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convert a std::string to const char* or char*

2017-05-09 00:00 351 查看

If you just want to pass a

std::string

to a function that needs

const char*

you can use

std::string str;
const char * c = str.c_str();

If you want to get a writable copy, like

char *

, you can do that with this:

std::string str;
char * writable = new char[str.size() + 1];
std::copy(str.begin(), str.end(), writable);
writable[str.size()] = '\0'; // don't forget the terminating 0

// don't forget to free the string after finished using it
delete[] writable;

Edit: Notice that the above is not exception safe. If anything between the

new

call and the

delete

call throws, you will leak memory, as nothing will call

delete

for you automatically. There are two immediate ways to solve this.

boost::scoped_array

boost::scoped_array

will delete the memory for you upon going out of scope:

std::string str;
boost::scoped_array<char> writable(new char[str.size() + 1]);
std::copy(str.begin(), str.end(), writable.get());
writable[str.size()] = '\0'; // don't forget the terminating 0

// get the char* using writable.get()

// memory is automatically freed if the smart pointer goes
// out of scope

std::vector

This is the standard way (does not require any external library). You use

std::vector

, which completely manages the memory for you.

std::string str;
std::vector<char> writable(str.begin(), str.end());
writable.push_back('\0');

// get the char* using &writable[0] or &*writable.begin()

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