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+/** @file
+ * IPRT - Timer.
+ */
+
+/*
+ * Copyright (C) 2006-2019 Oracle Corporation
+ *
+ * This file is part of VirtualBox Open Source Edition (OSE), as
+ * available from http://www.virtualbox.org. This file is free software;
+ * you can redistribute it and/or modify it under the terms of the GNU
+ * General Public License (GPL) as published by the Free Software
+ * Foundation, in version 2 as it comes in the "COPYING" file of the
+ * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
+ * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL) only, as it comes in the "COPYING.CDDL" file of the
+ * VirtualBox OSE distribution, in which case the provisions of the
+ * CDDL are applicable instead of those of the GPL.
+ *
+ * You may elect to license modified versions of this file under the
+ * terms and conditions of either the GPL or the CDDL or both.
+ */
+
+#ifndef IPRT_INCLUDED_timer_h
+#define IPRT_INCLUDED_timer_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+
+#include <iprt/cdefs.h>
+#include <iprt/types.h>
+
+
+RT_C_DECLS_BEGIN
+
+/** @defgroup grp_rt_timer RTTimer - Timer
+ *
+ * The IPRT timer API provides a simple abstraction of recurring and one-shot callback timers.
+ *
+ * Because of the great variation in the native APIs and the quality of
+ * the service delivered by those native APIs, the timers are operated
+ * on at best effort basis.
+ *
+ * All the ring-3 implementations are naturally at the mercy of the scheduler,
+ * which means that the callback rate might vary quite a bit and we might skip
+ * ticks. Many systems have a restriction that a process can only have one
+ * timer. IPRT currently makes no efforts at multiplexing timers in those kind
+ * of situations and will simply fail if you try to create more than one timer.
+ *
+ * Things are generally better in ring-0. The implementations will use interrupt
+ * time callbacks wherever available, and if not, resort to a high priority
+ * kernel thread.
+ *
+ * @ingroup grp_rt
+ * @{
+ */
+
+
+/** Timer handle. */
+typedef struct RTTIMER *PRTTIMER;
+
+/**
+ * Timer callback function.
+ *
+ * The context this call is made in varies with different platforms and
+ * kernel / user mode IPRT.
+ *
+ * In kernel mode a timer callback should not waste time, it shouldn't
+ * waste stack and it should be prepared that some APIs might not work
+ * correctly because of weird OS restrictions in this context that we
+ * haven't discovered and avoided yet. Please fix those APIs so they
+ * at least avoid panics and weird behaviour.
+ *
+ * @param pTimer Timer handle.
+ * @param pvUser User argument.
+ * @param iTick The current timer tick. This is always 1 on the first
+ * callback after the timer was started. For omni timers
+ * this will be 1 when a cpu comes back online.
+ */
+typedef DECLCALLBACK(void) FNRTTIMER(PRTTIMER pTimer, void *pvUser, uint64_t iTick);
+/** Pointer to FNRTTIMER() function. */
+typedef FNRTTIMER *PFNRTTIMER;
+
+
+/**
+ * Create a recurring timer.
+ *
+ * @returns iprt status code.
+ * @param ppTimer Where to store the timer handle.
+ * @param uMilliesInterval Milliseconds between the timer ticks.
+ * This is rounded up to the system granularity.
+ * @param pfnTimer Callback function which shall be scheduled for execution
+ * on every timer tick.
+ * @param pvUser User argument for the callback.
+ * @see RTTimerCreateEx, RTTimerStart, RTTimerStop, RTTimerChangeInterval,
+ * RTTimerDestroy, RTTimerGetSystemGranularity
+ */
+RTDECL(int) RTTimerCreate(PRTTIMER *ppTimer, unsigned uMilliesInterval, PFNRTTIMER pfnTimer, void *pvUser);
+
+/**
+ * Create a suspended timer.
+ *
+ * @returns iprt status code.
+ * @retval VERR_NOT_SUPPORTED if an unsupported flag was specfied.
+ * @retval VERR_CPU_NOT_FOUND if the specified CPU
+ *
+ * @param ppTimer Where to store the timer handle.
+ * @param u64NanoInterval The interval between timer ticks specified in nanoseconds if it's
+ * a recurring timer. This is rounded to the fit the system timer granularity.
+ * For one shot timers, pass 0.
+ * @param fFlags Timer flags.
