Can a std::string contain embedded nulls?

Question

For regular C strings, a null character '\0' signifies the end of data.

What about std::string, can I have a string with embedded null characters?

Answer 1

Yes you can have embedded nulls in your std::string.

Example:

std::string s; s.push_back('\0'); s.push_back('a'); assert(s.length() == 2); 

Note: std::string's c_str() member will always append a null character to the returned char buffer; However, std::string's data() member may or may not append a null character to the returned char buffer.

Be careful of operator+=

One thing to look out for is to not use operator+= with a char* on the RHS. It will only add up until the null character.

For example:

std::string s = "hello"; s += "\0world"; assert(s.length() == 5); 

The correct way:

std::string s = "hello"; s += std::string("\0world", 6); assert(s.length() == 11); 

Storing binary data more common to use std::vector

Generally it's more common to use std::vector to store arbitrary binary data.

std::vector<char> buf; buf.resize(1024); char *p = &buf.front(); 

It is probably more common since std::string's data() and c_str() members return const pointers so the memory is not modifiable. with &buf.front() you are free to modify the contents of the buffer directly.

Answer 2

Yes. A std::string is just a vector<char> with benefits.

However, be careful about passing such a beast to something that calls .c_str() and stops at the 0.