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wiktornwiktorn
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Introduce FileSlice
New class providing "windowed" view over the file objects. It gives the possibility to have a file-alike object that returns only some part of the file. Useful for multipart upload.
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‎src/onedrivesdk/helpers/file_slice.py‎

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# -*- coding: utf-8 -*-
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'''
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The MIT License (MIT)
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Copyright (c) 2015 Wiktor Niesiobędzki
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Permission is hereby granted, free of charge, to any person obtaining a copy of
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this software and associated documentation files (the "Software"), to deal in
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the Software without restriction, including without limitation the rights to
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use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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the Software, and to permit persons to whom the Software is furnished to do so,
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subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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'''
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import io
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import os
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class FileSlice(io.RawIOBase):
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'''
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This class represents a window over a file handle. It will allow only access
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and read of bytes above start and no further than end/length bytes
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'''
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def __init__(self, handle, start, end=None, length=None):
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'''
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Creates new instance of FileSlice on file-like object handle. It behaves
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like normal file object, but only allow reading of bytes above start and
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no further than end/lenght byte
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Args:
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handle (file-like object): file handle object to create a view over.
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File should be open in binary mode
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start (int): start byte number, makring the first byte that can be
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read from FileSlice
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end (int): Optional. Last byte of the file that can be read.
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length (int): Optional. Number of the bytes, starting from the
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start, that can be read from FileSlice
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One of end or length must be provided
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'''
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assert end or length, "You need to provide one of end or length parameter"
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assert not (end and length), "You need to proivde only one parameter: end or length, not both"
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if start < 0:
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raise ValueError("Start of the file smaller than 0")
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if end and end < start:
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raise ValueError("End of the tile smaller than start")
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if length and length < 0:
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raise ValueError("Length smaller than 0")
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self._handle = handle
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self._start = start
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if end:
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self._end = end
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else:
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self._end = start + length
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self._end = min(self._end, os.fstat(handle.fileno()).st_size)
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self.seek(0)
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@property
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def _bytes_left(self):
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current_pos = self._handle.tell()
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return self._end - current_pos
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def close(self):
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# do nothing, someone else might want to process this file
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return
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@property
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def closed(self):
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return self._handle.closed
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def fileno(self):
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return self._handle.fileno()
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def flush(self):
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return self._handle.flush()
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def len(self):
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# this is provided for requests, so it will properly recognize the size of the file
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return self._bytes_left
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def __len__(self):
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# this is provided for requests, so it will properly recognize the size of the file
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return self.len()
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def isatty(self):
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return self._handle.isatty()
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def readable(self):
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return self._handle.readable()
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def read(self, size=-1):
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if size == -1:
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read_size = self._bytes_left
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else:
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read_size = min(size, self._bytes_left)
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return self._handle.read(read_size)
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def readall(self):
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return self._handle.read(self._bytes_left)
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def readinto(self, b):
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if len(b) > self._bytes_left:
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r = self._handle.read(self._bytes_left)
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b[:len(r)] = r
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return len(r)
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return self._handle.readinto(b)
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def readline(self, size=-1):
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return self._handle.readline(max(size, self._bytes_left))
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def readlines(self, hint=-1):
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return self._handle.readlines(max(hint, self._bytes_left))
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def seek(self, offset, whence=io.SEEK_SET):
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if whence == io.SEEK_SET:
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desired_pos = self._start + offset
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if whence == io.SEEK_CUR:
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desired_pos = self._handle.tell() + offset
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if whence == io.SEEK_END:
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desired_pos = self._end + offset
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if desired_pos < self._start:
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raise ValueError("Seeking before the file slice")
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if desired_pos > self._end:
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raise ValueError("Seekeing past the end of file slice")
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ret = self._handle.seek(desired_pos, io.SEEK_SET)
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if ret:
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return ret - self._start
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else:
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return ret
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def seekable(self):
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return self._handle.seekable()
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def tell(self):
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return self._handle.tell() - self._start
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def truncate(self, size=None):
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raise IOError("Operation not supported")
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def writable(self):
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return False
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def write(self, b):
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raise IOError("Operation not supported")
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def writelines(self, lines):
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raise IOError("Operation not supported")
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‎testonedrivesdk/test_file_slice.py‎

