Implement multi-part messages for ZMQ.

module/Library/ZMQ.cpp

@@ -11,30 +11,109 @@ namespace SqMod {
 SQMOD_DECL_TYPENAME(SqZContext, _SC("SqZmqContext"))
 SQMOD_DECL_TYPENAME(SqZSocket, _SC("SqZmqSocket"))
 
+// ------------------------------------------------------------------------------------------------
+static void FlushSingleString(HSQUIRRELVM, Function & callback, Buffer & data)
+{
+    // Transform the message into a script object
+    LightObj o(static_cast< const SQChar * >(data.Get()),
+                static_cast< SQInteger >(data.Position()));
+    // Forward it to the callback
+    callback(o, false);
+}
+
+// ------------------------------------------------------------------------------------------------
+static void FlushSingleBuffer(HSQUIRRELVM vm, Function & callback, Buffer & data)
+{
+    // Transform the message into a script object
+    LightObj o(SqTypeIdentity< SqBuffer >{}, vm, std::move(data));
+    // Forward it to the callback
+    callback(o, false);
+}
+
+// ------------------------------------------------------------------------------------------------
+static void FlushMultiString(HSQUIRRELVM vm, Function & callback, ZMsg::List & list)
+{
+    // Create a script array
+    Array a(vm);
+    // Reserve space upfront
+    a.Reserve(static_cast< SQInteger >(list.size()));
+    // Populate the array with elements from the list
+    a.AppendFromCounted([&list](HSQUIRRELVM vm, SQInteger i) -> bool {
+        // Are we still withing range of our list?
+        if (static_cast< size_t >(i) < list.size())
+        {
+            // Transform the message into a script object
+            sq_pushstring(vm, static_cast< const SQChar * >(list[i].Get()),
+                                static_cast< SQInteger >(list[i].Position()));
+            // We have an element on the stack
+            return true;
+        }
+        // We don't have an element on the stack
+        return false;
+    });
+    // Forward it to the callback
+    callback(a, true);
+}
+
+// ------------------------------------------------------------------------------------------------
+static void FlushMultiBuffer(HSQUIRRELVM vm, Function & callback, ZMsg::List & list)
+{
+    // Create a script array
+    Array a(vm);
+    // Reserve space upfront
+    a.Reserve(static_cast< SQInteger >(list.size()));
+    // Populate the array with elements from the list
+    a.AppendFromCounted([&list](HSQUIRRELVM vm, SQInteger i) -> bool {
+        // Are we still withing range of our list?
+        if (static_cast< size_t >(i) < list.size())
+        {
+            // Transform the message into a script object
+            LightObj o(SqTypeIdentity< SqBuffer >{}, vm, std::move(list[i]));
+            // Push it on the stack
+            Var< LightObj >::push(vm, o);
+            // We have an element on the stack
+            return true;
+        }
+        // We don't have an element on the stack
+        return false;
+    });
+    // Forward it to the callback
+    callback(a, true);
+}
+
 // ------------------------------------------------------------------------------------------------
 void ZSkt::Flush(HSQUIRRELVM vm)
 {
     // Need someone to receive the message
-    Item data;
+    Item item;
     // Try to get a message from the queue
-    while (mOutputQueue.try_dequeue(data))
+    while (mOutputQueue.try_dequeue(item))
     {
         // Is there a callback to receive the message?
         if (!mOnData.IsNull())
         {
-            // Transform the message into a script object
+            // Is this a multi-part message?
-            if (mStringMessages)
+            if (!(item->mMulti))
             {
-                LightObj o(static_cast< const SQChar * >(data->Get()),
+                if (mStringMessages)
-                            static_cast< SQInteger >(data->Size< SQChar >()));
+                {
-                // Forward it to the callback
+                    FlushSingleString(vm, mOnData, item->mBuff);
-                mOnData(o);
+                }
+                else
+                {
+                    FlushSingleBuffer(vm, mOnData, item->mBuff);
+                }
             }
             else
             {
-                LightObj o(SqTypeIdentity< SqBuffer >{}, vm, std::move(*data));
+                if (mStringMessages)
-                // Forward it to the callback
+                {
-                mOnData(o);
+                    FlushMultiString(vm, mOnData, item->mList);
+                }
+                else
+                {
+                    FlushMultiBuffer(vm, mOnData, item->mList);
+                }
             }
         }
     }

module/Library/ZMQ.hpp

@@ -112,6 +112,135 @@ struct ZCtx
     operator void * () const noexcept { return mPtr; } // NOLINT(google-explicit-constructor)
 };
 
