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lazy_wheel.py
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"""Lazy ZIP over HTTP""" __all__ = ['HTTPRangeRequestUnsupported', 'dist_from_wheel_url'] from bisect import bisect_left, bisect_right from contextlib import contextmanager from tempfile import NamedTemporaryFile from zipfile import BadZipfile, ZipFile from pip._vendor.requests.models import CONTENT_CHUNK_SIZE from pip._vendor.six.moves import range from pip._internal.network.utils import ( HEADERS, raise_for_status, response_chunks, ) from pip._internal.utils.typing import MYPY_CHECK_RUNNING from pip._internal.utils.wheel import pkg_resources_distribution_for_wheel if MYPY_CHECK_RUNNING: from typing import Any, Dict, Iterator, List, Optional, Tuple from pip._vendor.pkg_resources import Distribution from pip._vendor.requests.models import Response from pip._internal.network.session import PipSession class HTTPRangeRequestUnsupported(Exception): pass def dist_from_wheel_url(name, url, session): # type: (str, str, PipSession) -> Distribution """Return a pkg_resources.Distribution from the given wheel URL. This uses HTTP range requests to only fetch the potion of the wheel containing metadata, just enough for the object to be constructed. If such requests are not supported, HTTPRangeRequestUnsupported is raised. """ with LazyZipOverHTTP(url, session) as wheel: # For read-only ZIP files, ZipFile only needs methods read, # seek, seekable and tell, not the whole IO protocol. zip_file = ZipFile(wheel) # type: ignore # After context manager exit, wheel.name # is an invalid file by intention. return pkg_resources_distribution_for_wheel(zip_file, name, wheel.name) class LazyZipOverHTTP(object): """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. If such requests are not supported by the server, raise HTTPRangeRequestUnsupported during initialization. """ def __init__(self, url, session, chunk_size=CONTENT_CHUNK_SIZE): # type: (str, PipSession, int) -> None head = session.head(url, headers=HEADERS) raise_for_status(head) 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.truncate(self._length) self._left = [] # type: List[int] self._right = [] # type: List[int] if 'bytes' not in head.headers.get('Accept-Ranges', 'none'): raise HTTPRangeRequestUnsupported('range request is not supported') self._check_zip() @property def mode(self): # type: () -> str """Opening mode, which is always rb.""" return 'rb' @property def name(self): # type: () -> str """Path to the underlying file.""" return self._file.name def seekable(self): # type: () -> bool """Return whether random access is supported, which is True.""" return True def close(self): # type: () -> None """Close the file.""" self._file.close() @property def closed(self): # type: () -> bool """Whether the file is closed.""" return self._file.closed def read(self, size=-1): # type: (int) -> 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. """ download_size = max(size, self._chunk_size) start, length = self.tell(), self._length stop = length if size < 0 else min(start+download_size, length) start = max(0, stop-download_size) self._download(start, stop-1) return self._file.read(size) def readable(self): # type: () -> bool """Return whether the file is readable, which is True.""" return True def seek(self, offset, whence=0): # type: (int, int) -> 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): # type: () -> int """Return the current possition.""" return self._file.tell() def truncate(self, size=None): # type: (Optional[int]) -> int """Resize the stream to the given size in bytes. If size is unspecified resize to the current position. The current stream position isn't changed. Return the new file size. """ return self._file.truncate(size) def writable(self): # type: () -> bool """Return False.""" return False def __enter__(self): # type: () -> LazyZipOverHTTP self._file.__enter__() return self def __exit__(self, *exc): # type: (*Any) -> Optional[bool] return self._file.__exit__(*exc) @contextmanager def _stay(self): # type: ()-> 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): # type: () -> None """Check and download until the file is a valid ZIP.""" end = self._length - 1 for start in reversed(range(0, end, self._chunk_size)): self._download(start, end) with self._stay(): try: # For read-only ZIP files, ZipFile only needs # methods read, seek, seekable and tell. ZipFile(self) # type: ignore except BadZipfile: pass else: break def _stream_response(self, start, end, base_headers=HEADERS): # type: (int, int, Dict[str, str]) -> Response """Return HTTP response to a range request from start to end.""" headers = base_headers.copy() headers['Range'] = 'bytes={}-{}'.format(start, end) # TODO: Get range requests to be correctly cached headers['Cache-Control'] = 'no-cache' return self._session.get(self._url, headers=headers, stream=True) def _merge(self, start, end, left, right): # type: (int, int, int, 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]+lslice[:1]) end = max([end]+rslice[-1:]) 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, end): # type: (int, int) -> None """Download bytes from start to end inclusively.""" with self._stay(): left = bisect_left(self._right, start) right = bisect_right(self._left, end) for start, end in self._merge(start, end, left, right): 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)