Thread: How do you return a value and pointer from a function?

Yeah, I understood your problem, but gave you an example of passing back values through parameters, so you could extrapolate for your situation. I didn't really want to write your whole solution for you. Note that passing a string (char array) to a function passes a pointer to the first element, so you don't need to do anything else. Treat it like an array in the function. Changing array[3] in the function will change array[3] in the calling code as well:

Code:

void parseIP(char *input, char *output)
{
    ...
    strcpy(output, "foobar");  // this will change the actual string you passed in
}

Tater,

Good suggestions. I'll try and put something together using these functions.

Bob

Anduril,

I'm not trying to change the contents of a string or other value. I'm trying to pass back a pointer to the 4th char (&str+4) in the string w/o using the return statement.

Thanks for your time,
Bob

Originally Posted by bobv

Anduril,

I'm not trying to change the contents of a string or other value. I'm trying to pass back a pointer to the 4th char (&str+4) in the string w/o using the return statement.

Thanks for your time,
Bob

Based Anduril's example in message #16...

Code:

void parseIP(char *input, char *output)
{
   // ...
   output = &input[4]; 
}

Thanks guys I think this is what I was looking for. Touche to both of you!!

Bob: I guess I got a little confused on what exactly you wanted. If you want to return a pointer, then, extrapolating from my first example, you need to pass a pointer to a pointer (my example in message #16, that Tater quoted, needs a small modification):

Code:

void parseIP(char *input, char **output)
{
    *output = input + 4;  // or whichever quad you left off at
    *output = &input[4];  // this is equivalent to the above
}
...
char *input;
char *next_spot_to_parse;
parseIP(input, &next_spot_to_parse);
// now next_spot_to_parse points to the next quad
// you can pass that in as your new starting point for the next time:
parseIP(next_spot_to_parse, &next_spot_to_parse);  // this works, since the first param is copied when passed in, so there is no conflict

Anduril,
Most Excellent! I tried your first example "input+4" but didn't use a "**" I just used a single '*', no wonder it didn't work. What you say makes perfect sense too I needed to specify a ptr to a ptr. Many thanks for the clarification, I'd still be spinning my wheels w/o it.

Tater,
Your help was awesome too. You made me rethink what I'm doing and am going to process a quadrant at a time at the user character input level which will give me more control and a much cleaner solution. If they bomb on any quadrant I'll send them back to the beginning and force them to start over and I wont let them enter more than 4 quadrants.

You're both slick coders, hat's off!!

Forever Grateful,
Very Rusty C Coder - Bob

Originally Posted by bobv

I know how to use return to pass back a value and/or a pointer but would like to do both.

Like this :

Code:

//EX:  Not sure I declared ptrStrgPlus4 correctly to have it be
// a pointer to strg+4 (ie '.') on return from the getBoth function
int num;  char strg[5]="123.456"; char *ptrStrgPlus4; 

   x = getBoth(10, strg, &ptrStrgPlus4);

// Would like to return the num*10, plus a pointer to the '.'
int function getBoth(int num, char *string, char **stringPtr) {
    // I know the next line doesn't work
      *stringPtr = string+4;     // Return pointer to 4th char in the string
     return (num*10);
}

Edit - should have read to the end of the thread, looks like I'm a day late.

KC,

Great, better late than never....another winner!!!
So simple when you know how. I was just a couple chars away.
Hate when that happens.

Many thanks; have a great Thanksgiving,
Bob