Mercurial > hg
annotate contrib/python-zstandard/zstandard/__init__.py @ 48875:6000f5b25c9b
py2: remove simple from __future__ statements
These were needed for Python 2 support. Now that our linter no longer
mandates these, we can start deleting them.
Differential Revision: https://phab.mercurial-scm.org/D12254
author | Gregory Szorc <gregory.szorc@gmail.com> |
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date | Thu, 03 Mar 2022 17:34:00 +0100 |
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1 # Copyright (c) 2017-present, Gregory Szorc |
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2 # All rights reserved. |
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3 # |
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4 # This software may be modified and distributed under the terms |
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5 # of the BSD license. See the LICENSE file for details. |
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6 |
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7 """Python interface to the Zstandard (zstd) compression library.""" |
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8 |
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9 |
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10 # This module serves 2 roles: |
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11 # |
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12 # 1) Export the C or CFFI "backend" through a central module. |
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13 # 2) Implement additional functionality built on top of C or CFFI backend. |
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14 |
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15 import os |
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16 import platform |
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17 |
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18 # Some Python implementations don't support C extensions. That's why we have |
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19 # a CFFI implementation in the first place. The code here import one of our |
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20 # "backends" then re-exports the symbols from this module. For convenience, |
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21 # we support falling back to the CFFI backend if the C extension can't be |
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22 # imported. But for performance reasons, we only do this on unknown Python |
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23 # implementation. Notably, for CPython we require the C extension by default. |
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24 # Because someone will inevitably want special behavior, the behavior is |
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25 # configurable via an environment variable. A potentially better way to handle |
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26 # this is to import a special ``__importpolicy__`` module or something |
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27 # defining a variable and `setup.py` could write the file with whatever |
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28 # policy was specified at build time. Until someone needs it, we go with |
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29 # the hacky but simple environment variable approach. |
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30 _module_policy = os.environ.get("PYTHON_ZSTANDARD_IMPORT_POLICY", "default") |
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31 |
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32 if _module_policy == "default": |
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33 if platform.python_implementation() in ("CPython",): |
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34 from zstd import * |
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35 |
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36 backend = "cext" |
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37 elif platform.python_implementation() in ("PyPy",): |
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38 from .cffi import * |
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39 |
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40 backend = "cffi" |
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41 else: |
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42 try: |
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43 from zstd import * |
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44 |
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45 backend = "cext" |
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46 except ImportError: |
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47 from .cffi import * |
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48 |
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49 backend = "cffi" |
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50 elif _module_policy == "cffi_fallback": |
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51 try: |
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52 from zstd import * |
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53 |
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54 backend = "cext" |
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55 except ImportError: |
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56 from .cffi import * |
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57 |
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58 backend = "cffi" |
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59 elif _module_policy == "cext": |
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60 from zstd import * |
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61 |
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62 backend = "cext" |
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63 elif _module_policy == "cffi": |
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64 from .cffi import * |
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65 |
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66 backend = "cffi" |
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67 else: |
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68 raise ImportError( |
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69 "unknown module import policy: %s; use default, cffi_fallback, " |
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70 "cext, or cffi" % _module_policy |
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71 ) |
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72 |
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73 # Keep this in sync with python-zstandard.h. |
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74 __version__ = "0.13.0" |