cdsa/cdsa_utilities/timeflow.h

   1 /*
   2  * Copyright (c) 2000-2001 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * The contents of this file constitute Original Code as defined in and are
   5  * subject to the Apple Public Source License Version 1.2 (the 'License').
   6  * You may not use this file except in compliance with the License. Please obtain
   7  * a copy of the License at http://www.apple.com/publicsource and read it before
   8  * using this file.
   9  *
  10  * This Original Code and all software distributed under the License are
  11  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
  12  * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
  13  * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  14  * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
  15  * specific language governing rights and limitations under the License.
  16  */
  17
  18
  19 //
  20 // timeflow - abstract view of the flow of time
  21 //
  22 // We happily publish both absolute and relative times as floating-point values.
  23 // Absolute times are off the UNIX Epoch (1/1/1970, midnight). This leaves us about
  24 // microsecond resolution in Modern Times.
  25 //
  26 #ifndef _H_TIMEFLOW
  27 #define _H_TIMEFLOW
  28
  29 #include <sys/time.h>
  30 #include <math.h>       // for MAXFLOAT
  31
  32
  33 namespace Security {
  34 namespace Time {
  35
  36
  37 //
  38 // A Time::Interval is a time difference (distance).
  39 //
  40 class Interval {
  41     friend class Absolute;
  42 public:
  43     Interval() { }
  44     Interval(int seconds)               { mValue = seconds; }
  45     Interval(double seconds)    { mValue = seconds; }
  46     explicit Interval(time_t seconds) { mValue = seconds; }
  47
  48     Interval &operator += (Interval rel)        { mValue += rel.mValue; return *this; }
  49     Interval &operator -= (Interval rel)        { mValue -= rel.mValue; return *this; }
  50     Interval &operator *= (double f)            { mValue *= f; return *this; }
  51     Interval &operator /= (double f)            { mValue /= f; return *this; }
  52
  53     bool operator <  (Interval other) const     { return mValue < other.mValue; }
  54     bool operator <= (Interval other) const     { return mValue <= other.mValue; }
  55     bool operator >  (Interval other) const     { return mValue > other.mValue; }
  56     bool operator >= (Interval other) const     { return mValue >= other.mValue; }
  57     bool operator == (Interval other) const     { return mValue == other.mValue; }
  58     bool operator != (Interval other) const     { return mValue != other.mValue; }
  59
  60     // express as (fractions of) seconds, milliseconds, or microseconds
  61     double seconds() const                                      { return mValue; }
  62     double mSeconds() const                                     { return mValue * 1E3; }
  63     double uSeconds() const                                     { return mValue * 1E6; }
  64
  65     // struct timeval is sometimes used for time intervals, but not often - so be explicit
  66     struct timeval timevalInterval() const;
  67
  68 private:
  69     double mValue;
  70 };
  71
  72
  73 //
  74 // A Time::Absolute is a moment in time.
  75 //
  76 class Absolute {
  77     friend class Interval;
  78     friend Interval operator - (Absolute, Absolute);
  79     friend Absolute now();
  80     friend Absolute bigBang();
  81     friend Absolute heatDeath();
  82 public:
  83     Absolute() { }                                              // uninitialized
  84     Absolute(time_t t) { mValue = t; }  // from time_t
  85     Absolute(const struct timeval &tv); // from timeval
  86
  87     // *crement operators
  88     Absolute &operator += (Interval rel)        { mValue += rel.mValue; return *this; }
  89     Absolute &operator -= (Interval rel)        { mValue -= rel.mValue; return *this; }
  90
  91     // comparisons
  92     bool operator <  (Absolute other) const     { return mValue < other.mValue; }
  93     bool operator <= (Absolute other) const     { return mValue <= other.mValue; }
  94     bool operator >  (Absolute other) const     { return mValue > other.mValue; }
  95     bool operator >= (Absolute other) const     { return mValue >= other.mValue; }
  96     bool operator == (Absolute other) const     { return mValue == other.mValue; }
  97     bool operator != (Absolute other) const     { return mValue != other.mValue; }
  98
  99     // express as conventional (absolute!) time measures
 100     operator struct timeval() const;
 101     operator time_t () const                            { return time_t(mValue); }
 102
 103     // internal form for debugging ONLY
 104     double internalForm() const                         { return mValue; }
 105
 106 private:
 107     double mValue;
 108
 109     Absolute(double value) : mValue(value) { }
 110 };
 111
 112
 113 //
 114 // Time::now produces the current time
 115 //
 116 Absolute now();                                         // get "now"
 117
 118
 119 //
 120 // Time::resolution(when) gives a conservative estimate of the available resolution
 121 // at a given time.
 122 //
 123 Interval resolution(Absolute at);       // estimate available resolution at given time
 124
 125
 126 //
 127 // Some useful "constants"
 128 //
 129 inline Absolute bigBang()                               { return -MAXFLOAT; }
 130 inline Absolute heatDeath()                             { return +MAXFLOAT; }
 131
 132
 133
 134 //
 135 // More inline arithmetic
 136 //
 137 inline Interval operator + (Interval r, Interval r2)    { r += r2; return r; }
 138 inline Interval operator - (Interval r, Interval r2)    { r -= r2; return r; }
 139 inline Interval operator * (Interval r, double f)               { r *= f; return r; }
 140 inline Interval operator / (Interval r, double f)               { r /= f; return r; }
 141
 142 inline Absolute operator + (Absolute a, Interval r)             { return a += r; }
 143 inline Absolute operator + (Interval r, Absolute a)             { return a += r; }
 144 inline Absolute operator - (Absolute a, Interval r)             { return a -= r; }
 145
 146 inline Interval operator - (Absolute t1, Absolute t0)
 147 { return t1.mValue - t0.mValue; }
 148
 149
 150 }       // end namespace Time
 151 }       // end namespace Security
 152
 153 #endif //_H_TIMEFLOW