"""Streaming file hashing (stdlib only)."""
import hashlib
import zlib

CHUNK = 1 << 23  # 8 MiB read chunks


class HashCancelled(Exception):
    """Raised when hashing is cancelled mid-read."""


def hash_file(path, cancel=None):
    crc = 0
    md5 = hashlib.md5()
    sha1 = hashlib.sha1()
    with open(path, "rb") as f:
        while True:
            if cancel is not None and cancel.is_set():
                raise HashCancelled()
            block = f.read(CHUNK)
            if not block:
                break
            crc = zlib.crc32(block, crc)
            md5.update(block)
            sha1.update(block)
    return {
        "crc32": f"{crc & 0xFFFFFFFF:08X}",
        "md5": md5.hexdigest().upper(),
        "sha1": sha1.hexdigest().upper(),
    }