+ * @param pfnTimer Callback function which shall be scheduled for execution
+ * on every timer tick.
+ * @param pvUser User argument for the callback.
+ * @see RTTimerStart, RTTimerStop, RTTimerChangeInterval, RTTimerDestroy,
+ * RTTimerGetSystemGranularity, RTTimerCanDoHighResolution
+ */
+RTDECL(int) RTTimerCreateEx(PRTTIMER *ppTimer, uint64_t u64NanoInterval, uint32_t fFlags, PFNRTTIMER pfnTimer, void *pvUser);
+
+/** @name RTTimerCreateEx flags
+ * @{ */
+/** Any CPU is fine. (Must be 0.) */
+#define RTTIMER_FLAGS_CPU_ANY UINT32_C(0)
+/** One specific CPU */
+#define RTTIMER_FLAGS_CPU_SPECIFIC RT_BIT(16)
+/** Omni timer, run on all online CPUs.
+ * @remarks The timer callback isn't necessarily running at the time same time on each CPU. */
+#define RTTIMER_FLAGS_CPU_ALL ( RTTIMER_FLAGS_CPU_MASK | RTTIMER_FLAGS_CPU_SPECIFIC )
+/** CPU mask. */
+#define RTTIMER_FLAGS_CPU_MASK UINT32_C(0xffff)
+/** Desire a high resolution timer that works with RTTimerChangeInterval and
+ * isn't subject to RTTimerGetSystemGranularity rounding.
+ * @remarks This is quietly ignored if the feature isn't supported. */
+#define RTTIMER_FLAGS_HIGH_RES RT_BIT(17)
+/** Convert a CPU set index (0-based) to RTTimerCreateEx flags.
+ * This will automatically OR in the RTTIMER_FLAGS_CPU_SPECIFIC flag. */
+#define RTTIMER_FLAGS_CPU(iCpu) ( (iCpu) | RTTIMER_FLAGS_CPU_SPECIFIC )
+/** Macro that validates the flags. */
+#define RTTIMER_FLAGS_ARE_VALID(fFlags) \
+ ( !((fFlags) & ~((fFlags) & RTTIMER_FLAGS_CPU_SPECIFIC ? UINT32_C(0x3ffff) : UINT32_C(0x30000))) )
+/** @} */
+
+/**
+ * Stops and destroys a running timer.
+ *
+ * @returns iprt status code.
+ * @retval VERR_INVALID_CONTEXT if executing at the wrong IRQL (windows), PIL
+ * (solaris), or similar. Portable code does not destroy timers with
+ * preemption (or interrupts) disabled.
+ * @param pTimer Timer to stop and destroy. NULL is ok.
+ */
+RTDECL(int) RTTimerDestroy(PRTTIMER pTimer);
+
+/**
+ * Starts a suspended timer.
+ *
+ * @returns IPRT status code.
+ * @retval VERR_INVALID_HANDLE if pTimer isn't valid.
+ * @retval VERR_TIMER_ACTIVE if the timer isn't suspended.
+ * @retval VERR_CPU_OFFLINE if the CPU the timer was created to run on is not
+ * online (this include the case where it's not present in the
+ * system).
+ *
+ * @param pTimer The timer to activate.
+ * @param u64First The RTTimeSystemNanoTS() for when the timer should start
+ * firing (relative). If 0 is specified, the timer will
+ * fire ASAP.
+ * @remarks When RTTimerCanDoHighResolution returns true, this API is
+ * callable with preemption disabled in ring-0.
+ * @see RTTimerStop
+ */
+RTDECL(int) RTTimerStart(PRTTIMER pTimer, uint64_t u64First);
+
+/**
+ * Stops an active timer.
+ *
+ * @todo May return while the timer callback function is being services on
+ * some platforms (ring-0 Windows, ring-0 linux). This needs to be
+ * addressed at some point...
+ *
+ * @returns IPRT status code.
+ * @retval VERR_INVALID_HANDLE if pTimer isn't valid.
+ * @retval VERR_TIMER_SUSPENDED if the timer isn't active.
+ * @retval VERR_NOT_SUPPORTED if the IPRT implementation doesn't support
+ * stopping a timer.
+ *
+ * @param pTimer The timer to suspend.
+ * @remarks Can be called from the timer callback function to stop it.
