Basic fragmented send feature

src/WebSocket.h

@@ -73,9 +73,23 @@ public:
         DROPPED
     };
 
+    /* Sending fragmented messages puts a bit of effort on the user; you must not interleave regular sends
+     * with fragmented sends and you must sendFirstFragment, [sendFragment], then finally sendLastFragment. */
+    SendStatus sendFirstFragment(std::string_view message, OpCode opCode = OpCode::BINARY, bool compress = false) {
+        return send(message, opCode, compress, false);
+    }
+
+    SendStatus sendFragment(std::string_view message, bool compress = false) {
+        return send(message, CONTINUATION, compress, false);
+    }
+
+    SendStatus sendLastFragment(std::string_view message, bool compress = false) {
+        return send(message, CONTINUATION, compress, true);
+    }
+
     /* Send or buffer a WebSocket frame, compressed or not. Returns BACKPRESSURE on increased user space backpressure,
      * DROPPED on dropped message (due to backpressure) or SUCCCESS if you are free to send even more now. */
-    SendStatus send(std::string_view message, OpCode opCode = OpCode::BINARY, bool compress = false) {
+    SendStatus send(std::string_view message, OpCode opCode = OpCode::BINARY, bool compress = false, bool fin = true) {
         WebSocketContextData<SSL, USERDATA> *webSocketContextData = (WebSocketContextData<SSL, USERDATA> *) us_socket_context_ext(SSL,
             (us_socket_context_t *) us_socket_context(SSL, (us_socket_t *) this)
         );
@@ -117,7 +131,7 @@ public:
         /* Get size, allocate size, write if needed */
         size_t messageFrameSize = protocol::messageFrameSize(message.length());
         auto [sendBuffer, sendBufferAttribute] = Super::getSendBuffer(messageFrameSize);
-        protocol::formatMessage<isServer>(sendBuffer, message.data(), message.length(), opCode, message.length(), compress);
+        protocol::formatMessage<isServer>(sendBuffer, message.data(), message.length(), opCode, message.length(), compress, fin);
 
         /* Depending on size of message we have different paths */
         if (sendBufferAttribute == SendBufferAttribute::NEEDS_DRAIN) {

src/WebSocketProtocol.h

@@ -35,6 +35,7 @@ const std::string_view ERR_TOO_BIG_MESSAGE_INFLATION("Received too big message,
 const std::string_view ERR_INVALID_CLOSE_PAYLOAD("Received invalid close payload");
 
 enum OpCode : unsigned char {
+    CONTINUATION = 0,
     TEXT = 1,
     BINARY = 2,
     CLOSE = 8,
@@ -205,7 +206,7 @@ enum {
 };
 
 template <bool isServer>
-static inline size_t formatMessage(char *dst, const char *src, size_t length, OpCode opCode, size_t reportedLength, bool compressed) {
+static inline size_t formatMessage(char *dst, const char *src, size_t length, OpCode opCode, size_t reportedLength, bool compressed, bool fin) {
     size_t messageLength;
     size_t headerLength;
     if (reportedLength < 126) {
@@ -223,11 +224,9 @@ static inline size_t formatMessage(char *dst, const char *src, size_t length, Op
         memcpy(&dst[2], &tmp, sizeof(uint64_t));
     }
 
-    int flags = 0;
-    dst[0] = (char) ((flags & SND_NO_FIN ? 0 : 128) | (compressed ? SND_COMPRESSED : 0));
-    if (!(flags & SND_CONTINUATION)) {
-        dst[0] |= (char) opCode;
-    }
+    dst[0] = (char) ((fin ? 128 : 0) | ((compressed && opCode) ? SND_COMPRESSED : 0) | (char) opCode);
+
+    //printf("%d\n", (int)dst[0]);
 
     char mask[4];
     if (!isServer) {