From 05c9569586b18b0a276fceb65f0464c0c524b05c Mon Sep 17 00:00:00 2001
From: mezzode <toranos@gmail.com>
Date: Sun, 10 Nov 2019 16:59:32 -0800
Subject: [PATCH] Implement multithreading on server

---
 .gitignore |  1 +
 client.cpp | 12 ++++++++++
 client.h   |  4 +++-
 common.h   |  2 ++
 server.cpp | 68 +++++++++++++++++++++++++++++++++++-------------------
 server.h   |  1 +
 6 files changed, 63 insertions(+), 25 deletions(-)

diff --git a/.gitignore b/.gitignore
index 2b4392f..13c64ae 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,4 @@ CTestTestfile.cmake
 _deps
 .vs
 out
+CMakeSettings.json
diff --git a/client.cpp b/client.cpp
index bf92ee2..0e33ca3 100644
--- a/client.cpp
+++ b/client.cpp
@@ -29,3 +29,15 @@ void sendHeader(HANDLE h, string key) {
 	}
 	cout << "Sent header." << endl;
 }
+
+bool awaitSendSuccess(HANDLE h) {
+	std::vector<char> buf(bufSize);
+
+	DWORD bytesRead;
+	const BOOL readSuccess = ReadFile(h, buf.data(), buf.size(), &bytesRead, nullptr); // Use ReadFileEx for async
+	if (!readSuccess) {
+		throw GetLastError();
+	}
+
+	return string{ buf.data(), bytesRead } == saveSuccessStatus;
+}
diff --git a/client.h b/client.h
index 3471445..38287a9 100644
--- a/client.h
+++ b/client.h
@@ -13,6 +13,7 @@
 using std::string;
 
 void sendHeader(HANDLE h, string key);
+bool awaitSendSuccess(HANDLE h);
 
 template <class T>
 void send(string key, T data) {
@@ -41,9 +42,10 @@ void send(string key, T data) {
 
 	sendHeader(h, key);
 	sendData(h, data);
+	const bool success = awaitSendSuccess(h);
 
 	CloseHandle(h);
-	cout << "Send success." << endl;
+	cout << "Send " << (success ? "success" : "fail") << endl;
 }
 
 template<class T>
diff --git a/common.h b/common.h
index 608b7ef..87f3ff3 100644
--- a/common.h
+++ b/common.h
@@ -19,3 +19,5 @@ struct Action {
 		archive(type, key);
 	}
 };
+
+const std::string saveSuccessStatus{ "saveSuccess" };
diff --git a/server.cpp b/server.cpp
index 4de690f..2e107a7 100644
--- a/server.cpp
+++ b/server.cpp
@@ -2,6 +2,7 @@
 //
 
 #include <windows.h>
+#include <thread>
 #include <sstream>
 #include <unordered_map>
 #include <string>
@@ -15,26 +16,25 @@ int main()
 {
 	cout << "I am the server." << endl;
 
+	// TODO: add mutex. stl allows multiple threads reading and one writing
 	auto store = unordered_map<string, string>{};
 
-	const DWORD pipeMode{ PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT };
-	// don't use PIPE_NOWAIT for async, see https://docs.microsoft.com/en-us/windows/win32/ipc/synchronous-and-overlapped-input-and-output
-
-	const HANDLE h{ CreateNamedPipe(
-		pipeName,
-		PIPE_ACCESS_DUPLEX,
-		pipeMode,
-		PIPE_UNLIMITED_INSTANCES,
-		bufSize,
-		bufSize,
-		0,
-		nullptr
-	) };
-	if (h == INVALID_HANDLE_VALUE) {
-		throw GetLastError();
-	}
-
 	while (TRUE) {
+		const DWORD pipeMode{ PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT };
+		const HANDLE h{ CreateNamedPipe(
+			pipeName,
+			PIPE_ACCESS_DUPLEX,
+			pipeMode,
+			PIPE_UNLIMITED_INSTANCES,
+			bufSize,
+			bufSize,
+			0,
+			nullptr
+		) };
+		if (h == INVALID_HANDLE_VALUE) {
+			throw GetLastError();
+		}
+
 		const BOOL success = ConnectNamedPipe(h, nullptr);
 		if (!success) {
 			cout << "0x" << hex << GetLastError() << endl;
@@ -42,13 +42,16 @@ int main()
 		}
 		cout << "Connected." << endl;
 
-		read(h, store);
-
-		const BOOL dSuccess = DisconnectNamedPipe(h);
-		if (!dSuccess) {
-			cout << "0x" << hex << GetLastError() << endl;
-			throw GetLastError();
-		}
+		// create a separate thread so can handle clients asynchronously
+		thread{[h, &store]() {
+			read(h, store);
+			const BOOL dSuccess = DisconnectNamedPipe(h);
+			if (!dSuccess) {
+				cout << "0x" << hex << GetLastError() << endl;
+				throw GetLastError();
+			}
+			CloseHandle(h);
+		}}.detach();
 	}
 }
 
@@ -59,6 +62,7 @@ void read(HANDLE h, Store &store) {
 			cout << "Saving data for key " << action.key << endl;
 			store[action.key] = readData(h);
 			cout << "Saved data for key " << action.key << endl;
+			saveSuccess(h);
 			break;
 		}
 		case Type::Get: {
@@ -70,6 +74,22 @@ void read(HANDLE h, Store &store) {
 	}
 }
 
+void saveSuccess(HANDLE h) {
+	DWORD bytesWritten{ 0 };
+	const BOOL success = WriteFile(
+		h,
+		&saveSuccessStatus[0],
+		saveSuccessStatus.size(),
+		&bytesWritten,
+		nullptr
+	);
+	FlushFileBuffers(h);
+	if (!success) {
+		cout << "0x" << hex << GetLastError() << endl;
+		throw GetLastError();
+	}
+}
+
 void returnData(HANDLE h, string data) {
 	DWORD bytesWritten{ 0 };
 	const BOOL success = WriteFile(
diff --git a/server.h b/server.h
index 936f1b2..546fc9a 100644
--- a/server.h
+++ b/server.h
@@ -16,3 +16,4 @@ void read(HANDLE h, Store &store);
 Action readHeader(HANDLE h);
 string readData(HANDLE h);
 void returnData(HANDLE h, string data);
+void saveSuccess(HANDLE h);