From 19f3ddb901a7da5512a183d62849cb84013ba891 Mon Sep 17 00:00:00 2001
From: Martin Felis <martin@fysx.org>
Date: Sun, 5 Feb 2017 10:37:49 +0100
Subject: [PATCH] Refactored reload heuristic of modified modules

Previously I used a fixed time offset when a file change was detected.
Now I trigger a reload no module file size has changed over the last
5 updates.
---
 src/RuntimeModuleManager.cc | 35 +++++++++++++++++++++++++++++++----
 src/RuntimeModuleManager.h  |  2 ++
 src/main.cc                 |  1 -
 3 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/src/RuntimeModuleManager.cc b/src/RuntimeModuleManager.cc
index 1d4aeaa..825c047 100644
--- a/src/RuntimeModuleManager.cc
+++ b/src/RuntimeModuleManager.cc
@@ -51,7 +51,8 @@ void RuntimeModuleManager::LoadModule(RuntimeModule* module) {
 	if ( stat_result == 0 && 
 			(module->id != attr.st_ino || module->mtime != attr.st_mtime)
 			) {
-		std::cout << "Opening module " << module->name << std::endl;
+		std::cout << "Opening module " << module->name 
+			<< " (size = " << attr.st_size << ")" << std::endl;
 		void *handle = dlopen(module->name.c_str(), RTLD_NOW | RTLD_GLOBAL);
 		if (handle) {
 			module->handle = handle;
@@ -94,17 +95,43 @@ void RuntimeModuleManager::Update(float dt) {
 bool RuntimeModuleManager::CheckModulesChanged() {
 	struct stat attr;
 
+	double current_time = gGetTimeSinceStart();
+	mNumUpdatesSinceLastModuleChange++;
+
 	for (int i = 0; i < mModules.size(); i++) {
 		RuntimeModule* module = mModules[i];
 		bool stat_result = stat(module->name.c_str(), &attr);
 
-		if ( stat_result == 0 && 
-				(module->id != attr.st_ino || module->mtime != attr.st_mtime)
+		if (stat_result != 0) {
+			gLog ("Error: could not stat module %s", module->name.c_str());
+			abort();
+		}
+		
+		if (    module->id != attr.st_ino 
+				 || module->mtime != attr.st_mtime
+				 || module->fsize != attr.st_size
+				 || module->fsize == 0 
 			 ) {
-			return true;
+			module->id = attr.st_ino;
+			module->mtime = attr.st_mtime;
+			module->mtimensec = attr.st_mtim.tv_nsec;
+			module->fsize = attr.st_size;
+			mNumUpdatesSinceLastModuleChange = 0;
+
+			gLog ("Detected file change of %s: new size %d",
+					module->name.c_str(), attr.st_size);
 		}
 	}
 
+	// We have to delay the actual reload trigger to make
+	// sure all writes to the dynamic libraries are complete.
+	if (mNumUpdatesSinceLastModuleChange == 5) {
+		gLog ("Triggering reload");
+
+		return true;
+	}
+
+
 	return false;
 }
 
diff --git a/src/RuntimeModuleManager.h b/src/RuntimeModuleManager.h
index 13e4f2c..ce9051b 100644
--- a/src/RuntimeModuleManager.h
+++ b/src/RuntimeModuleManager.h
@@ -14,6 +14,7 @@ struct RuntimeModule {
 	void *data = nullptr;
 	int mtime = 0;
 	int mtimensec = 0;
+	off_t fsize = 0;
 
 	struct module_api api;
 	struct module_state *state = nullptr;
@@ -21,6 +22,7 @@ struct RuntimeModule {
 
 struct RuntimeModuleManager {
 	std::vector<RuntimeModule*> mModules;
+	int mNumUpdatesSinceLastModuleChange = 0;
 
 	void RegisterModule(const char* name);
 	void UnregisterModules();
diff --git a/src/main.cc b/src/main.cc
index 951856c..5adb71a 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -135,7 +135,6 @@ int main(void)
 			std::cout << "Detected module update. Unloading all modules." << std::endl;
 			module_manager.UnloadModules();
 			// We need to sleep to make sure we load the new files
-			usleep(300000);
 			module_manager.LoadModules();
 			// We need to update our last timestamp to ignore the delay due
 			// to reloading of the modules.