std::string::data() in C++
Last Updated :
06 Jul, 2017
The data() function writes the characters of the string into an array. It returns a pointer to the array, obtained from conversion of string to the array. Its Return type is not a valid C-string as no ‘\0’ character gets appended at the end of array.
Syntax:
const char* data() const;
char* is the pointer to the obtained array.
Parameters : None
- std::string::data() returns an array that is owned by the string. Thus, the caller must not modify or free the memory.
Let’s take same example where ptr points to final array.
ptr[2] = 'a';
this will raise an error as ptr points to an array that
is owned by the string, in other words ptr is now pointing
to constant array and assigning it a new value is now not allowed.
- Return value of data() is valid only until the next call of a non-constant member function for the same string.
Explanation :
Suppose, str be the original string which is required to be converted in an array
// converts str in an array pointed by pointer ptr.
const char* ptr = str.data();
// Bad access of str after modification
// of original string to an array
str += "hello"; // invalidates ptr
// Now displaying str with reference of ptr
// will give garbage value
cout << ptr; // Will give garbage value
#include <iostream>
#include <string>
#include <cstring>
using namespace std;
void dataDemo(string str1)
{
const char * str2;
str2 = str1.data();
cout << "Content of transformed string : " ;
cout << str2 << endl;
cout << "After data(), length: " ;
cout << strlen (str2);
}
int main()
{
string str( "GeeksforGeeks" );
cout << "Content of Original String : " ;
cout << str << endl;
cout << "Length of original String : " ;
cout << str.size() << endl;
dataDemo(str);
return 0;
}
|
Output:
Content of Original String : GeeksforGeeks
Length of original String : 13
Content of transformed string : GeeksforGeeks
After data(), length: 13
Here, we can easily notice, both contents and length of original string and transformed array are same.
If you like GeeksforGeeks (We know you do!) and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org.
Like Article
Suggest improvement
Share your thoughts in the comments
Please Login to comment...