Andy Shulman Andy Shulman - 28 days ago 6
C++ Question

Tokenizing multiple strings simultaneously

Say I have three c-style strings,

char buf_1[1024]
,
char buf_2[1024]
, and
char buf_3[1024]
. I want to tokenize them, and do things with the first token from all three, then do the same with the second token from all three, etc. Obviously, I could call
strtok
and loop through them from the beginning each time I want a new token. Or alternatively, pre-process all the tokens, stick them into three arrays and go from there, but I'd like a cleaner solution, if there is one.

Answer

It sounds like you want the reentrant version of strtok, strtok_r which uses a third parameter to save its position in the string instead of a static variable in the function.

Here's some example skeleton code:

char buf_1[1024], buf_2[1024], buf_3[1024];
char *save_ptr1, *save_ptr2, *save_ptr3;
char *token1, *token2, *token3;

// Populate buf_1, buf_2, and buf_3

// get the initial tokens
token1 = strtok_r(buf_1, " ", &save_ptr1);
token2 = strtok_r(buf_2, " ", &save_ptr2);
token3 = strtok_r(buf_3, " ", &save_ptr3);

while(token1 && token2 && token3) {
    // do stuff with tokens

    // get next tokens
    token1 = strtok_r(NULL, " ", &save_ptr1);
    token2 = strtok_r(NULL, " ", &save_ptr2);
    token3 = strtok_r(NULL, " ", &save_ptr3);
}
Comments