inthash.c

/* * * * * * * * *
 * Module containing hash functions for 64-bit unsigned integers
 *
 * created for COMP20007 Design of Algorithms - Assignment 2, 2017
 * by Matt Farrugia <matt.farrugia@unimelb.edu.au>
 *
 * Student Comment: These functions return a 31bit integer
 * as determined by #define constant p_i
 */

#include "inthash.h"

// constants for first hash function
#define A1 885390553
#define B1 639360243
#define p1 2147483629

// constants for second hash function
// are these prime...
#define A2 853977193
#define B2 306837493

// 2^31, the greatest possible non negative two's complement int.
// Non negative since operations will start to fail if neg.
// Ie, if we return a hash greater than p2 and mod that with the size, cast
// it to an int, it could be a negative value. Which will then result in access of non
// allocated memory.
#define p2 2147483563

// first available hash function
int h1(int64 k) {
	return (A1 * k + B1) % p1;
}

// second available hash function
int h2(int64 k) {
	return (A2 * k + B2) % p2;
}