deal with safari fragmented pong data

Pong in Chrome
8A 80 8B 9B 7E 64
Pong in Safari
8A 80
46 DC 9F 25

This commit addresses the pointer corruption that occurs when Safari sends a Pong. Without this change, the library will use the mask as beginning of the data packet and misbehave.

Use _pinfo.masked as a counter to minimize change of the code.

Author: DeqingSun

src/AsyncWebSocket.cpp

@@ -515,7 +515,7 @@ void AsyncWebSocketClient::_onData(void *pbuf, size_t plen) {
       _pinfo.index = 0;
       _pinfo.final = (fdata[0] & 0x80) != 0;
       _pinfo.opcode = fdata[0] & 0x0F;
-      _pinfo.masked = (fdata[1] & 0x80) != 0;
+      _pinfo.masked = ((fdata[1] & 0x80) != 0) ? 1 : 0;
       _pinfo.len = fdata[1] & 0x7F;
 
       // async_ws_log_d("WS[%" PRIu32 "]: _onData: %" PRIu32, _clientId, plen);
@@ -536,12 +536,20 @@ void AsyncWebSocketClient::_onData(void *pbuf, size_t plen) {
         data += 8;
         plen -= 8;
       }
+    }
 
-      if (_pinfo.masked
-          && plen >= 4) {  // if ws.close() is called, Safari sends a close frame with plen 2 and masked bit set. We must not decrement plen which is already 0.
-        memcpy(_pinfo.mask, data, 4);
-        data += 4;
-        plen -= 4;
+    if (_pinfo.masked > 0 && _pinfo.masked < 5) {
+      //mask not fully read yet
+      while (_pinfo.masked < 5) {
+        if (plen == 0) {
+          //wait for more data
+          _pstate = 1;
+          return;
+        }
+        _pinfo.mask[_pinfo.masked - 1] = data[0];
+        data += 1;
+        plen -= 1;
+        _pinfo.masked++;
       }
     }