From 3306281dcc77de7560ecec7ac286085a01422152 Mon Sep 17 00:00:00 2001
From: jyelon <jyelon@gmail.com>
Date: Wed, 5 Jan 2022 13:24:12 -0500
Subject: [PATCH] use the linux monotonic clock instead of gettimeofday

---
 luprex/core/cpp/driver-linux.cpp | 39 ++++++++++++++++++++++----------
 luprex/core/cpp/util.cpp         | 10 --------
 luprex/core/cpp/util.hpp         |  4 ++--
 3 files changed, 29 insertions(+), 24 deletions(-)

diff --git a/luprex/core/cpp/driver-linux.cpp b/luprex/core/cpp/driver-linux.cpp
index 8bcd12bb..d11e9ac8 100644
--- a/luprex/core/cpp/driver-linux.cpp
+++ b/luprex/core/cpp/driver-linux.cpp
@@ -117,6 +117,32 @@ SOCKET listen_on_port(int port, std::string &err) {
     return sock;
 }
 
+class MonoClock {
+private:
+    struct timespec base_;
+public:
+    MonoClock() {
+        int status = clock_gettime(CLOCK_MONOTONIC, &base_);
+        assert(status == 0);
+    }
+    double get() {
+        struct timespec t;
+        int status = clock_gettime(CLOCK_MONOTONIC, &t);
+        assert(status == 0);
+        double tv_sec = t.tv_sec - base_.tv_sec;
+        double tv_nsec = t.tv_nsec - base_.tv_nsec;
+        return tv_sec + (tv_nsec * 1.0E-9);
+    }
+};
+
+static MonoClock monoclock;
+
+namespace util {
+    double profiling_clock() {
+        return monoclock.get();
+    }
+}
+
 class Driver {
 public:
     enum ChanState {
@@ -135,15 +161,6 @@ public:
     bool short_sleep_;
     std::map<int, SOCKET> listen_sockets_;
     std::unique_ptr<char[]> chbuf;
-    int64_t basetime_;
-
-    int64_t get_now() {
-        struct timeval tv;
-        gettimeofday(&tv, nullptr);
-        int64_t tv_sec = tv.tv_sec;
-        int64_t tv_usec = tv.tv_usec;
-        return tv_sec * 1000000 + tv_usec;
-    }
 
     void init(DrivenEngine *de) {
         driven_ = de;
@@ -228,8 +245,7 @@ public:
     }
 
     void handle_clock() {
-        int64_t now = get_now() - basetime_;
-        driven_->drv_set_clock(double(now) / 1000000.0);
+        driven_->drv_set_clock(monoclock.get());
     }
 
     void close_channel(int chid, const std::string err) {
@@ -340,7 +356,6 @@ public:
         enableRawMode();
         init(de);
         DrivenEngine::set(de);
-        basetime_ = get_now();
         driven_->drv_set_lua_source(util::read_lua_source("lua"));
         driven_->drv_invoke_event_init(argc, argv);
         handle_listen_ports();
diff --git a/luprex/core/cpp/util.cpp b/luprex/core/cpp/util.cpp
index 5ef0f848..1e56a5d7 100644
--- a/luprex/core/cpp/util.cpp
+++ b/luprex/core/cpp/util.cpp
@@ -20,16 +20,6 @@
 
 namespace util {
 
-int64_t profiling_clock() {
-#ifdef WIN32
-    return 0.0;
-#else
-    struct timespec ts;
-    assert(0 == clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts));
-    return int64_t(ts.tv_nsec) + (int64_t(ts.tv_sec)*int64_t(1000000000));
-#endif
-}
-
 static bool ascii_isalpha(char c) {
     return ((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z'));
 }
diff --git a/luprex/core/cpp/util.hpp b/luprex/core/cpp/util.hpp
index 999d0b56..e0f905c0 100644
--- a/luprex/core/cpp/util.hpp
+++ b/luprex/core/cpp/util.hpp
@@ -37,8 +37,8 @@ using LuaSourcePtr = std::unique_ptr<LuaSourceVec>;
 using HashValue = std::pair<uint64_t, uint64_t>;
 using IdVector = std::vector<int64_t>;
 
-// Return nanoseconds elapsed, for profiling purposes.
-int64_t profiling_clock();
+// Return seconds elapsed, for profiling purposes.
+double profiling_clock();
 
 // Return true if the string is a valid lua identifier.
 bool is_identifier(const std::string &str);