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import unittest
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try:
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from unittest.mock import patch, mock_open
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except ImportError:
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from mock import patch, mock_open
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import io
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import os
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import math
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import tempfile
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from onedrivesdk.helpers.file_slice import FileSlice
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class TestFileSlice(unittest.TestCase):
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def testSliceFileStartEnd(self):
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with tempfile.TemporaryFile() as f:
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f.write(b'123456789')
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f.flush()
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part = FileSlice(f, 0, 5)
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self.assertEqual(len(part), 5)
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self.assertEqual(part.read(), b'12345')
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self.assertEqual(part.read(3), b'')
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part.seek(0, io.SEEK_SET)
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self.assertEqual(part.read(3), b'123')
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self.assertEqual(part.tell(), 3)
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part.seek(-3, io.SEEK_CUR)
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self.assertEqual(part.tell(), 0)
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part.seek(-2, io.SEEK_END)
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self.assertEqual(part.tell(), 3)
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self.assertEqual(part.readall(), b'45')
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with self.assertRaises(IOError):
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part.write('abc')
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with self.assertRaises(IOError):
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part.writelines(['foo', 'bar'])
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def testSliceFileStartLength(self):
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with tempfile.TemporaryFile() as f:
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f.write(b'123456789')
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f.flush()
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part = FileSlice(f, 0, length=5)
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self.assertEqual(len(part), 5)
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self.assertEqual(part.read(), b'12345')
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self.assertEqual(part.read(3), b'')
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part.seek(0)
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self.assertEqual(part.read(3), b'123')
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self.assertEqual(part.tell(), 3)
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part.seek(-3, io.SEEK_CUR)
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self.assertEqual(part.readall(), b'12345')
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with self.assertRaises(IOError):
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part.write('abc')
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with self.assertRaises(IOError):
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part.writelines(['foo', 'bar'])
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def testSliceFileMiddleStartEnd(self):
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with tempfile.TemporaryFile() as f:
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f.write(b'123456789')
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f.flush()
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part = FileSlice(f, 1, 5)
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self.assertEqual(len(part), 4)
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self.assertEqual(part.read(3), b'234')
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self.assertEqual(part.readall(), b'5')
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self.assertEqual(part.read(), b'')
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self.assertEqual(part.tell(), 4)
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def testSliceFileMiddleStartLength(self):
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with tempfile.TemporaryFile() as f:
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f.write(b'123456789')
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f.flush()
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part = FileSlice(f, 1, length=5)
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self.assertEqual(len(part), 5)
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self.assertEqual(part.read(3), b'234')
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self.assertEqual(part.readall(), b'56')
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self.assertEqual(part.read(), b'')
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self.assertEqual(part.tell(), 5)
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def testSliceFileMiddleStartEnd_afterEOF(self):
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with tempfile.TemporaryFile() as f:
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f.write(b'123456789')
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f.flush()
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part = FileSlice(f, 8, 15)
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self.assertEqual(len(part), 1)
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self.assertEqual(part.read(3), b'9')
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self.assertEqual(part.readall(), b'')
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self.assertEqual(part.read(), b'')
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self.assertEqual(part.tell(), 1)
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part.seek(-1, io.SEEK_END)
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self.assertEqual(part.tell(), 0)
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self.assertEqual(part.readall(), b'9')
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def testSliceFileMiddleStartLength_afterEOF(self):
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with tempfile.TemporaryFile() as f:
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f.write(b'123456789')
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f.flush()
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part = FileSlice(f, 8, length=15)
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self.assertEqual(len(part), 1)
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self.assertEqual(part.read(3), b'9')
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self.assertEqual(part.readall(), b'')
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self.assertEqual(part.read(), b'')
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self.assertEqual(part.tell(), 1)
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part.seek(0)
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self.assertEqual(part.tell(), 0)
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self.assertEqual(part.readall(), b'9')
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def testSeek(self):
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with tempfile.TemporaryFile() as f:
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f.write(b'123456789')
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f.flush()
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part = FileSlice(f, 2, 7)
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part.seek(3)
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part.seek(part.tell(), io.SEEK_SET)
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self.assertEqual(part.tell(), 3)
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def testSanityChecks(self):
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with tempfile.TemporaryFile() as f:
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f.write(b'123456789')
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f.flush()
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with self.assertRaises(ValueError):
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part = FileSlice(f, -5, -2)
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with self.assertRaises(ValueError):
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part = FileSlice(f, 0, -2)
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with self.assertRaises(ValueError):
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part = FileSlice(f, -10, 2)
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with self.assertRaises(ValueError):
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part = FileSlice(f, 10, 2)
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with self.assertRaises(ValueError):
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part = FileSlice(f, 10, length=-2)
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part = FileSlice(f, 1, 5)
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with self.assertRaises(ValueError):
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part.seek(8)
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with self.assertRaises(ValueError):
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part.seek(8, io.SEEK_SET)
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part.seek(3)
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with self.assertRaises(ValueError):
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part.seek(4, io.SEEK_CUR)
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with self.assertRaises(ValueError):
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part.seek(-5, io.SEEK_END)
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if __name__ == '__main__':
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unittest.main()

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