Thanks for the patch. A couple of comments:
- the C code is misindented in some places (using 8 spaces rather than 4)
- you should use support.unlink consistently in the tests (rather than sometimes os.unlink or posix.unlink)
- when cleaning up in tests (through unlink() or rmdir()), it's better to use finally clauses so that cleaning up gets done even on error; or, alternatively, to use self.addCleanup() (see http://docs.python.org/dev/library/unittest.html#unittest.TestCase.addCleanup)

(I haven't looked at the C code in detail since you say it's mostly copy/paste from existing code)