149 lines
5.2 KiB
Python
149 lines
5.2 KiB
Python
# -*- coding: utf-8 -*-
|
|
"""
|
|
monotonic
|
|
~~~~~~~~~
|
|
|
|
This module provides a ``monotonic()`` function which returns the
|
|
value (in fractional seconds) of a clock which never goes backwards.
|
|
|
|
On Python 3.3 or newer, ``monotonic`` will be an alias of
|
|
``time.monotonic`` from the standard library. On older versions,
|
|
it will fall back to an equivalent implementation:
|
|
|
|
+-------------+--------------------+
|
|
| Linux, BSD | clock_gettime(3) |
|
|
+-------------+--------------------+
|
|
| Windows | GetTickCount64 |
|
|
+-------------+--------------------+
|
|
| OS X | mach_absolute_time |
|
|
+-------------+--------------------+
|
|
|
|
If no suitable implementation exists for the current platform,
|
|
attempting to import this module (or to import from it) will
|
|
cause a RuntimeError exception to be raised.
|
|
|
|
|
|
Copyright 2014 Ori Livneh <ori@wikimedia.org>
|
|
|
|
Licensed under the Apache License, Version 2.0 (the "License");
|
|
you may not use this file except in compliance with the License.
|
|
You may obtain a copy of the License at
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
See the License for the specific language governing permissions and
|
|
limitations under the License.
|
|
|
|
"""
|
|
import ctypes
|
|
import ctypes.util
|
|
import os
|
|
import platform
|
|
import re
|
|
import sys
|
|
import time
|
|
|
|
|
|
__all__ = ('monotonic',)
|
|
|
|
|
|
def get_os_release():
|
|
"""Get the leading numeric component of the OS release."""
|
|
return re.match('[\d.]+', platform.release()).group(0)
|
|
|
|
|
|
def compare_versions(v1, v2):
|
|
"""Compare two version strings."""
|
|
def normalize(v):
|
|
return map(int, re.sub(r'(\.0+)*$', '', v).split('.'))
|
|
return cmp(normalize(v1), normalize(v2))
|
|
|
|
|
|
try:
|
|
monotonic = time.monotonic
|
|
except AttributeError:
|
|
try:
|
|
if sys.platform == 'darwin': # OS X, iOS
|
|
# See Technical Q&A QA1398 of the Mac Developer Library:
|
|
# <https://developer.apple.com/library/mac/qa/qa1398/>
|
|
libc = ctypes.CDLL('/usr/lib/libc.dylib', use_errno=True)
|
|
|
|
class mach_timebase_info_data_t(ctypes.Structure):
|
|
"""System timebase info. Defined in <mach/mach_time.h>."""
|
|
_fields_ = (('numer', ctypes.c_uint32),
|
|
('denom', ctypes.c_uint32))
|
|
|
|
mach_absolute_time = libc.mach_absolute_time
|
|
mach_absolute_time.restype = ctypes.c_uint64
|
|
|
|
timebase = mach_timebase_info_data_t()
|
|
libc.mach_timebase_info(ctypes.byref(timebase))
|
|
ticks_per_second = timebase.numer / timebase.denom * 1.0e9
|
|
|
|
def monotonic():
|
|
"""Monotonic clock, cannot go backward."""
|
|
return mach_absolute_time() / ticks_per_second
|
|
|
|
elif sys.platform.startswith('win32'):
|
|
# Windows Vista / Windows Server 2008 or newer.
|
|
GetTickCount64 = ctypes.windll.kernel32.GetTickCount64
|
|
GetTickCount64.restype = ctypes.c_ulonglong
|
|
|
|
def monotonic():
|
|
"""Monotonic clock, cannot go backward."""
|
|
return GetTickCount64() / 1000.0
|
|
|
|
elif sys.platform.startswith('cygwin'):
|
|
# Cygwin
|
|
kernel32 = ctypes.cdll.LoadLibrary('kernel32.dll')
|
|
GetTickCount64 = kernel32.GetTickCount64
|
|
GetTickCount64.restype = ctypes.c_ulonglong
|
|
|
|
def monotonic():
|
|
"""Monotonic clock, cannot go backward."""
|
|
return GetTickCount64() / 1000.0
|
|
|
|
else:
|
|
try:
|
|
clock_gettime = ctypes.CDLL(ctypes.util.find_library('c'),
|
|
use_errno=True).clock_gettime
|
|
except AttributeError:
|
|
clock_gettime = ctypes.CDLL(ctypes.util.find_library('rt'),
|
|
use_errno=True).clock_gettime
|
|
|
|
class timespec(ctypes.Structure):
|
|
"""Time specification, as described in clock_gettime(3)."""
|
|
_fields_ = (('tv_sec', ctypes.c_long),
|
|
('tv_nsec', ctypes.c_long))
|
|
|
|
ts = timespec()
|
|
|
|
if sys.platform.startswith('linux'):
|
|
if compare_versions(get_os_release(), '2.6.28') > 0:
|
|
CLOCK_MONOTONIC = 4 # CLOCK_MONOTONIC_RAW
|
|
else:
|
|
CLOCK_MONOTONIC = 1
|
|
elif sys.platform.startswith('freebsd'):
|
|
CLOCK_MONOTONIC = 4
|
|
elif sys.platform.startswith('sunos5'):
|
|
CLOCK_MONOTONIC = 4
|
|
elif 'bsd' in sys.platform:
|
|
CLOCK_MONOTONIC = 3
|
|
|
|
def monotonic():
|
|
"""Monotonic clock, cannot go backward."""
|
|
if clock_gettime(CLOCK_MONOTONIC, ctypes.pointer(ts)):
|
|
errno = ctypes.get_errno()
|
|
raise OSError(errno, os.strerror(errno))
|
|
return ts.tv_sec + ts.tv_nsec / 1.0e9
|
|
|
|
# Perform a sanity-check.
|
|
if monotonic() - monotonic() > 0:
|
|
raise ValueError('monotonic() is not monotonic!')
|
|
|
|
except Exception:
|
|
raise RuntimeError('no suitable implementation for this system')
|