From 0f083843bc31bf985991728125ef74efca6ef7b7 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Sun, 27 Dec 2015 10:07:24 +0100
Subject: Introduce thread synchronization for tracking init and logging

This obviously leads to synchronizing syscalls that would otherwise happen in parallel. Luckily the goal of this library is to monitor file changes performed by single, user facing applications and as such it doesn't matter if some operations are slightly slower.
---
 src/tracking/change_tracker.cc | 4 ++++
 src/tracking/change_tracker.h  | 2 ++
 src/utility/logger.h           | 7 +++++++
 3 files changed, 13 insertions(+)

diff --git a/src/tracking/change_tracker.cc b/src/tracking/change_tracker.cc
index 1b554aa..ca07214 100644
--- a/src/tracking/change_tracker.cc
+++ b/src/tracking/change_tracker.cc
@@ -82,6 +82,8 @@ bool ChangeTracker::track(const std::string& file_path) {
 		boost::filesystem::canonical(file_path).string()
 	};
 
+	std::unique_lock<std::mutex> guard(this->write_mutex_);
+
 	auto result = this->children_.emplace(
 		full_file_path,
 		std::make_unique<boost::process::child>(
@@ -92,6 +94,8 @@ bool ChangeTracker::track(const std::string& file_path) {
 		)
 	);
 
+	guard.unlock();
+
 	if ( std::get<EMPLACE_SUCCESS>(result) ) {
 		boost::filesystem::ifstream file(
 			std::get<FILE_NAME>(*result.first)
diff --git a/src/tracking/change_tracker.h b/src/tracking/change_tracker.h
index 24251e5..e694b56 100644
--- a/src/tracking/change_tracker.h
+++ b/src/tracking/change_tracker.h
@@ -2,6 +2,7 @@
 #define CHANGE_SRC_TRACKING_CHANGE_TRACKER_H_
 
 #include <unordered_map>
+#include <mutex>
 
 #include <boost/process.hpp>
 
@@ -22,6 +23,7 @@ class ChangeTracker {
 	private:
 		const std::string      diff_cmd_;
 		utility::Logger* const logger_;
+		std::mutex             write_mutex_;
 
 		std::unordered_map<
 			std::string, std::unique_ptr<boost::process::child>
diff --git a/src/utility/logger.h b/src/utility/logger.h
index e21f6fd..30a6b44 100644
--- a/src/utility/logger.h
+++ b/src/utility/logger.h
@@ -1,6 +1,8 @@
 #ifndef CHANGE_SRC_LOGGER_H_
 #define CHANGE_SRC_LOGGER_H_
 
+#include <mutex>
+
 #include <ext/stdio_filebuf.h>
 
 #include <boost/process.hpp>
@@ -14,6 +16,8 @@ class Logger {
 			stream_(&this->buffer_) { }
 
 		void append(const std::string& msg) {
+			std::lock_guard<std::mutex> guard(this->write_mutex_);
+
 			this->stream_ << msg << std::endl;
 		}
 
@@ -25,6 +29,8 @@ class Logger {
 		// flag.
 		//
 		void forward(boost::process::pistream& stream) {
+			std::lock_guard<std::mutex> guard(this->write_mutex_);
+
 			this->stream_ << std::string(
 				(std::istreambuf_iterator<char>(stream)),
 				(std::istreambuf_iterator<char>())
@@ -34,6 +40,7 @@ class Logger {
 	private:
 		__gnu_cxx::stdio_filebuf<char> buffer_;
 		std::ostream                   stream_;
+		std::mutex                     write_mutex_;
 
 };
 
-- 
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