Avoid unnecessary memory allocation in the jpeg handler's image detection

The handler calls peek with 2 bytes to inspect the first two bytes. Instead
of calling the overload of peek() that returns a new QByteArray with just
two bytes, allocate 2 bytes on the stack and call the overload of peek()
that writes into the specified buffer.

Reviewed-by: Joao

1 files changed, 5 insertions, 1 deletions

diff --git a/src/plugins/imageformats/jpeg/qjpeghandler.cpp b/src/plugins/imageformats/jpeg/qjpeghandler.cpp
index 6cb93ad..98bd88f 100644
--- a/src/plugins/imageformats/jpeg/qjpeghandler.cpp
+++ b/src/plugins/imageformats/jpeg/qjpeghandler.cpp
@@ -1188,7 +1188,11 @@ bool QJpegHandler::canRead(QIODevice *device)
         return false;
     }
 
-    return device->peek(2) == "\xFF\xD8";
+    char buffer[2];
+    if (device->peek(buffer, 2) != 2)
+        return false;
+
+    return uchar(buffer[0]) == 0xff && uchar(buffer[1]) == 0xd8;
 }
 
 bool QJpegHandler::read(QImage *image)