Passing C++ String to C libraries for memory management - c++

Question

I am trying to use a C Library, which requires that I pass in dynamically allocated c-strings for the functions to modify. However, I want to avoid using new/delete operators because I feel it is better practice to have memory management done under the hood by STL libraries, rather than by me.
Below, I'm trying to use std::string (and vectors) to solve this problem, and preallocating them before passing them to the C function. The examples with one string (CChar, CVoid) work, but I'm still unsure if this is the correct way, or even if it is a safe way (bug-free) to do it. Using vectors does not seem to work at all.
I have included the "C"-way of doing what I want to achieve for both strings and vectors.
#include <string>
#include <iostream>
#include <vector>
// ----------------------------------------------------
// Example C library Code
void CChar(char* data, int len)
{
int i;
for (i = 0; i < len; ++i)
data[i] = 'A' + (i % 26);
}
void CVoid(void* data, int len)
{
char* d = (char*)data;
int i;
for (i = 0; i < len; ++i)
d[i] = 'Z' - (i % 26);
}
void CStrings(char** strings, int count, int lengths)
{
int i, j;
for (i = 0; i < count; ++i)
for (j = 0; j < lengths; ++j)
strings[i][j] = 'A' + ((i * j + i) % 26);
}
// ----------------------------------------------------
// C++ code
int main()
{
// Traditional way, using new/delete.
char* c = new char[11];
CChar(c, 10);
c[10] = '\0';
std::cout << c << std::endl; // ABCDEFGHIJ
delete [] c;
std::string s(10, '\0');
CChar(&s[0], 10);
std::cout << s << std::endl; // ABCDEFGHIJ
CVoid(&s[0], 10);
std::cout << s << std::endl; // ZYXWVUTSRQ
std::vector<std::string> v(5, std::string(10, '\0'));
// Traditional way with arrays of arrays.
char** cc = new char*[5];
for (int i = 0; i < 5; ++i)
{
cc[i] = new char[11];
cc[i][10] = '\0';
}
CStrings(cc, 5, 10);
for (int i = 0; i < 5; ++i)
{
std::cout << cc[i] << std::endl; // AAAAAAAAAA, BCDEFGHIJK, CEGIKMOQSU, DGJMPSVYBE, EIMQUYCGKO
delete [] cc[i];
}
delete [] cc;
// Doesn't compile
// CStrings(&v[0], 5, 10);
// for (int i = 0; i < 5; ++i)
// std::cout << v[i] << std::endl;
return 0;
}
Summary: Is there a good way to use C++'s STL libraries so that I don't need to do my own resource management when trying to use C libraries.
edit: Error cleaning up array of arrays

Answer 1

Sure, you can just use std::vector<char> is you don't want to think about allocation. Here's how you do it:
#include <vector>
int main()
{
std::vector<char> str(100, 0); //Allocate an array of 100 chars and initialize them to 0
SomeFunction(&str[0], str.size()); //Pass the address to the array and its size
return 0;
}

Answer 2

For arrays of arrays, can store a vector<char*> which refers to the starts of the already dynamically allocated std::vector<std::string>.
int main()
{
std::vector<std::string> v(5, std::string(10, '\0'));
std::vector<char*> vc(5);
for (int i = 0; i < 5; ++i)
vc[i] = &(v[i])[0];
CStrings(&vc[0], 5, 10);
for (int i = 0; i < 5; ++i)
std::cout << v[i] << std::endl;
return 0;
}