From b03c7d5ebd083997cb907273c9544b66e9ed7d0e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Reimar=20D=C3=B6ffinger?= <Reimar.Doeffinger@gmx.de>
Date: Sat, 2 Feb 2019 15:50:14 +0100
Subject: [PATCH] Implement generic CPU time limiter.

---
 impl11/ddraw/config.cpp   | 16 ++++++++++++++++
 impl11/ddraw/joystick.cpp | 26 ++++++++++++++++++++++++++
 impl11/ddraw/joystick.h   |  1 +
 3 files changed, 43 insertions(+)

diff --git a/impl11/ddraw/config.cpp b/impl11/ddraw/config.cpp
index 9089d28f..841ef246 100644
--- a/impl11/ddraw/config.cpp
+++ b/impl11/ddraw/config.cpp
@@ -22,6 +22,14 @@ static int isspace_wrapper(char c)
     return std::isspace(static_cast<unsigned char>(c));
 }
 
+static void patchTimeGetTime(unsigned *addr)
+{
+	DWORD old, dummy;
+	VirtualProtect(addr, 4, PAGE_READWRITE, &old);
+	*addr = reinterpret_cast<unsigned>(emulGetTime);
+	VirtualProtect(addr, 4, old, &dummy);
+}
+
 Config g_config;
 
 Config::Config()
@@ -219,6 +227,14 @@ Config::Config()
 		*(unsigned *)0x4f3e54 = 0;
 	}
 
+	if (AutoPatch >= 2 && RefreshLimit == 1)
+	{
+		if (isBoP) patchTimeGetTime((unsigned *)0xbb96b8);
+		if (isXvT) patchTimeGetTime((unsigned *)0x86070c);
+		if (isXWing) patchTimeGetTime((unsigned *)0x4c31ec);
+		if (isTIE) patchTimeGetTime((unsigned *)0x4dc264);
+	}
+
 	if (this->JoystickEmul != 0 && isXWing)
 	{
 		// TODO: How to check if this is a supported binary?
diff --git a/impl11/ddraw/joystick.cpp b/impl11/ddraw/joystick.cpp
index c6101035..5f9773fc 100755
--- a/impl11/ddraw/joystick.cpp
+++ b/impl11/ddraw/joystick.cpp
@@ -16,6 +16,32 @@
 #undef max
 #include <algorithm>
 
+// timeGetTime emulation.
+// if it is called in a tight loop it will call Sleep()
+// prevents high CPU usage due to busy loop
+DWORD emulGetTime()
+{
+	static DWORD oldtime;
+	static DWORD count;
+	DWORD time = timeGetTime();
+	if (time != oldtime)
+	{
+		oldtime = time;
+		count = 0;
+	}
+	// Trigger value and sleep value derived by trial and error.
+	// Trigger values down to 10 with sleep value 8 do not seem to affect performance
+	// even at 60 FPS, and trigger values up to 1000 with sleep value 1 still seem effective
+	// to reduce CPU load on fast modern computers.
+	if (++count >= 20)
+	{
+		Sleep(2);
+		time = timeGetTime();
+		count = 0;
+	}
+	return time;
+}
+
 static int needsJoyEmul()
 {
 	JOYCAPS caps = {};
diff --git a/impl11/ddraw/joystick.h b/impl11/ddraw/joystick.h
index d9dd0c96..921c20d6 100755
--- a/impl11/ddraw/joystick.h
+++ b/impl11/ddraw/joystick.h
@@ -5,6 +5,7 @@
 
 #include "common.h"
 
+extern "C" DWORD emulGetTime(void);
 extern "C" UINT WINAPI emulJoyGetNumDevs(void);
 extern "C" UINT WINAPI emulJoyGetDevCaps(UINT_PTR, struct tagJOYCAPSA *, UINT);
 extern "C" UINT WINAPI emulJoyGetPosEx(UINT, struct joyinfoex_tag *);