I have a struct that stores the integer value as a custom string type.
typedef char OneLine[MAX_LINE + 1];
So I have some instances where I want the string that contains "12" to be converted to
C.
OneLine testString;
strcpy(testString, "12");
I'd like a way for me to convert testString to be "C"
How should I tackle this?
Thanks in advance.
You can use sscanf to convert "12" to an integer 12. Then you can use sprintf with %x format to convert integer 12 to "C"
The conversion can be done using stringstreams
#include <iostream>
#include <sstream>
#include <string>
#include <ios>
int main()
{
char const *str = "12";
std::istringstream iss( str );
int val;
if( !( iss >> val ) ) {
// handle error
}
std::ostringstream oss;
oss << std::hex << val;
std::cout << oss.str() << std::endl;
}
Or slightly less verbose way with C++11
char const *str = "12";
auto val = std::stoi( str );
std::ostringstream oss;
oss << std::hex << val;
std::cout << oss.str() << std::endl;
First, even if you were to do this manually, you shouldn't use char arrays for strings. Use std::[w]string.
Second, you can do this with std::[w][i|o]stringstream:
istringstream iss("12");
int number;
iss >> number;
ostringstream oss;
oss << hex << number;
const string& hexNumber = oss.str();
// hexNumber now contains "C"
Related
I'm working with VS 2010 on Windows. I have a function which takes a char pointer. Now, inside the function, I am calling std::hex to convert it to decimal, but for some reason it is not working. It is outputting a large value which makes me think that it is converting the address instead.
void convertHexToDec(char* hex, char * dec)
{
long long decimal;
std::stringstream ss;
ss << hex;
ss >> std::hex >> decimal;
sprintf (dec, "%llu", decimal);
}
So, if the pass in a char pointer containing "58", the output decimal value is something like 1D34E78xxxxxxxxx. Looks like it is converting the address of the hex.
I tried these ways too:
ss << *hex;
ss << (char*)hex[0];
ss << (int *)&hex[0];
None of the above worked.
Any idea how I can make this function work?
The reason for your error is, probably, the wrong printf specifier. Also, sprintf is not safe: it assumes the destination buffer (dec) is large enough.
A possible solution using your function signature - not recommended since you do not know the size of the destination:
void convertHexToDec( char* hex, char * dec )
{
std::sprintf( dec, "%lld", std::strtoll( hex, 0, 16 ) );
}
A safe solution:
std::string convertHexToDec( const char* h )
{
return std::to_string( std::strtoll( h, 0, 16 ) );
}
A safe solution using streams:
std::string convertHexToDec( const char* h )
{
long long lld;
std::istringstream( h ) >> std::hex >> lld;
std::ostringstream os;
os << lld;
return os.str();
}
Apart from you not using std::string and refrences, I tried the following code:
#include <iostream>
#include <sstream>
void convertHexToDec(char* hex, char* dec)
{
long long decimal;
std::stringstream ss;
ss << hex;
ss >> std::hex >> decimal;
std::cout << "Decimal: " << decimal << "\n";
sprintf (dec, "%llu", decimal);
}
int main()
{
char hex[] = "58";
char dec[4];
convertHexToDec(hex, dec);
std::cout << "Output string: " << dec << "\n";
}
Output:
Decimal: 88
Output string: 88
live example
So what's your problem?
I am trying to convert in C++ a stringstream of "1.txt" so that it is equal to a char* value of "1.txt". I need the raw char* as an argument for a function, so it can't be const char or anything else. When I run it, I get a blank output. Why, and how do I fix it?
#define SSTR(x) dynamic_cast< std::stringstream & >( (std::stringstream() << std::dec << x ) ).str()
int booknum = 1;
std::stringstream stringstream;
stringstream << SSTR(booknum) << ".txt";
std::vector<std::string> argv;
std::vector<char*> argc;
std::string arg;
std::string arg3;
while (stringstream >> arg) argv.push_back(arg);
for (auto i = argv.begin(); i != argv.end(); i++)
argc.push_back(const_cast<char*>(i->c_str()));
argc.push_back(0);
int arg4 = argc.size();
for (int i = 0; i < arg4; i++)
std::cout << &arg3[i] << std::endl;
That seems very complicated, instead of e.g.
std::ostringstream oss;
oss << booknum << ".txt";
std::string s = oss.str();
char* pString = new char[s.length() + 1];
std::copy(s.c_str(), s.c_str() + s.length() + 1, pString);
yourFunctionThatTakesCharPtr(pString);
delete[] pString;
Here's a sample conversion code:
#include <iostream>
#include <sstream>
#include <typeinfo> //it's just to print the resultant type to be sure
int main() {int booknum=1;
std::stringstream ss;
ss << booknum<<"1.txt";
char* x=new char[ss.str().length()+1];
ss >> x;
std::cout<<typeid(x).name();
return 0;}
Output:
Pc
I'm loosing my mind at the moment and below is what I'm trying to do.
char* buffer;
sprintf(buffer, "0x%08x", 5);
*(int *)(0x834AF2AC + 0x1a) = ?buffer?;
Buffer = 0x05000000
I need to set that in memory, if I just set 05 it will set 0x00000005
Question asked better.