+ * @see RTTimerStart
+ */
+RTDECL(int) RTTimerStop(PRTTIMER pTimer);
+
+/**
+ * Changes the interval of a periodic timer.
+ *
+ * If the timer is active, it is implementation dependent whether the change
+ * takes place immediately or after the next tick. To get defined behavior,
+ * stop the timer before calling this API.
+ *
+ * @returns IPRT status code.
+ * @retval VERR_INVALID_HANDLE if pTimer isn't valid.
+ * @retval VERR_NOT_SUPPORTED if not supported.
+ * @retval VERR_INVALID_STATE if not a periodic timer.
+ *
+ * @param pTimer The timer to activate.
+ * @param u64NanoInterval The interval between timer ticks specified in
+ * nanoseconds. This is rounded to the fit the
+ * system timer granularity.
+ * @remarks Callable from the timer callback. Callable with preemption
+ * disabled in ring-0.
+ */
+RTDECL(int) RTTimerChangeInterval(PRTTIMER pTimer, uint64_t u64NanoInterval);
+
+/**
+ * Gets the (current) timer granularity of the system.
+ *
+ * @returns The timer granularity of the system in nanoseconds.
+ * @see RTTimerRequestSystemGranularity
+ */
+RTDECL(uint32_t) RTTimerGetSystemGranularity(void);
+
+/**
+ * Requests a specific system timer granularity.
+ *
+ * Successfull calls to this API must be coupled with the exact same number of
+ * calls to RTTimerReleaseSystemGranularity() in order to undo any changes made.
+ *
+ *
+ * @returns IPRT status code.
+ * @retval VERR_NOT_SUPPORTED if the requested value isn't supported by the host platform
+ * or if the host platform doesn't support modifying the system timer granularity.
+ * @retval VERR_PERMISSION_DENIED if the caller doesn't have the necessary privilege to
+ * modify the system timer granularity.
+ *
+ * @param u32Request The requested system timer granularity in nanoseconds.
+ * @param pu32Granted Where to store the granted system granularity. This is the value
+ * that should be passed to RTTimerReleaseSystemGranularity(). It
+ * is what RTTimerGetSystemGranularity() would return immediately
+ * after the change was made.
+ *
+ * The value differ from the request in two ways; rounding and
+ * scale. Meaning if your request is for 10.000.000 you might
+ * be granted 10.000.055 or 1.000.000.
+ * @see RTTimerReleaseSystemGranularity, RTTimerGetSystemGranularity
+ */
+RTDECL(int) RTTimerRequestSystemGranularity(uint32_t u32Request, uint32_t *pu32Granted);
+
+/**
+ * Releases a system timer granularity grant acquired by RTTimerRequestSystemGranularity().
+ *
+ * @returns IPRT status code.
+ * @retval VERR_NOT_SUPPORTED if the host platform doesn't have any way of modifying
+ * the system timer granularity.
+ * @retval VERR_WRONG_ORDER if nobody call RTTimerRequestSystemGranularity() with the
+ * given grant value.
+ * @param u32Granted The granted system granularity.
+ * @see RTTimerRequestSystemGranularity
+ */
+RTDECL(int) RTTimerReleaseSystemGranularity(uint32_t u32Granted);
+
+/**
+ * Checks if the system support high resolution timers.
+ *
+ * The kind of support we are checking for is the kind of dynamically
+ * reprogrammable timers employed by recent Solaris and Linux kernels. It also
+ * implies that we can specify microsecond (or even better maybe) intervals
+ * without getting into trouble.
+ *
+ * @returns true if supported, false it not.
+ *
+ * @remarks Returning true also means RTTimerChangeInterval must be implemented
+ * and RTTimerStart be callable with preemption disabled.
+ */
+RTDECL(bool) RTTimerCanDoHighResolution(void);
+
+
+/**
+ * Timer callback function for low res timers.
+ *
+ * This is identical to FNRTTIMER except for the first parameter, so
+ * see FNRTTIMER for details.
+ *
+ * @param hTimerLR The low resolution timer handle.
+ * @param pvUser User argument.
+ * @param iTick The current timer tick. This is always 1 on the first
+ * callback after the timer was started. Will jump if we've
+ * skipped ticks when lagging behind.
+ */
+typedef DECLCALLBACK(void) FNRTTIMERLR(RTTIMERLR hTimerLR, void *pvUser, uint64_t iTick);
+/** Pointer to FNRTTIMER() function. */
+typedef FNRTTIMERLR *PFNRTTIMERLR;
+
+
+/**
+ * Create a recurring low resolution timer.
