From bafc8a13309251938a5bea35fc1e0550914a4ee4 Mon Sep 17 00:00:00 2001
From: Bartosz Taudul <wolf.pld@gmail.com>
Date: Sun, 24 Feb 2019 19:02:49 +0100
Subject: [PATCH] Implement getting CPU usage in linux.

---
 client/TracySysTime.cpp | 59 ++++++++++++++++++++++++++---------------
 client/TracySysTime.hpp |  6 ++---
 2 files changed, 41 insertions(+), 24 deletions(-)

diff --git a/client/TracySysTime.cpp b/client/TracySysTime.cpp
index ab21f973..f0decd96 100644
--- a/client/TracySysTime.cpp
+++ b/client/TracySysTime.cpp
@@ -4,6 +4,10 @@
 
 #  if defined _WIN32 || defined __CYGWIN__
 #    include <windows.h>
+#  elif defined __linux__
+#    include <assert.h>
+#    include <stdio.h>
+#    include <inttypes.h>
 #  endif
 
 namespace tracy
@@ -16,7 +20,7 @@ static inline uint64_t ConvertTime( const FILETIME& t )
     return ( uint64_t( t.dwHighDateTime ) << 32 ) | uint64_t( t.dwLowDateTime );
 }
 
-SysTime::SysTime()
+void SysTime::ReadTimes()
 {
     FILETIME idleTime;
     FILETIME kernelTime;
@@ -30,29 +34,42 @@ SysTime::SysTime()
     used = kernel + user;
 }
 
-float SysTime::Get()
+#  elif defined __linux__
+
+void SysTime::ReadTimes()
 {
-    FILETIME idleTime;
-    FILETIME kernelTime;
-    FILETIME userTime;
-
-    GetSystemTimes( &idleTime, &kernelTime, &userTime );
-
-    const auto newIdle = ConvertTime( idleTime );
-    const auto kernel = ConvertTime( kernelTime );
-    const auto user = ConvertTime( userTime );
-    const auto newUsed = kernel + user;
-
-    const auto diffIdle = newIdle - idle;
-    const auto diffUsed = newUsed - used;
-
-    idle = newIdle;
-    used = newUsed;
-
-    return diffUsed == 0 ? 0 : ( diffUsed - diffIdle ) * 100.f / diffUsed;
+    uint64_t user, nice, system;
+    FILE* f = fopen( "/proc/stat", "r" );
+    assert( f );
+    fscanf( f, "cpu %" PRIu64 " %" PRIu64 " %" PRIu64" %" PRIu64, &user, &nice, &system, &idle );
+    fclose( f );
+    used = user + nice + system;
 }
 
-#  endif
+#endif
+
+SysTime::SysTime()
+{
+    ReadTimes();
+}
+
+float SysTime::Get()
+{
+    const auto oldUsed = used;
+    const auto oldIdle = idle;
+
+    ReadTimes();
+
+    const auto diffIdle = idle - oldIdle;
+    const auto diffUsed = used - oldUsed;
+
+#if defined _WIN32 || defined __CYGWIN__
+    return diffUsed == 0 ? 0 : ( diffUsed - diffIdle ) * 100.f / diffUsed;
+#elif defined __linux__
+    const auto total = diffUsed + diffIdle;
+    return total == 0 ? 0 : diffUsed * 100.f / total;
+#endif
+}
 
 }
 
diff --git a/client/TracySysTime.hpp b/client/TracySysTime.hpp
index 07dafc14..32ce5fa0 100644
--- a/client/TracySysTime.hpp
+++ b/client/TracySysTime.hpp
@@ -1,7 +1,7 @@
 #ifndef __TRACYSYSTIME_HPP__
 #define __TRACYSYSTIME_HPP__
 
-#if defined _WIN32 || defined __CYGWIN__
+#if defined _WIN32 || defined __CYGWIN__ || defined __linux__
 #  define TRACY_HAS_SYSTIME
 #endif
 
@@ -18,10 +18,10 @@ public:
     SysTime();
     float Get();
 
+    void ReadTimes();
+
 private:
-#  if defined _WIN32 || defined __CYGWIN__
     uint64_t idle, used;
-#  endif
 };
 
 }