OSX/libsecurity_utilities/lib/timeflow.h

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  23
  24
  25 //
  26 // timeflow - abstract view of the flow of time
  27 //
  28 // We happily publish both absolute and relative times as floating-point values.
  29 // Absolute times are off the UNIX Epoch (1/1/1970, midnight). This leaves us about
  30 // microsecond resolution in Modern Times.
  31 //
  32 #ifndef _H_TIMEFLOW
  33 #define _H_TIMEFLOW
  34
  35 #include <sys/time.h>
  36 #include <limits.h>
  37 #include <math.h>       // for MAXFLOAT
  38
  39
  40 namespace Security {
  41 namespace Time {
  42
  43
  44 //
  45 // A Time::Interval is a time difference (distance).
  46 //
  47 class Interval {
  48     friend class Absolute;
  49 public:
  50     Interval() { }
  51     Interval(int seconds)               { mValue = seconds; }
  52     Interval(double seconds)    { mValue = seconds; }
  53     explicit Interval(time_t seconds) { mValue = seconds; }
  54
  55     Interval &operator += (Interval rel)        { mValue += rel.mValue; return *this; }
  56     Interval &operator -= (Interval rel)        { mValue -= rel.mValue; return *this; }
  57     Interval &operator *= (double f)            { mValue *= f; return *this; }
  58     Interval &operator /= (double f)            { mValue /= f; return *this; }
  59
  60     bool operator <  (Interval other) const     { return mValue < other.mValue; }
  61     bool operator <= (Interval other) const     { return mValue <= other.mValue; }
  62     bool operator >  (Interval other) const     { return mValue > other.mValue; }
  63     bool operator >= (Interval other) const     { return mValue >= other.mValue; }
  64     bool operator == (Interval other) const     { return mValue == other.mValue; }
  65     bool operator != (Interval other) const     { return mValue != other.mValue; }
  66
  67     // express as (fractions of) seconds, milliseconds, or microseconds
  68     double seconds() const                                      { return mValue; }
  69     double mSeconds() const                                     { return mValue * 1E3; }
  70     double uSeconds() const                                     { return mValue * 1E6; }
  71
  72     // struct timeval is sometimes used for time intervals, but not often - so be explicit
  73     struct timeval timevalInterval() const;
  74
  75 private:
  76     double mValue;
  77 };
  78
  79
  80 //
  81 // A Time::Absolute is a moment in time.
  82 //
  83 class Absolute {
  84     friend class Interval;
  85     friend Interval operator - (Absolute, Absolute);
  86     friend Absolute now();
  87     friend Absolute bigBang();
  88     friend Absolute heatDeath();
  89 public:
  90     Absolute() { }                                              // uninitialized
  91     Absolute(time_t t) { mValue = t; }  // from time_t
  92     Absolute(const struct timeval &tv); // from timeval
  93         Absolute(const struct timespec &ts); // from timespec
  94
  95     // *crement operators
  96     Absolute &operator += (Interval rel)        { mValue += rel.mValue; return *this; }
  97     Absolute &operator -= (Interval rel)        { mValue -= rel.mValue; return *this; }
  98
  99     // comparisons
 100     bool operator <  (Absolute other) const     { return mValue < other.mValue; }
 101     bool operator <= (Absolute other) const     { return mValue <= other.mValue; }
 102     bool operator >  (Absolute other) const     { return mValue > other.mValue; }
 103     bool operator >= (Absolute other) const     { return mValue >= other.mValue; }
 104     bool operator == (Absolute other) const     { return mValue == other.mValue; }
 105     bool operator != (Absolute other) const     { return mValue != other.mValue; }
 106
 107     // express as conventional (absolute!) time measures
 108     operator struct timeval() const;
 109         operator struct timespec() const;
 110     operator time_t () const                            { return time_t(mValue); }
 111
 112     // internal form for debugging ONLY
 113     double internalForm() const                         { return mValue; }
 114
 115 private:
 116     double mValue;
 117
 118     Absolute(double value) : mValue(value) { }
 119 };
 120
 121
 122 //
 123 // Time::now produces the current time
 124 //
 125 Absolute now();                                         // get "now"
 126
 127
 128 //
 129 // Time::resolution(when) gives a conservative estimate of the available resolution
 130 // at a given time.
 131 //
 132 Interval resolution(Absolute at);       // estimate available resolution at given time
 133
 134
 135 //
 136 // Some useful "constants"
 137 //
 138 inline Absolute bigBang()                               { return -MAXFLOAT; }
 139 inline Absolute heatDeath()                             { return +MAXFLOAT; }
 140
 141
 142
 143 //
 144 // More inline arithmetic
 145 //
 146 inline Interval operator + (Interval r, Interval r2)    { r += r2; return r; }
 147 inline Interval operator - (Interval r, Interval r2)    { r -= r2; return r; }
 148 inline Interval operator * (Interval r, double f)               { r *= f; return r; }
 149 inline Interval operator / (Interval r, double f)               { r /= f; return r; }
 150
 151 inline Absolute operator + (Absolute a, Interval r)             { return a += r; }
 152 inline Absolute operator + (Interval r, Absolute a)             { return a += r; }
 153 inline Absolute operator - (Absolute a, Interval r)             { return a -= r; }
 154
 155 inline Interval operator - (Absolute t1, Absolute t0)
 156 { return t1.mValue - t0.mValue; }
 157
 158
 159 }       // end namespace Time
 160 }       // end namespace Security
 161
 162 #endif //_H_TIMEFLOW