add monotonic utility (#59)

* add monotonic utility
* linux only

.gitignore

@@ -43,6 +43,11 @@ htmlcov/
 nosetests.xml
 coverage.xml
 
+# Eclipse
+.project
+.pydevproject
+.settings/
+
 # Translations
 *.mo
 *.pot

luma/core/sprite_system.py

@@ -13,6 +13,8 @@
 
 from PIL import Image
 
+from luma.core.util import monotonic
+
 
 class dict_wrapper(object):
     """
@@ -184,7 +186,7 @@ def __init__(self, fps=16.67):
         self.last_time = None
 
     def __enter__(self):
-        self.enter_time = time.time()
+        self.enter_time = monotonic()
         if not self.start_time:
             self.start_time = self.enter_time
             self.last_time = self.enter_time
@@ -199,15 +201,15 @@ def __exit__(self, *args):
         it simply exits without blocking.
         """
         self.called += 1
-        self.total_transit_time += time.time() - self.enter_time
+        self.total_transit_time += monotonic() - self.enter_time
         if self.max_sleep_time >= 0:
-            elapsed = time.time() - self.last_time
+            elapsed = monotonic() - self.last_time
             sleep_for = self.max_sleep_time - elapsed
 
             if sleep_for > 0:
                 time.sleep(sleep_for)
 
-        self.last_time = time.time()
+        self.last_time = monotonic()
 
     def effective_FPS(self):
         """
@@ -218,7 +220,7 @@ def effective_FPS(self):
         :returns: the effective frame rate
         :rtype: float
         """
-        elapsed = time.time() - self.start_time
+        elapsed = monotonic() - self.start_time
         return self.called / elapsed
 
     def average_transit_time(self):

luma/core/util.py

@@ -2,10 +2,42 @@
 # Copyright (c) 2017 Richard Hull and contributors
 # See LICENSE.rst for details.
 
+import os
+import time
 import warnings
+import ctypes.util
 
 
-__all__ = ["deprecation"]
+__all__ = ["deprecation", "monotonic"]
+
+
+try:
+    # only available since python 3.3
+    monotonic = time.monotonic
+except AttributeError:
+    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))
+
+    def monotonic():
+        """
+        Monotonic clock that cannot go backward.
+        """
+        ts = timespec()
+        if clock_gettime(1, ctypes.pointer(ts)):
+            errno = ctypes.get_errno()
+            raise OSError(errno, os.strerror(errno))
+        return ts.tv_sec + ts.tv_nsec / 1.0e9
 
 
 def deprecation(message):

luma/core/virtual.py

@@ -6,6 +6,7 @@
 
 from PIL import Image, ImageDraw, ImageFont
 
+from luma.core.util import monotonic
 from luma.core import mixin, ansi_color
 from luma.core.threadpool import threadpool
 
@@ -169,19 +170,20 @@ def should_redraw(self):
         """
         Only requests a redraw after ``interval`` seconds have elapsed
         """
-        return time.time() - self.last_updated > self.interval
+        return monotonic() - self.last_updated > self.interval
 
     def paste_into(self, image, xy):
         super(snapshot, self).paste_into(image, xy)
-        self.last_updated = time.time()
+        self.last_updated = monotonic()
 
 
 class terminal(object):
     """
     Provides a terminal-like interface to a device (or a device-like object
     that has :class:`mixin.capabilities` characteristics).
     """
-    def __init__(self, device, font=None, color="white", bgcolor="black", tabstop=4, line_height=None, animate=True):
+    def __init__(self, device, font=None, color="white", bgcolor="black",
+                 tabstop=4, line_height=None, animate=True):
         self._device = device
         self.font = font or ImageFont.load_default()
         self.default_fgcolor = color

setup.py

@@ -33,7 +33,12 @@ def read_file(fname):
     download_url="https://github.com/rm-hull/luma.core/tarball/" + version,
     namespace_packages=["luma"],
     packages=["luma.core", "luma.core.legacy"],
-    install_requires=["pillow>=4.0.0", "smbus2", "spidev", "RPi.GPIO"],
+    install_requires=[
+        "pillow>=4.0.0",
+        "smbus2",
+        "spidev",
+        "RPi.GPIO"
+    ],
     setup_requires=pytest_runner,
     tests_require=test_deps,
     extras_require={

tests/test_framerate_regulator.py

@@ -7,10 +7,9 @@
 Tests for the :py:class:`luma.core.sprite_system.framerate_regulator` class.
 """
 
-import time
-
 import pytest
 
+from luma.core.util import monotonic
 from luma.core.sprite_system import framerate_regulator
 
 
@@ -19,10 +18,10 @@ def test_init_default():
     assert regulator.start_time is None
     assert regulator.last_time is None
     assert regulator.called == 0
-    before = time.time()
+    before = monotonic()
     with regulator:
         pass
-    after = time.time()
+    after = monotonic()
 
     assert regulator.max_sleep_time == 1 / 16.67
     assert before <= regulator.start_time <= after
@@ -31,10 +30,10 @@ def test_init_default():
 
 def test_init_unlimited():
     regulator = framerate_regulator(fps=0)
-    before = time.time()
+    before = monotonic()
     with regulator:
         pass
-    after = time.time()
+    after = monotonic()
 
     assert regulator.max_sleep_time == -1
     assert before <= regulator.start_time <= after
@@ -43,10 +42,10 @@ def test_init_unlimited():
 
 def test_init_30fps():
     regulator = framerate_regulator(fps=30)
-    before = time.time()
+    before = monotonic()
     with regulator:
         pass
-    after = time.time()
+    after = monotonic()
 
     assert regulator.max_sleep_time == 1 / 30.00
     assert before <= regulator.start_time <= after
@@ -55,11 +54,11 @@ def test_init_30fps():
 
 def test_sleep():
     regulator = framerate_regulator(fps=100.00)
-    before = time.time()
+    before = monotonic()
     for _ in range(200):
         with regulator:
             pass
-    after = time.time()
+    after = monotonic()
 
     assert regulator.called == 200
     assert after - before >= 2.0