Add QFileDevice::MemoryMapFlags::MapPrivateOption flag.

Passing this flag to QFileDevice::map() will allow writes to the mapped memory
without modifying the file that was mapped. These writes will be lost when the
memory is unmapped.

Change-Id: I7d46b044fc370585de8c06fdb4059f1f1be12d7d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/corelib/io/qfiledevice.cpp b/src/corelib/io/qfiledevice.cpp
index f7e58a7bed..33cb6037f5 100644
--- a/src/corelib/io/qfiledevice.cpp
+++ b/src/corelib/io/qfiledevice.cpp
@@ -680,6 +680,13 @@ bool QFileDevice::setPermissions(Permissions permissions)
     function.
 
     \value NoOptions        No options.
+    \value MapPrivateOption The mapped memory will be private, so any
+    modifications will not be visible to other processes and will not
+    be written to disk.  Any such modifications will be lost when the
+    memory is unmapped.  It is unspecified whether modifications made
+    to the file made after the mapping is created will be visible through
+    the mapped memory.  This flag is not supported on Windows CE.
+    This enum value was introduced in Qt 5.4.
 */
 
 /*!
@@ -689,6 +696,10 @@ bool QFileDevice::setPermissions(Permissions permissions)
     or a new file is opened with this object, any maps that have not been
     unmapped will automatically be unmapped.
 
+    The mapping will have the same open mode as the file (read and/or write),
+    except when using MapPrivateOption, in which case it is always possible
+    to write to the mapped memory.
+
     Any mapping options can be passed through \a flags.
 
     Returns a pointer to the memory or 0 if there is an error.