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ByteArrayMethods.java
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ByteArrayMethods.java
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.spark.unsafe.array;
import org.apache.spark.unsafe.Platform;
import static org.apache.spark.unsafe.Platform.BYTE_ARRAY_OFFSET;
public class ByteArrayMethods {
private ByteArrayMethods() {
// Private constructor, since this class only contains static methods.
}
/** Returns the next number greater or equal num that is power of 2. */
public static long nextPowerOf2(long num) {
final long highBit = Long.highestOneBit(num);
return (highBit == num) ? num : highBit << 1;
}
public static int roundNumberOfBytesToNearestWord(int numBytes) {
return (int)roundNumberOfBytesToNearestWord((long)numBytes);
}
public static long roundNumberOfBytesToNearestWord(long numBytes) {
long remainder = numBytes & 0x07; // This is equivalent to `numBytes % 8`
if (remainder == 0) {
return numBytes;
} else {
return numBytes + (8 - remainder);
}
}
// Some JVMs can't allocate arrays of length Integer.MAX_VALUE; actual max is somewhat smaller.
// Be conservative and lower the cap a little.
// Refer to "http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/tip/src/share/classes/java/util/ArrayList.java#l229"
// This value is word rounded. Use this value if the allocated byte arrays are used to store other
// types rather than bytes.
public static final int MAX_ROUNDED_ARRAY_LENGTH = Integer.MAX_VALUE - 15;
private static final boolean unaligned = Platform.unaligned();
/**
* Optimized byte array equality check for byte arrays.
* @return true if the arrays are equal, false otherwise
*/
public static boolean arrayEquals(
Object leftBase, long leftOffset, Object rightBase, long rightOffset, final long length) {
int i = 0;
// check if stars align and we can get both offsets to be aligned
if (!unaligned && ((leftOffset % 8) == (rightOffset % 8))) {
while ((leftOffset + i) % 8 != 0 && i < length) {
if (Platform.getByte(leftBase, leftOffset + i) !=
Platform.getByte(rightBase, rightOffset + i)) {
return false;
}
i += 1;
}
}
// for architectures that support unaligned accesses, chew it up 8 bytes at a time
if (unaligned || (((leftOffset + i) % 8 == 0) && ((rightOffset + i) % 8 == 0))) {
while (i <= length - 8) {
if (Platform.getLong(leftBase, leftOffset + i) !=
Platform.getLong(rightBase, rightOffset + i)) {
return false;
}
i += 8;
}
}
// this will finish off the unaligned comparisons, or do the entire aligned
// comparison whichever is needed.
while (i < length) {
if (Platform.getByte(leftBase, leftOffset + i) !=
Platform.getByte(rightBase, rightOffset + i)) {
return false;
}
i += 1;
}
return true;
}
public static boolean contains(byte[] arr, byte[] sub) {
if (sub.length == 0) {
return true;
}
byte first = sub[0];
for (int i = 0; i <= arr.length - sub.length; i++) {
if (arr[i] == first && matchAt(arr, sub, i)) {
return true;
}
}
return false;
}
public static boolean startsWith(byte[] array, byte[] target) {
if (target.length > array.length) {
return false;
}
return arrayEquals(array, BYTE_ARRAY_OFFSET, target, BYTE_ARRAY_OFFSET, target.length);
}
public static boolean endsWith(byte[] array, byte[] target) {
if (target.length > array.length) {
return false;
}
return arrayEquals(array, BYTE_ARRAY_OFFSET + array.length - target.length,
target, BYTE_ARRAY_OFFSET, target.length);
}
public static boolean matchAt(byte[] arr, byte[] sub, int pos) {
if (sub.length + pos > arr.length || pos < 0) {
return false;
}
return arrayEquals(arr, BYTE_ARRAY_OFFSET + pos, sub, BYTE_ARRAY_OFFSET, sub.length);
}
}