bloomfilter.py

'''
sonicskye
bloomfilter.py

Requirements:
bitarray (https://github.com/ilanschnell/bitarray)
pybloof (https://github.com/jhgg/pybloof)

Pybloof library is used due to its built-in export and import features
These features are convenient for storing the bloom filter information to the smart contract
    and import them if needed
'''

import pybloof
import utilities as u


def createstringbloomfilter(wordlist):
    # if the size is too small then the result is inaccurate
    # makes sure that there is an extra 500 allowance; false positive still exists
    # the input wordlist is converted into setwordlist to remove duplicates
    setwordlist = set(wordlist)
    sz = len(setwordlist) + 500
    bf = pybloof.StringBloomFilter(size=sz, hashes=9)
    for word in wordlist:
        #bf.add(word)
        if word not in bf:
            bf.add(word)
    return bf.to_base64().decode('utf-8')


def teststringbloomfilter(bfValue, wordlist):
    bf = pybloof.StringBloomFilter.from_base64(bfValue.encode('utf-8'))
    setwordlist = set(wordlist)
    wlength = len(setwordlist)
    #print (str(wlength))
    positive = 0
    for word in setwordlist:
        if word in bf:
            positive += 1;
    res = round(positive/wlength *100)
    return res


##################################### test ################################