From fbcd8042436d3754f9cb368f39741a507e43f392 Mon Sep 17 00:00:00 2001
From: Glenn Maynard <gmaynard@users.sourceforge.net>
Date: Sat, 12 Jul 2003 22:51:27 +0000
Subject: [PATCH] Fixes two major problems: time wrapping every 42 days, and
 timer resolution getting poor after a couple days of play.

(for some value of "major")
---
 stepmania/src/RageTimer.cpp | 82 ++++++++++++++++++-------------------
 stepmania/src/RageTimer.h   | 64 +++++++++++++++++++++--------
 2 files changed, 87 insertions(+), 59 deletions(-)

diff --git a/stepmania/src/RageTimer.cpp b/stepmania/src/RageTimer.cpp
index bcbc0c43b2..b1a485bb00 100644
--- a/stepmania/src/RageTimer.cpp
+++ b/stepmania/src/RageTimer.cpp
@@ -1,15 +1,4 @@
 #include "global.h"
-/*
------------------------------------------------------------------------------
- File: RageTimer.cpp
-
- Desc: See header.
-
- Copyright (c) 2001-2002 by the person(s) listed below.  All rights reserved.
-	Chris Danford
------------------------------------------------------------------------------
-*/
-
 
 #include "RageTimer.h"
 #include "RageLog.h"
@@ -17,49 +6,56 @@
 #include "SDL-1.2.5/include/SDL.h"
 #include "SDL-1.2.5/include/SDL_timer.h"
  
-const float SECS_IN_DAY	=	60*60*24;
+/* We only actually get 1000 using SDL. */
+#define TIMESTAMP_RESOLUTION 1000000
 
-/* XXX: SDL_GetTicks() wraps every month or so.  Handle it. */
-RageTimer::RageTimer()
+static RageTimer g_Start;
+
+float RageTimer::GetTimeSinceStart()
 {
-	Init();
-	GetDeltaTime(); /* so the next call to GetDeltaTime is from the construction of this object */
+	return g_Start.Ago();
 }
 
-void RageTimer::Init()
+void RageTimer::Touch()
 {
-/*
- This is needed for the "timer" system, not the "ticks" system; it often starts
- a thread, so let's not do it--we don't need it.
-	static bool SDL_Initialized = false;
-	if(!SDL_Initialized) {
-		SDL_InitSubSystem(SDL_INIT_TIMER);
-		SDL_Initialized = true;
-	}
-*/
+	unsigned ms = SDL_GetTicks();
+	this->m_secs = ms / 1000;
+	ms %= 1000;
+
+	unsigned mult = TIMESTAMP_RESOLUTION / 1000;
+	this->m_us = ms*mult;
+}
+
+float RageTimer::Ago() const
+{
+	const RageTimer Now;
+	return Difference(*this, Now);
 }
 
 float RageTimer::GetDeltaTime()
 {
-	/* Store the LDT in integral milliseconds, to avoid rounding error. */
-	int now = SDL_GetTicks();
-	int ret = now - m_iLastDeltaTime;
-	m_iLastDeltaTime = now;
-	return ret / 1000.f;
+	const RageTimer Now;
+	const float diff = Difference( Now, *this );
+	*this = Now;
+	return diff;
 }
 
-float RageTimer::PeekDeltaTime() const
+float RageTimer::Difference(const RageTimer &lhs, const RageTimer &rhs)
 {
-	return (SDL_GetTicks() - m_iLastDeltaTime) / 1000.f;
+	int secs = lhs.m_secs - rhs.m_secs;
+	int us = lhs.m_us - rhs.m_us;
+
+	if( us < 0 )
+	{
+		us += TIMESTAMP_RESOLUTION;
+		--secs;
+	}
+
+	return float(secs) + float(us) / TIMESTAMP_RESOLUTION;
 }
 
-float RageTimer::GetTimeSinceStart()
-{
-	return SDL_GetTicks() / 1000.f;
-}
-
-/* XXX: SDL_GetTicks() wraps every month or so.  Handle it. */
-unsigned int GetTicks()
-{
-	return SDL_GetTicks();
-}
+/*
+ * Copyright (c) 2001-2003 by the person(s) listed below.  All rights reserved.
+ *	Chris Danford
+ *	Glenn Maynard
+ */
diff --git a/stepmania/src/RageTimer.h b/stepmania/src/RageTimer.h
index bdea8d6839..a3d14fe7e0 100644
--- a/stepmania/src/RageTimer.h
+++ b/stepmania/src/RageTimer.h
@@ -1,29 +1,61 @@
 #ifndef RAGE_TIMER_H
 #define RAGE_TIMER_H
 
+/* Timer services. */
+
 /*
------------------------------------------------------------------------------
- File: RageTimer.h
-
- Desc: Timer services.
-
- Copyright (c) 2001-2002 by the person(s) listed below.  All rights reserved.
-	Chris Danford
------------------------------------------------------------------------------
-*/
-
+ * This can be used in two ways: as a timestamp or as a timer.
+ *
+ * As a timer,
+ * RageTimer Timer;
+ * while(1) {
+ *   printf( "Will be approximately: %f", Timer.PeekDeltaTime()) ;
+ *   float fDeltaTime = Timer.GetDeltaTime();
+ * }
+ * 
+ * or as a timestamp:
+ * void foo( RageTimer &timestamp ) {
+ *     if( timestamp.IsZero() )
+ *         printf( "The timestamp isn't set." );
+ *     else
+ *         printf( "The timestamp happened %f ago", timestamp.Ago() );
+ *     timestamp.Touch();
+ *     printf( "Near zero: %f", timestamp.Age() );
+ * }
+ */
 class RageTimer
 {
 public:
-	RageTimer();
-	unsigned int GetTicks();
-	float GetDeltaTime();	// time between last call to GetDeltaTime()
-	float PeekDeltaTime() const;
+	RageTimer() { Touch(); }
+
+	/* Time ago this RageTimer represents. */
+	float Ago() const;
+	inline void Touch();
+	inline bool IsZero() const { return m_secs == 0 && m_us == 0; }
+	inline void SetZero() { m_secs = m_us = 0; }
+
+	/* Time between last call to GetDeltaTime() (Ago() + Touch()): */
+	float GetDeltaTime();
+	/* (alias) */
+	float PeekDeltaTime() const { return Ago(); }
+
+	/* deprecated: */
 	static float GetTimeSinceStart();	// seconds since the program was started
 
 private:
-	static void Init();
-	int m_iLastDeltaTime;
+	static float Difference(const RageTimer &lhs, const RageTimer &rhs);
+
+	/* "float" is bad for a "time since start" RageTimer.  If the game is running for
+	 * several days, we'll lose a lot of resolution.  I don't want to use double
+	 * everywhere, since it's slow.  I'd rather not use double just for RageTimers, since
+	 * it's too easy to get a type wrong and end up with obscure resolution problems. */
+	unsigned m_secs, m_us;
 };
 
 #endif
+
+/*
+ * Copyright (c) 2001-2003 by the person(s) listed below.  All rights reserved.
+ *	Chris Danford
+ *	Glenn Maynard
+ */