Merge pull request #520 from dylanede/master

Support for taking differences of extension and feature sets

vulkano/src/features.rs

@@ -89,6 +89,17 @@ macro_rules! features {
                     )+
                 }
             }
+
+            /// Builds a `Features` that is the difference of another `Features` object from `self`.
+            ///
+            /// The result's field will be true if it is true in `self` but not `other`.
+            pub fn difference(&self, other: &Features) -> Features {
+                Features {
+                    $(
+                        $name: self.$name && !other.$name,
+                    )+
+                }
+            }
         }
 
         #[doc(hidden)]

vulkano/src/instance/extensions.rs

@@ -61,6 +61,17 @@ macro_rules! extensions {
                     _unbuildable: Unbuildable(())
                 }
             }
+
+            /// Returns the difference of another list from this list.
+            #[inline]
+            pub fn difference(&self, other: &$sname) -> $sname {
+                $sname {
+                    $(
+                        $ext: self.$ext && !other.$ext,
+                    )*
+                    _unbuildable: Unbuildable(())
+                }
+            }
         }
 
         impl fmt::Debug for $sname {
@@ -110,6 +121,11 @@ macro_rules! extensions {
                 $rawname(self.0.intersection(&other.0).cloned().collect())
             }
 
+            /// Returns the difference of another set from this one.
+            pub fn difference(&self, other: &Self) -> Self {
+                $rawname(self.0.difference(&other.0).cloned().collect())
+            }
+
             // TODO: impl Iterator
             pub fn iter(&self) -> ::std::collections::hash_set::Iter<CString> { self.0.iter() }
         }