Add the ability to get keys and values from KeyFMap

platform/util/src/com/intellij/util/keyFMap/ArrayBackedFMap.java

@@ -140,7 +140,25 @@ public class ArrayBackedFMap implements KeyFMap {
     return keys;
   }
 
+  @NotNull
+  @Override
+  public Key[] getKeys() {
+    return getKeysByIndices(keys);
+  }
+
+  @NotNull
   public Object[] getValues() {
     return values;
   }
+
+  @NotNull
+  static Key[] getKeysByIndices(int[] indexes) {
+    Key[] result = new Key[indexes.length];
+
+    for (int i =0; i < indexes.length; i++) {
+      result[i] = Key.getKeyByIndex(indexes[i]);
+    }
+
+    return result;
+  }
 }

platform/util/src/com/intellij/util/keyFMap/EmptyFMap.java

@@ -19,6 +19,8 @@ import com.intellij.openapi.util.Key;
 import org.jetbrains.annotations.NotNull;
 
 class EmptyFMap implements KeyFMap {
+  private static final Key[] EMPTY_KEYS_ARRAY = {};
+
   EmptyFMap() {
   }
 
@@ -39,6 +41,12 @@ class EmptyFMap implements KeyFMap {
     return null;
   }
 
+  @NotNull
+  @Override
+  public Key[] getKeys() {
+    return EMPTY_KEYS_ARRAY;
+  }
+
   @Override
   public String toString() {
     return "<empty>";

platform/util/src/com/intellij/util/keyFMap/KeyFMap.java

@@ -36,6 +36,9 @@ public interface KeyFMap {
   @Nullable
   <V> V get(@NotNull Key<V> key);
 
+  @NotNull
+  Key[] getKeys();
+
   String toString();
 
   boolean isEmpty();

platform/util/src/com/intellij/util/keyFMap/MapBackedFMap.java

@@ -21,6 +21,8 @@ import gnu.trove.TIntObjectHashMap;
 import gnu.trove.TIntObjectProcedure;
 import org.jetbrains.annotations.NotNull;
 
+import static com.intellij.util.keyFMap.ArrayBackedFMap.getKeysByIndices;
+
 class MapBackedFMap extends TIntObjectHashMap<Object> implements KeyFMap {
   private MapBackedFMap(@NotNull MapBackedFMap oldMap, final int exclude) {
     super(oldMap.size());
@@ -86,6 +88,12 @@ class MapBackedFMap extends TIntObjectHashMap<Object> implements KeyFMap {
     return (V)get(key.hashCode());
   }
 
+  @NotNull
+  @Override
+  public Key[] getKeys() {
+    return getKeysByIndices(keys());
+  }
+
   @Override
   public String toString() {
     final StringBuilder s = new StringBuilder();

platform/util/src/com/intellij/util/keyFMap/OneElementFMap.java

@@ -46,6 +46,12 @@ public class OneElementFMap<V> implements KeyFMap {
     return myKey == key ? (V)myValue : null;
   }
 
+  @NotNull
+  @Override
+  public Key[] getKeys() {
+    return new Key[] { myKey };
+  }
+
   @Override
   public String toString() {
     return "<" + myKey + " -> " + myValue+">";

platform/util/src/com/intellij/util/keyFMap/PairElementsFMap.java

@@ -54,6 +54,12 @@ public class PairElementsFMap implements KeyFMap {
     return key == key1 ? (V)value1 : key == key2 ? (V)value2 : null;
   }
 
+  @NotNull
+  @Override
+  public Key[] getKeys() {
+    return new Key[] { key1, key2 };
+  }
+
   @Override
   public String toString() {
     return "Pair: (" + key1 + " -> " + value1 + "; " + key2 + " -> " + value2 + ")";

platform/util/testSrc/com/intellij/util/keyFMap/KeyFMapTest.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2000-2015 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.intellij.util.keyFMap;
+
+import com.intellij.openapi.util.Key;
+import com.intellij.util.ArrayUtil;
+import junit.framework.TestCase;
+
+public class KeyFMapTest extends TestCase {
+  private final static Key[] KEYS = {
+    Key.create("K0"),
+    Key.create("K1"),
+    Key.create("K2"),
+    Key.create("K3"),
+    Key.create("K4"),
+    Key.create("K5"),
+    Key.create("K6"),
+    Key.create("K7"),
+    Key.create("K8"),
+    Key.create("K9")
+  };
+
+  private final static Object[] VALUES = { "V0", "V1", "V2", "V3", "V4", "V5", "V6", "V7", "V8", "V9" };
+
+  private static KeyFMap createKeyFMap(Key[] keys, Object[] values, int size) {
+    KeyFMap fmap = KeyFMap.EMPTY_MAP;
+
+    for (int i = 0; i < size; i++) {
+      fmap = fmap.plus(keys[i], values[i]);
+    }
+
+    return fmap;
+  }
+
+  private static void doTestGetKeys(int size) {
+    KeyFMap map = createKeyFMap(KEYS, VALUES, size);
+
+    Key[] keys = map.getKeys();
+
+    assertEquals(size, keys.length);
+
+    for (int i = 0; i < size; i++) {
+      int index = ArrayUtil.indexOf(keys, KEYS[i], 0, size);
+      assertTrue("Key" + " not found: " + KEYS[i], index >= 0);
+    }
+  }
+
+  public void testGetKeysOnEmptyFMap() {
+    doTestGetKeys(0);
+  }
+
+  public void testGetKeysOnOneElementFMap() {
+    doTestGetKeys(1);
+  }
+
+  public void testGetKeysOnTwoElementFMap() {
+    doTestGetKeys(2);
+  }
+
+  public void testGetKeysOnArrayBackedFMap() {
+    doTestGetKeys(5);
+  }
+
+  public void testGetKeysOnMapBackedFMap() {
+    doTestGetKeys(10);
+  }
+}