# DJB2 Hash Function

The code that I will be referencing is [here](http://www.cse.yorku.ca/~oz/hash.html).
## C

/*
Define a function called "hash" which returns an 
unsigned (positive) long number.
This function takes in a pointer to a char * data type.
Note that C doesn't have str data types unlike Python.
Instead, it lays out chars contiguously in memory and
ends it with a null '\0' terminator character 
to denote the ending of a string. This is why strings are a pain
to deal with in C.
*/
unsigned long hash(unsigned char *str) {
/* 
Initialize a variable named hash to some prime number. 
Prime numbers are very useful in generating pseudo-
random numbers. You don't need to know why it's 5381 as 
it gets very theoretical as to why this is the number 
being used (other than it's a prime number).
*/
    unsigned long hash = 5381;
    int c; // Initialize a variable c

    /* 
    This is by far the most confusing, but this
    loop simply goes through each char and assigns
    it to c until you encounter a null-terminator 
    */
    while (c = *str++)
        /*
        This is the secret-sauce of the hash function
        which simply does some bit manipulation and
        arithmetic to get the hash
        */
        hash = ((hash << 5) + hash) + c; /* hash * 33 + c */

    return hash;
}

## Python
After realizing the annotation above, converting it to Python is pretty straightforward:

def hash_djb2(s):                                       
    hash = 5381
    for x in s:
        # ord(x) simply returns the unicode rep of the
        # character x
        hash = (( hash << 5) + hash) + ord(x)
    # Note to clamp the value so that the hash is 
    # related to the power of 2
    return hash & 0xFFFFFFFF