merge the io-c branch: C implementation of the io module

The main io module now uses the C implementation.  The Python one still exists
in Lib/_pyio.py for ease of testing new features and usefulness to other
implementers.

The rewrite was done by Antoine Pitrou and Amaury Forgeot d'Arc.  I was slightly
helpful at the end. :)


Following are the log messages from the io-c branch:

Merged revisions 68683-68685,68687-68689,68693,68704,68741-68743,68745,68747,68752-68754,68756,68758,68812,68816-68817,68820-68822,68824-68825,68828,68876-68877,69037,69044,69104,69115,69194,69626-69629,69636,69638,69641-69642,69644-69654,69656-69661,69671,69677,69812-69815,69817,69827-69830,69839,69841-69845,69848,69850,69852,69854,69860,69865-69866,69868,69872-69873,69885,69888,69891-69893,69911,69913-69916,69963,70033,70035,70038,70041-70048,70067-70070,70075,70112,70133,70135,70140 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/branches/io-c

........
  r68683 | antoine.pitrou | 2009-01-17 17:13:48 -0600 (Sat, 17 Jan 2009) | 3 lines

  Merge in changes from the io-c sandbox. Tests will follow in separate commits.
........
  r68684 | antoine.pitrou | 2009-01-17 17:17:26 -0600 (Sat, 17 Jan 2009) | 3 lines

  Fixes and additions to test_io.py
........
  r68685 | antoine.pitrou | 2009-01-17 17:22:04 -0600 (Sat, 17 Jan 2009) | 1 line

  Fix test_fileio
........
  r68687 | antoine.pitrou | 2009-01-17 17:35:11 -0600 (Sat, 17 Jan 2009) | 3 lines

  Add dependency to _iomodule.h for the various C sources
........
  r68688 | antoine.pitrou | 2009-01-17 17:38:18 -0600 (Sat, 17 Jan 2009) | 3 lines

  These precautions are not needed anymore!
........
  r68689 | antoine.pitrou | 2009-01-17 17:41:48 -0600 (Sat, 17 Jan 2009) | 3 lines

  Fix another test
........
  r68693 | antoine.pitrou | 2009-01-17 17:49:58 -0600 (Sat, 17 Jan 2009) | 3 lines

  Fix test_uu (which was using private attributes of TextIOWrapper)
........
  r68704 | antoine.pitrou | 2009-01-17 18:45:29 -0600 (Sat, 17 Jan 2009) | 3 lines

  Most io sources are Py_ssize_t-clean (I don't know about bytesio and stringio)
........
  r68741 | antoine.pitrou | 2009-01-18 15:20:30 -0600 (Sun, 18 Jan 2009) | 3 lines

  Check return type in TextIOWrapper.__next__
........
  r68742 | antoine.pitrou | 2009-01-18 15:28:48 -0600 (Sun, 18 Jan 2009) | 4 lines

  Make binary buffered readline and iteration much faster
  (8x as fast as the IOBase generic implementation)
........
  r68743 | antoine.pitrou | 2009-01-18 15:47:47 -0600 (Sun, 18 Jan 2009) | 3 lines

  Reinsert test_io_after_close (was removed by mistake)
........
  r68745 | antoine.pitrou | 2009-01-18 16:16:06 -0600 (Sun, 18 Jan 2009) | 3 lines

  Add read, read1 and write methods to BufferedIOBase
........
  r68747 | antoine.pitrou | 2009-01-18 16:35:58 -0600 (Sun, 18 Jan 2009) | 3 lines

  Kill test failure
........
  r68752 | amaury.forgeotdarc | 2009-01-18 17:05:43 -0600 (Sun, 18 Jan 2009) | 3 lines

  Fix a segfault when e.g a BufferedReader is created with a FileIO in
  read mode.
........
  r68753 | antoine.pitrou | 2009-01-18 17:13:09 -0600 (Sun, 18 Jan 2009) | 3 lines

  Add truncate() to text IO objects
........
  r68754 | antoine.pitrou | 2009-01-18 17:51:08 -0600 (Sun, 18 Jan 2009) | 3 lines

  Remove IOBase.__del__ and replace it with custom code with tp_dealloc
........
  r68756 | antoine.pitrou | 2009-01-18 18:10:16 -0600 (Sun, 18 Jan 2009) | 3 lines

