137 lines
4.2 KiB
Java
137 lines
4.2 KiB
Java
/*
|
|
* Copyright (C) 2006 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 com.android.utils;
|
|
|
|
import java.lang.reflect.Array;
|
|
|
|
// XXX these should be changed to reflect the actual memory allocator we use.
|
|
// it looks like right now objects want to be powers of 2 minus 8
|
|
// and the array size eats another 4 bytes
|
|
|
|
/**
|
|
* ArrayUtils contains some methods that you can call to find out
|
|
* the most efficient increments by which to grow arrays.
|
|
*/
|
|
/* package */ class ArrayUtils
|
|
{
|
|
private static final Object[] EMPTY = new Object[0];
|
|
private static final int CACHE_SIZE = 73;
|
|
private static Object[] sCache = new Object[CACHE_SIZE];
|
|
|
|
private ArrayUtils() { /* cannot be instantiated */ }
|
|
|
|
public static int idealByteArraySize(int need) {
|
|
for (int i = 4; i < 32; i++)
|
|
if (need <= (1 << i) - 12)
|
|
return (1 << i) - 12;
|
|
|
|
return need;
|
|
}
|
|
|
|
public static int idealBooleanArraySize(int need) {
|
|
return idealByteArraySize(need);
|
|
}
|
|
|
|
public static int idealShortArraySize(int need) {
|
|
return idealByteArraySize(need * 2) / 2;
|
|
}
|
|
|
|
public static int idealCharArraySize(int need) {
|
|
return idealByteArraySize(need * 2) / 2;
|
|
}
|
|
|
|
public static int idealIntArraySize(int need) {
|
|
return idealByteArraySize(need * 4) / 4;
|
|
}
|
|
|
|
public static int idealFloatArraySize(int need) {
|
|
return idealByteArraySize(need * 4) / 4;
|
|
}
|
|
|
|
public static int idealObjectArraySize(int need) {
|
|
return idealByteArraySize(need * 4) / 4;
|
|
}
|
|
|
|
public static int idealLongArraySize(int need) {
|
|
return idealByteArraySize(need * 8) / 8;
|
|
}
|
|
|
|
/**
|
|
* Checks if the beginnings of two byte arrays are equal.
|
|
*
|
|
* @param array1 the first byte array
|
|
* @param array2 the second byte array
|
|
* @param length the number of bytes to check
|
|
* @return true if they're equal, false otherwise
|
|
*/
|
|
public static boolean equals(byte[] array1, byte[] array2, int length) {
|
|
if (array1 == array2) {
|
|
return true;
|
|
}
|
|
if (array1 == null || array2 == null || array1.length < length || array2.length < length) {
|
|
return false;
|
|
}
|
|
for (int i = 0; i < length; i++) {
|
|
if (array1[i] != array2[i]) {
|
|
return false;
|
|
}
|
|
}
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* Returns an empty array of the specified type. The intent is that
|
|
* it will return the same empty array every time to avoid reallocation,
|
|
* although this is not guaranteed.
|
|
*/
|
|
@SuppressWarnings("unchecked")
|
|
public static <T> T[] emptyArray(Class<T> kind) {
|
|
if (kind == Object.class) {
|
|
return (T[]) EMPTY;
|
|
}
|
|
|
|
int bucket = ((System.identityHashCode(kind) / 8) & 0x7FFFFFFF) % CACHE_SIZE;
|
|
Object cache = sCache[bucket];
|
|
|
|
if (cache == null || cache.getClass().getComponentType() != kind) {
|
|
cache = Array.newInstance(kind, 0);
|
|
sCache[bucket] = cache;
|
|
|
|
// Log.e("cache", "new empty " + kind.getName() + " at " + bucket);
|
|
}
|
|
|
|
return (T[]) cache;
|
|
}
|
|
|
|
/**
|
|
* Checks that value is present as at least one of the elements of the array.
|
|
* @param array the array to check in
|
|
* @param value the value to check for
|
|
* @return true if the value is present in the array
|
|
*/
|
|
public static <T> boolean contains(T[] array, T value) {
|
|
for (T element : array) {
|
|
if (element == null) {
|
|
if (value == null) return true;
|
|
} else {
|
|
if (value != null && element.equals(value)) return true;
|
|
}
|
|
}
|
|
return false;
|
|
}
|
|
}
|