Add DriverIterator to iterate though the registered drivers

CHANGES.md

@@ -1,6 +1,8 @@
 # Changes
 
 ## Unreleased
+- Add `DriverIterator` format to iterate through drivers, as well as `DriverManager::all()` method that provides the iterator.
+
 - **Breaking**: `Feature::set_field_xxx` now take `&mut self`
   - <https://github.com/georust/gdal/pull/505>
 

src/driver.rs

@@ -451,6 +451,39 @@ impl DriverManager {
             gdal_sys::GDALDestroyDriverManager();
         }
     }
+
+    /// Get an `Iterator` for all the drivers.
+    ///
+    /// Warning: Adding or removing drivers while comsuming the
+    /// Iterator can have unexpected results.
+    pub fn all() -> DriverIterator {
+        DriverIterator::new()
+    }
+}
+
+/// Iterator for the registered `Driver`s in `DriverManager`
+pub struct DriverIterator {
+    current: usize,
+}
+
+impl DriverIterator {
+    pub fn new() -> Self {
+        DriverIterator { current: 0 }
+    }
+}
+
+impl Iterator for DriverIterator {
+    type Item = Driver;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match DriverManager::get_driver(self.current) {
+            Ok(d) => {
+                self.current += 1;
+                Some(d)
+            }
+            Err(_) => None,
+        }
+    }
 }
 
 #[cfg(test)]
@@ -466,4 +499,10 @@ mod tests {
         assert!(DriverManager::count() > 0);
         assert!(DriverManager::get_driver(0).is_ok());
     }
+
+    #[test]
+    fn test_driver_iterator() {
+        assert_eq!(DriverManager::count(), DriverIterator::new().count());
+        assert_eq!(DriverManager::count(), DriverManager::all().count());
+    }
 }