  Remove irrelevant comment.
........
  r68758 | antoine.pitrou | 2009-01-18 18:36:16 -0600 (Sun, 18 Jan 2009) | 3 lines

  in importlib:_fileio._FileIO -> _io.FileIO
........
  r68812 | antoine.pitrou | 2009-01-20 14:15:51 -0600 (Tue, 20 Jan 2009) | 3 lines

  Add garbage collection support to FileIO objects
........
  r68816 | antoine.pitrou | 2009-01-20 14:56:28 -0600 (Tue, 20 Jan 2009) | 3 lines

  Add GC support to Buffered and Text IO objects
........
  r68817 | antoine.pitrou | 2009-01-20 15:19:45 -0600 (Tue, 20 Jan 2009) | 3 lines

  Add some file headers
........
  r68820 | antoine.pitrou | 2009-01-20 15:29:59 -0600 (Tue, 20 Jan 2009) | 3 lines

  Add class TextIOBase
........
  r68821 | antoine.pitrou | 2009-01-20 15:36:16 -0600 (Tue, 20 Jan 2009) | 3 lines

  Add properties to TextIOBase
........
  r68822 | antoine.pitrou | 2009-01-20 15:41:19 -0600 (Tue, 20 Jan 2009) | 3 lines

  Disable the pure Python TextIOBase class, and inject C the implementation instead
........
  r68824 | antoine.pitrou | 2009-01-20 16:36:28 -0600 (Tue, 20 Jan 2009) | 3 lines

  Fix two leaks
........
  r68825 | antoine.pitrou | 2009-01-20 16:38:29 -0600 (Tue, 20 Jan 2009) | 3 lines

  FileIO.name is just a plain attribute, we can set it directly
........
  r68828 | antoine.pitrou | 2009-01-20 17:06:33 -0600 (Tue, 20 Jan 2009) | 3 lines

  Speed up closed checks on text IO objects. Good for a 25% speedup on small ops.
........
  r68876 | antoine.pitrou | 2009-01-23 17:01:25 -0600 (Fri, 23 Jan 2009) | 3 lines

  Two typos
........
  r68877 | antoine.pitrou | 2009-01-23 18:13:20 -0600 (Fri, 23 Jan 2009) | 3 lines

  Remove two unused functions
........
  r69037 | amaury.forgeotdarc | 2009-01-27 17:10:25 -0600 (Tue, 27 Jan 2009) | 2 lines

  Update the win32 project files
........
  r69044 | antoine.pitrou | 2009-01-27 18:51:07 -0600 (Tue, 27 Jan 2009) | 3 lines

  Improve heuristic in IncrementalNewlineDecoder + some micro-optimizations
........
  r69104 | antoine.pitrou | 2009-01-29 15:23:42 -0600 (Thu, 29 Jan 2009) | 3 lines

  Fix some crashers found by Victor
........
  r69115 | hirokazu.yamamoto | 2009-01-29 20:36:28 -0600 (Thu, 29 Jan 2009) | 1 line

  Updated VC6 project file.
........
  r69194 | antoine.pitrou | 2009-02-01 16:57:18 -0600 (Sun, 01 Feb 2009) | 3 lines

  Fix downcasting warnings in 32-bit mode with 64-bit offsets (Windows)
........
  r69626 | benjamin.peterson | 2009-02-14 17:33:34 -0600 (Sat, 14 Feb 2009) | 1 line

  only catch AttributeError and UnsupportedOperation
........
  r69627 | benjamin.peterson | 2009-02-14 21:35:28 -0600 (Sat, 14 Feb 2009) | 1 line

  give the IO module its own state and store the os and locale modules in it
........
  r69628 | benjamin.peterson | 2009-02-14 22:08:32 -0600 (Sat, 14 Feb 2009) | 1 line

  put interned strings in the module state structure
........
  r69629 | benjamin.peterson | 2009-02-14 22:15:29 -0600 (Sat, 14 Feb 2009) | 1 line

  put UnsupportedOperation in the module state
........
  r69636 | benjamin.peterson | 2009-02-15 08:31:42 -0600 (Sun, 15 Feb 2009) | 1 line

