/* * Copyright (C) 2011 The Android Open Source Project * * 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 android.util; import com.android.internal.util.ArrayUtils; /** * SparseLongArrays map integers to longs. Unlike a normal array of longs, * there can be gaps in the indices. It is intended to be more memory efficient * than using a HashMap to map Integers to Longs, both because it avoids * auto-boxing keys and values and its data structure doesn't rely on an extra entry object * for each mapping. * *
Note that this container keeps its mappings in an array data structure, * using a binary search to find keys. The implementation is not intended to be appropriate for * data structures * that may contain large numbers of items. It is generally slower than a traditional * HashMap, since lookups require a binary search and adds and removes require inserting * and deleting entries in the array. For containers holding up to hundreds of items, * the performance difference is not significant, less than 50%.
*/ public class SparseLongArray implements Cloneable { static final long[] EMPTY_LONGS = new long[0]; private int[] mKeys; private long[] mValues; private int mSize; /** * Creates a new SparseLongArray containing no mappings. */ public SparseLongArray() { this(10); } /** * Creates a new SparseLongArray containing no mappings that will not * require any additional memory allocation to store the specified * number of mappings. If you supply an initial capacity of 0, the * sparse array will be initialized with a light-weight representation * not requiring any additional array allocations. */ public SparseLongArray(int initialCapacity) { if (initialCapacity == 0) { mKeys = SparseArray.EMPTY_INTS; mValues = EMPTY_LONGS; } else { initialCapacity = ArrayUtils.idealLongArraySize(initialCapacity); mKeys = new int[initialCapacity]; mValues = new long[initialCapacity]; } mSize = 0; } @Override public SparseLongArray clone() { SparseLongArray clone = null; try { clone = (SparseLongArray) super.clone(); clone.mKeys = mKeys.clone(); clone.mValues = mValues.clone(); } catch (CloneNotSupportedException cnse) { /* ignore */ } return clone; } /** * Gets the long mapped from the specified key, or0
* if no such mapping has been made.
*/
public long get(int key) {
return get(key, 0);
}
/**
* Gets the long mapped from the specified key, or the specified value
* if no such mapping has been made.
*/
public long get(int key, long valueIfKeyNotFound) {
int i = SparseArray.binarySearch(mKeys, mSize, key);
if (i < 0) {
return valueIfKeyNotFound;
} else {
return mValues[i];
}
}
/**
* Removes the mapping from the specified key, if there was any.
*/
public void delete(int key) {
int i = SparseArray.binarySearch(mKeys, mSize, key);
if (i >= 0) {
removeAt(i);
}
}
/**
* Removes the mapping at the given index.
*/
public void removeAt(int index) {
System.arraycopy(mKeys, index + 1, mKeys, index, mSize - (index + 1));
System.arraycopy(mValues, index + 1, mValues, index, mSize - (index + 1));
mSize--;
}
/**
* Adds a mapping from the specified key to the specified value,
* replacing the previous mapping from the specified key if there
* was one.
*/
public void put(int key, long value) {
int i = SparseArray.binarySearch(mKeys, mSize, key);
if (i >= 0) {
mValues[i] = value;
} else {
i = ~i;
if (mSize >= mKeys.length) {
growKeyAndValueArrays(mSize + 1);
}
if (mSize - i != 0) {
System.arraycopy(mKeys, i, mKeys, i + 1, mSize - i);
System.arraycopy(mValues, i, mValues, i + 1, mSize - i);
}
mKeys[i] = key;
mValues[i] = value;
mSize++;
}
}
/**
* Returns the number of key-value mappings that this SparseIntArray
* currently stores.
*/
public int size() {
return mSize;
}
/**
* Given an index in the range 0...size()-1
, returns
* the key from the index
th key-value mapping that this
* SparseLongArray stores.
*/
public int keyAt(int index) {
return mKeys[index];
}
/**
* Given an index in the range 0...size()-1
, returns
* the value from the index
th key-value mapping that this
* SparseLongArray stores.
*/
public long valueAt(int index) {
return mValues[index];
}
/**
* Returns the index for which {@link #keyAt} would return the
* specified key, or a negative number if the specified
* key is not mapped.
*/
public int indexOfKey(int key) {
return SparseArray.binarySearch(mKeys, mSize, key);
}
/**
* Returns an index for which {@link #valueAt} would return the
* specified key, or a negative number if no keys map to the
* specified value.
* Beware that this is a linear search, unlike lookups by key,
* and that multiple keys can map to the same value and this will
* find only one of them.
*/
public int indexOfValue(long value) {
for (int i = 0; i < mSize; i++)
if (mValues[i] == value)
return i;
return -1;
}
/**
* Removes all key-value mappings from this SparseIntArray.
*/
public void clear() {
mSize = 0;
}
/**
* Puts a key/value pair into the array, optimizing for the case where
* the key is greater than all existing keys in the array.
*/
public void append(int key, long value) {
if (mSize != 0 && key <= mKeys[mSize - 1]) {
put(key, value);
return;
}
int pos = mSize;
if (pos >= mKeys.length) {
growKeyAndValueArrays(pos + 1);
}
mKeys[pos] = key;
mValues[pos] = value;
mSize = pos + 1;
}
private void growKeyAndValueArrays(int minNeededSize) {
int n = ArrayUtils.idealLongArraySize(minNeededSize);
int[] nkeys = new int[n];
long[] nvalues = new long[n];
System.arraycopy(mKeys, 0, nkeys, 0, mKeys.length);
System.arraycopy(mValues, 0, nvalues, 0, mValues.length);
mKeys = nkeys;
mValues = nvalues;
}
}