C ++，从字符串到char数组的转换

Question

I would like to perform the above mentioned operation, however I would like to make sure that the char array is exactly the same size with the string at hand.

So the real question is, how can I make an array with a size that is going to be determined in the run time?

Answer 1

allocating memory on the free store, and copying the string in one go:

std::string s("abcdef");

...
char* chars=strdup(s.c_str());

You need to free the memory manually, of course. Documentation eg on the man page . As @Loki mentions: freeing this memory is done through free(chars) , not through delete . Also, you need to include the <cstring> header.

If you want to stay in the c++ world, use a vector ; it can be created with two iterators to copy it's data from, and will allocate on the heap, and will cleanup by itself. Isn't that a treat?

std::vector<char> vec( s.begin(), s.end() );

Answer 2

You can create an array of size known at runtime with the "new" operator:

char* res = new char[str.size()+1];
strncpy(res, str.c_str(), str.size()+1);

Answer 3

std::string s = "hello";
char* c = new char[s.length() + 1]; // '+ 1' is for trailing NULL character.

strcpy(c, s.c_str());

Answer 4

#include <string>

int main(int argc, char *argv[])
{
   std::string random_data("This is a string");

   char *array=new char[random_data.size()+1];

   // do stuff

   delete[] array;

   return 0;
}

Answer 5

Try:

char* res = new char[str.size()+1]();   // Note the () makes sure it is '0' filled.
std::copy(str.begin(), str.end(), res); // Don't need to copy the '\0' as underlying
                                        // array already has '\0' at the end position.
...
delete [] res;                          // Must not forget to delete.

Or: (preferably)

std::vector<char> res(str.begin(), str.end());

Or: If all you want to do is call a C-unction:

str.c_str()

Answer 6

使用strlen（）查找字符串的长度，然后使用malloc（）一个具有该大小的char数组。