  dealloc unsupported_operation
........
  r69638 | benjamin.peterson | 2009-02-15 09:24:45 -0600 (Sun, 15 Feb 2009) | 1 line

  actually test the C implementation
........
  r69641 | benjamin.peterson | 2009-02-15 10:12:37 -0600 (Sun, 15 Feb 2009) | 5 lines

  make interned strings globals again ;(

  putting them in the module state was asking for trouble when the module
  was dealloced before the classes in it were
........
  r69642 | benjamin.peterson | 2009-02-15 10:19:45 -0600 (Sun, 15 Feb 2009) | 1 line

  actually test the python implementations
........
  r69644 | antoine.pitrou | 2009-02-15 11:59:30 -0600 (Sun, 15 Feb 2009) | 3 lines

  Fix memory leak in destructor when a Python class inherits from IOBase (or an IOBase-derived type)
........
  r69645 | antoine.pitrou | 2009-02-15 12:23:26 -0600 (Sun, 15 Feb 2009) | 3 lines

  Add a warning about the embarassing state of IOBase finalization
........
  r69646 | antoine.pitrou | 2009-02-15 13:14:42 -0600 (Sun, 15 Feb 2009) | 3 lines

  Fix opening of 8-bit filenames with FileIO
........
  r69647 | antoine.pitrou | 2009-02-15 13:20:22 -0600 (Sun, 15 Feb 2009) | 3 lines

  Fix leak in FileIO constructor
........
  r69648 | antoine.pitrou | 2009-02-15 13:58:16 -0600 (Sun, 15 Feb 2009) | 3 lines

  Fix some refleaks
........
  r69649 | antoine.pitrou | 2009-02-15 14:05:13 -0600 (Sun, 15 Feb 2009) | 3 lines

  Fix a leak in IOBase.writelines
........
  r69650 | antoine.pitrou | 2009-02-15 14:11:56 -0600 (Sun, 15 Feb 2009) | 3 lines

  Fix memory leak in BufferedWriter.truncate
........
  r69651 | antoine.pitrou | 2009-02-15 14:25:34 -0600 (Sun, 15 Feb 2009) | 3 lines

  Fix a leak in TextIOWrapper.seek
........
  r69652 | antoine.pitrou | 2009-02-15 14:26:28 -0600 (Sun, 15 Feb 2009) | 3 lines

  Unify implementations of truncate for buffered objects
........
  r69653 | antoine.pitrou | 2009-02-15 15:15:15 -0600 (Sun, 15 Feb 2009) | 3 lines

  Fix more leaks in TextIOWrapper
........
  r69654 | antoine.pitrou | 2009-02-15 15:21:57 -0600 (Sun, 15 Feb 2009) | 3 lines

  Smaller chunk size for a faster test
........
  r69656 | benjamin.peterson | 2009-02-15 17:29:48 -0600 (Sun, 15 Feb 2009) | 1 line

  braces make this much clearer
........
  r69657 | benjamin.peterson | 2009-02-15 17:46:07 -0600 (Sun, 15 Feb 2009) | 1 line

  use the correct macro
........
  r69658 | antoine.pitrou | 2009-02-15 19:38:59 -0600 (Sun, 15 Feb 2009) | 5 lines

  Fix crash in test_urllib2_localnet in debug mode. It was due to an HTTPResponse
  object being revived when calling its close() method in IOBase's tp_dealloc.
  _PyIOBase_finalize() starts looking scary...
........
  r69659 | benjamin.peterson | 2009-02-15 20:55:48 -0600 (Sun, 15 Feb 2009) | 1 line

  fix segfault on initialization failing
........
  r69660 | benjamin.peterson | 2009-02-15 21:09:31 -0600 (Sun, 15 Feb 2009) | 1 line

  apparently locale.getprefferedencoding() can raise a ImportError, too
........
  r69661 | benjamin.peterson | 2009-02-15 21:54:15 -0600 (Sun, 15 Feb 2009) | 1 line

  it's amazing this worked at all; I was using the wrong structs!
........
  r69671 | benjamin.peterson | 2009-02-16 08:38:27 -0600 (Mon, 16 Feb 2009) | 1 line

  add garbage collection support to bytesio
........
  r69677 | benjamin.peterson | 2009-02-16 10:31:03 -0600 (Mon, 16 Feb 2009) | 5 lines

  reduce ImportError catching code duplication

  I'm not sure this makes the code clearer with its new gotos, but
  at least I added a big fat comment
........
  r69812 | antoine.pitrou | 2009-02-20 13:50:16 -0600 (Fri, 20 Feb 2009) | 3 lines

