strtok_s() Why do we need address of a pointer?

Question

I am back with C++ after 15 years...I just can't remember why we need the address of a pointer. Like in this statement:

char *next_token = NULL;
char *pszMozilla = strtok_s(szCopyVariable, "/", &next_token);

Is there an assumption that the address of the pointer will represent eventually the start of a list of pointers ?

Answer 1

strtok_s is a reentrant function, and it needs to store some state somewhere. That state is a pointer to the character one after the last one it processed. (Think about it, that's really all you need to resume tokenizing.)

If a function wants to store an X in a user-provided space, the user needs to provide a pointer to an X, pointing to where the X will go. In our case, X is a "pointer to char".

Answer 2

那是因为strtok_s()通过在每次调用时移动next_token维护状态。