Related
While doing cppcheck, cppcheck is showing 'invalid scanf' and it is saying:
scanf without field width limits can crash with huge input data on some versions of libc.
Does it give any crash for my program? How to get rid of this issue?
int a;
char str[32];
int part[4];
// after this i am storing some string in 'str'.
a = sscanf(str, "%d%d%d%d", &part[0], &part[1], &part[2], &part[3]); // here i am getting that cppcheck portability error.
How to get rid of this issue
By writing C++ rather than C, and using C++ Standard Library tools rather than the out-dated and often unsafe C Standard Library tools.
#include <iostream>
#include <sstream>
void test()
{
std::string str("4 5 6 7");
int part[4];
std::istringstream ss(str);
ss >> part[0]
>> part[1]
>> part[2]
>> part[3];
}
What you are getting is just a warning: some libc implementations might crash if, say, you give too long strings to %s etc. CPPCheck recommends you to use other, typesafe, c++ methods to achieve your aim (i.e. streams and std::to_string() convertors etc.)
This question already has answers here:
Easiest way to convert int to string in C++
(30 answers)
Closed 7 years ago.
I was wondering if there was an alternative to itoa() for converting an integer to a string because when I run it in visual Studio I get warnings, and when I try to build my program under Linux, I get a compilation error.
In C++11 you can use std::to_string:
#include <string>
std::string s = std::to_string(5);
If you're working with prior to C++11, you could use C++ streams:
#include <sstream>
int i = 5;
std::string s;
std::stringstream out;
out << i;
s = out.str();
Taken from http://notfaq.wordpress.com/2006/08/30/c-convert-int-to-string/
boost::lexical_cast works pretty well.
#include <boost/lexical_cast.hpp>
int main(int argc, char** argv) {
std::string foo = boost::lexical_cast<std::string>(argc);
}
Archeology
itoa was a non-standard helper function designed to complement the atoi standard function, and probably hiding a sprintf (Most its features can be implemented in terms of sprintf): http://www.cplusplus.com/reference/clibrary/cstdlib/itoa.html
The C Way
Use sprintf. Or snprintf. Or whatever tool you find.
Despite the fact some functions are not in the standard, as rightly mentioned by "onebyone" in one of his comments, most compiler will offer you an alternative (e.g. Visual C++ has its own _snprintf you can typedef to snprintf if you need it).
The C++ way.
Use the C++ streams (in the current case std::stringstream (or even the deprecated std::strstream, as proposed by Herb Sutter in one of his books, because it's somewhat faster).
Conclusion
You're in C++, which means that you can choose the way you want it:
The faster way (i.e. the C way), but you should be sure the code is a bottleneck in your application (premature optimizations are evil, etc.) and that your code is safely encapsulated to avoid risking buffer overruns.
The safer way (i.e., the C++ way), if you know this part of the code is not critical, so better be sure this part of the code won't break at random moments because someone mistook a size or a pointer (which happens in real life, like... yesterday, on my computer, because someone thought it "cool" to use the faster way without really needing it).
Try sprintf():
char str[12];
int num = 3;
sprintf(str, "%d", num); // str now contains "3"
sprintf() is like printf() but outputs to a string.
Also, as Parappa mentioned in the comments, you might want to use snprintf() to stop a buffer overflow from occuring (where the number you're converting doesn't fit the size of your string.) It works like this:
snprintf(str, sizeof(str), "%d", num);
Behind the scenes, lexical_cast does this:
std::stringstream str;
str << myint;
std::string result;
str >> result;
If you don't want to "drag in" boost for this, then using the above is a good solution.
We can define our own iota function in c++ as:
string itoa(int a)
{
string ss=""; //create empty string
while(a)
{
int x=a%10;
a/=10;
char i='0';
i=i+x;
ss=i+ss; //append new character at the front of the string!
}
return ss;
}
Don't forget to #include <string>.
С++11 finally resolves this providing std::to_string.