+/* ------------------------------------------------------------------------------------------------
+ * Core implementation and management for a message.
+*/
+struct ZMsg
+{
+    /* --------------------------------------------------------------------------------------------
+     * List of messages.
+    */
+    using List = std::vector< Buffer >;
+
+    /* --------------------------------------------------------------------------------------------
+     * Raw union data size.
+    */
+    static constexpr size_t SIZE = sizeof(Buffer) > sizeof(List) ? sizeof(Buffer) : sizeof(List);
+
+    /* --------------------------------------------------------------------------------------------
+     * Tag used to indicate a multi-part message.
+    */
+    struct Multipart { };
+
+    /* --------------------------------------------------------------------------------------------
+     * Message contents.
+    */
+    union
+    {
+        Buffer      mBuff;
+        List        mList;
+        uint8_t     mData[SIZE];
+    };
+
+    /* --------------------------------------------------------------------------------------------
+     * Whether this is a multi-part-message.
+    */
+    const bool  mMulti;
+
+    /* --------------------------------------------------------------------------------------------
+     * Default constructor.
+    */
+    ZMsg() // NOLINT(cppcoreguidelines-pro-type-member-init)
+        : mBuff(), mMulti(false)
+    {
+    }
+
+    /* --------------------------------------------------------------------------------------------
+     * Default multi-part constructor.
+    */
+    explicit ZMsg(Multipart) // NOLINT(cppcoreguidelines-pro-type-member-init)
+        : mList(), mMulti(true)
+    {
+    }
+
+    /* --------------------------------------------------------------------------------------------
+     * Copy constructor.
+    */
+    explicit ZMsg(const Buffer & b) // NOLINT(cppcoreguidelines-pro-type-member-init,modernize-pass-by-value)
+        : mBuff(b), mMulti(false)
+    {
+    }
+
+    /* --------------------------------------------------------------------------------------------
+     * Copy multi-part constructor.
+    */
+    explicit ZMsg(const List & l) // NOLINT(cppcoreguidelines-pro-type-member-init,modernize-pass-by-value)
+        : mList(l), mMulti(true)
+    {
+    }
+
+    /* --------------------------------------------------------------------------------------------
+     * Move constructor.
+    */
+    explicit ZMsg(Buffer && b) // NOLINT(cppcoreguidelines-pro-type-member-init)
+        : mBuff(std::move(b)), mMulti(false)
+    {
+    }
+
+    /* --------------------------------------------------------------------------------------------
+     * Move multi-part constructor.
+    */
+    explicit ZMsg(List && l) // NOLINT(cppcoreguidelines-pro-type-member-init)
+        : mList(std::move(l)), mMulti(true)
+    {
+    }
+
+    /* --------------------------------------------------------------------------------------------
+     * Copy constructor (disabled).
+    */
+    ZMsg(const ZMsg &) = delete;
+
+    /* --------------------------------------------------------------------------------------------
+     * Move constructor (disabled).
+    */
+    ZMsg(ZMsg &&) noexcept = delete;
+
+    /* --------------------------------------------------------------------------------------------
+     * Destructor.
+    */
+    ~ZMsg()
+    {
+        // Is this multi-part?
+        if (mMulti)
+        {
+            mList.~List(); // Invoke list destructor
+        }
+        else
+        {
+            mBuff.~Buffer(); // Invoke buffer destructor
+        }
+    }
+
+    /* --------------------------------------------------------------------------------------------
+     * Assignment operator (disabled).
+    */
+    ZMsg & operator = (const ZMsg &) = delete;
+
+    /* --------------------------------------------------------------------------------------------
+     * Move assignment (disabled).
+    */
+    ZMsg & operator = (ZMsg &&) noexcept = delete;
+
+    /* --------------------------------------------------------------------------------------------
+     * Push the specified message to the multi-part list.
+    */
+    void Push(zmq_msg_t & msg)
+    {
+        mList.emplace_back(static_cast< Buffer::ConstPtr >(zmq_msg_data(&msg)),
+                            static_cast< Buffer::SzType >(zmq_msg_size(&msg)));
+    }
+};
+
 /* ------------------------------------------------------------------------------------------------
  * Core implementation and management for a ZMQ socket.
 */
@@ -125,28 +254,13 @@ struct ZSkt : SqChainedInstances< ZSkt >
     /* --------------------------------------------------------------------------------------------
      * Message queue type.
     */
-    using Item = std::unique_ptr< Buffer >;
+    using Item = std::unique_ptr< ZMsg >;
 
     /* --------------------------------------------------------------------------------------------
      * Message queue type.
     */
     using Queue = moodycamel::ConcurrentQueue< Item >;
 
-    /* --------------------------------------------------------------------------------------------
-     * List of messages.
-    */
-    using List = std::vector< Buffer >;
-
-    /* --------------------------------------------------------------------------------------------
-     * Message list item.
-    */
-    using ListItem = std::unique_ptr< List >;
-
-    /* --------------------------------------------------------------------------------------------
-     * Message list queue type.
-    */
-    using ListQueue = moodycamel::ConcurrentQueue< ListItem >;
-
     /* --------------------------------------------------------------------------------------------
      * Context pointer.
     */
@@ -182,11 +296,6 @@ struct ZSkt : SqChainedInstances< ZSkt >
     */
     Queue mInputQueue;
 
