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http_backoff retry with SliceFileObj (#2542)
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# coding=utf-8 | ||
# Copyright 2019-present, the HuggingFace Inc. team. | ||
# | ||
# Licensed under the Apache License, Version 2.0 (the "License"); | ||
# you may not use this file except in compliance with the License. | ||
# You may obtain a copy of the License at | ||
# | ||
# http://www.apache.org/licenses/LICENSE-2.0 | ||
# | ||
# Unless required by applicable law or agreed to in writing, software | ||
# distributed under the License is distributed on an "AS IS" BASIS, | ||
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
# See the License for the specific language governing permissions and | ||
# limitations under the License. | ||
"""Git LFS related utilities""" | ||
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import io | ||
import os | ||
from contextlib import AbstractContextManager | ||
from typing import BinaryIO | ||
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class SliceFileObj(AbstractContextManager): | ||
""" | ||
Utility context manager to read a *slice* of a seekable file-like object as a seekable, file-like object. | ||
This is NOT thread safe | ||
Inspired by stackoverflow.com/a/29838711/593036 | ||
Credits to @julien-c | ||
Args: | ||
fileobj (`BinaryIO`): | ||
A file-like object to slice. MUST implement `tell()` and `seek()` (and `read()` of course). | ||
`fileobj` will be reset to its original position when exiting the context manager. | ||
seek_from (`int`): | ||
The start of the slice (offset from position 0 in bytes). | ||
read_limit (`int`): | ||
The maximum number of bytes to read from the slice. | ||
Attributes: | ||
previous_position (`int`): | ||
The previous position | ||
Examples: | ||
Reading 200 bytes with an offset of 128 bytes from a file (ie bytes 128 to 327): | ||
```python | ||
>>> with open("path/to/file", "rb") as file: | ||
... with SliceFileObj(file, seek_from=128, read_limit=200) as fslice: | ||
... fslice.read(...) | ||
``` | ||
Reading a file in chunks of 512 bytes | ||
```python | ||
>>> import os | ||
>>> chunk_size = 512 | ||
>>> file_size = os.getsize("path/to/file") | ||
>>> with open("path/to/file", "rb") as file: | ||
... for chunk_idx in range(ceil(file_size / chunk_size)): | ||
... with SliceFileObj(file, seek_from=chunk_idx * chunk_size, read_limit=chunk_size) as fslice: | ||
... chunk = fslice.read(...) | ||
``` | ||
""" | ||
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def __init__(self, fileobj: BinaryIO, seek_from: int, read_limit: int): | ||
self.fileobj = fileobj | ||
self.seek_from = seek_from | ||
self.read_limit = read_limit | ||
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def __enter__(self): | ||
self._previous_position = self.fileobj.tell() | ||
end_of_stream = self.fileobj.seek(0, os.SEEK_END) | ||
self._len = min(self.read_limit, end_of_stream - self.seek_from) | ||
# ^^ The actual number of bytes that can be read from the slice | ||
self.fileobj.seek(self.seek_from, io.SEEK_SET) | ||
return self | ||
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def __exit__(self, exc_type, exc_value, traceback): | ||
self.fileobj.seek(self._previous_position, io.SEEK_SET) | ||
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def read(self, n: int = -1): | ||
pos = self.tell() | ||
if pos >= self._len: | ||
return b"" | ||
remaining_amount = self._len - pos | ||
data = self.fileobj.read(remaining_amount if n < 0 else min(n, remaining_amount)) | ||
return data | ||
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def tell(self) -> int: | ||
return self.fileobj.tell() - self.seek_from | ||
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def seek(self, offset: int, whence: int = os.SEEK_SET) -> int: | ||
start = self.seek_from | ||
end = start + self._len | ||
if whence in (os.SEEK_SET, os.SEEK_END): | ||
offset = start + offset if whence == os.SEEK_SET else end + offset | ||
offset = max(start, min(offset, end)) | ||
whence = os.SEEK_SET | ||
elif whence == os.SEEK_CUR: | ||
cur_pos = self.fileobj.tell() | ||
offset = max(start - cur_pos, min(offset, end - cur_pos)) | ||
else: | ||
raise ValueError(f"whence value {whence} is not supported") | ||
return self.fileobj.seek(offset, whence) - self.seek_from | ||
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def __iter__(self): | ||
yield self.read(n=4 * 1024 * 1024) |
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