QWebSocket: Add 'bytesToWrite'

Add the well-known 'bytesToWrite' function to QWebSocket. Previously
the only way to know how many bytes were left to be written was to
make a guesstimate on the overhead your message would get and then
keep track of the amount sent using the 'bytesWritten' signal.

The tests compare using '>' because there is overhead from the headers.

[ChangeLog][QWebSocket] Added the bytesToWrite function to
QWebSocket. Call this function to see how many bytes are left to write.

Change-Id: I82f17a98b582ee3bc02f0c47597b4a6717761f12
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

2 files changed, 15 insertions, 0 deletions

diff --git a/src/websockets/qwebsocket.cpp b/src/websockets/qwebsocket.cpp
index 1b0fc35..64d5e4c 100644
--- a/src/websockets/qwebsocket.cpp
+++ b/src/websockets/qwebsocket.cpp
@@ -772,4 +772,17 @@ bool QWebSocket::isValid() const
     return d->isValid();
 }
 
+/*!
+    \since 5.12
+    Returns the number of bytes that are waiting to be written. The bytes are written when control
+    goes back to the event loop or when flush() is called.
+
+    \sa flush
+ */
+qint64 QWebSocket::bytesToWrite() const
+{
+    Q_D(const QWebSocket);
+    return d->m_pSocket ? d->m_pSocket->bytesToWrite() : 0;
+}
+
 QT_END_NAMESPACE
diff --git a/src/websockets/qwebsocket.h b/src/websockets/qwebsocket.h
index a80c47a..b8742e8 100644
--- a/src/websockets/qwebsocket.h
+++ b/src/websockets/qwebsocket.h
@@ -113,6 +113,8 @@ public:
     QSslConfiguration sslConfiguration() const;
 #endif
 
+    qint64 bytesToWrite() const;
+
 public Q_SLOTS:
     void close(QWebSocketProtocol::CloseCode closeCode = QWebSocketProtocol::CloseCodeNormal,
                const QString &reason = QString());