-    /* --------------------------------------------------------------------------------------------
-     * Multi-part messages to be sent through the socket.
-    */
-    ListQueue mInputListQueue;
-
     /* --------------------------------------------------------------------------------------------
      * Message received callback.
     */
@@ -208,7 +317,7 @@ struct ZSkt : SqChainedInstances< ZSkt >
     ZSkt(const ZCtx::Ptr & ctx, int type)
         : SqChainedInstances< ZSkt >()
         , mPtr(nullptr), mRun(true), mStringMessages(true), mType(type), mMtx()
-        , mOutputQueue(4096), mInputQueue(4096), mInputListQueue(1024)
+        , mOutputQueue(4096), mInputQueue(4096)
         , mOnData(), mThread(), mContext(ctx)
     {
         // Validate the context
@@ -317,7 +426,7 @@ struct ZSkt : SqChainedInstances< ZSkt >
             // Acquire exclusive access to the socket
             mMtx.lock();
             // Perform tasks until there's none left
-            if (!Recv() && !Send() && !SendMore())
+            if (!Recv() && !Send())
             {
                 // Release exclusive access to the socket
                 mMtx.unlock();
@@ -380,7 +489,7 @@ struct ZSkt : SqChainedInstances< ZSkt >
     */
     void Send(const Buffer & data)
     {
-        mInputQueue.enqueue(std::make_unique< Buffer >(data));
+        mInputQueue.enqueue(std::make_unique< ZMsg >(data));
     }
 
     /* --------------------------------------------------------------------------------------------
@@ -388,15 +497,23 @@ struct ZSkt : SqChainedInstances< ZSkt >
     */
     void Send(Buffer && data)
     {
-        mInputQueue.enqueue(std::make_unique< Buffer >(std::move(data)));
+        mInputQueue.enqueue(std::make_unique< ZMsg >(std::move(data)));
     }
 
     /* --------------------------------------------------------------------------------------------
      * Queue a multi-part message to be sent through the socket.
     */
-    void Send(List && list)
+    void Send(const ZMsg::List & list)
     {
-        mInputListQueue.enqueue(std::make_unique< List >(std::move(list)));
+        mInputQueue.enqueue(std::make_unique< ZMsg >(list));
+    }
+
+    /* --------------------------------------------------------------------------------------------
+     * Queue a multi-part message to be sent through the socket.
+    */
+    void Send(ZMsg::List && list)
+    {
+        mInputQueue.enqueue(std::make_unique< ZMsg >(std::move(list)));
     }
 
 protected:
@@ -419,16 +536,21 @@ protected:
         }
         // Ask for a message, if any
         r = zmq_msg_recv(&msg, mPtr, ZMQ_DONTWAIT);
+        // Is this a multi-part message?
+        if (zmq_msg_more(&msg) == 1)
+        {
+            return RecvMore(msg, r);
+        }
         // Extract the message data
-        Item data = std::make_unique< Buffer >(static_cast< Buffer::ConstPtr >(zmq_msg_data(&msg)),
+        Item item = std::make_unique< ZMsg >(Buffer(static_cast< Buffer::ConstPtr >(zmq_msg_data(&msg)),
-                                               static_cast< Buffer::SzType >(zmq_msg_size(&msg)));
+                                                        static_cast< Buffer::SzType >(zmq_msg_size(&msg))));
         // Release this message
         zmq_msg_close(&msg);
         // Did we have a message?
         if (r >= 0)
         {
             // Put it in the queue
-            mOutputQueue.enqueue(std::move(data));
+            mOutputQueue.enqueue(std::move(item));
             // We received a message
             return true;
         }
@@ -437,7 +559,61 @@ protected:
     }
 