+ *
+ * @returns iprt status code.
+ * @param phTimerLR Where to store the timer handle.
+ * @param uMilliesInterval Milliseconds between the timer ticks, at least 100 ms.
+ * If higher resolution is required use the other API.
+ * @param pfnTimer Callback function which shall be scheduled for execution
+ * on every timer tick.
+ * @param pvUser User argument for the callback.
+ * @see RTTimerLRCreateEx, RTTimerLRDestroy, RTTimerLRStop
+ */
+RTDECL(int) RTTimerLRCreate(PRTTIMERLR phTimerLR, uint32_t uMilliesInterval, PFNRTTIMERLR pfnTimer, void *pvUser);
+
+/**
+ * Create a suspended low resolution timer.
+ *
+ * @returns iprt status code.
+ * @retval VERR_NOT_SUPPORTED if an unsupported flag was specfied.
+ *
+ * @param phTimerLR Where to store the timer handle.
+ * @param u64NanoInterval The interval between timer ticks specified in nanoseconds if it's
+ * a recurring timer, the minimum for is 100000000 ns.
+ * For one shot timers, pass 0.
+ * @param fFlags Timer flags. Same as RTTimerCreateEx.
+ * @param pfnTimer Callback function which shall be scheduled for execution
+ * on every timer tick.
+ * @param pvUser User argument for the callback.
+ * @see RTTimerLRStart, RTTimerLRStop, RTTimerLRDestroy
+ */
+RTDECL(int) RTTimerLRCreateEx(PRTTIMERLR phTimerLR, uint64_t u64NanoInterval, uint32_t fFlags, PFNRTTIMERLR pfnTimer, void *pvUser);
+
+/**
+ * Stops and destroys a running low resolution timer.
+ *
+ * @returns iprt status code.
+ * @param hTimerLR The low resolution timer to stop and destroy.
+ * NIL_RTTIMERLR is accepted.
+ */
+RTDECL(int) RTTimerLRDestroy(RTTIMERLR hTimerLR);
+
+/**
+ * Starts a low resolution timer.
+ *
+ * @returns IPRT status code.
+ * @retval VERR_INVALID_HANDLE if pTimer isn't valid.
+ * @retval VERR_TIMER_ACTIVE if the timer isn't suspended.
+ *
+ * @param hTimerLR The low resolution timer to activate.
+ * @param u64First The RTTimeSystemNanoTS() for when the timer should start
+ * firing (relative), the minimum is 100000000 ns.
+ * If 0 is specified, the timer will fire ASAP.
+ *
+ * @see RTTimerLRStop
+ */
+RTDECL(int) RTTimerLRStart(RTTIMERLR hTimerLR, uint64_t u64First);
+
+/**
+ * Stops an active low resolution timer.
+ *
+ * @returns IPRT status code.
+ * @retval VERR_INVALID_HANDLE if pTimer isn't valid.
+ * @retval VERR_TIMER_SUSPENDED if the timer isn't active.
+ * @retval VERR_NOT_SUPPORTED if the IPRT implementation doesn't support stopping a timer.
+ *
+ * @param hTimerLR The low resolution timer to suspend.
+ *
+ * @see RTTimerLRStart
+ */
+RTDECL(int) RTTimerLRStop(RTTIMERLR hTimerLR);
+
+/**
+ * Changes the interval of a low resolution timer.
+ *
+ * If the timer is active, the next tick will occure immediately just like with
+ * RTTimerLRStart() when u64First parameter is zero.
+ *
+ * @returns IPRT status code.
+ * @retval VERR_INVALID_HANDLE if pTimer isn't valid.
+ * @retval VERR_NOT_SUPPORTED if not supported.
+ *
+ * @param hTimerLR The low resolution timer to update.
+ * @param u64NanoInterval The interval between timer ticks specified in
+ * nanoseconds. This is rounded to the fit the
+ * system timer granularity.
+ * @remarks Callable from the timer callback.
+ */
+RTDECL(int) RTTimerLRChangeInterval(RTTIMERLR hTimerLR, uint64_t u64NanoInterval);
+
+/** @} */
+
+RT_C_DECLS_END
+
+#endif /* !IPRT_INCLUDED_timer_h */