Also boost::lexical_cast is handy tool for older compilers.
I use these templates
template <typename T> string toStr(T tmp)
{
ostringstream out;
out << tmp;
return out.str();
}
template <typename T> T strTo(string tmp)
{
T output;
istringstream in(tmp);
in >> output;
return output;
}
Try Boost.Format or FastFormat, both high-quality C++ libraries:
int i = 10;
std::string result;
WIth Boost.Format
result = str(boost::format("%1%", i));
or FastFormat
fastformat::fmt(result, "{0}", i);
fastformat::write(result, i);
Obviously they both do a lot more than a simple conversion of a single integer
You can actually convert anything to a string with one cleverly written template function. This code example uses a loop to create subdirectories in a Win-32 system. The string concatenation operator, operator+, is used to concatenate a root with a suffix to generate directory names. The suffix is created by converting the loop control variable, i, to a C++ string, using the template function, and concatenating that with another string.
//Mark Renslow, Globe University, Minnesota School of Business, Utah Career College
//C++ instructor and Network Dean of Information Technology
#include <cstdlib>
#include <iostream>
#include <string>
#include <sstream> // string stream
#include <direct.h>
using namespace std;
string intToString(int x)
{
/**************************************/
/* This function is similar to itoa() */
/* "integer to alpha", a non-standard */
/* C language function. It takes an */
/* integer as input and as output, */
/* returns a C++ string. */
/* itoa() returned a C-string (null- */
/* terminated) */
/* This function is not needed because*/
/* the following template function */
/* does it all */
/**************************************/
string r;
stringstream s;
s << x;
r = s.str();
return r;
}
template <class T>
string toString( T argument)
{
/**************************************/
/* This template shows the power of */
/* C++ templates. This function will */
/* convert anything to a string! */
/* Precondition: */
/* operator<< is defined for type T */
/**************************************/
string r;
stringstream s;
s << argument;
r = s.str();
return r;
}
int main( )
{
string s;
cout << "What directory would you like me to make?";
cin >> s;
try
{
mkdir(s.c_str());
}
catch (exception& e)
{
cerr << e.what( ) << endl;
}
chdir(s.c_str());
//Using a loop and string concatenation to make several sub-directories
for(int i = 0; i < 10; i++)
{
s = "Dir_";
s = s + toString(i);
mkdir(s.c_str());
}
system("PAUSE");
return EXIT_SUCCESS;
}
Allocate a string of sufficient length, then use snprintf.
int number = 123;
stringstream = s;
s << number;
cout << ss.str() << endl;
I wrote this thread-safe function some time ago, and am very happy with the results and feel the algorithm is lightweight and lean, with performance that is about 3X the standard MSVC _itoa() function.
Here's the link. Optimal Base-10 only itoa() function? Performance is at least 10X that of sprintf(). The benchmark is also the function's QA test, as follows.
start = clock();
for (int i = LONG_MIN; i < LONG_MAX; i++) {
if (i != atoi(_i32toa(buff, (int32_t)i))) {
printf("\nError for %i", i);
}
if (!i) printf("\nAt zero");
}
printf("\nElapsed time was %f milliseconds", (double)clock() - (double)(start));
There are some silly suggestions made about using the caller's storage that would leave the result floating somewhere in a buffer in the caller's address space. Ignore them. The code I listed works perfectly, as the benchmark/QA code demonstrates.
I believe this code is lean enough to use in an embedded environment. YMMV, of course.
The best answer, IMO, is the function provided here:
http://www.jb.man.ac.uk/~slowe/cpp/itoa.html
It mimics the non-ANSI function provided by many libs.
char* itoa(int value, char* result, int base);
It's also lightning fast and optimizes well under -O3, and the reason you're not using c++ string_format() ... or sprintf is that they are too slow, right?