     /* --------------------------------------------------------------------------------------------
-     * Send one message to the socket.
+     * Receive multiple messages from the socket.
+    */
+    bool RecvMore(zmq_msg_t & msg, int r)
+    {
+        size_t more_sz = sizeof(int);
+        // Used to see if more parts follow
+        int more = 1;
+        // Create an empty multi-part message container
+        Item item = std::make_unique< ZMsg >(ZMsg::Multipart{});
+        // Add the initial message to the list
+        if (r >= 0)
+        {
+            // Save it to the list
+            item->Push(msg);
+            // Close the message
+            zmq_msg_close(&msg);
+        }
+        // Keep receiving messages while there's more
+        do
+        {
+            // Initialize an empty message
+            r = zmq_msg_init(&msg);
+            // Make sure we have a message
+            if (r != 0)
+            {
+                LogErr("Unable to initialize ZMQ message part");
+                // Abort everything
+                return false;
+            }
+            // Ask for another message, if any (blocking operation!)
+            r = zmq_msg_recv(&msg, mPtr, 0);
+            // Do we actually have a message?
+            if (r >= 0)
+            {
+                // Save it to the list
+                item->Push(msg);
+                // Close the message
+                zmq_msg_close(&msg);
+            }
+            // See if the message part last received from the socket was a data part with more parts to follow.
+            zmq_getsockopt(mPtr, ZMQ_RCVMORE, &more, &more_sz);
+        } while (more);
+        // Did we actually have any valid messages?
+        if (!(item->mList.empty()))
+        {
+            mOutputQueue.enqueue(std::move(item));
+            // Messages were present in the list
+            return true;
+        }
+        // No messages were added
+        return false;
+    }
+
+    /* --------------------------------------------------------------------------------------------
+     * Send one queued message to the socket.
     */
     bool Send()
     {
@@ -446,13 +622,13 @@ protected:
         // Try to get a message from the queue
         if (mInputQueue.try_dequeue(data))
         {
-            // Attempt to send the message
+            if (data->mMulti)
-            int r = zmq_send(mPtr, data->Data(), data->Size(), ZMQ_DONTWAIT);
-            // Could we send what the message had?
-            if (r >= 0 && static_cast< Buffer::SzType >(r) != data->Size())
             {
-                LogErr("Unable to send data to socket: [%d], {%s}", r, zmq_strerror(errno));
+                SendMore(data->mList);
-                // NOTE: Should we put the buffer back into the queue?
+            }
+            else
+            {
+                SendOne(data->mBuff);
             }
             // One item was found in the queue
             return true;
@@ -463,33 +639,37 @@ protected:
         }
     }
 
+    /* --------------------------------------------------------------------------------------------
+     * Send a single message to the socket.
+    */
+    void SendOne(Buffer & buff) const
+    {
+        // Attempt to send the message
+        int r = zmq_send(mPtr, buff.Data(), buff.Position(), ZMQ_DONTWAIT);
+        // Could we send what the message had?
+        if (r >= 0 && static_cast< Buffer::SzType >(r) != buff.Position())
+        {
+            LogErr("Unable to send data to socket: [%d], {%s}", r, zmq_strerror(errno));
+            // NOTE: Should we put the buffer back into the queue?
+        }
+    }
+
     /* --------------------------------------------------------------------------------------------
      * Send a multi-part message to the socket.
     */
-    bool SendMore()
+    void SendMore(ZMsg::List & list) const
     {
-        ListItem mp_msg;
+        // Send all message parts
-        // Try to get a multi-part message from the queue
+        for (size_t i = 0, n = list.size(); i < n; ++i)
-        if (mInputListQueue.try_dequeue(mp_msg))
         {
-            // Send all message parts
+            // Attempt to send the message
-            for (size_t i = 0, n = mp_msg->size(); i < n; ++i)
+            int r = zmq_send(mPtr, list[i].Data(), list[i].Position(), (i + 1) == n ? ZMQ_DONTWAIT : ZMQ_SNDMORE);
+            // Could we send what the message had?
+            if (r >= 0 && static_cast< Buffer::SzType >(r) != list[i].Position())
             {
-                // Attempt to send the message
+                LogErr("Unable to send multi-part data to socket: [%d], %s", r, zmq_strerror(errno));
-                int r = zmq_send(mPtr, (*mp_msg)[i].Data(), (*mp_msg)[i].Size(), (i + 1) == n ? ZMQ_DONTWAIT : ZMQ_SNDMORE);
+                // NOTE: Should we abort the whole thing? But we probably already sent some.
-                // Could we send what the message had?
-                if (r >= 0 && static_cast< Buffer::SzType >(r) != (*mp_msg)[i].Size())
-                {
-                    LogErr("Unable to send multi-part data to socket: [%d], %s", r, zmq_strerror(errno));
-                    // NOTE: Should we abort the whole thing? But we probably already sent some.
-                }
             }
-            // One item was found in the queue
-            return true;
-        }
-        else
-        {
-            return false; // No item in the queue
         }
     }
 };
@@ -851,7 +1031,7 @@ struct ZSocket
     {
         Validate();
 
-        ZSkt::List list;
+        ZMsg::List list;
         // Extract the messages from the array
         arr.Foreach([&list](HSQUIRRELVM vm, SQInteger) {
             // Extract the buffer from the stack
@@ -878,7 +1058,7 @@ struct ZSocket
     {
         Validate();
 
-        ZSkt::List list;
+        ZMsg::List list;
         // Extract the messages from the array
         arr.Foreach([&list](HSQUIRRELVM vm, SQInteger) {
             StackStrF str(vm, -1);