iframe-proxy | Sunbelt Computer Software

37 lines (31 loc) · 1.31 KB

"""

This algorithm was created for sdbm (a public-domain reimplementation of ndbm)

database library.

It was found to do well in scrambling bits, causing better distribution of the keys

and fewer splits.

It also happens to be a good general hashing function with good distribution.

The actual function (pseudo code) is:

for i in i..len(str):

hash(i) = hash(i - 1) * 65599 + str[i];

What is included below is the faster version used in gawk. [there is even a faster,

duff-device version]

The magic constant 65599 was picked out of thin air while experimenting with

different constants.

It turns out to be a prime.

This is one of the algorithms used in berkeley db (see sleepycat) and elsewhere.

source: http://www.cse.yorku.ca/~oz/hash.html

"""

def sdbm(plain_text: str) -> str:

"""

Function implements sdbm hash, easy to use, great for bits scrambling.

iterates over each character in the given string and applies function to each of

them.

>>> sdbm('Algorithms')

1462174910723540325254304520539387479031000036

>>> sdbm('scramble bits')

730247649148944819640658295400555317318720608290373040936089

"""

hash = 0

for plain_chr in plain_text:

hash = ord(plain_chr) + (hash << 6) + (hash << 16) - hash

return hash

Sunbelt Computer Software