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