If you are interested in fast as well as safe integer to string conversion method and not limited to the standard library, I can recommend the format_int method from the {fmt} library:
fmt::format_int(42).str(); // convert to std::string
fmt::format_int(42).c_str(); // convert and get as a C string
// (mind the lifetime, same as std::string::c_str())
According to the integer to string conversion benchmarks from Boost Karma, this method several times faster than glibc's sprintf or std::stringstream. It is even faster than Boost Karma's own int_generator as was confirm by an independent benchmark.
Disclaimer: I'm the author of this library.
Note that all of the stringstream methods may involve locking around the use of the locale object for formatting. This may be something to be wary of if you're using this conversion from multiple threads...
See here for more. Convert a number to a string with specified length in C++
On Windows CE derived platforms, there are no iostreams by default. The way to go there is preferaby with the _itoa<> family, usually _itow<> (since most string stuff are Unicode there anyway).
Most of the above suggestions technically aren't C++, they're C solutions.
Look into the use of std::stringstream.
Is there a function that could replace atoi in c++.
I made some research and didn't find anything to replace it, the only solutions would be using cstdlib or implementing it myself
If you don't want to use Boost, C++11 added std::stoi for strings. Similar methods exist for all types.
std::string s = "123"
int num = std::stoi(s);
Unlike atoi, if no conversion can be made, an invalid_argument exception is thrown. Also, if the value is out of range for an int, an out_of_range exception is thrown.
boost::lexical_cast is your friend
#include <string>
#include <boost/lexical_cast.hpp>
int main()
{
std::string s = "123";
try
{
int i = boost::lexical_cast<int>(s); //i == 123
}
catch(const boost::bad_lexical_cast&)
{
//incorrect format
}
}
You can use the Boost function boost::lexical_cast<> as follows:
char* numericString = "911";
int num = boost::lexical_cast<int>( numericString );
More information can be found here (latest Boost version 1.47). Remember to handle exceptions appropriately.
Without boost:
stringstream ss(my_string_with_a_number); int my_res; ss >> my_res;
About as annoying as the boost version but without the added dependency. Could possibly waste more ram.
You don't say why atoi is unsuitable so I am going to guess it has something to do with performance. Anyway, clarification would be helpful.
Using Boost Spirit.Qi is about an order of magnitude faster than atoi, at least in tests done by Alex Ott.
I don't have a reference but the last time I tested it, Boost lexical_cast was about an order of magnitude slower than atoi. I think the reason is that it constructs a stringstream, which is quite expensive.
Update: Some more recent tests
This question already has answers here:
Easiest way to convert int to string in C++
(30 answers)
Closed 7 years ago.
I was wondering if there was an alternative to itoa() for converting an integer to a string because when I run it in visual Studio I get warnings, and when I try to build my program under Linux, I get a compilation error.
In C++11 you can use std::to_string:
#include <string>
std::string s = std::to_string(5);
If you're working with prior to C++11, you could use C++ streams:
#include <sstream>
int i = 5;
std::string s;
std::stringstream out;
out << i;
s = out.str();
Taken from http://notfaq.wordpress.com/2006/08/30/c-convert-int-to-string/
boost::lexical_cast works pretty well.
#include <boost/lexical_cast.hpp>
int main(int argc, char** argv) {
std::string foo = boost::lexical_cast<std::string>(argc);
}
Archeology
itoa was a non-standard helper function designed to complement the atoi standard function, and probably hiding a sprintf (Most its features can be implemented in terms of sprintf): http://www.cplusplus.com/reference/clibrary/cstdlib/itoa.html
The C Way
Use sprintf. Or snprintf. Or whatever tool you find.
Despite the fact some functions are not in the standard, as rightly mentioned by "onebyone" in one of his comments, most compiler will offer you an alternative (e.g. Visual C++ has its own _snprintf you can typedef to snprintf if you need it).
The C++ way.
Use the C++ streams (in the current case std::stringstream (or even the deprecated std::strstream, as proposed by Herb Sutter in one of his books, because it's somewhat faster).
