From 9260f05025174d8e17edf0de300aa8260e7b1324 Mon Sep 17 00:00:00 2001
From: Iliyas Jorio <iliyas@jor.io>
Date: Mon, 22 Feb 2021 21:52:11 +0100
Subject: [PATCH] Implement TickCount

---
 CMakeLists.txt             |  1 -
 src/Pomme.cpp              |  2 --
 src/PommeTime.h            |  6 ------
 src/Text/TextUtilities.cpp |  1 -
 src/Time/TimeManager.cpp   | 39 +++++++++++++++++++-------------------
 5 files changed, 19 insertions(+), 30 deletions(-)
 delete mode 100644 src/PommeTime.h

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2db9926..bb9e241 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,7 +15,6 @@ set(POMME_SOURCES
 	${POMME_SRCDIR}/PommeInit.h
 	${POMME_SRCDIR}/PommeInput.h
 	${POMME_SRCDIR}/PommeSound.h
-	${POMME_SRCDIR}/PommeTime.h
 	${POMME_SRCDIR}/PommeTypes.h
 	${POMME_SRCDIR}/PommeVideo.h
 	${POMME_SRCDIR}/Files/Files.cpp
diff --git a/src/Pomme.cpp b/src/Pomme.cpp
index 7168bf4..1e5b29e 100644
--- a/src/Pomme.cpp
+++ b/src/Pomme.cpp
@@ -3,7 +3,6 @@
 
 #include "Pomme.h"
 #include "PommeInit.h"
-#include "PommeTime.h"
 #include "PommeFiles.h"
 #include "PommeGraphics.h"
 #include "PommeSound.h"
@@ -68,7 +67,6 @@ void ShowCursor()
 
 void Pomme::Init()
 {
-	Pomme::Time::Init();
 	Pomme::Files::Init();
 	Pomme::Graphics::Init();
 	Pomme::Sound::Init();
diff --git a/src/PommeTime.h b/src/PommeTime.h
deleted file mode 100644
index 4ccd08e..0000000
--- a/src/PommeTime.h
+++ /dev/null
@@ -1,6 +0,0 @@
-#pragma once
-
-namespace Pomme::Time
-{
-	void Init();
-}
diff --git a/src/Text/TextUtilities.cpp b/src/Text/TextUtilities.cpp
index 298705f..61a1db2 100644
--- a/src/Text/TextUtilities.cpp
+++ b/src/Text/TextUtilities.cpp
@@ -1,5 +1,4 @@
 #include "Pomme.h"
-#include "PommeTime.h"
 #include "PommeTypes.h"
 #include "PommeDebug.h"
 
diff --git a/src/Time/TimeManager.cpp b/src/Time/TimeManager.cpp
index 68be19e..8b078e2 100644
--- a/src/Time/TimeManager.cpp
+++ b/src/Time/TimeManager.cpp
@@ -1,42 +1,41 @@
 #include "Pomme.h"
-#include "PommeTime.h"
 #include "PommeTypes.h"
-#include "PommeDebug.h"
 
 #include <chrono>
-#include <iostream>
 #include <ctime>
-#include <iomanip>
 
-std::chrono::time_point<std::chrono::high_resolution_clock> bootTP;
+using namespace std::chrono;
 
-// timestamp (from unix epoch) of the mac epoch, Jan 1, 1904, 00:00:00
-constexpr int JANUARY_1_1904 = -2'082'844'800;
+// System time point on application start
+static const time_point<high_resolution_clock> gBootTimePoint = high_resolution_clock::now();
+
+// Timestamp of the Mac epoch (Jan 1, 1904, 00:00:00), relative to UNIX epoch (Jan 1, 1970, 00:00:00)
+static constexpr int JANUARY_1_1904 = -2'082'844'800;
+
+static int64_t GetMicrosecondsSinceBoot()
+{
+	auto now = high_resolution_clock::now();
+	microseconds usecs = duration_cast<microseconds>(now - gBootTimePoint);
+	return usecs.count();
+}
 
 //-----------------------------------------------------------------------------
 // Time Manager
 
-void Pomme::Time::Init()
-{
-	bootTP = std::chrono::high_resolution_clock::now();
-}
-
 void GetDateTime(unsigned long* secs)
 {
 	*secs = (unsigned long) (std::time(nullptr) + JANUARY_1_1904);
 }
 
-void Microseconds(UnsignedWide* usecs)
+void Microseconds(UnsignedWide* usecsOut)
 {
-	auto now = std::chrono::high_resolution_clock::now();
-	auto usecs1 = std::chrono::duration_cast<std::chrono::microseconds>(now - bootTP);
-	auto usecs2 = usecs1.count();
-	usecs->lo = usecs2 & 0xFFFFFFFFL;
-	usecs->hi = (usecs2 >> 32) & 0xFFFFFFFFL;
+	auto usecs = GetMicrosecondsSinceBoot();
+	usecsOut->lo = (usecs      ) & 0xFFFFFFFFL;
+	usecsOut->hi = (usecs >> 32) & 0xFFFFFFFFL;
 }
 
 UInt32 TickCount()
 {
-	TODO();
-	return 0;
+	// A tick is approximately 1/60 of a second
+	return (UInt32) (60L * GetMicrosecondsSinceBoot() / 1'000'000L);
 }