  _StringIO now belongs to the _io modules, rather to its own _stringio module
........
  r69813 | antoine.pitrou | 2009-02-20 13:58:22 -0600 (Fri, 20 Feb 2009) | 3 lines

  Add a test for StringIO properties
........
  r69814 | antoine.pitrou | 2009-02-20 14:06:03 -0600 (Fri, 20 Feb 2009) | 3 lines

  Reimplement a few trivial StringIO functions and properties in C
........
  r69815 | antoine.pitrou | 2009-02-20 14:13:11 -0600 (Fri, 20 Feb 2009) | 3 lines

  Add the line_buffering property to TextIOWrapper, and test for it
........
  r69817 | antoine.pitrou | 2009-02-20 14:45:50 -0600 (Fri, 20 Feb 2009) | 4 lines

  Allow IncrementalNewlineDecoder to take unicode objects as decoding input if the decoder parameter is None
  This will help rewriting StringIO to C
........
  r69827 | antoine.pitrou | 2009-02-20 19:00:30 -0600 (Fri, 20 Feb 2009) | 3 lines

  Rewrite most of StringIO in C. Some almost empty stubs remain to be converted.
........
  r69828 | antoine.pitrou | 2009-02-20 19:09:25 -0600 (Fri, 20 Feb 2009) | 3 lines

  Plug a leak, and remove an unused string
........
  r69829 | benjamin.peterson | 2009-02-20 20:02:28 -0600 (Fri, 20 Feb 2009) | 1 line

  this assertions makes more sense here
........
  r69830 | benjamin.peterson | 2009-02-20 20:03:04 -0600 (Fri, 20 Feb 2009) | 1 line

  PyModule_AddObject can fail; simplify this code with a macro
........
  r69839 | antoine.pitrou | 2009-02-21 12:54:01 -0600 (Sat, 21 Feb 2009) | 3 lines

  StringIO is now written entirely in C (and blazingly fast)
........
  r69841 | benjamin.peterson | 2009-02-21 14:05:40 -0600 (Sat, 21 Feb 2009) | 1 line

  split the Python implementation of io into another module and rewrite the tests to test both implementations
........
  r69842 | benjamin.peterson | 2009-02-21 14:10:00 -0600 (Sat, 21 Feb 2009) | 1 line

  closed is not a function
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  r69843 | benjamin.peterson | 2009-02-21 14:13:04 -0600 (Sat, 21 Feb 2009) | 1 line

  fix __all__ test
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  r69844 | benjamin.peterson | 2009-02-21 14:21:24 -0600 (Sat, 21 Feb 2009) | 1 line

  fix the rest of the Misc tests
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  r69845 | benjamin.peterson | 2009-02-21 14:26:59 -0600 (Sat, 21 Feb 2009) | 1 line

  RawIOBase is better for FileIO
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  r69848 | benjamin.peterson | 2009-02-21 15:33:53 -0600 (Sat, 21 Feb 2009) | 1 line

  fix some more tests broken by bag argument validation
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  r69850 | benjamin.peterson | 2009-02-21 16:16:42 -0600 (Sat, 21 Feb 2009) | 1 line

  make the python IncrementalNewineDecoder support a None decoder
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  r69852 | benjamin.peterson | 2009-02-21 16:36:09 -0600 (Sat, 21 Feb 2009) | 1 line

  fix a BlockingIOError.characters_written bug
........
  r69854 | benjamin.peterson | 2009-02-21 16:49:02 -0600 (Sat, 21 Feb 2009) | 1 line

  check whence
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  r69860 | benjamin.peterson | 2009-02-21 17:42:50 -0600 (Sat, 21 Feb 2009) | 1 line

  fix some of these Misbehaving io tests
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  r69865 | benjamin.peterson | 2009-02-21 18:59:52 -0600 (Sat, 21 Feb 2009) | 1 line

  don't use super here()
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  r69866 | benjamin.peterson | 2009-02-21 19:05:28 -0600 (Sat, 21 Feb 2009) | 1 line

  use implementation specific classes
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  r69868 | benjamin.peterson | 2009-02-21 22:12:05 -0600 (Sat, 21 Feb 2009) | 1 line

  use a more DRY friendly approach to injecting module contents into test classes
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  r69872 | antoine.pitrou | 2009-02-22 13:39:45 -0600 (Sun, 22 Feb 2009) | 3 lines

