Fix the '0z' bug in linux

[UnknownObject000]

I use this in linux,its 'encodebytes' function can work,but when I use the 'decodebytes' function,it cause errors as follows.

File "/data/data/com.termux/files/usr/lib/python3.7/site-packages/base62.py", line 95, in decodebytes
    decoded = decode(s, charset=charset)
  File "/data/data/com.termux/files/usr/lib/python3.7/site-packages/base62.py", line 77, in decode
    if b.startswith('0z'):
TypeError: startswith first arg must be bytes or a tuple of bytes, not str

I changed the 'base62.py' file,and it works.

[coveralls]

Coverage decreased (-4.4%) to 93.86% when pulling cd52f77 on master into a9b9e7e on develop.

[UnknownObject000]

I want to add the new 'base62.py' in this pull request,but I can't.Here are the source code.

# -*- coding: utf-8 -*-
"""
base62
~~~~~~

Originated from http://blog.suminb.com/archives/558
"""

__title__ = 'base62'
__author__ = 'Sumin Byeon'
__email__ = 'suminb@gmail.com'
__version__ = '0.4.1'

BASE = 62
CHARSET_DEFAULT = (
    '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
)
CHARSET_INVERTED = (
    '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
)


def bytes_to_int(s, byteorder='big', signed=False):
    """Converts a byte array to an integer value.

    Python 3 comes with a built-in function to do this, but we would like to
    keep our code Python 2 compatible.
    """

    try:
        return int.from_bytes(s, byteorder, signed=signed)
    except AttributeError:
        # For Python 2.x
        if byteorder != 'big' or signed:
            raise NotImplementedError()

        # NOTE: This won't work if a generator is given
        n = len(s)
        ds = (x << (8 * (n - 1 - i)) for i, x in enumerate(bytearray(s)))

        return sum(ds)


def encode(n, minlen=1, charset=CHARSET_DEFAULT):
    """Encodes a given integer ``n``."""

    chs = []
    while n > 0:
        r = n % BASE
        n //= BASE

        chs.append(charset[r])

    if len(chs) > 0:
        chs.reverse()
    else:
        chs.append('0')

    s = ''.join(chs)
    s = charset[0] * max(minlen - len(s), 0) + s
    return s


def encodebytes(s, charset=CHARSET_DEFAULT):
    """Encodes a bytestring into a base62 string.

    :param s: A byte array
    """

    _check_bytes_type(s)
    return encode(bytes_to_int(s), charset=charset)


def decode(b, charset=CHARSET_DEFAULT):
    """Decodes a base62 encoded value ``b``."""

    if b.startswith(b'0z'):
        b = b[2:]

    l, i, v = len(b), 0, 0
    for x in b:
        v += _value(x, charset=charset) * (BASE ** (l - (i + 1)))
        i += 1

    return v


def decodebytes(s, charset=CHARSET_DEFAULT):
    """Decodes a string of base62 data into a bytes object.

    :param s: A string to be decoded in base62
    :rtype: bytes
    """

    decoded = decode(s, charset=charset)
    buf = bytearray()
    while decoded > 0:
        buf.append(decoded & 0xff)
        decoded //= 256
    buf.reverse()

    return bytes(buf)


def _value(ch, charset):
    """Decodes an individual digit of a base62 encoded string."""

    try:
        return charset.index(chr(ch))
        #return charset[ch]
    except ValueError:
        raise ValueError('base62: Invalid character (%s)' % ch)


def _check_bytes_type(s):
    """Checks if the input is in an appropriate type."""

    if not isinstance(s, bytes):
        msg = 'expected bytes-like object, not %s' % s.__class__.__name__
        raise TypeError(msg)

[suminb]

decodebytes() decodes str into bytes. Would you be able to share your code that causes the issue you described?

[UnknownObject000]

Here are my code.By the way,it works fine in Windows10,python 3.7.4.

import base62

def EncodeBase62(string):
    return base62.encodebytes(string.encode('utf-8'))

def DecodeBase62(string):
    return str(base62.decodebytes(string.encode('utf-8')),'utf-8')

if __name__ == "__main__":
    cmd=input("Task(\"1\" for encode and \"2\" for decode):")
    string=input("Input string:")
    if cmd == "1":
        print("Base62 code:",EncodeBase62(string))
    if cmd == "2":
        print("Decoded str:",DecodeBase62(string))

[suminb]

decodebytes() is expected to take str types as an input. In your case, it should've been base62.decodebytes(string), assuming string is a str type. I understand their namings could be somewhat confusing, but they are intended to be communicative, so that they hold the following relationships:

• value == encodebytes(decodebytes(value))
• value == decodebytes(encodebytes(value))

I've added some documentations in README.rst. You may also refer the latest documentation on https://pypi.org/project/pybase62/ or https://github.com/suminb/base62/blob/develop/README.rst. See the bottom part of the Usage section.