[shotwell] gphoto: Don't copy buffer when creating input stream from CameraFile

[Jens Georg <jensgeorg src gnome org>]

commit e6ffdef23a0a93d2e658366b4902e0e864b60967
Author: Jens Georg <mail jensge org>
Date:   Thu May 18 22:25:15 2017 +0200

    gphoto: Don't copy buffer when creating input stream from CameraFile

 src/camera/GPhoto.vala |   19 +++++++++----------
 1 files changed, 9 insertions(+), 10 deletions(-)
---
diff --git a/src/camera/GPhoto.vala b/src/camera/GPhoto.vala
index 5acc4a3..fb0fd4a 100644
--- a/src/camera/GPhoto.vala
+++ b/src/camera/GPhoto.vala
@@ -251,17 +251,20 @@ namespace GPhoto {
             throw new GPhotoError.LIBRARY("[%d] Error retrieving file object for %s/%s: %s", 
                 (int) res, folder, filename, res.as_string());
         
-        // if entire file fits in memory, return a stream from that ... can't merely wrap
-        // MemoryInputStream around the camera_file buffer, as that will be destroyed when the
-        // function returns
+        // if entire file fits in memory, return a stream from that ...
+        // The camera_file is set as data on the object to keep it alive while
+        // the MemoryInputStream is alive.
         unowned uint8 *data;
         ulong data_len;
         res = camera_file.get_data_and_size(out data, out data_len);
         if (res == Result.OK) {
-            uint8[] buffer = new uint8[data_len];
-            Memory.copy(buffer, data, buffer.length);
+            unowned uint8[] buffer = (uint8[])data;
+            buffer.length = (int) data_len;
             
-            return new MemoryInputStream.from_data(buffer, on_mins_destroyed);
+            var mis = new MemoryInputStream.from_data(buffer, () => {});
+            mis.set_data<GPhoto.CameraFile>("camera-file", camera_file);
+
+            return mis;
         }
 
         // if not stored in memory, try copying it to a temp file and then reading out of that
@@ -274,10 +277,6 @@ namespace GPhoto {
         return temp.read(null);
     }
     
-    private static void on_mins_destroyed(void *data) {
-        free(data);
-    }
-    
     // Returns a buffer with the requested file, if within reason.  Use load_file for larger files.
     public uint8[]? load_file_into_buffer(Context context, Camera camera, string folder,
         string filename, CameraFileType filetype) throws Error {