This page on string::string
gives two potential constructors that would do what you want:
string ( const char * s, size_t n );
string ( const string& str, size_t pos, size_t n = npos );
Example:
#include<cstdlib>
#include<cstring>
#include<string>
#include<iostream>
using namespace std;
int main(){
char* p= (char*)calloc(30, sizeof(char));
strcpy(p, "Hello world");
string s(p, 15);
cout << s.size() << ":[" << s << "]" << endl;
string t(p, 0, 15);
cout << t.size() << ":[" << t << "]" << endl;
free(p);
return 0;
}
Output:
15:[Hello world]
11:[Hello world]
The first form considers p
to be a simple array, and so will create (in our case) a string of length 15, which however prints as a 11-character null-terminated string with cout << ...
. Probably not what you’re looking for.
The second form will implicitly convert the char*
to a string, and then keep the maximum between its length and the n
you specify. I think this is the simplest solution, in terms of what you have to write.