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54 lines
1.9 KiB
Python
54 lines
1.9 KiB
Python
import os
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class AnalyzeFileObjBug(Exception):
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msg = ("\n"
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"Expected file object to have %d bytes, instead we read %d bytes.\n"
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"File size detection may have failed (see dropbox.util.AnalyzeFileObj)\n")
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def __init__(self, expected, actual):
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self.expected = expected
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self.actual = actual
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def __str__(self):
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return self.msg % (self.expected, self.actual)
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def analyze_file_obj(obj):
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""" Get the size and contents of a file-like object.
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Returns: (size, raw_data)
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size: The amount of data waiting to be read
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raw_data: If not None, the entire contents of the stream (as a string).
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None if the stream should be read() in chunks.
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"""
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pos = 0
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if hasattr(obj, 'tell'):
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pos = obj.tell()
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# Handle cStringIO and StringIO
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if hasattr(obj, 'getvalue'):
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# Why using getvalue() makes sense:
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# For StringIO, this string is pre-computed anyway by read().
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# For cStringIO, getvalue() is the only way
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# to determine the length without read()'ing the whole thing.
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raw_data = obj.getvalue()
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if pos == 0:
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return (len(raw_data), raw_data)
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else:
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# We could return raw_data[pos:], but that could drastically
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# increase memory usage. Better to read it block at a time.
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size = max(0, len(raw_data) - pos)
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return (size, None)
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# Handle real files
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if hasattr(obj, 'fileno'):
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size = max(0, os.fstat(obj.fileno()).st_size - pos)
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return (size, None)
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# User-defined object with len()
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if hasattr(obj, '__len__'):
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size = max(0, len(obj) - pos)
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return (size, None)
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# We don't know what kind of stream this is.
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# To determine the size, we must read the whole thing.
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raw_data = obj.read()
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return (len(raw_data), raw_data)
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