From b07511ef22303f969b6aae2bcb026891b355d0b0 Mon Sep 17 00:00:00 2001
From: "Matthias P. Braendli" <matthias.braendli@mpb.li>
Date: Tue, 21 Apr 2020 15:56:49 +0200
Subject: Common 33a8362: EDI TCP output: handle disconnects

---
 lib/Socket.cpp        | 70 ++++++++++++++++++++++++++++++++++++++++++++++++---
 lib/Socket.h          | 28 +++++++++++++++++++++
 lib/ThreadsafeQueue.h | 23 ++++++++++++++---
 3 files changed, 114 insertions(+), 7 deletions(-)

diff --git a/lib/Socket.cpp b/lib/Socket.cpp
index bfbef93..159de7e 100644
--- a/lib/Socket.cpp
+++ b/lib/Socket.cpp
@@ -199,10 +199,11 @@ UDPPacket UDPSocket::receive(size_t max_size)
 
         // This suppresses the -Wlogical-op warning
 #if EAGAIN == EWOULDBLOCK
-        if (errno == EAGAIN) {
+        if (errno == EAGAIN)
 #else
-        if (errno == EAGAIN or errno == EWOULDBLOCK) {
+        if (errno == EAGAIN or errno == EWOULDBLOCK)
 #endif
+        {
             return 0;
         }
         throw runtime_error(string("Can't receive data: ") + strerror(errno));
@@ -733,7 +734,9 @@ TCPConnection::~TCPConnection()
     m_running = false;
     vector<uint8_t> termination_marker;
     queue.push(termination_marker);
-    m_sender_thread.join();
+    if (m_sender_thread.joinable()) {
+        m_sender_thread.join();
+    }
 }
 
 void TCPConnection::process()
@@ -905,4 +908,65 @@ void TCPReceiveServer::process()
     }
 }
 
+TCPSendClient::TCPSendClient(const std::string& hostname, int port) :
+    m_hostname(hostname),
+    m_port(port),
+    m_running(true)
+{
+    m_sender_thread = std::thread(&TCPSendClient::process, this);
+}
+
+TCPSendClient::~TCPSendClient()
+{
+    m_running = false;
+    m_queue.trigger_wakeup();
+    if (m_sender_thread.joinable()) {
+        m_sender_thread.join();
+    }
+}
+
+void TCPSendClient::sendall(const std::vector<uint8_t>& buffer)
+{
+    if (not m_running) {
+        throw runtime_error(m_exception_data);
+    }
+
+    m_queue.push(buffer);
+}
+
+void TCPSendClient::process()
+{
+    try {
+        while (m_running) {
+            if (m_is_connected) {
+                try {
+                    vector<uint8_t> incoming;
+                    m_queue.wait_and_pop(incoming);
+                    if (m_sock.sendall(incoming.data(), incoming.size()) == -1) {
+                        m_is_connected = false;
+                        m_sock = TCPSocket();
+                    }
+                }
+                catch (const ThreadsafeQueueWakeup&) {
+                    break;
+                }
+            }
+            else {
+                try {
+                    m_sock.connect(m_hostname, m_port);
+                    m_is_connected = true;
+                }
+                catch (const runtime_error& e) {
+                    m_is_connected = false;
+                    this_thread::sleep_for(chrono::seconds(1));
+                }
+            }
+        }
+    }
+    catch (const runtime_error& e) {
+        m_exception_data = e.what();
+        m_running = false;
+    }
+}
+
 }
diff --git a/lib/Socket.h b/lib/Socket.h
index b9f6317..84def40 100644
--- a/lib/Socket.h
+++ b/lib/Socket.h
@@ -291,4 +291,32 @@ class TCPReceiveServer {
         TCPSocket m_listener_socket;
 };
 
+/* A TCP client that abstracts the handling of connects and disconnects.
+ */
+class TCPSendClient {
+    public:
+        TCPSendClient(const std::string& hostname, int port);
+        ~TCPSendClient();
+
+        /* Throws a runtime_error on error
+         */
+        void sendall(const std::vector<uint8_t>& buffer);
+
+    private:
+        void process();
+
+        std::string m_hostname;
+        int m_port;
+
+        bool m_is_connected = false;
+
+        TCPSocket m_sock;
+        static constexpr size_t MAX_QUEUE_SIZE = 1024;
+        ThreadsafeQueue<std::vector<uint8_t> > m_queue;
+        std::atomic<bool> m_running;
+        std::string m_exception_data;
+        std::thread m_sender_thread;
+        TCPSocket m_listener_socket;
+};
+
 }
diff --git a/lib/ThreadsafeQueue.h b/lib/ThreadsafeQueue.h
index 62f4c96..815dfe0 100644
--- a/lib/ThreadsafeQueue.h
+++ b/lib/ThreadsafeQueue.h
@@ -52,12 +52,21 @@ public:
     /* Push one element into the queue, and notify another thread that
      * might be waiting.
      *
+     * if max_size > 0 and the queue already contains at least max_size elements,
+     * the element gets discarded.
+     *
      * returns the new queue size.
      */
-    size_t push(T const& val)
+    size_t push(T const& val, size_t max_size = 0)
     {
         std::unique_lock<std::mutex> lock(the_mutex);
-        the_queue.push(val);
+        size_t queue_size_before = the_queue.size();
+        if (max_size == 0) {
+            the_queue.push(val);
+        }
+        else if (queue_size_before < max_size) {
+            the_queue.push(val);
+        }
         size_t queue_size = the_queue.size();
         lock.unlock();
 
@@ -66,10 +75,16 @@ public:
         return queue_size;
     }
 
-    size_t push(T&& val)
+    size_t push(T&& val, size_t max_size = 0)
     {
         std::unique_lock<std::mutex> lock(the_mutex);
-        the_queue.emplace(std::move(val));
+        size_t queue_size_before = the_queue.size();
+        if (max_size == 0) {
+            the_queue.emplace(std::move(val));
+        }
+        else if (queue_size_before < max_size) {
+            the_queue.emplace(std::move(val));
+        }
         size_t queue_size = the_queue.size();
         lock.unlock();
 
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