/usr/lib/python2.7/dist-packages/genpy/generate_struct.py is in python-genpy 0.5.7-6.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#
# Copyright (c) 2008, Willow Garage, Inc.
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#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following
# disclaimer in the documentation and/or other materials provided
# with the distribution.
# * Neither the name of Willow Garage, Inc. nor the names of its
# contributors may be used to endorse or promote products derived
# from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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from .base import SIMPLE_TYPES_DICT
_context_patterns = []
def add_pattern(p):
"""
Record struct pattern that's been used for (de)serialization
"""
_context_patterns.append(p)
def clear_patterns():
"""
Clear record of struct pattern that have been used for (de)serialization
"""
del _context_patterns[:]
def get_patterns():
"""
:returns: record of struct pattern that have been used for (de)serialization
"""
return _context_patterns[:]
def compute_struct_pattern(types):
"""
:param types: type names, ``[str]``
:returns: format string for struct if types are all simple. Otherwise, return None, ``str``
"""
if not types: #important to filter None and empty first
return None
try:
return ''.join([SIMPLE_TYPES_DICT[t] for t in types])
except:
return None
def reduce_pattern(pattern):
"""
Optimize the struct format pattern.
:param pattern: struct pattern, ``str``
:returns: optimized struct pattern, ``str``
"""
if not pattern or len(pattern) == 1 or '%' in pattern:
return pattern
prev = pattern[0]
count = 1
new_pattern = ''
nums = [str(i) for i in range(0, 9)]
for c in pattern[1:]:
if c == prev and not c in nums:
count += 1
else:
if count > 1:
new_pattern = new_pattern + str(count) + prev
else:
new_pattern = new_pattern + prev
prev = c
count = 1
if count > 1:
new_pattern = new_pattern + str(count) + c
else:
new_pattern = new_pattern + prev
return new_pattern
## :param expr str: string python expression that is evaluated for serialization
## :returns str: python call to write value returned by expr to serialization buffer
def serialize(expr):
return "buff.write(%s)"%expr
# int32 is very common due to length serialization, so it is special cased
def int32_pack(var):
"""
:param var: variable name, ``str``
:returns: struct packing code for an int32
"""
return serialize('_struct_I.pack(%s)'%var)
# int32 is very common due to length serialization, so it is special cased
def int32_unpack(var, buff):
"""
:param var: variable name, ``str``
:returns: struct unpacking code for an int32
"""
return '(%s,) = _struct_I.unpack(%s)'%(var, buff)
#NOTE: '<' = little endian
def pack(pattern, vars):
"""
create struct.pack call for when pattern is a string pattern
:param pattern: pattern for pack, ``str``
:param vars: name of variables to pack, ``str``
"""
# - store pattern in context
pattern = reduce_pattern(pattern)
add_pattern(pattern)
return serialize("_struct_%s.pack(%s)"%(pattern, vars))
def pack2(pattern, vars):
"""
create struct.pack call for when pattern is the name of a variable
:param pattern: name of variable storing string pattern, ``struct``
:param vars: name of variables to pack, ``str``
"""
return serialize("struct.pack(%s, %s)"%(pattern, vars))
def unpack(var, pattern, buff):
"""
create struct.unpack call for when pattern is a string pattern
:param var: name of variable to unpack, ``str``
:param pattern: pattern for pack, ``str``
:param buff: buffer to unpack from, ``str``
"""
# - store pattern in context
pattern = reduce_pattern(pattern)
add_pattern(pattern)
return var + " = _struct_%s.unpack(%s)"%(pattern, buff)
def unpack2(var, pattern, buff):
"""
Create struct.unpack call for when pattern refers to variable
:param var: variable the stores the result of unpack call, ``str``
:param pattern: name of variable that unpack will read from, ``str``
:param buff: buffer that the unpack reads from, ``StringIO``
"""
return "%s = struct.unpack(%s, %s)"%(var, pattern, buff)
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