Add iterator helper for filtering

lib/entry/libimagentryutil/src/iter.rs

@@ -0,0 +1,45 @@
+//
+// imag - the personal information management suite for the commandline
+// Copyright (C) 2015, 2016 Matthias Beyer <mail@beyermatthias.de> and contributors
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; version
+// 2.1 of the License.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+//
+
+use filters::filter::Filter;
+
+pub trait NextWhere<T> {
+    type Item;
+
+    fn next_where<F>(&mut self, f: &F) -> Option<Self::Item>
+        where F: Filter<T>;
+}
+
+impl<T, I> NextWhere<T> for I
+    where I: Iterator<Item = T>
+{
+    type Item = T;
+
+    fn next_where<F>(&mut self, f: &F) -> Option<Self::Item>
+        where F: Filter<T>
+    {
+        while let Some(next) = self.next() {
+            if f.filter(&next) {
+                return Some(next);
+            }
+        }
+        None
+    }
+}
+

lib/entry/libimagentryutil/src/lib.rs

@@ -46,4 +46,5 @@ extern crate libimagerror;
 pub mod error;
 pub mod isa;
 pub mod isincollection;
+pub mod iter;