Browse Source

Draft the initial version

This is inspired by Daniel Holth's module httpfile and is based on
the discussion over https://github.com/pypa/pip/issues/7819
master
Nguyễn Gia Phong 2 years ago
parent
commit
1e8b470737
  1. 9
      .travis.yml
  2. 187
      lazip.py
  3. 24
      pyproject.toml
  4. 18
      tox.ini

9
.travis.yml

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branches:
only:
- master
- /^\d+(\.\d+)+((a|b|rc)\d+)?(\.post\d+)?(\.dev\d+)?$/
language: python
install: pip install tox
script: tox

187
lazip.py

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# Lazy ZIP over HTTP
# Copyright (C) 2020 Nguyễn Gia Phong
#
# This file is part of lazip.
#
# lazip 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 3 of the License,
# or (at your option) any later version.
#
# lazip 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 palace. If not, see <https://www.gnu.org/licenses/>.
"""Lazy ZIP over HTTP"""
__version__ = '0.0.1'
__all__ = ['Lazip']
from bisect import bisect_left, bisect_right
from contextlib import contextmanager
from tempfile import NamedTemporaryFile
from typing import Dict, Iterator, List, Optional, Tuple
from zipfile import BadZipFile, ZipFile
from pip._internal.network.utils import response_chunks
from pip._internal.utils.wheel import pkg_resources_distribution_for_wheel
from requests import Session
from requests.models import CONTENT_CHUNK_SIZE, Response
HEADERS: Dict[str, str] = {'Accept-Encoding': 'identity'}
def init_range(stop: int, size: int) -> Iterator[Tuple[int, int]]:
"""Return an iterator of intervals to fetch a file reversedly."""
start = stop - size
while start > 0:
yield start, stop-1
stop = start
start -= size
yield 0, stop-1
class Lazip:
"""File-like object mapped to a ZIP file over HTTP.
This uses HTTP range requests to lazily fetch the file's content,
which is supposed to be fed to ZipFile.
"""
def __init__(self, session: Session, url: str,
chunk_size: int = CONTENT_CHUNK_SIZE) -> None:
head = session.head(url, headers=HEADERS)
head.raise_for_status()
assert head.status_code == 200
self.session, self.url, self.chunk_size = session, url, chunk_size
self.length = int(head.headers['Content-Length'])
self.file = NamedTemporaryFile()
self.file.truncate(self.length)
self.left: List[int] = []
self.right: List[int] = []
self.check_zip('bytes' in head.headers.get('Accept-Ranges', 'none'))
def __enter__(self) -> 'Lazip':
self.file.__enter__()
return self
def __exit__(self, *exc) -> Optional[bool]:
return self.file.__exit__(*exc)
@property
def name(self):
"""File name."""
return self.file.name
def seekable(self):
"""Return whether random access is supported, which is True."""
return True
@contextmanager
def stay(self) -> Iterator[None]:
"""Return a context manager keeping the position.
At the end of the block, seek back to original position.
"""
pos = self.tell()
try:
yield
finally:
self.seek(pos)
def check_zip(self, range_request: bool):
"""Check and download until the file is a valid ZIP."""
if not range_request:
end = self.length - 1
self.download(0, end)
self.left, self.right = [0], [end]
return
for start, end in init_range(self.length, self.chunk_size):
self.download(start, end)
with self.stay():
try:
ZipFile(self)
except BadZipFile:
pass
else:
break
def stream_response(self, start: int, end: int,
base_headers: Dict[str, str] = HEADERS) -> Response:
"""Return HTTP response to a range request from start to end."""
headers = {'Range': f'bytes={start}-{end}'}
headers.update(base_headers)
return self.session.get(self.url, headers=headers, stream=True)
def merge(self, start: int, end: int,
left: int, right: int) -> Iterator[Tuple[int, int]]:
"""Return an iterator of intervals to be fetched.
Args:
start (int): Start of needed interval
end (int): End of needed interval
left (int): Index of first overlapping downloaded data
right (int): Index after last overlapping downloaded data
"""
lslice, rslice = self.left[left:right], self.right[left:right]
i = start = min(start, min(lslice, default=start))
end = min(end, min(rslice, default=end))
for j, k in zip(lslice, rslice):
if j > i: yield i, j-1
i = k + 1
if i <= end: yield i, end
self.left[left:right], self.right[left:right] = [start], [end]
def download(self, start: int, end: int):
"""Download bytes from start to end inclusively."""
with self.stay():
i, j = bisect_left(self.right, start), bisect_right(self.left, end)
for start, end in self.merge(start, end, i, j):
response = self.stream_response(start, end)
response.raise_for_status()
self.seek(start)
for chunk in response_chunks(response, self.chunk_size):
self.file.write(chunk)
def read(self, size: int = -1) -> bytes:
"""Read up to size bytes from the object and return them.
As a convenience, if size is unspecified or -1,
all bytes until EOF are returned. Fewer than
size bytes may be returned if EOF is reached.
"""
start = self.tell()
stop = start + size if 0 <= size <= self.length-start else self.length
self.download(start, stop-1)
return self.file.read(size)
def seek(self, offset: int, whence: int = 0) -> int:
"""Change stream position and return the new absolute position.
Seek to offset relative position indicated by whence:
* 0: Start of stream (the default). pos should be >= 0;
* 1: Current position - pos may be negative;
* 2: End of stream - pos usually negative.
"""
return self.file.seek(offset, whence)
def tell(self) -> int:
"""Return the current possition."""
return self.file.tell()
def close(self) -> None:
"""Close the file."""
self.file.close()
if __name__ == '__main__':
url = ('https://files.pythonhosted.org/packages/17/d9/'
'ff8955ce17c080c956cd5eed9c2da4de139d5eeabb9f9ebf2d981acef31d/'
'brutalmaze-0.9.2-py3-none-any.whl')
with Lazip(Session(), url) as wheel:
print(pkg_resources_distribution_for_wheel(
ZipFile(wheel), 'brutalmaze', wheel.name).requires())

24
pyproject.toml

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[build-system]
requires = ['flit_core >=2,<3']
build-backend = 'flit_core.buildapi'
[tool.flit.metadata]
module = 'lazip'
author = 'Nguyễn Gia Phong'
author-email = 'mcsinyx@disroot.org'
home-page = 'https://github.com/McSinyx/lazip'
requires = ['pip', 'requests']
description-file = 'README.md'
classifiers = [
'Development Status :: 1 - Planning',
'Intended Audience :: Developers',
'License :: OSI Approved :: GNU Lesser General Public License v3 or later (LGPLv3+)',
'Natural Language :: English',
'Operating System :: OS Independent',
'Programming Language :: Python',
'Programming Language :: Python :: 3 :: Only',
'Topic :: Internet :: WWW/HTTP',
'Typing :: Typed']
requires-python = '>=3.6'
keywords = 'zip,http,range,lazy'
license = 'LGPLv3+'

18
tox.ini

@ -0,0 +1,18 @@
[tox]
envlist = py
minversion = 3.3
isolated_build = true
[testenv]
deps =
flake8-builtins
isort[requirements]
commands =
flake8
isort -c --diff
[flake8]
hang-closing = True
ignore = W503, E125, E225, E226, E227, E701, E704
; See https://github.com/PyCQA/pycodestyle/issues/906
;max-doc-length = 72
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