ArrayBackedFMap.java

/*
 * 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 org.jetbrains.annotations.NotNull;

import java.util.Arrays;

public class ArrayBackedFMap implements KeyFMap {
  static final int ARRAY_THRESHOLD = 8;
  // Invariant: keys are always sorted
  private final int[] keys;
  private final Object[] values;

  ArrayBackedFMap(@NotNull int[] keys, @NotNull Object[] values) {
    this.keys = keys;
    this.values = values;
  }

  @NotNull
  @Override
  public <V> KeyFMap plus(@NotNull Key<V> key, @NotNull V value) {
    int oldSize = size();
    int keyCode = key.hashCode();
    int keyPos = Arrays.binarySearch(keys, keyCode);
    if (keyPos >= 0) {
      if (values[keyPos] == value) {
        return this;
      }
      Object[] newValues = values.clone();
      newValues[keyPos] = value;
      // Can reuse keys as it is never mutated
      return new ArrayBackedFMap(keys, newValues);
    }
    if (oldSize < ARRAY_THRESHOLD) {
      int[] newKeys = ArrayUtil.insert(keys, -keyPos - 1, keyCode);
      Object[] newValues = ArrayUtil.insert(values, -keyPos - 1, value);
      return new ArrayBackedFMap(newKeys, newValues);
    }
    return new MapBackedFMap(keys, keyCode, values, value);
  }

  public int size() {
    return keys.length;
  }

  @NotNull
  @Override
  public KeyFMap minus(@NotNull Key<?> key) {
    int oldSize = size();
    int keyCode = key.hashCode();
    for (int i = 0; i< oldSize; i++) {
      int oldKey = keys[i];
      if (keyCode == oldKey) {
        if (oldSize == 3) {
          int i1 = (2-i)/2;
          int i2 = 3 - (i+2)/2;
          Key<Object> key1 = Key.getKeyByIndex(keys[i1]);
          Key<Object> key2 = Key.getKeyByIndex(keys[i2]);
          if (key1 == null && key2 == null) return EMPTY_MAP;
          if (key1 == null) return new OneElementFMap(key2, values[i2]);
          if (key2 == null) return new OneElementFMap(key1, values[i1]);
          return new PairElementsFMap(key1, values[i1], key2, values[i2]);
        }
        int[] newKeys = ArrayUtil.remove(keys, i);
        Object[] newValues = ArrayUtil.remove(values, i, ArrayUtil.OBJECT_ARRAY_FACTORY);
        return new ArrayBackedFMap(newKeys, newValues);
      }
    }
    return this;
  }

  @Override
  public <V> V get(@NotNull Key<V> key) {
    int oldSize = size();
    int keyCode = key.hashCode();
    for (int i = 0; i < oldSize; i++) {
      int oldKey = keys[i];
      if (keyCode == oldKey) {
        //noinspection unchecked
        return (V)values[i];
      }
    }
    return null;
  }

  @Override
  public String toString() {
    StringBuilder s = new StringBuilder("{");
    for (int i = 0; i < keys.length; i++) {
      int key = keys[i];
      Object value = values[i];
      s.append((s.length() == 1) ? "" : ", ").append(Key.getKeyByIndex(key)).append("=").append(value);
    }
    return s.append("}").toString();
  }

  @Override
  public boolean isEmpty() {
    return false;
  }

  @Override
  public int getValueIdentityHashCode() {
    int hash = 0;
    for (int i = 0; i < keys.length; i++) {
      hash = hash * 31 + keys[i];
      hash = hash * 31 + System.identityHashCode(values[i]);
    }
    return hash;
  }

  @NotNull
  @Override
  public Key[] getKeys() {
    return getKeysByIndices(keys);
  }

  @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;
  }

  @Override
  public int hashCode() {
    int hash = 0;
    int length = keys.length;
    for (int i = 0; i < length; i++) {
      // key index is its hashcode
      hash += (keys[i] ^ values[i].hashCode());
    }
    return hash;
  }

  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (!(o instanceof ArrayBackedFMap)) return false;

    ArrayBackedFMap map = (ArrayBackedFMap)o;
    if (map.size() != size()) return false;

    int length = keys.length;
    for (int i = 0; i < length; i++) {
      if (keys[i] != map.keys[i] || !values[i].equals(map.values[i])) return false;
    }
    return true;
  }

  @Override
  public boolean equalsByReference(KeyFMap o) {
    if (this == o) return true;
    if (!(o instanceof ArrayBackedFMap)) return false;

    ArrayBackedFMap map = (ArrayBackedFMap)o;
    if (map.size() != size()) return false;

    int length = keys.length;
    for (int i = 0; i < length; i++) {
      if (keys[i] != map.keys[i] || values[i] != map.values[i]) return false;
    }
    return true;
  }
}