pyppmd-gentee 1.4.0

PPMd compression/decompression library with Gentee installer variant decoder

A fork of pyppmd that adds the Gentee PPMd-I variant decoder (Ppmd8gDecoder). Installable alongside the official pyppmd package.

Install with pip install pyppmd-gentee, then import pyppmd_gentee.

Introduction

pyppmd_gentee provides the same classes and functions as pyppmd for compressing and decompressing data using the PPMd algorithm, plus Ppmd8gDecoder — a variant of PPMd-I that implements the Gentee installer’s modified codec.

Development status

A project status is considered as Stable.

Gentee PPMd-I variant

Ppmd8gDecoder decodes data compressed with the PPMd variant used in Gentee installers. It differs from the standard PPMd-I codec in BinSumm initialization, frequency updates, and model restore behaviour.

import pyppmd_gentee

dec = pyppmd_gentee.Ppmd8gDecoder(max_order=6, mem_size=16 << 20)
result = dec.decode(compressed_data, expected_length)

For streaming across multiple files (as in GEA archives), use lightweight_reset() or reinit() between entries to manage the decoder state:

dec = pyppmd_gentee.Ppmd8gDecoder(max_order=6, mem_size=16 << 20)

first_file = dec.decode(chunk_0, length_0)

dec.lightweight_reset()  # keeps model, resets context to root
second_file = dec.decode(chunk_1, length_1)

dec.reinit(6)  # full model rebuild
third_file = dec.decode(chunk_2, length_2)

See examples/extract_stardef.py for a complete example that downloads and extracts a Gentee-based installer using Ppmd8gDecoder.

Extra input byte

PPMd algorithm and implementation is designed to use Extra input byte. The encoder will omit a last null (b”0”) byte when last byte is b”0”. You may need to provide an extra null byte when you don’t get expected size of extracted data.

You can do like as:

dec = pyppmd.Ppmd7Decoder(max_order=6, mem_size=16 << 10)
result = dec.decode(compressed, length)
if len(result) < length:
    if dec.needs_input:
        # ppmd need an extra null byte
        result += dec.decode(b"\0", length - len(result))
    else:
        result += dec.decode(b"", length - len(result))

Warning

When use it on MSYS2/MINGW64 environment, you should set environment variable SETUPTOOLS_USE_DISTUTILS=stdlib

Copyright and License

Some codes are derived from p7zip/7zip and pyzstd project. Details are shown in LicenseNotices.rst

• SPDX-License-Identifier: LGPL-2.1-or-later

• SPDX-URL: https://spdx.org/licenses/LGPL-2.1-or-later.html

PyPPMd is licensed under GNU Lesser General Public License v2.1 or later.

• Copyright (C) 2020-2025 Hiroshi Miura

• Copyright (C) 2020-2021 Ma Lin

• Copyright (C) 2010-2012 Lockless Inc.

• Copyright (C) 1999-2017 Igor Pavlov

This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA