get_role.py

class Succinct:

    def __init__(self, name_prefix: str, bin_bits: int):
        self.name_prefix = name_prefix

        # number of bins
        bin_count = 2**bin_bits

        # length of string prefix to get from targetpath hash
        self.prefix_len = math.ceil(math.log(bin_count, 16))

        # how many different prefixes are there?
        prefix_count = 16**self.prefix_len

        # how many prefixes per bin
        self.prefixes_per_bin = prefix_count // bin_count

    def get_role(self, target_path_hash: str) -> str:

        # prefix of the hash of the targetpath we are looking for
        prefix_number = int(target_path_hash[:self.prefix_len], 16)

        # number of the bin that contains prefix
        bin_number = prefix_number // self.prefixes_per_bin

        # form the rolename: bin number is in hex with leading zero
        return f"{self.name_prefix}-{bin_number:0{self.prefix_len}x}"