211 lines
7.5 KiB
Python
211 lines
7.5 KiB
Python
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"""Lazy ZIP over HTTP"""
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__all__ = ["HTTPRangeRequestUnsupported", "dist_from_wheel_url"]
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from bisect import bisect_left, bisect_right
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from contextlib import contextmanager
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from tempfile import NamedTemporaryFile
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from typing import Any, Dict, Generator, List, Optional, Tuple
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from zipfile import BadZipfile, ZipFile
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from pip._vendor.packaging.utils import canonicalize_name
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from pip._vendor.requests.models import CONTENT_CHUNK_SIZE, Response
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from pip._internal.metadata import BaseDistribution, MemoryWheel, get_wheel_distribution
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from pip._internal.network.session import PipSession
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from pip._internal.network.utils import HEADERS, raise_for_status, response_chunks
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class HTTPRangeRequestUnsupported(Exception):
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pass
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def dist_from_wheel_url(name: str, url: str, session: PipSession) -> BaseDistribution:
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"""Return a distribution object from the given wheel URL.
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This uses HTTP range requests to only fetch the portion of the wheel
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containing metadata, just enough for the object to be constructed.
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If such requests are not supported, HTTPRangeRequestUnsupported
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is raised.
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"""
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with LazyZipOverHTTP(url, session) as zf:
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# For read-only ZIP files, ZipFile only needs methods read,
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# seek, seekable and tell, not the whole IO protocol.
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wheel = MemoryWheel(zf.name, zf) # type: ignore
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# After context manager exit, wheel.name
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# is an invalid file by intention.
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return get_wheel_distribution(wheel, canonicalize_name(name))
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class LazyZipOverHTTP:
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"""File-like object mapped to a ZIP file over HTTP.
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This uses HTTP range requests to lazily fetch the file's content,
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which is supposed to be fed to ZipFile. If such requests are not
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supported by the server, raise HTTPRangeRequestUnsupported
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during initialization.
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"""
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def __init__(
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self, url: str, session: PipSession, chunk_size: int = CONTENT_CHUNK_SIZE
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) -> None:
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head = session.head(url, headers=HEADERS)
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raise_for_status(head)
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assert head.status_code == 200
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self._session, self._url, self._chunk_size = session, url, chunk_size
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self._length = int(head.headers["Content-Length"])
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self._file = NamedTemporaryFile()
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self.truncate(self._length)
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self._left: List[int] = []
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self._right: List[int] = []
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if "bytes" not in head.headers.get("Accept-Ranges", "none"):
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raise HTTPRangeRequestUnsupported("range request is not supported")
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self._check_zip()
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@property
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def mode(self) -> str:
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"""Opening mode, which is always rb."""
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return "rb"
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@property
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def name(self) -> str:
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"""Path to the underlying file."""
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return self._file.name
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def seekable(self) -> bool:
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"""Return whether random access is supported, which is True."""
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return True
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def close(self) -> None:
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"""Close the file."""
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self._file.close()
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@property
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def closed(self) -> bool:
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"""Whether the file is closed."""
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return self._file.closed
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def read(self, size: int = -1) -> bytes:
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"""Read up to size bytes from the object and return them.
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As a convenience, if size is unspecified or -1,
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all bytes until EOF are returned. Fewer than
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size bytes may be returned if EOF is reached.
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"""
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download_size = max(size, self._chunk_size)
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start, length = self.tell(), self._length
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stop = length if size < 0 else min(start + download_size, length)
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start = max(0, stop - download_size)
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self._download(start, stop - 1)
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return self._file.read(size)
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def readable(self) -> bool:
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"""Return whether the file is readable, which is True."""
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return True
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def seek(self, offset: int, whence: int = 0) -> int:
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"""Change stream position and return the new absolute position.
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Seek to offset relative position indicated by whence:
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* 0: Start of stream (the default). pos should be >= 0;
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* 1: Current position - pos may be negative;
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* 2: End of stream - pos usually negative.
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"""
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return self._file.seek(offset, whence)
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def tell(self) -> int:
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"""Return the current position."""
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return self._file.tell()
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def truncate(self, size: Optional[int] = None) -> int:
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"""Resize the stream to the given size in bytes.
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If size is unspecified resize to the current position.
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The current stream position isn't changed.
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Return the new file size.
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"""
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return self._file.truncate(size)
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def writable(self) -> bool:
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"""Return False."""
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return False
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def __enter__(self) -> "LazyZipOverHTTP":
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self._file.__enter__()
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return self
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def __exit__(self, *exc: Any) -> None:
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self._file.__exit__(*exc)
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@contextmanager
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def _stay(self) -> Generator[None, None, None]:
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"""Return a context manager keeping the position.
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At the end of the block, seek back to original position.
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"""
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pos = self.tell()
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try:
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yield
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finally:
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self.seek(pos)
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def _check_zip(self) -> None:
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"""Check and download until the file is a valid ZIP."""
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end = self._length - 1
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for start in reversed(range(0, end, self._chunk_size)):
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self._download(start, end)
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with self._stay():
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try:
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# For read-only ZIP files, ZipFile only needs
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# methods read, seek, seekable and tell.
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ZipFile(self) # type: ignore
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except BadZipfile:
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pass
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else:
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break
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def _stream_response(
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self, start: int, end: int, base_headers: Dict[str, str] = HEADERS
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) -> Response:
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"""Return HTTP response to a range request from start to end."""
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headers = base_headers.copy()
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headers["Range"] = f"bytes={start}-{end}"
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# TODO: Get range requests to be correctly cached
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headers["Cache-Control"] = "no-cache"
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return self._session.get(self._url, headers=headers, stream=True)
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def _merge(
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self, start: int, end: int, left: int, right: int
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) -> Generator[Tuple[int, int], None, None]:
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"""Return a generator of intervals to be fetched.
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Args:
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start (int): Start of needed interval
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end (int): End of needed interval
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left (int): Index of first overlapping downloaded data
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right (int): Index after last overlapping downloaded data
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"""
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lslice, rslice = self._left[left:right], self._right[left:right]
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i = start = min([start] + lslice[:1])
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end = max([end] + rslice[-1:])
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for j, k in zip(lslice, rslice):
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if j > i:
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yield i, j - 1
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i = k + 1
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if i <= end:
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yield i, end
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self._left[left:right], self._right[left:right] = [start], [end]
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def _download(self, start: int, end: int) -> None:
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"""Download bytes from start to end inclusively."""
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with self._stay():
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left = bisect_left(self._right, start)
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right = bisect_right(self._left, end)
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for start, end in self._merge(start, end, left, right):
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response = self._stream_response(start, end)
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response.raise_for_status()
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self.seek(start)
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for chunk in response_chunks(response, self._chunk_size):
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self._file.write(chunk)
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