Conclusion
You're in C++, which means that you can choose the way you want it:
The faster way (i.e. the C way), but you should be sure the code is a bottleneck in your application (premature optimizations are evil, etc.) and that your code is safely encapsulated to avoid risking buffer overruns.
The safer way (i.e., the C++ way), if you know this part of the code is not critical, so better be sure this part of the code won't break at random moments because someone mistook a size or a pointer (which happens in real life, like... yesterday, on my computer, because someone thought it "cool" to use the faster way without really needing it).
Try sprintf():
char str[12];
int num = 3;
sprintf(str, "%d", num); // str now contains "3"
sprintf() is like printf() but outputs to a string.
Also, as Parappa mentioned in the comments, you might want to use snprintf() to stop a buffer overflow from occuring (where the number you're converting doesn't fit the size of your string.) It works like this:
snprintf(str, sizeof(str), "%d", num);
Behind the scenes, lexical_cast does this:
std::stringstream str;
str << myint;
std::string result;
str >> result;
If you don't want to "drag in" boost for this, then using the above is a good solution.
We can define our own iota function in c++ as:
string itoa(int a)
{
string ss=""; //create empty string
while(a)
{
int x=a%10;
a/=10;
char i='0';
i=i+x;
ss=i+ss; //append new character at the front of the string!
}
return ss;
}
Don't forget to #include <string>.
С++11 finally resolves this providing std::to_string.
Also boost::lexical_cast is handy tool for older compilers.
I use these templates
template <typename T> string toStr(T tmp)
{
ostringstream out;
out << tmp;
return out.str();
}
template <typename T> T strTo(string tmp)
{
T output;
istringstream in(tmp);
in >> output;
return output;
}
Try Boost.Format or FastFormat, both high-quality C++ libraries:
int i = 10;
std::string result;
WIth Boost.Format
result = str(boost::format("%1%", i));
or FastFormat
fastformat::fmt(result, "{0}", i);
fastformat::write(result, i);
Obviously they both do a lot more than a simple conversion of a single integer
You can actually convert anything to a string with one cleverly written template function. This code example uses a loop to create subdirectories in a Win-32 system. The string concatenation operator, operator+, is used to concatenate a root with a suffix to generate directory names. The suffix is created by converting the loop control variable, i, to a C++ string, using the template function, and concatenating that with another string.
//Mark Renslow, Globe University, Minnesota School of Business, Utah Career College
//C++ instructor and Network Dean of Information Technology
#include <cstdlib>
#include <iostream>
#include <string>
#include <sstream> // string stream
#include <direct.h>
using namespace std;
string intToString(int x)
{
/**************************************/
/* This function is similar to itoa() */
/* "integer to alpha", a non-standard */
/* C language function. It takes an */
/* integer as input and as output, */
/* returns a C++ string. */
/* itoa() returned a C-string (null- */
/* terminated) */
/* This function is not needed because*/
/* the following template function */
/* does it all */
/**************************************/
string r;
stringstream s;
s << x;
r = s.str();
return r;
}
template <class T>
string toString( T argument)
{
/**************************************/
/* This template shows the power of */
/* C++ templates. This function will */
/* convert anything to a string! */
/* Precondition: */
/* operator<< is defined for type T */
/**************************************/
string r;
stringstream s;
s << argument;
r = s.str();
return r;
}
int main( )
{
string s;
cout << "What directory would you like me to make?";
cin >> s;
try
{
mkdir(s.c_str());
}
catch (exception& e)
{
cerr << e.what( ) << endl;
}
chdir(s.c_str());
//Using a loop and string concatenation to make several sub-directories
for(int i = 0; i < 10; i++)
{
s = "Dir_";
s = s + toString(i);
mkdir(s.c_str());
}
system("PAUSE");
return EXIT_SUCCESS;
}
Allocate a string of sufficient length, then use snprintf.
int number = 123;
stringstream = s;
s << number;
cout << ss.str() << endl;
I wrote this thread-safe function some time ago, and am very happy with the results and feel the algorithm is lightweight and lean, with performance that is about 3X the standard MSVC _itoa() function.
