cleaner and safer code

src/sdl2/render.rs

@@ -702,14 +702,13 @@ impl Texture {
         else { Err(get_error()) }
     }
 
-    pub fn lock(&self, rect: Option<Rect>) -> SdlResult<(CVec<u8>, i32)> {
+    fn unsafe_lock(&self, rect: Option<Rect>) -> SdlResult<(CVec<u8>, i32)> {
         let q = try!(self.query());
         unsafe {
             let actual_rect = match rect {
                 Some(ref rect) => rect as *const _,
                 None => ptr::null()
             };
-
             let pixels : *const c_void = ptr::null();
             let pitch = 0i32;
             let ret = ll::SDL_LockTexture(self.raw, actual_rect, &pixels, &pitch);
@@ -722,6 +721,17 @@ impl Texture {
         }
     }
 
+    pub fn lock(&self, rect: Option<Rect>, func: |CVec<u8>, i32| -> ()) -> SdlResult<()> {
+        match self.unsafe_lock(rect) {
+            Ok((cvec, pitch)) => {
+                func(cvec, pitch); 
+                self.unlock();
+                Ok(())
+            }
+            Err(e) => Err(e),
+        }
+    }
+
     pub fn unlock(&self) {
         unsafe { ll::SDL_UnlockTexture(self.raw) }
     }