如何在C ++的basic_string内部具有空值

Question

Is there a way to have and process null value inside std::basic_string ?

Sometimes the string sequence being passed has null values. For example below code outputs 1234,5678 instead of whole string.

#include <iostream>
#include <string>
#include <cstring>
int main ()
{
   int length;
   std::string str = "1234,5678\000,ABCD,EFG#";
   std::cout << "length"<<str.c_str();
}

I need to get the complete string.

Answer 1

First, you'll have to tell the string constructor the size; it can only determine the size if the input is null-terminated. Something like this would work:

std::string str("1234,5678\000,ABCD,EFG#", sizeof("1234,5678\000,ABCD,EFG#")-1);

There's no particularly nice way to avoid the duplication; you could declare a local array

char c_str[] = "1234,5678\000,ABCD,EFG#"; // In C++11, perhaps 'auto const & c_str = "...";'
std::string str(c_str, sizeof(c_str)-1);

which might have a run-time cost; or you could use a macro; or you could build the string in pieces

std::string str = "1234,5678";
str += '\0';
str += ",ABCD,EFG#";

Finally, stream the string itself (for which the size is known) rather than extracting a c-string pointer (for which the size will be determined by looking for a null terminator):

std::cout << "length" << str;

UPDATE: as pointed out in the comments, C++14 adds a suffix for basic_string literals:

std::string str = "1234,5678\000,ABCD,EFG#"s;
                                           ^

which, by my reading of the draft standard, should work even if there is an embedded null character.

Answer 2

You can do this with std::string(std::initalizer_list<char> il) it's just a little bit of a pain in the neck:

string str{'1', '2', '3', '4', ',', '5', '6', '7', '8', '\0', '0', '0', ',', 'A', 'B', 'C', 'D', ',', 'E', 'F', 'G', '#'};
cout << "length: " << str.size() << ": " << str;

Outputs:

length: 22: 1234,567800,ABCD,EFG#