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# -*- coding: utf-8 -*-
# Python 2.7 workaround
try:
import pathlib
except ImportError:
pass
_NUM_SIGNATURE_BYTES = 8192
def get_signature_bytes(path):
"""
Reads file from disk and returns the first 8192 bytes
of data representing the magic number header signature.
Args:
path: path string to file.
Returns:
First 8192 bytes of the file content as bytearray type.
"""
with open(path, 'rb') as fp:
return bytearray(fp.read(_NUM_SIGNATURE_BYTES))
def signature(array):
"""
Returns the first 8192 bytes of the given bytearray
as part of the file header signature.
Args:
array: bytearray to extract the header signature.
Returns:
First 8192 bytes of the file content as bytearray type.
"""
length = len(array)
index = _NUM_SIGNATURE_BYTES if length > _NUM_SIGNATURE_BYTES else length
return array[:index]
def get_bytes(obj):
"""
Infers the input type and reads the first 8192 bytes,
returning a sliced bytearray.
Args:
obj: path to readable, file-like object(with read() method), bytes,
bytearray or memoryview
Returns:
First 8192 bytes of the file content as bytearray type.
Raises:
TypeError: if obj is not a supported type.
"""
if isinstance(obj, bytearray):
return signature(obj)
if isinstance(obj, str):
return get_signature_bytes(obj)
if isinstance(obj, bytes):
return signature(obj)
if isinstance(obj, memoryview):
return bytearray(signature(obj).tolist())
if isinstance(obj, pathlib.PurePath):
return get_signature_bytes(obj)
if hasattr(obj, 'read'):
if hasattr(obj, 'tell') and hasattr(obj, 'seek'):
start_pos = obj.tell()
obj.seek(0)
magic_bytes = obj.read(_NUM_SIGNATURE_BYTES)
obj.seek(start_pos)
return get_bytes(magic_bytes)
return get_bytes(obj.read(_NUM_SIGNATURE_BYTES))
raise TypeError('Unsupported type as file input: %s' % type(obj))
|