  Sanitize destructor behaviour of IOBase. Now Python-defined attributes can be accessed from close().
........
  r69873 | antoine.pitrou | 2009-02-22 13:50:14 -0600 (Sun, 22 Feb 2009) | 4 lines

  Only set the internal fd after it has been checked to be valid
  (otherwise, the destructor will attempt to close it)
........
  r69885 | benjamin.peterson | 2009-02-22 15:30:14 -0600 (Sun, 22 Feb 2009) | 1 line

  convert some other tests to use both io implementations
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  r69888 | antoine.pitrou | 2009-02-22 17:03:16 -0600 (Sun, 22 Feb 2009) | 3 lines

  Silence all exceptions when finalizing
........
  r69891 | benjamin.peterson | 2009-02-22 17:27:24 -0600 (Sun, 22 Feb 2009) | 1 line

  convert another test to test both io implementations
........
  r69892 | benjamin.peterson | 2009-02-22 17:32:15 -0600 (Sun, 22 Feb 2009) | 1 line

  help poor people like me to find their io tests (did I miss any?)
........
  r69893 | benjamin.peterson | 2009-02-22 17:37:56 -0600 (Sun, 22 Feb 2009) | 1 line

  put a big note in the test telling people to write tests for both implementations now
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  r69911 | antoine.pitrou | 2009-02-23 13:57:18 -0600 (Mon, 23 Feb 2009) | 3 lines

  expose DEFAULT_BUFFER_SIZE again (fixes a bunch of test failures)
........
  r69913 | antoine.pitrou | 2009-02-23 14:10:30 -0600 (Mon, 23 Feb 2009) | 4 lines

  Do the cyclic garbage collection tests only on the C version.
  The Python version is helpless as it uses __del__.
........
  r69914 | antoine.pitrou | 2009-02-23 14:21:41 -0600 (Mon, 23 Feb 2009) | 3 lines

  Adapt test_largefile to test both implementations
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  r69915 | antoine.pitrou | 2009-02-23 14:25:14 -0600 (Mon, 23 Feb 2009) | 3 lines

  One small failure
........
  r69916 | antoine.pitrou | 2009-02-23 14:28:33 -0600 (Mon, 23 Feb 2009) | 3 lines

  Add a comment, at BP's request
........
  r69963 | antoine.pitrou | 2009-02-25 09:42:59 -0600 (Wed, 25 Feb 2009) | 3 lines

  Add a test of ABC inheritance
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  r70033 | antoine.pitrou | 2009-02-27 15:49:50 -0600 (Fri, 27 Feb 2009) | 3 lines

  The base classes now are ABCs.
........
  r70035 | benjamin.peterson | 2009-02-27 15:57:41 -0600 (Fri, 27 Feb 2009) | 1 line

  good house keeping
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  r70038 | antoine.pitrou | 2009-02-27 17:05:23 -0600 (Fri, 27 Feb 2009) | 4 lines

  Make the buffer allocation overflow tests specific to the C implementation, since the Python implementation resizes its buffers when needed rather than allocating them up front.
........
  r70041 | benjamin.peterson | 2009-02-27 18:26:12 -0600 (Fri, 27 Feb 2009) | 1 line

  kill java naming for sanity
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  r70042 | benjamin.peterson | 2009-02-27 18:28:53 -0600 (Fri, 27 Feb 2009) | 2 lines

  timingTest is superseded by iobench
........
  r70043 | antoine.pitrou | 2009-02-27 19:13:50 -0600 (Fri, 27 Feb 2009) | 3 lines

