overflow (that means, avoids it), doesn't it?
Yes. And the main problem of atoi() in my opinion is the absence of error checking both for overflow situations, but also regarding the contents of the string.
It stops at the first non numeric character and returns an int. Seems simple but it's actually a quiet strange function:
There's no error with the third atoi() call. But it poses a serious problem... there's no user-made error checking possible when the atoi parameter can be 0.Code:int foo = atoi("643bar") // returns 643. No error checking.
int foo = atoi("bar") // return 0(!!). No error checking.
int foo = atoi("0") // obviously returns 0 too.
Actually I like that it does this:
Usually there's no need to do anything when 0 is returned. But yes, this can be a problem.Code:int foo = atoi("643bar") // returns 643. No error checking.
Using atoi() and itoa() is a bad idea...
This is the overflow I was talking about
http://www.hmug.org/man/3/atoi.phpCode:#include<stdio.h>
#include<stdlib.h>
#include<errno.h>
int main() {
char *big = "12345678901234567890";
int i = atoi(big);
perror( "Anything?" );
printf( "%s = %d\n", big, i );
return 0;
}
$ gcc -W -Wall -ansi -pedantic -O2 new.c
$ ./a.exe
Anything?: Numerical result out of range
12345678901234567890 = 2147483647
Some key phases
"The atoi() function has been deprecated by strtol()"
"The function atoi() need not affect the value of errno on an error."
My implementation would seem to use the strtol() equivalence, so your mileage may vary.
>You can only make atoi() or itoa() "fail", if you make a serious bug in your program...
atoi is a serious bug in your program. Short of a complete integer validation on the string before calling atoi (which I've only seen in my own code), you're risking undefined behavior every time you use it.
So, which do you think is better to use in C++, stringstreams or strtol()?
Stringstreams, but as others said once lexical_cast makes its way into the standard, it will be the best option by far.
I would agree lexical_cast or stringstreams. However, truth be told, for simple conversions where the string is well contained within accepted values, strtol can become a more practical option. (at least until lexical_cast doesn't make it to the standard)
And lexical_cast basically uses stringstreams internally itself.
Does it? I've never had the pleasure of seeing the code myself. Does it actually use stringstreams or just the same background logic as stringstreams? I guess once it's standard that may just depend on your compiler's implementation.Quote:
Originally Posted by Daved
Right, it will depend on the implementation. The boost version I have uses basic_stringstream unless your compiler doesn't support stringstreams, in which case it uses strstreams.
So it is MS specific. I didn't know that.Quote:
Originally Posted by MSDN