1 /*
2 File: CAHostTimeBase.cpp
3 Abstract: CAHostTimeBase.h
4 Version: 1.1
5
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44 Copyright (C) 2014 Apple Inc. All Rights Reserved.
45
46 */
47 //=============================================================================
48 // Includes
49 //=============================================================================
50
51 #include "CAHostTimeBase.h"
52
53 Float64 CAHostTimeBase::sFrequency = 0;
54 Float64 CAHostTimeBase::sInverseFrequency = 0;
55 UInt32 CAHostTimeBase::sMinDelta = 0;
56 UInt32 CAHostTimeBase::sToNanosNumerator = 0;
57 UInt32 CAHostTimeBase::sToNanosDenominator = 0;
58 pthread_once_t CAHostTimeBase::sIsInited = PTHREAD_ONCE_INIT;
59 #if Track_Host_TimeBase
60 UInt64 CAHostTimeBase::sLastTime = 0;
61 #endif
62
63 //=============================================================================
64 // CAHostTimeBase
65 //
66 // This class provides platform independent access to the host's time base.
67 //=============================================================================
68
Initialize()69 void CAHostTimeBase::Initialize()
70 {
71 // get the info about Absolute time
72 #if TARGET_OS_MAC
73 struct mach_timebase_info theTimeBaseInfo;
74 mach_timebase_info(&theTimeBaseInfo);
75 sMinDelta = 1;
76 sToNanosNumerator = theTimeBaseInfo.numer;
77 sToNanosDenominator = theTimeBaseInfo.denom;
78
79 // the frequency of that clock is: (sToNanosDenominator / sToNanosNumerator) * 10^9
80 sFrequency = static_cast<Float64>(sToNanosDenominator) / static_cast<Float64>(sToNanosNumerator);
81 sFrequency *= 1000000000.0;
82 #elif TARGET_OS_WIN32
83 LARGE_INTEGER theFrequency;
84 QueryPerformanceFrequency(&theFrequency);
85 sMinDelta = 1;
86 sToNanosNumerator = 1000000000ULL;
87 sToNanosDenominator = *((UInt64*)&theFrequency);
88 sFrequency = static_cast<Float64>(*((UInt64*)&theFrequency));
89 #endif
90 sInverseFrequency = 1.0 / sFrequency;
91
92 #if Log_Host_Time_Base_Parameters
93 DebugPrintf("Host Time Base Parameters");
94 DebugPrintf(" Minimum Delta: %lu", (unsigned long)sMinDelta);
95 DebugPrintf(" Frequency: %f", sFrequency);
96 DebugPrintf(" To Nanos Numerator: %lu", (unsigned long)sToNanosNumerator);
97 DebugPrintf(" To Nanos Denominator: %lu", (unsigned long)sToNanosDenominator);
98 #endif
99 }
100