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+# -*- coding: utf-8 -*-
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+#
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+# SPDX-License-Identifier: Apache-2.0
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+"""
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+ monotonic
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+ ~~~~~~~~~
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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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+
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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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+ +-------------+----------------------------------------+
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+ | Linux, BSD | ``clock_gettime(3)`` |
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+ +-------------+----------------------------------------+
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+ | Windows | ``GetTickCount`` or ``GetTickCount64`` |
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+ +-------------+----------------------------------------+
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+ | OS X | ``mach_absolute_time`` |
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+ +-------------+----------------------------------------+
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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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+
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+
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+ Copyright 2014, 2015, 2016 Ori Livneh <ori@wikimedia.org>
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+
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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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+
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+ http://www.apache.org/licenses/LICENSE-2.0
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+
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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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+"""
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+import time
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+
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+
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+__all__ = ('monotonic',)
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+
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+
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+try:
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+ monotonic = time.monotonic
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+except AttributeError:
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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 threading
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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('/usr/lib/libc.dylib', use_errno=True)
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+
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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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+
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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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+
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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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+
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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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+
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+ elif sys.platform.startswith('win32') or sys.platform.startswith('cygwin'):
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+ if sys.platform.startswith('cygwin'):
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+ # Note: cygwin implements clock_gettime (CLOCK_MONOTONIC = 4) since
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+ # version 1.7.6. Using raw WinAPI for maximum version compatibility.
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+
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+ # Ugly hack using the wrong calling convention (in 32-bit mode)
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+ # because ctypes has no windll under cygwin (and it also seems that
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+ # the code letting you select stdcall in _ctypes doesn't exist under
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+ # the preprocessor definitions relevant to cygwin).
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+ # This is 'safe' because:
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+ # 1. The ABI of GetTickCount and GetTickCount64 is identical for
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+ # both calling conventions because they both have no parameters.
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+ # 2. libffi masks the problem because after making the call it doesn't
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+ # touch anything through esp and epilogue code restores a correct
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+ # esp from ebp afterwards.
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+ try:
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+ kernel32 = ctypes.cdll.kernel32
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+ except OSError: # 'No such file or directory'
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+ kernel32 = ctypes.cdll.LoadLibrary('kernel32.dll')
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+ else:
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+ kernel32 = ctypes.windll.kernel32
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+
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+ GetTickCount64 = getattr(kernel32, 'GetTickCount64', None)
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+ if GetTickCount64:
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+ # Windows Vista / Windows Server 2008 or newer.
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+ GetTickCount64.restype = ctypes.c_ulonglong
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+
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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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+
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+ else:
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+ # Before Windows Vista.
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+ GetTickCount = kernel32.GetTickCount
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+ GetTickCount.restype = ctypes.c_uint32
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+
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+ get_tick_count_lock = threading.Lock()
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+ get_tick_count_last_sample = 0
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+ get_tick_count_wraparounds = 0
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+
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+ def monotonic():
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+ """Monotonic clock, cannot go backward."""
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+ global get_tick_count_last_sample
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+ global get_tick_count_wraparounds
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+
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+ with get_tick_count_lock:
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+ current_sample = GetTickCount()
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+ if current_sample < get_tick_count_last_sample:
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+ get_tick_count_wraparounds += 1
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+ get_tick_count_last_sample = current_sample
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+
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+ final_milliseconds = get_tick_count_wraparounds << 32
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+ final_milliseconds += get_tick_count_last_sample
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+ return final_milliseconds / 1000.0
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+
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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 Exception:
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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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+
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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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+
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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 sys.platform.startswith('sunos5'):
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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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+ elif sys.platform.startswith('aix'):
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+ CLOCK_MONOTONIC = ctypes.c_longlong(10)
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+
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+ def monotonic():
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+ """Monotonic clock, cannot go backward."""
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+ ts = timespec()
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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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+
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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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+
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+ except Exception as e:
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+ raise RuntimeError('no suitable implementation for this system: ' + repr(e))
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Ilya Mashchenko