121 lines
4.3 KiB
Python
121 lines
4.3 KiB
Python
# -*- coding: utf-8 -*-
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"""
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monotonic
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~~~~~~~~~
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This module provides a ``monotonic()`` function which returns the
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value (in fractional seconds) of a clock which never goes backwards.
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On Python 3.3 or newer, ``monotonic`` will be an alias of
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``time.monotonic`` from the standard library. On older versions,
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it will fall back to an equivalent implementation:
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+-------------+--------------------+
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| Linux, BSD | clock_gettime(3) |
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+-------------+--------------------+
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| Windows | GetTickCount64 |
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+-------------+--------------------+
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| OS X | mach_absolute_time |
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+-------------+--------------------+
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If no suitable implementation exists for the current platform,
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attempting to import this module (or to import from it) will
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cause a RuntimeError exception to be raised.
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Copyright 2014 Ori Livneh <ori@wikimedia.org>
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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"""
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from __future__ import absolute_import, division
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import ctypes
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import ctypes.util
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import os
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import sys
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import time
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__all__ = ('monotonic',)
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try:
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monotonic = time.monotonic
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except AttributeError:
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try:
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if sys.platform == 'darwin': # OS X, iOS
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# See Technical Q&A QA1398 of the Mac Developer Library:
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# <https://developer.apple.com/library/mac/qa/qa1398/>
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libc = ctypes.CDLL('libc.dylib', use_errno=True)
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class mach_timebase_info_data_t(ctypes.Structure):
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"""System timebase info. Defined in <mach/mach_time.h>."""
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_fields_ = (('numer', ctypes.c_uint32),
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('denom', ctypes.c_uint32))
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mach_absolute_time = libc.mach_absolute_time
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mach_absolute_time.restype = ctypes.c_uint64
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timebase = mach_timebase_info_data_t()
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libc.mach_timebase_info(ctypes.byref(timebase))
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ticks_per_second = timebase.numer / timebase.denom * 1.0e9
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def monotonic():
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"""Monotonic clock, cannot go backward."""
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return mach_absolute_time() / ticks_per_second
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elif sys.platform.startswith('win32'):
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# Windows Vista / Windows Server 2008 or newer.
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GetTickCount64 = ctypes.windll.kernel32.GetTickCount64
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GetTickCount64.restype = ctypes.c_ulonglong
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def monotonic():
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"""Monotonic clock, cannot go backward."""
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return GetTickCount64() / 1000.0
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else:
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try:
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clock_gettime = ctypes.CDLL(ctypes.util.find_library('c'),
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use_errno=True).clock_gettime
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except AttributeError:
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clock_gettime = ctypes.CDLL(ctypes.util.find_library('rt'),
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use_errno=True).clock_gettime
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class timespec(ctypes.Structure):
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"""Time specification, as described in clock_gettime(3)."""
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_fields_ = (('tv_sec', ctypes.c_long),
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('tv_nsec', ctypes.c_long))
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ts = timespec()
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if sys.platform.startswith('linux'):
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CLOCK_MONOTONIC = 1
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elif sys.platform.startswith('freebsd'):
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CLOCK_MONOTONIC = 4
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elif 'bsd' in sys.platform:
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CLOCK_MONOTONIC = 3
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def monotonic():
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"""Monotonic clock, cannot go backward."""
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if clock_gettime(CLOCK_MONOTONIC, ctypes.pointer(ts)):
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errno = ctypes.get_errno()
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raise OSError(errno, os.strerror(errno))
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return ts.tv_sec + ts.tv_nsec / 1.0e9
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# Perform a sanity-check.
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if monotonic() - monotonic() >= 0:
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raise ValueError('monotonic() is not monotonic!')
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except Exception:
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raise RuntimeError('no suitable implementation for this system')
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