1 files changed, 18 insertions, 3 deletions
diff --git a/src/corelib/io/qbuffer.cpp b/src/corelib/io/qbuffer.cpp
index c244dacab3..763620692c 100644
--- a/src/corelib/io/qbuffer.cpp
+++ b/src/corelib/io/qbuffer.cpp
@@ -267,16 +267,31 @@ void QBuffer::setData(const QByteArray &data)
 }
 
 /*!
-    \fn void QBuffer::setData(const char *data, int size)
-
     \overload
 
     Sets the contents of the internal buffer to be the first \a size
     bytes of \a data.
+
+    \note In Qt versions prior to 6.5, this function took the length as
+    an \c{int} parameter, potentially truncating sizes.
 */
+void QBuffer::setData(const char *data, qsizetype size)
+{
+    Q_D(QBuffer);
+    if (isOpen()) {
+        qWarning("QBuffer::setData: Buffer is open");
+        return;
+    }
+    d->buf->replace(qsizetype(0), d->buf->size(), // ### QByteArray lacks assign(ptr, n)
+                    data, size);
+}
 
 /*!
    \reimp
+
+   Unlike QFile, opening a QBuffer QIODevice::WriteOnly does not truncate it.
+   However, pos() is set to 0. Use QIODevice::Append or QIODevice::Truncate to
+   change either behavior.
 */
 bool QBuffer::open(OpenMode flags)
 {
@@ -386,7 +401,7 @@ qint64 QBuffer::writeData(const char *data, qint64 len)
 
     if (required > quint64(d->buf->size())) { // capacity exceeded
         // The following must hold, since qsizetype covers half the virtual address space:
-        Q_ASSUME(required <= quint64((std::numeric_limits<qsizetype>::max)()));
+        Q_ASSERT(required <= quint64((std::numeric_limits<qsizetype>::max)()));
         d->buf->resize(qsizetype(required));
         if (quint64(d->buf->size()) != required) { // could not resize
             qWarning("QBuffer::writeData: Memory allocation error");