From 04243db77904a9d735e545a1114e0dd926649ac9 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Sun, 6 Aug 2023 18:44:35 +0300
Subject: [PATCH] Synchronize stdout & stderr for logging

---
 libs/io/include/psemek/io/synchronized.hpp | 15 ++++++
 libs/io/source/synchronized.cpp            | 60 ++++++++++++++++++++++
 libs/sdl2/source/main.cpp                  | 10 +++-
 3 files changed, 83 insertions(+), 2 deletions(-)
 create mode 100644 libs/io/include/psemek/io/synchronized.hpp
 create mode 100644 libs/io/source/synchronized.cpp

diff --git a/libs/io/include/psemek/io/synchronized.hpp b/libs/io/include/psemek/io/synchronized.hpp
new file mode 100644
index 00000000..60df8257
--- /dev/null
+++ b/libs/io/include/psemek/io/synchronized.hpp
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <psemek/io/stream.hpp>
+
+#include <vector>
+
+namespace psemek::io
+{
+
+	// Convert a set of output streams to a set of mutually
+	// synchronized streams: writing to any of the streams
+	// flushes all the other streams
+	std::vector<std::unique_ptr<ostream>> synchronized(std::vector<std::unique_ptr<ostream>> streams);
+
+}
diff --git a/libs/io/source/synchronized.cpp b/libs/io/source/synchronized.cpp
new file mode 100644
index 00000000..0672201f
--- /dev/null
+++ b/libs/io/source/synchronized.cpp
@@ -0,0 +1,60 @@
+#include <psemek/io/synchronized.hpp>
+
+namespace psemek::io
+{
+
+	namespace
+	{
+
+		struct synchronized_stream_impl
+			: ostream
+		{
+			synchronized_stream_impl(std::shared_ptr<ostream> stream, std::vector<std::weak_ptr<ostream>> others)
+				: stream_(std::move(stream))
+				, others_(std::move(others))
+			{}
+
+			std::size_t write(char const * p, std::size_t size) override
+			{
+				for (auto const & ptr : others_)
+					if (auto stream = ptr.lock())
+						stream->flush();
+				return stream_->write(p, size);
+			}
+
+			void flush() override
+			{
+				stream_->flush();
+			}
+
+		private:
+			std::shared_ptr<ostream> stream_;
+			std::vector<std::weak_ptr<ostream>> others_;
+		};
+
+	}
+
+	// Convert a set of output streams to a set of mutually
+	// synchronized streams: writing to any of the streams
+	// flushes all the other streams
+	std::vector<std::unique_ptr<ostream>> synchronized(std::vector<std::unique_ptr<ostream>> streams)
+	{
+		std::vector<std::shared_ptr<ostream>> shared_streams(streams.size());
+		for (std::size_t i = 0; i < streams.size(); ++i)
+			shared_streams[i] = std::move(streams[i]);
+
+		std::vector<std::unique_ptr<ostream>> result;
+		for (std::size_t i = 0; i < streams.size(); ++i)
+		{
+			std::vector<std::weak_ptr<ostream>> others;
+			for (std::size_t j = 0; j < streams.size(); ++j)
+				if (i != j)
+					others.push_back(shared_streams[i]);
+
+			result.push_back(std::make_unique<synchronized_stream_impl>(shared_streams[i], std::move(others)));
+		}
+
+		return result;
+	}
+
+}
diff --git a/libs/sdl2/source/main.cpp b/libs/sdl2/source/main.cpp
index db692325..dfc702f1 100644
--- a/libs/sdl2/source/main.cpp
+++ b/libs/sdl2/source/main.cpp
@@ -6,6 +6,7 @@
 #include <psemek/util/clock.hpp>
 #include <psemek/util/pretty_print.hpp>
 #include <psemek/log/log.hpp>
+#include <psemek/io/synchronized.hpp>
 #include <psemek/util/exception.hpp>
 
 #undef main
@@ -22,8 +23,13 @@ int main(int argc, char ** argv) try
 	log::level const stdio_log_level = log::level::debug;
 #endif
 
-	log::add_sink(log::default_sink(io::std_out(), stdio_log_level, log::level::info));
-	log::add_sink(log::default_sink(io::std_err(), log::level::warning, log::level::error));
+	std::vector<std::unique_ptr<io::ostream>> synchronized_stdout_stderr;
+	synchronized_stdout_stderr.push_back(io::std_out());
+	synchronized_stdout_stderr.push_back(io::std_err());
+	synchronized_stdout_stderr = io::synchronized(std::move(synchronized_stdout_stderr));
+
+	log::add_sink(log::default_sink(std::move(synchronized_stdout_stderr[0]), stdio_log_level, log::level::info));
+	log::add_sink(log::default_sink(std::move(synchronized_stdout_stderr[1]), log::level::warning, log::level::error));
 	log::register_thread("main");
 
 	auto const factory = app::make_application_factory();