[libgee] Add map_iterator to MultiMap, partial fix for bug #675067

[Maciej Marcin Piechotka <mpiechotka src gnome org>]

commit f6f8f08b5f8c9a7ab2f9a2673e51f6e465dc383b
Author: Maciej Piechotka <uzytkownik2 gmail com>
Date:   Sun Aug 19 23:56:04 2012 -0700

    Add map_iterator to MultiMap, partial fix for bug #675067

 gee/abstractmultimap.vala |   86 +++++++++++++++++++++++++++++++++++++++++---
 gee/multimap.vala         |    7 ++++
 2 files changed, 87 insertions(+), 6 deletions(-)
---
diff --git a/gee/abstractmultimap.vala b/gee/abstractmultimap.vala
index 1f08b0b..2c71ed5 100644
--- a/gee/abstractmultimap.vala
+++ b/gee/abstractmultimap.vala
@@ -45,12 +45,6 @@ public abstract class Gee.AbstractMultiMap<K,V> : Object, MultiMap<K,V> {
 		this._empty_value_set = Set.empty<V> ();
 	}
 
-	protected abstract Collection<V> create_value_storage ();
-
-	protected abstract MultiSet<K> create_multi_key_set ();
-
-	protected abstract EqualDataFunc<V> get_value_equal_func ();
-
 	public Set<K> get_keys () {
 		return _storage_map.keys;
 	}
@@ -131,10 +125,90 @@ public abstract class Gee.AbstractMultiMap<K,V> : Object, MultiMap<K,V> {
 		_nitems = 0;
 	}
 
+	public Gee.MapIterator<K, V> map_iterator () {
+		return new MapIterator<K, V> (_storage_map.map_iterator ());
+	}
+
+	protected abstract Collection<V> create_value_storage ();
+
+	protected abstract MultiSet<K> create_multi_key_set ();
+
+	protected abstract EqualDataFunc<V> get_value_equal_func ();
+
 	public Type key_type { get { return typeof(K); } }
 
 	public Type value_type { get { return typeof(V); } }
 
+	private class MappingIterator<K, V> : Object {
+		protected Gee.MapIterator<K, Collection<V>> outer;
+		protected Iterator<V>? inner = null;
+
+		public MappingIterator (Gee.MapIterator<K, Collection<V>>? outer) {
+			this.outer = outer;
+		}
+
+		public bool next () {
+			if (inner.next ()) {
+				return true;
+			} else if (outer.next ()) {
+				inner = outer.get_value ().iterator ();
+				assert (inner.next ());
+				return true;
+			} else {
+				return false;
+			}
+		}
+
+		public bool has_next () {
+			return inner.has_next () || outer.has_next ();
+		}
+
+		public void remove () {
+			assert_not_reached ();
+		}
+
+		public virtual bool read_only {
+			get {
+				return true;
+			}
+		}
+
+		public void unset () {
+			inner.remove ();
+			if (outer.get_value ().is_empty) {
+				outer.unset ();
+			}
+		}
+
+		public bool valid {
+			get {
+				return inner != null && inner.valid;
+			}
+		}
+	}
+
+	private class MapIterator<K, V> : MappingIterator<K, V>, Gee.MapIterator<K, V> {
+		public MapIterator (Gee.MapIterator<K, Collection<V>>? outer) {
+			base (outer);
+		}
+
+		public K get_key () {
+			assert (valid);
+			return outer.get_key ();
+		}
+
+		public V get_value () {
+			assert (valid);
+			return inner.get ();
+		}
+
+		public void set_value (V value) {
+			assert_not_reached ();
+		}
+
+		public bool mutable { get { return false; } }
+	}
+
 	// Future-proofing
 	internal virtual void reserved0() {}
 	internal virtual void reserved1() {}
diff --git a/gee/multimap.vala b/gee/multimap.vala
index a3f153d..49a17fc 100644
--- a/gee/multimap.vala
+++ b/gee/multimap.vala
@@ -108,6 +108,13 @@ public interface Gee.MultiMap<K,V> : Object {
 	public abstract void clear ();
 
 	/**
+	 * Returns an iterator for this map.
+	 *
+	 * @return a map iterator
+	 */
+	public abstract MapIterator<K, V> map_iterator ();
+
+	/**
 	 * The type of the keys in this multimap.
 	 */
 	public abstract Type key_type { get; }