  Remove the last traces of java naming in test_io
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  r70044 | antoine.pitrou | 2009-02-27 19:18:34 -0600 (Fri, 27 Feb 2009) | 3 lines

  Better resource cleanup
........
  r70045 | antoine.pitrou | 2009-02-27 19:29:00 -0600 (Fri, 27 Feb 2009) | 3 lines

  Remove dubious uses of super(), and fix one test
........
  r70046 | antoine.pitrou | 2009-02-27 19:31:00 -0600 (Fri, 27 Feb 2009) | 3 lines

  Bump up CHUNK_SIZE (no need to make the Python version look slower than it is)
........
  r70047 | benjamin.peterson | 2009-02-27 20:03:26 -0600 (Fri, 27 Feb 2009) | 1 line

  fix typo
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  r70048 | benjamin.peterson | 2009-02-27 21:35:11 -0600 (Fri, 27 Feb 2009) | 1 line

  move code to a better place
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  r70067 | benjamin.peterson | 2009-02-28 10:43:20 -0600 (Sat, 28 Feb 2009) | 4 lines

  1. make sure to undo buffered read aheads in BufferedRandom.seek()
  2. refill the buffer if have <= 0
  3. fix the last failing test_io test!
........
  r70068 | benjamin.peterson | 2009-02-28 10:57:50 -0600 (Sat, 28 Feb 2009) | 1 line

  define read1() on the python implementation's BufferedIOBase
........
  r70069 | benjamin.peterson | 2009-02-28 11:01:17 -0600 (Sat, 28 Feb 2009) | 1 line

  document read1() in BufferedIOBase
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  r70070 | benjamin.peterson | 2009-02-28 11:06:42 -0600 (Sat, 28 Feb 2009) | 1 line

  give credit where credit is due
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  r70075 | antoine.pitrou | 2009-02-28 13:34:59 -0600 (Sat, 28 Feb 2009) | 3 lines

  Amaury's name
........
  r70112 | antoine.pitrou | 2009-03-02 17:11:55 -0600 (Mon, 02 Mar 2009) | 4 lines

  Looks like this is necessary in order to build cleanly under Windows
  (someone correct this if it's wrong, I'm no Windows user)
........
  r70133 | benjamin.peterson | 2009-03-03 15:23:32 -0600 (Tue, 03 Mar 2009) | 1 line

  fix test_newline_property on _pyio.StringIO
........
  r70135 | benjamin.peterson | 2009-03-03 15:47:30 -0600 (Tue, 03 Mar 2009) | 1 line

  fix typos and inconsistencies. thanks to Daniel Diniz
........
  r70140 | benjamin.peterson | 2009-03-03 16:21:10 -0600 (Tue, 03 Mar 2009) | 1 line

  add the test from #5266
........
diff --git a/Modules/_bytesio.c b/Modules/_bytesio.c
index 2cea0fc..0068cb7 100644
--- a/Modules/_bytesio.c
+++ b/Modules/_bytesio.c
@@ -1,4 +1,6 @@
 #include "Python.h"
+#include "structmember.h"       /* for offsetof() */
+#include "_iomodule.h"
 
 typedef struct {
     PyObject_HEAD
@@ -6,6 +8,8 @@
     Py_ssize_t pos;
     Py_ssize_t string_size;
     size_t buf_size;
+    PyObject *dict;
+    PyObject *weakreflist;
 } BytesIOObject;
 
 #define CHECK_CLOSED(self)                                  \
@@ -144,10 +148,12 @@
 static PyObject *
 bytesio_get_closed(BytesIOObject *self)
 {
-    if (self->buf == NULL)
+    if (self->buf == NULL) {
         Py_RETURN_TRUE;
-    else
+    }
+    else {
         Py_RETURN_FALSE;
+    }
 }
 
 /* Generic getter for the writable, readable and seekable properties */
@@ -532,22 +538,22 @@
 static PyObject *
 bytesio_write(BytesIOObject *self, PyObject *obj)
 {
-    const char *bytes;
-    Py_ssize_t size;
     Py_ssize_t n = 0;
+    Py_buffer buf;
+    PyObject *result = NULL;
 
     CHECK_CLOSED(self);
 
