70 lines
1.8 KiB
Python
70 lines
1.8 KiB
Python
''' Byteorder utilities for system - numpy byteorder encoding
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Converts a variety of string codes for little endian, big endian,
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native byte order and swapped byte order to explicit numpy endian
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codes - one of '<' (little endian) or '>' (big endian)
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'''
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from __future__ import division, print_function, absolute_import
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import sys
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sys_is_le = sys.byteorder == 'little'
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native_code = sys_is_le and '<' or '>'
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swapped_code = sys_is_le and '>' or '<'
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aliases = {'little': ('little', '<', 'l', 'le'),
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'big': ('big', '>', 'b', 'be'),
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'native': ('native', '='),
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'swapped': ('swapped', 'S')}
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def to_numpy_code(code):
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"""
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Convert various order codings to numpy format.
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Parameters
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----------
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code : str
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The code to convert. It is converted to lower case before parsing.
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Legal values are:
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'little', 'big', 'l', 'b', 'le', 'be', '<', '>', 'native', '=',
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'swapped', 's'.
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Returns
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-------
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out_code : {'<', '>'}
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Here '<' is the numpy dtype code for little endian,
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and '>' is the code for big endian.
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Examples
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--------
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>>> import sys
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>>> sys_is_le == (sys.byteorder == 'little')
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True
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>>> to_numpy_code('big')
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'>'
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>>> to_numpy_code('little')
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'<'
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>>> nc = to_numpy_code('native')
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>>> nc == '<' if sys_is_le else nc == '>'
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True
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>>> sc = to_numpy_code('swapped')
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>>> sc == '>' if sys_is_le else sc == '<'
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True
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"""
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code = code.lower()
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if code is None:
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return native_code
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if code in aliases['little']:
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return '<'
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elif code in aliases['big']:
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return '>'
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elif code in aliases['native']:
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return native_code
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elif code in aliases['swapped']:
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return swapped_code
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else:
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raise ValueError(
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'We cannot handle byte order %s' % code)
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