Convert char to int in C

/** Return the value corresponding to a character.

* @param radix - the base you are working in (2-36)
* @param digit - character '0'..'9' or 'A'..'Z' or 'a'..'z'
* @return - value in the range of 0 - (radix-1) correspondingto
* the given digit if the digit is valid in the given radix.Otherwise return
* -1
*/

function name:
int char2int (int radix, char digit);