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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//
// CycleTimer has methods related to getting cycle timer values.
// It uses an all-statics class as a namespace mechanism.
//
#ifndef _CYCLETIMER_H_
#define _CYCLETIMER_H_
#include "windef.h"
class CycleTimer
{
// This returns the value of the *non-thread-virtualized* cycle counter.
static unsigned __int64 GetCycleCount64();
// This wraps GetCycleCount64 in the signature of QueryThreadCycleTime -- but note
// that it ignores the "thrd" argument.
static BOOL WINAPI DefaultQueryThreadCycleTime(__in HANDLE thrd, __out PULONG64 cyclesPtr);
// The function pointer type for QueryThreadCycleTime.
typedef BOOL (WINAPI *QueryThreadCycleTimeSig)(__in HANDLE, __out PULONG64);
// Returns a function pointer for QueryThreadCycleTime, or else BadFPtr.
static QueryThreadCycleTimeSig GetQueryThreadCycleTime();
// Initialized once from NULL to either BadFPtr or QueryThreadCycleTime.
static QueryThreadCycleTimeSig s_QueryThreadCycleTimeFPtr;
public:
// This method computes the number of cycles/sec for the current machine. The cycles are those counted
// by GetThreadCycleTime; we assume that these are of equal duration, though that is not necessarily true.
// If any OS interaction fails, returns 0.0.
static double CyclesPerSecond();
// Does a large number of queries, and returns the average of their overhead, so other measurements
// can adjust for this.
static unsigned __int64 QueryOverhead();
// There's no "native" atomic add for 64 bit, so we have this convenience function.
static void InterlockedAddU64(unsigned __int64* loc, unsigned __int64 amount);
// Attempts to query the cycle counter of the current thread. If successful, returns "true" and sets
// *cycles to the cycle counter value. Otherwise, returns false. Note that the value returned is (currently)
// virtualized to the current thread only on Windows; on non-windows x86/x64 platforms, directly reads
// the cycle counter and returns that value.
static bool GetThreadCyclesS(unsigned __int64* cycles);
};
#endif // _CYCLETIMER_H_
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