examples: add python utils for examples

We need common operations from the python scripts.
For example, to print the boot-time.

Move such utils to a separate nmex.py file ("ex" for
example). This file should contain helper functions that
are pure python (or, if the have requirements, load them
only on demand, so that examples that need those have
additional dependencies). It should also be simple to extract
individual helpers from nmex, so that the user can take an
example, merge parts of nmex.py in, and modify it to his needs.

1 files changed, 72 insertions, 0 deletions

diff --git a/examples/python/nmex.py b/examples/python/nmex.py
new file mode 100644
index 0000000000..a85eecaf87
--- /dev/null
+++ b/examples/python/nmex.py
@@ -0,0 +1,72 @@
+#!/usr/bin/env python
+# -*- Mode: Python; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+# vim: ft=python ts=4 sts=4 sw=4 et ai
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+# Copyright 2018 Red Hat, Inc.
+
+###############################################################################
+# nmex.py contains helper functions used by some examples. The helper functions
+# should be simple and independent, so that the user can extract them easily
+# when modifying the example to his needs.
+###############################################################################
+
+def _sys_clock_gettime_ns_lazy():
+    import ctypes
+
+    class timespec(ctypes.Structure):
+        _fields_ = [
+                ('tv_sec', ctypes.c_long),
+                ('tv_nsec', ctypes.c_long)
+        ]
+
+    librt = ctypes.CDLL('librt.so.1', use_errno=True)
+    clock_gettime = librt.clock_gettime
+    clock_gettime.argtypes = [ctypes.c_int, ctypes.POINTER(timespec)]
+
+    t = timespec()
+    def f(clock_id):
+        if clock_gettime(clock_id, ctypes.pointer(t)) != 0:
+            import os
+            errno_ = ctypes.get_errno()
+            raise OSError(errno_, os.strerror(errno_))
+        return (t.tv_sec * 1000000000) + t.tv_nsec
+    return f
+
+_sys_clock_gettime_ns = None
+
+# call POSIX clock_gettime() and return it as integer (in nanoseconds)
+def sys_clock_gettime_ns(clock_id):
+    global _sys_clock_gettime_ns
+    if _sys_clock_gettime_ns is None:
+        _sys_clock_gettime_ns = _sys_clock_gettime_ns_lazy()
+    return _sys_clock_gettime_ns(clock_id)
+
+def nm_boot_time_ns():
+    # NetworkManager exposes some timestamps as CLOCK_BOOTTIME.
+    # Try that first (number 7).
+    try:
+        return sys_clock_gettime_ns(7)
+    except OSError as e:
+        # On systems, where this is not available, fallback to
+        # CLOCK_MONOTONIC (numeric 1).
+        # That is what NetworkManager does as well.
+        import errno
+        if e.errno == errno.EINVAL:
+            return sys_clock_gettime_ns(1)
+        raise
+def nm_boot_time_us():
+    return nm_boot_time_ns() / 1000
+def nm_boot_time_ms():
+    return nm_boot_time_ns() / 1000000
+def nm_boot_time_s():
+    return nm_boot_time_ns() / 1000000000
+
+###############################################################################