How can I convert an INT into a format of "0x%08x"
So 5 becomes 0x05000000
ANSWERD:
The correct answer is *(int *)(0x834AF2AC + 0x1a) = 5<<24;
Something like this:
#include <iostream> // for std::cout, std::endl
#include <string> // for std::string, std::stoi
int main()
{
std::string s{"0x05"};
int i = std::stoi(s, nullptr, 16); // convert base 16 number in s to int
std::cout << i << std::endl;
}
Two result from google which points to stackoverflow (result 1 and 2).
Convert char to int in C and C++
C char* to int conversion
I'm not sure if I understand correctly but if you want to convert an entire string to int, then I would suggest stringstream.
http://www.cplusplus.com/reference/sstream/stringstream/stringstream/
For hexadecimal string:
#include <string> // std::string
#include <iostream> // std::cout
#include <sstream> // std::stringstream
int main () {
std::stringstream ss;
ss << std::hex << 0x05;
int foo;
ss >> foo;
std::cout << "foo: " << foo << '\n';
return 0;
}
I would like to know what is the easiest way to convert an int to C++ style string and from C++ style string to int.
edit
Thank you very much. When converting form string to int what happens if I pass a char string ? (ex: "abce").
Thanks & Regards,
Mousey
Probably the easiest is to use operator<< and operator>> with a stringstream (you can initialize a stringstream from a string, and use the stream's .str() member to retrieve a string after writing to it.
Boost has a lexical_cast that makes this particularly easy (though hardly a paragon of efficiency). Normal use would be something like int x = lexical_cast<int>(your_string);
You can change "%x" specifier to "%d" or any other format supported by sprintf. Ensure to appropriately adjust the buffer size 'buf'
int main(){
char buf[sizeof(int)*2 + 1];
int x = 0x12345678;
sprintf(buf, "%x", x);
string str(buf);
int y = atoi(str.c_str());
}
EDIT 2:
int main(){
char buf[sizeof(int)*2 + 1];
int x = 42;
sprintf(buf, "%x", x);
string str(buf);
//int y = atoi(str.c_str());
int y = static_cast<int>(strtol(str.c_str(), NULL, 16));
}
This is to convert string to number.
#include "stdafx.h"
#include <iostream>
#include <string>
#include <sstream>
int convert_string_to_number(const std::string& st)
{
std::istringstream stringinfo(st);
int num = 0;
stringinfo >> num;
return num;
}
int main()
{
int number = 0;
std::string number_as_string("425");
number = convert_string_to_number(number_as_string);
std::cout << "The number is " << number << std::endl;
std::cout << "Number of digits are " << number_as_string.length() << std::endl;
}
Like wise, the following is to convert number to string.
#include "stdafx.h"
#include <iostream>
#include <string>
#include <sstream>
std::string convert_number_to_string(const int& number_to_convert)
{
std::ostringstream os;
os << number_to_convert;
return (os.str());
}
int main()
{
int number = 425;
std::string stringafterconversion;
stringafterconversion = convert_number_to_string(number);
std::cout << "After conversion " << stringafterconversion << std::endl;
std::cout << "Number of digits are " << stringafterconversion.length() << std::endl;
}
Use atoi to convert a string to an int. Use a stringstream to convert the other way.
i have a string and i need to add a number to it i.e a int. like:
string number1 = ("dfg");
int number2 = 123;
number1 += number2;
this is my code:
name = root_enter; // pull name from another string.
size_t sz;
sz = name.size(); //find the size of the string.
name.resize (sz + 5, account); // add the account number.
cout << name; //test the string.
this works... somewhat but i only get the "*name*88888" and... i don't know why.
i just need a way to add the value of a int to the end of a string
There are no in-built operators that do this. You can write your own function, overload an operator+ for a string and an int. If you use a custom function, try using a stringstream:
string addi2str(string const& instr, int v) {
stringstream s(instr);
s << v;
return s.str();
}
Use a stringstream.
#include <iostream>
#include <sstream>
using namespace std;
int main () {
int a = 30;
stringstream ss(stringstream::in | stringstream::out);
ss << "hello world";
ss << '\n';
ss << a;
cout << ss.str() << '\n';
return 0;
}
You can use string streams:
template<class T>
std::string to_string(const T& t) {
std::ostringstream ss;
ss << t;
return ss.str();
}
// usage:
std::string s("foo");
s.append(to_string(12345));
Alternatively you can use utilities like Boosts lexical_cast():
s.append(boost::lexical_cast<std::string>(12345));
Use a stringstream.
int x = 29;
std::stringstream ss;
ss << "My age is: " << x << std::endl;
std::string str = ss.str();
you can use lexecal_cast from boost, then C itoa and of course stringstream from STL