264 lines
6.8 KiB
C++
264 lines
6.8 KiB
C++
/*
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Copyright (c) 2003, 2018, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2.0,
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as published by the Free Software Foundation.
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This program is also distributed with certain software (including
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but not limited to OpenSSL) that is licensed under separate terms,
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as designated in a particular file or component or in included license
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documentation. The authors of MySQL hereby grant you an additional
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permission to link the program and your derivative works with the
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separately licensed software that they have included with MySQL.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License, version 2.0, for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef NDB_TICK_H
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#define NDB_TICK_H
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#include <assert.h>
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#include <ndb_types.h>
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void NdbTick_Init();
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/**
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* NDB_TICKS is a high resolution monotonic timer representing
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* timer 'ticks' from some epoch start like boot time, 1/1 -1970 or
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* whatever.
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* Its actual resolution and duration of a 'tick' is platform
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* dependent. Make no assumption about it representing a specific time.
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* Functions are provided to compare ticks and calculate time
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* interval between ticks
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*
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* NOTE: Even if the platform specific implementation of 'ticks'
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* should be in nanoseconds, the 64bit NDB_TICK will not wrap until
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* ~585 years has passed. So it should be pretty safe....
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*/
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typedef struct NDB_TICKS {
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Uint64 t;
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public:
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NDB_TICKS()
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{ t = 0; }
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/**
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* Provide functionality for fetch and reconstruct of tick value.
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* Usefull when a 'tick' is sent as part of a signal, or when
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* the clock is used to generate a pseudo random number.
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*/
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Uint64 getUint64() const
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{ return t; }
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explicit NDB_TICKS(Uint64 val)
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{ t = val; }
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} NDB_TICKS;
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/**
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* Returns whether the 'ticks' are provided by a monotonic timer.
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* Must be called after NdbTick_Init()
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*/
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bool
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NdbTick_IsMonotonic();
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/**
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* Returns number of 'ticks' since some
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* platforms dependent epoch start.
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*/
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const NDB_TICKS
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NdbTick_getCurrentTicks(void);
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/**
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* Add specified number of milliseconds to a 'ticks' value.
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*/
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const NDB_TICKS NdbTick_AddMilliseconds(NDB_TICKS ticks, Uint64 ms);
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static void NdbTick_Invalidate(NDB_TICKS *ticks);
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static int NdbTick_IsValid(NDB_TICKS ticks);
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/**
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* Compare ticks and return an integer greater than,
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* equal to, or less than 0, if the 'tick value' in t1
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* is greater than, equal to, or less than the t2 tick
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* respectively.
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*/
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static int NdbTick_Compare(NDB_TICKS t1, NDB_TICKS t2);
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/**
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* Get time elapsed between start and end time.
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*/
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static const class NdbDuration
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NdbTick_Elapsed(NDB_TICKS start, NDB_TICKS end);
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/**
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* Returns the current millisecond since some epoch start.
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*
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* Treat this function as deprecated. Elapsed time intervals
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* should be calculated by using the pattern
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* start/end = NdbTick_getCurrentTicks() and
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* elapsed = NdbTick_Elapsed...(start,end).
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*
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* All usage except in test utilties, should be considdered
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* a bug.
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*/
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static Uint64 NdbTick_CurrentMillisecond(void);
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class NdbDuration {
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public:
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Uint64 seconds() const;
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Uint64 milliSec() const;
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Uint64 microSec() const;
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Uint64 nanoSec() const;
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private:
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Uint64 t;
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static Uint64 tick_frequency;
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friend const NdbDuration
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NdbTick_Elapsed(NDB_TICKS start, NDB_TICKS end);
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friend Uint64
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NdbTick_CurrentMillisecond(void);
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friend const NDB_TICKS
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NdbTick_AddMilliseconds(NDB_TICKS ticks, Uint64 ms);
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friend void NdbTick_Init();
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NdbDuration(Uint64 ticks) : t(ticks) {}
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}; //class NdbDuration
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/******************************************************
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* Implementation of NdbTick_foo functions.
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******************************************************/
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inline
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void NdbTick_Invalidate(NDB_TICKS *ticks)
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{
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ticks->t = 0;
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}
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static inline
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int NdbTick_IsValid(NDB_TICKS ticks)
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{
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return(ticks.t != 0);
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}
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static inline
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int NdbTick_Compare(NDB_TICKS t1, NDB_TICKS t2)
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{
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assert(NdbTick_IsValid(t1));
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assert(NdbTick_IsValid(t2));
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return (t1.t > t2.t) ? 1
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:(t1.t < t2.t) ? -1
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: 0;
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}
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static inline
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const NdbDuration
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NdbTick_Elapsed(NDB_TICKS start, NDB_TICKS end)
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{
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assert(NdbTick_IsValid(start));
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assert(NdbTick_IsValid(end));
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if (end.t >= start.t)
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{
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return NdbDuration(end.t - start.t);
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}
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/**
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* Clock has ticked backwards!
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* We protect agains backward leaping timers by returning 0
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* if detected. This is less harmfull than returning a huge
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* Uint64 which would be the result of that subtraction.
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* Even the monotonic clock is known buggy
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* on some older BIOS and virtualized platforms.
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*/
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else if (NdbTick_IsMonotonic())
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{
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/* Don't accept more than 10ms 'noise' if monotonic */
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assert(NdbDuration(start.t-end.t).milliSec() <= 10);
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}
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return NdbDuration(0);
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}
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static inline Uint64
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NdbTick_CurrentMillisecond(void)
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{
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const Uint64 ticks = NdbTick_getCurrentTicks().t;
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if (ticks < (UINT_MAX64 / 1000))
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return ((ticks*1000) / NdbDuration::tick_frequency); // Best precision
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else
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return (ticks / (NdbDuration::tick_frequency/1000)); // Avoids oveflow,
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}
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/******************************************************
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* Implementation of NdbDuration methods.
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*
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* In order to avoid precision loss, we multiply ticks
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* by the scale factor before dividing by the frequency.
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******************************************************/
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inline
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Uint64 NdbDuration::seconds() const
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{
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return (t / tick_frequency);
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}
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inline
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Uint64 NdbDuration::milliSec() const
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{
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assert(t < (UINT_MAX64 / 1000)); //Overflow?
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return ((t*1000) / tick_frequency);
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}
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/**
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* To avoid overflow in intermediate results when
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* multiplying 'tick' (t) with micro- or nanoScale
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* factor below, we handle the tick conversion in a
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* 'second' and a 'fraction' (of seconds) part.
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*/
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inline
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Uint64 NdbDuration::microSec() const
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{
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static const Uint64 microScale = 1000*1000;
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const Uint64 seconds = (t / tick_frequency);
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const Uint64 fraction = (t % tick_frequency);
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const Uint64 microsec = ((fraction*microScale) / tick_frequency);
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return microsec + (seconds*microScale);
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}
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inline
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Uint64 NdbDuration::nanoSec() const
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{
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static const Uint64 nanoScale = 1000*1000*1000;
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const Uint64 seconds = (t / tick_frequency);
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const Uint64 fraction = (t % tick_frequency);
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const Uint64 nanosec = ((fraction*nanoScale) / tick_frequency);
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return nanosec + (seconds*nanoScale);
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}
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#endif
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