From 052ea6a8bd39d9570e69bb14558a08f92cd95518 Mon Sep 17 00:00:00 2001
From: Alibek Omarov <a1ba.omarov@gmail.com>
Date: Tue, 11 Feb 2025 22:57:37 +0300
Subject: [PATCH] engine: platform: introduce for Platform_NanoSleep, to be
 used for better sleeping in between frames for lowering CPU usage

---
 engine/common/host.c            |  6 +++---
 engine/common/net_ws.c          |  2 +-
 engine/platform/platform.h      | 35 +++++++++++++++++++++++++++++++++
 engine/platform/win32/sys_win.c | 29 +++++++++++++++++++++++++++
 4 files changed, 68 insertions(+), 4 deletions(-)

diff --git a/engine/common/host.c b/engine/common/host.c
index b30063ff..2f2ada49 100644
--- a/engine/common/host.c
+++ b/engine/common/host.c
@@ -698,17 +698,17 @@ static qboolean Host_Autosleep( double dt, double scale )
 		static double timewindow; // allocate a time window for sleeps
 		static int counter; // for debug
 		static double realsleeptime;
-		const double sleeptime = sleep * 0.001;
+		const double sleeptime = sleep * 0.000001;
 
 		if( dt < targetframetime * scale )
 		{
 			// if we have allocated time window, try to sleep
 			if( timewindow > realsleeptime )
 			{
-				// Platform_Sleep isn't guaranteed to sleep an exact amount of milliseconds
+				// Platform_Sleep isn't guaranteed to sleep an exact amount of microseconds
 				// so we measure the real sleep time and use it to decrease the window
 				double t1 = Sys_DoubleTime(), t2;
-				Platform_Sleep( sleep ); // in msec!
+				Platform_NanoSleep( sleep * 1000 ); // in usec!
 				t2 = Sys_DoubleTime();
 				realsleeptime = t2 - t1;
 
diff --git a/engine/common/net_ws.c b/engine/common/net_ws.c
index db74a595..52ffccf5 100644
--- a/engine/common/net_ws.c
+++ b/engine/common/net_ws.c
@@ -1512,7 +1512,7 @@ static int NET_SendLong( netsrc_t sock, int net_socket, const char *buf, size_t
 				total_sent += size;
 			len -= size;
 			packet_number++;
-			Platform_Sleep( 1 );
+			Platform_NanoSleep( 100 * 1000 );
 		}
 
 		return total_sent;
diff --git a/engine/platform/platform.h b/engine/platform/platform.h
index 5bc6b35a..0caa313b 100644
--- a/engine/platform/platform.h
+++ b/engine/platform/platform.h
@@ -70,6 +70,8 @@ void Android_Shutdown( void );
 #endif
 
 #if XASH_WIN32
+void Win32_Init( void );
+void Win32_Shutdown( void );
 void Wcon_CreateConsole( qboolean con_showalways );
 void Wcon_DestroyConsole( void );
 void Wcon_InitConsoleCommands( void );
@@ -124,6 +126,7 @@ static inline void Platform_Init( qboolean con_showalways, const char *basedir )
 #elif XASH_DOS
 	DOS_Init( );
 #elif XASH_WIN32
+	Win32_Init( );
 	Wcon_CreateConsole( con_showalways );
 #elif XASH_LINUX
 	Linux_Init( );
@@ -140,6 +143,7 @@ static inline void Platform_Shutdown( void )
 	DOS_Shutdown( );
 #elif XASH_WIN32
 	Wcon_DestroyConsole( );
+	Win32_Shutdown( );
 #elif XASH_LINUX
 	Linux_Shutdown( );
 #endif
@@ -178,6 +182,37 @@ static inline void Platform_Sleep( int msec )
 #endif
 }
 
+static inline qboolean Platform_NanoSleep( int nsec )
+{
+	// SDL2 doesn't have nanosleep, so use low-level functions here
+	// When this code will be ported to SDL3, use SDL_DelayNS
+#if XASH_POSIX
+	struct timespec ts = {
+		.tv_sec = 0,
+		.tv_nsec = nsec, // just don't put large numbers here
+	};
+	return nanosleep( &ts, NULL ) == 0;
+#elif XASH_WIN32
+	extern HANDLE g_waitable_timer;
+	const LARGE_INTEGER ts = { -nsec };
+
+	if( !g_waitable_timer )
+		return false;
+
+	if( !SetWaitableTimer( g_waitable_timer, &ts, 0, NULL, NULL, FALSE ))
+	{
+		CloseHandle( g_waitable_timer );
+		g_waitable_timer = 0;
+		return false;
+	}
+
+	if( WaitForSingleObject( g_waitable_timer, 1000 ) != WAIT_OBJECT_0 )
+		return false;
+
+	return true;
+#endif
+}
+
 #if XASH_WIN32 || XASH_FREEBSD || XASH_NETBSD || XASH_OPENBSD || XASH_ANDROID || XASH_LINUX || XASH_APPLE
 void Sys_SetupCrashHandler( const char *argv0 );
 void Sys_RestoreCrashHandler( void );
diff --git a/engine/platform/win32/sys_win.c b/engine/platform/win32/sys_win.c
index 41ea86c5..6f1dd547 100644
--- a/engine/platform/win32/sys_win.c
+++ b/engine/platform/win32/sys_win.c
@@ -18,6 +18,8 @@ GNU General Public License for more details.
 #include "server.h"
 #include <shellapi.h>
 
+HANDLE g_waitable_timer;
+
 #if XASH_TIMER == TIMER_WIN32
 double Platform_DoubleTime( void )
 {
@@ -36,6 +38,33 @@ double Platform_DoubleTime( void )
 }
 #endif // XASH_TIMER == TIMER_WIN32
 
+void Win32_Init( void )
+{
+	HMODULE hModule = LoadLibrary( "kernel32.dll" );
+
+	if( hModule )
+	{
+		HANDLE ( __stdcall *pfnCreateWaitableTimerExW)( LPSECURITY_ATTRIBUTES lpTimerAttributes, LPCWSTR lpTimerName, DWORD dwFlags, DWORD dwDesiredAccess );
+
+		if(( pfnCreateWaitableTimerExW = GetProcAddress( hModule, "CreateWaitableTimerExW" )))
+		{
+			// CREATE_WAITABLE_TIMER_MANUAL_RESET | CREATE_WAITABLE_TIMER_HIGH_RESOLUTION
+			g_waitable_timer = pfnCreateWaitableTimerExW( NULL, NULL, 0x1 | 0x2, 0 );
+		}
+
+		FreeLibrary( "kernel32.dll" );
+	}
+
+	if( !g_waitable_timer )
+		g_waitable_timer = CreateWaitableTimer( NULL, TRUE, NULL );
+}
+
+void Win32_Shutdown( void )
+{
+	if( g_waitable_timer )
+		CloseHandle( g_waitable_timer );
+}
+
 qboolean Platform_DebuggerPresent( void )
 {
 	return IsDebuggerPresent();