pointer to a chunk of memory to use, or NULL
the size of data
a function with realloc() semantics (like g_realloc()) to be called when data needs to be grown, or NULL
a function to be called on data when the stream is finalized, or NULL
ConstructionException GTK+ fails to create the object.
Creates a new GMemoryOutputStream. If data is non-NULL, the stream will use that for its internal storage. If realloc_fn is non-NULL, it will be used for resizing the internal storage when necessary. To construct a fixed-size output stream, pass NULL as realloc_fn.