system_clock.hpp

00001 /*
00002  * System clock driver interface.
00003  * Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
00004  */
00005 
00006 #ifndef UAVCAN_DRIVER_SYSTEM_CLOCK_HPP_INCLUDED
00007 #define UAVCAN_DRIVER_SYSTEM_CLOCK_HPP_INCLUDED
00008 
00009 #include <uavcan/std.hpp>
00010 #include <uavcan/build_config.hpp>
00011 #include <uavcan/time.hpp>
00012 
00013 namespace uavcan
00014 {
00015 
00016 /**
00017  * System clock interface - monotonic and UTC.
00018  */
00019 class UAVCAN_EXPORT ISystemClock
00020 {
00021 public:
00022     virtual ~ISystemClock() { }
00023 
00024     /**
00025      * Monototic system clock.
00026      *
00027      * This clock shall never jump or change rate; the base time is irrelevant.
00028      * This clock is mandatory and must remain functional at all times.
00029      *
00030      * On POSIX systems use clock_gettime() with CLOCK_MONOTONIC.
00031      */
00032     virtual MonotonicTime getMonotonic() const = 0;
00033 
00034     /**
00035      * Global network clock.
00036      * It doesn't have to be UTC, the name is a bit misleading - actual time base doesn't matter.
00037      *
00038      * This clock can be synchronized with other nodes on the bus, hence it can jump and/or change
00039      * rate occasionally.
00040      * This clock is optional; if it is not supported, return zero. Also return zero if the UTC time
00041      * is not available yet (e.g. the device has just started up with no battery clock).
00042      *
00043      * For POSIX refer to clock_gettime(), gettimeofday().
00044      */
00045     virtual UtcTime getUtc() const = 0;
00046 
00047     /**
00048      * Adjust the network-synchronized clock.
00049      * Refer to @ref getUtc() for details.
00050      *
00051      * For POSIX refer to adjtime(), settimeofday().
00052      *
00053      * @param [in] adjustment Amount of time to add to the clock value.
00054      */
00055     virtual void adjustUtc(UtcDuration adjustment) = 0;
00056 };
00057 
00058 }
00059 
00060 #endif // UAVCAN_DRIVER_SYSTEM_CLOCK_HPP_INCLUDED