Python BKDR Hash Code Example (Online Runner)

Python BKDR hash examples with seed parsing, number/hex output, and file hashing to match the BKDR tool.

Online calculator: use the site BKDR text tool.

Calculation method

BKDRHash is a fast rolling hash that multiplies the running value by a seed and adds each byte. The online tool lets you set the seed (decimal or hex) and choose number or hex output.

Implementation notes

Package: no external dependencies; this is a pure Python implementation.
Implementation: the hash is computed over UTF-8 bytes (or file bytes) and masked to 32 bits to match the tool output.
Notes: BKDR is not cryptographic. Different seeds produce different hashes, so keep the seed consistent across systems.

from pathlib import Path
from typing import Literal

OutputFormat = Literal["number", "hex"]


DEFAULT_SEED = 131
UINT32_MASK = 0xFFFFFFFF


def parse_seed(value: str, fallback: int = DEFAULT_SEED) -> int:
    if not value.strip():
        return fallback
    cleaned = value.strip()
    base = 16 if cleaned.startswith(("0x", "0X")) else 10
    return int(cleaned, base) & UINT32_MASK


def bkdr_hash_bytes(data: bytes, seed: int = DEFAULT_SEED) -> int:
    if seed <= 0:
        raise ValueError("Seed must be positive")
    value = 0
    for byte in data:
        value = (value * seed + byte) & UINT32_MASK
    return value


def format_bkdr(value: int, output_format: OutputFormat = "number") -> str:
    if output_format == "hex":
        return f"{value:08x}"
    return str(value)


def bkdr_text(text: str, seed: int = DEFAULT_SEED, encoding: str = "utf-8", output_format: OutputFormat = "number") -> str:
    value = bkdr_hash_bytes(text.encode(encoding), seed)
    return format_bkdr(value, output_format)


def bkdr_file(path: Path, seed: int = DEFAULT_SEED, output_format: OutputFormat = "number") -> str:
    data = path.read_bytes()
    value = bkdr_hash_bytes(data, seed)
    return format_bkdr(value, output_format)

# Example usage
message = "hello"
seed = parse_seed("0x83")  # 131 in hex

print(bkdr_text(message, seed=seed, output_format="number"))
print(bkdr_text(message, seed=seed, output_format="hex"))

File hashing example

from pathlib import Path
import tempfile

DEFAULT_SEED = 131
UINT32_MASK = 0xFFFFFFFF


def bkdr_hash_bytes(data: bytes, seed: int = DEFAULT_SEED, initial: int = 0) -> int:
    value = initial & UINT32_MASK
    for byte in data:
        value = (value * seed + byte) & UINT32_MASK
    return value


def bkdr_file(path: Path, seed: int = DEFAULT_SEED, output_format: str = "hex") -> str:
    value = bkdr_hash_bytes(path.read_bytes(), seed)
    return f"{value:08x}" if output_format == "hex" else str(value)


with tempfile.TemporaryDirectory() as temp_dir:
    sample_path = Path(temp_dir) / "sample.txt"
    sample_path.write_text("hello", encoding="utf-8")
    print(bkdr_file(sample_path, seed=131, output_format="hex"))

Complete script (implementation + tests)

from pathlib import Path
import tempfile

DEFAULT_SEED = 131
UINT32_MASK = 0xFFFFFFFF


def bkdr_hash_bytes(data: bytes, seed: int = DEFAULT_SEED) -> int:
    value = 0
    for byte in data:
        value = (value * seed + byte) & UINT32_MASK
    return value


def bkdr_text(text: str, seed: int = DEFAULT_SEED) -> str:
    return f"{bkdr_hash_bytes(text.encode('utf-8'), seed):08x}"


def run_tests() -> None:
    assert bkdr_text("") == "00000000"
    assert bkdr_text("abc") == "001998f2"

    with tempfile.TemporaryDirectory() as temp_dir:
        sample_path = Path(temp_dir) / "sample.txt"
        sample_path.write_bytes(b"abc")
        assert bkdr_text("abc") == f"{bkdr_hash_bytes(sample_path.read_bytes()):08x}"

    print("BKDR tests passed")


if __name__ == "__main__":
    run_tests()