Merge pull request #54 from messense/feature/dict-iter

Add PyDict::iter

src/objects/dict.rs

@@ -120,9 +120,6 @@ impl PyDict {
 
     /// Returns the list of (key, value) pairs in this dictionary.
     pub fn items_vec(&self) -> Vec<(PyObject, PyObject)> {
-        // Note that we don't provide an iterator because
-        // PyDict_Next() is unsafe to use when the dictionary might be changed
-        // by other python code.
         let mut vec = Vec::with_capacity(self.len());
         unsafe {
             let mut pos = 0;
@@ -135,6 +132,37 @@ impl PyDict {
         }
         vec
     }
+
+    /// Returns a iterator of (key, value) pairs in this dictionary
+    /// Note that it's unsafe to use when the dictionary might be changed
+    /// by other python code.
+    #[inline]
+    pub fn iter(&self) -> PyDictIterator {
+        PyDictIterator { dict: self, pos: 0 }
+    }
+}
+
+pub struct PyDictIterator<'a> {
+    dict: &'a PyDict,
+    pos: isize
+}
+
+impl<'a> Iterator for PyDictIterator<'a> {
+    type Item = (&'a PyObjectRef, &'a PyObjectRef);
+
+    #[inline]
+    fn next(&mut self) -> Option<Self::Item> {
+        unsafe {
+            let mut key: *mut ffi::PyObject = mem::uninitialized();
+            let mut value: *mut ffi::PyObject = mem::uninitialized();
+            if ffi::PyDict_Next(self.dict.as_ptr(), &mut self.pos, &mut key, &mut value) != 0 {
+                let py = self.dict.py();
+                Some((py.cast_from_borrowed_ptr(key), py.cast_from_borrowed_ptr(value)))
+            } else {
+                None
+            }
+        }
+    }
 }
 
 impl <K, V> ToPyObject for collections::HashMap<K, V>
@@ -382,6 +410,26 @@ mod test {
         assert_eq!(32 + 42 + 123, value_sum);
     }
 
+    #[test]
+    fn test_dict_iter() {
+        let gil = Python::acquire_gil();
+        let py = gil.python();
+        let mut v = HashMap::new();
+        v.insert(7, 32);
+        v.insert(8, 42);
+        v.insert(9, 123);
+        let ob = v.to_object(py);
+        let dict = PyDict::downcast_from(ob.as_ref(py)).unwrap();
+        let mut key_sum = 0;
+        let mut value_sum = 0;
+        for (key, value) in dict.iter() {
+            key_sum += key.extract::<i32>().unwrap();
+            value_sum += value.extract::<i32>().unwrap();
+        }
+        assert_eq!(7 + 8 + 9, key_sum);
+        assert_eq!(32 + 42 + 123, value_sum);
+    }
+
     #[test]
     fn test_hashmap_to_python() {
         let gil = Python::acquire_gil();