/Lib/ctypes/test/test_objects.py
http://unladen-swallow.googlecode.com/ · Python · 70 lines · 63 code · 4 blank · 3 comment · 3 complexity · ffb2f5a9ba99acdfffcc7ce85727c8cd MD5 · raw file
- r'''
- This tests the '_objects' attribute of ctypes instances. '_objects'
- holds references to objects that must be kept alive as long as the
- ctypes instance, to make sure that the memory buffer is valid.
- WARNING: The '_objects' attribute is exposed ONLY for debugging ctypes itself,
- it MUST NEVER BE MODIFIED!
- '_objects' is initialized to a dictionary on first use, before that it
- is None.
- Here is an array of string pointers:
- >>> from ctypes import *
- >>> array = (c_char_p * 5)()
- >>> print array._objects
- None
- >>>
- The memory block stores pointers to strings, and the strings itself
- assigned from Python must be kept.
- >>> array[4] = 'foo bar'
- >>> array._objects
- {'4': 'foo bar'}
- >>> array[4]
- 'foo bar'
- >>>
- It gets more complicated when the ctypes instance itself is contained
- in a 'base' object.
- >>> class X(Structure):
- ... _fields_ = [("x", c_int), ("y", c_int), ("array", c_char_p * 5)]
- ...
- >>> x = X()
- >>> print x._objects
- None
- >>>
- The'array' attribute of the 'x' object shares part of the memory buffer
- of 'x' ('_b_base_' is either None, or the root object owning the memory block):
- >>> print x.array._b_base_ # doctest: +ELLIPSIS
- <ctypes.test.test_objects.X object at 0x...>
- >>>
- >>> x.array[0] = 'spam spam spam'
- >>> x._objects
- {'0:2': 'spam spam spam'}
- >>> x.array._b_base_._objects
- {'0:2': 'spam spam spam'}
- >>>
- '''
- import unittest, doctest, sys
- import ctypes.test.test_objects
- class TestCase(unittest.TestCase):
- if sys.hexversion > 0x02040000:
- # Python 2.3 has no ELLIPSIS flag, so we don't test with this
- # version:
- def test(self):
- doctest.testmod(ctypes.test.test_objects)
- if __name__ == '__main__':
- if sys.hexversion > 0x02040000:
- doctest.testmod(ctypes.test.test_objects)