-    if (PyObject_AsReadBuffer(obj, (void *)&bytes, &size) < 0)
+    if (PyObject_GetBuffer(obj, &buf, PyBUF_CONTIG_RO) < 0)
         return NULL;
 
-    if (size != 0) {
-        n = write_bytes(self, bytes, size);
-        if (n < 0)
-            return NULL;
-    }
+    if (buf.len != 0)
+        n = write_bytes(self, buf.buf, buf.len);
+    if (n >= 0)
+        result = PyLong_FromSsize_t(n);
 
-    return PyLong_FromSsize_t(n);
+    PyBuffer_Release(&buf);
+    return result;
 }
 
 PyDoc_STRVAR(writelines_doc,
@@ -607,6 +613,7 @@
         PyMem_Free(self->buf);
         self->buf = NULL;
     }
+    Py_TYPE(self)->tp_clear((PyObject *)self);
     Py_TYPE(self)->tp_free(self);
 }
 
@@ -656,6 +663,24 @@
     return 0;
 }
 
+static int
+bytesio_traverse(BytesIOObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->dict);
+    Py_VISIT(self->weakreflist);
+    return 0;
+}
+
+static int
+bytesio_clear(BytesIOObject *self)
+{
+    Py_CLEAR(self->dict);
+    if (self->weakreflist != NULL)
+        PyObject_ClearWeakRefs((PyObject *)self);
+    return 0;
+}
+
+
 static PyGetSetDef bytesio_getsetlist[] = {
     {"closed",  (getter)bytesio_get_closed, NULL,
      "True if the file is closed."},
@@ -689,9 +714,9 @@
 "Create a buffered I/O implementation using an in-memory bytes\n"
 "buffer, ready for reading and writing.");
 
-static PyTypeObject BytesIO_Type = {
+PyTypeObject PyBytesIO_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
-    "_bytesio._BytesIO",                       /*tp_name*/
+    "_io.BytesIO",                             /*tp_name*/
     sizeof(BytesIOObject),                     /*tp_basicsize*/
     0,                                         /*tp_itemsize*/
     (destructor)bytesio_dealloc,               /*tp_dealloc*/
@@ -709,12 +734,13 @@
     0,                                         /*tp_getattro*/
     0,                                         /*tp_setattro*/
     0,                                         /*tp_as_buffer*/
-    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE |
+    Py_TPFLAGS_HAVE_GC,                        /*tp_flags*/
     bytesio_doc,                               /*tp_doc*/
-    0,                                         /*tp_traverse*/
-    0,                                         /*tp_clear*/
+    (traverseproc)bytesio_traverse,            /*tp_traverse*/
+    (inquiry)bytesio_clear,                    /*tp_clear*/
     0,                                         /*tp_richcompare*/
-    0,                                         /*tp_weaklistoffset*/
+    offsetof(BytesIOObject, weakreflist),      /*tp_weaklistoffset*/
     PyObject_SelfIter,                         /*tp_iter*/
     (iternextfunc)bytesio_iternext,            /*tp_iternext*/
     bytesio_methods,                           /*tp_methods*/
@@ -724,36 +750,8 @@
     0,                                         /*tp_dict*/
     0,                                         /*tp_descr_get*/
     0,                                         /*tp_descr_set*/
-    0,                                         /*tp_dictoffset*/
+    offsetof(BytesIOObject, dict),             /*tp_dictoffset*/
     (initproc)bytesio_init,                    /*tp_init*/
     0,                                         /*tp_alloc*/
     bytesio_new,                               /*tp_new*/
 };
-
-
-static struct PyModuleDef _bytesiomodule = {
-	PyModuleDef_HEAD_INIT,
-	"_bytesio",
-	NULL,
-	-1,
-	NULL,
-	NULL,
-	NULL,
-	NULL,
-	NULL
-};
-
-PyMODINIT_FUNC
-PyInit__bytesio(void)
-{
-    PyObject *m;
-
-    if (PyType_Ready(&BytesIO_Type) < 0)
-        return NULL;
-    m = PyModule_Create(&_bytesiomodule);
-    if (m == NULL)
-        return NULL;
-    Py_INCREF(&BytesIO_Type);
-    PyModule_AddObject(m, "_BytesIO", (PyObject *)&BytesIO_Type);
-    return m;
-}