Here's the link. Optimal Base-10 only itoa() function? Performance is at least 10X that of sprintf(). The benchmark is also the function's QA test, as follows.
start = clock();
for (int i = LONG_MIN; i < LONG_MAX; i++) {
if (i != atoi(_i32toa(buff, (int32_t)i))) {
printf("\nError for %i", i);
}
if (!i) printf("\nAt zero");
}
printf("\nElapsed time was %f milliseconds", (double)clock() - (double)(start));
There are some silly suggestions made about using the caller's storage that would leave the result floating somewhere in a buffer in the caller's address space. Ignore them. The code I listed works perfectly, as the benchmark/QA code demonstrates.
I believe this code is lean enough to use in an embedded environment. YMMV, of course.
The best answer, IMO, is the function provided here:
http://www.jb.man.ac.uk/~slowe/cpp/itoa.html
It mimics the non-ANSI function provided by many libs.
char* itoa(int value, char* result, int base);
It's also lightning fast and optimizes well under -O3, and the reason you're not using c++ string_format() ... or sprintf is that they are too slow, right?
If you are interested in fast as well as safe integer to string conversion method and not limited to the standard library, I can recommend the format_int method from the {fmt} library:
fmt::format_int(42).str(); // convert to std::string
fmt::format_int(42).c_str(); // convert and get as a C string
// (mind the lifetime, same as std::string::c_str())
According to the integer to string conversion benchmarks from Boost Karma, this method several times faster than glibc's sprintf or std::stringstream. It is even faster than Boost Karma's own int_generator as was confirm by an independent benchmark.
Disclaimer: I'm the author of this library.
Note that all of the stringstream methods may involve locking around the use of the locale object for formatting. This may be something to be wary of if you're using this conversion from multiple threads...
See here for more. Convert a number to a string with specified length in C++
On Windows CE derived platforms, there are no iostreams by default. The way to go there is preferaby with the _itoa<> family, usually _itow<> (since most string stuff are Unicode there anyway).
Most of the above suggestions technically aren't C++, they're C solutions.
Look into the use of std::stringstream.
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
How to parse a string to an int in C++?
How do you convert a C++ string to an int?
Assume you are expecting the string to have actual numbers in it ("1", "345", "38944", for example).
Also, let's assume you don't have boost, and you really want to do it the C++ way, not the crufty old C way.
#include <sstream>
// st is input string
int result;
stringstream(st) >> result;
Use the C++ streams.
std::string plop("123");
std::stringstream str(plop);
int x;
str >> x;
/* Lets not forget to error checking */
if (!str)
{
// The conversion failed.
// Need to do something here.
// Maybe throw an exception
}
PS. This basic principle is how the boost library lexical_cast<> works.
My favorite method is the boost lexical_cast<>
#include <boost/lexical_cast.hpp>
int x = boost::lexical_cast<int>("123");
It provides a method to convert between a string and number formats and back again. Underneath it uses a string stream so anything that can be marshaled into a stream and then un-marshaled from a stream (Take a look at the >> and << operators).
I have used something like the following in C++ code before:
#include <sstream>
int main()
{
char* str = "1234";
std::stringstream s_str( str );
int i;
s_str >> i;
}
C++ FAQ Lite
[39.2] How do I convert a std::string to a number?
https://isocpp.org/wiki/faq/misc-technical-issues#convert-string-to-num
Let me add my vote for boost::lexical_cast
#include <boost/lexical_cast.hpp>
int val = boost::lexical_cast<int>(strval) ;
It throws bad_lexical_cast on error.
Use atoi
Perhaps I am misunderstanding the question, by why exactly would you not want to use atoi? I see no point in reinventing the wheel.
Am I just missing the point here?
in "stdapi.h"
StrToInt
This function tells you the result, and how many characters participated in the conversion.