Is the bottom of the string of C + + really implemented with a char array?

First, Introduction

There is a problem: Encrypt the data using an encrypted library, get the ciphertext, save and transfer it using a string, and then decrypt it correctly, but using STRING.C_STR () for parameter passing does not correctly decrypt the plaintext.

The reason is that there is a byte in the ciphertext is 0, which causes the char array to be truncated when the argument is passed, but why is the string class not truncated using a char array?

Second, step

First of all think to see the source, Mr. Houtie said: Source code before, no secret.

Well, read the source code, but did not understand, the skill is not enough ah, still need to continue to cultivate

Is the bottom of the string of C + + really implemented with a char array?