# misc.py
"""Miscellaneous helper functions"""
# Copyright (c) 2009 Darcy Mason
# This file is part of pydicom, released under a modified MIT license.
# See the file LICENSE included with this distribution, also
# available at https://github.com/pydicom/pydicom
_size_factors = dict(KB=1024, MB=1024 * 1024, GB=1024 * 1024 * 1024)
[docs]def size_in_bytes(expr):
"""Return the number of bytes for a defer_size argument to dcmread()
"""
if expr is None or expr == float('inf'):
return None
try:
return int(expr)
except ValueError:
unit = expr[-2:].upper()
if unit in _size_factors.keys():
val = float(expr[:-2]) * _size_factors[unit]
return val
else:
raise ValueError(
"Unable to parse length with unit '{0:s}'".format(unit))
[docs]def is_dicom(file_path):
"""Boolean specifying if file is a proper DICOM file.
This function is a pared down version of read_preamble meant for a
fast return.
The file is read for a proper preamble ('DICM'), returning True if so,
and False otherwise. This is a conservative approach.
Parameters
----------
file_path : str
The path to the file.
See Also
--------
filereader.read_preamble
filereader.read_partial
"""
with open(file_path, 'rb') as fp:
fp.read(0x80) # preamble
magic = fp.read(4)
return magic == b"DICM"