qvarint.py

from typing import Tuple


def decode_integer(data: bytes) -> Tuple[int, int]:
    v = data[0]
    prefix = v >> 6
    length = 1 << prefix
    v = v & 0x3F
    for i in range(1, length):
        v = (v << 8) + data[i]
    return length, v


uint8 = 256


def encode_integer(i: int) -> bytearray:
    if i <= 63:
        return bytearray([i])
    if i <= 16383:
        return bytearray([i >> 8 | 0x40, i % uint8])
    if i <= 1073741823:
        return bytearray(
            [i >> 24 | 0x80, (i >> 16) % uint8, (i >> 8) % uint8, i % uint8]
        )
    if i <= 4611686018427387903:
        return bytearray(
            [
                (i >> 56) % uint8 | 0xC0,
                (i >> 48) % uint8,
                (i >> 40) % uint8,
                (i >> 32) % uint8,
                (i >> 24) % uint8,
                (i >> 16) % uint8,
                (i >> 8) % uint8,
                i % uint8,
            ]
        )
    raise ValueError(f"{integer} doesn't fit into 62 bits")