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// Copyright 2016 The Bazel Authors. All Rights Reserved.
//
// 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.google.testing.coverage;
import java.util.Arrays;
/**
* Abstracts bit field operations.
*/
public class BitField {
private byte[] bytes;
private static final int[] BIT_COUNT_LOOKUP = new int[256];
static {
BIT_COUNT_LOOKUP[0] = 0;
BIT_COUNT_LOOKUP[1] = 1;
for (int i = 2; i < 256; i += 2) {
int count = BIT_COUNT_LOOKUP[i / 2];
BIT_COUNT_LOOKUP[i] = count;
BIT_COUNT_LOOKUP[i + 1] = count + 1;
}
}
public BitField() {
this(new byte[0]);
}
public BitField(byte[] bytes) {
this.bytes = bytes.clone();
}
/**
* Returns a copy of the underlying byte array.
*
* @return byte array copy
*/
public byte[] getBytes() {
return bytes.clone();
}
/**
* Sets or clears a bit at the given index.
*
* @param index bit index
*/
public void setBit(int index) {
setBit(index, true);
}
/**
* Clears a bit at the given index
*
* @param index bit index
*/
public void clearBit(int index) {
setBit(index, false);
}
/**
* Sets or clears a bit at the given index.
*
* @param index bit index
*/
private void setBit(int index, boolean isSet) {
int byteIndex = index / 8;
int newByteSize = byteIndex + 1;
if (bytes.length < newByteSize) {
bytes = Arrays.copyOf(bytes, newByteSize);
}
int bitIndex = index % 8;
int mask = 1 << bitIndex;
if (isSet) {
bytes[byteIndex] = (byte) (bytes[byteIndex] | mask);
} else {
bytes[byteIndex] = (byte) (bytes[byteIndex] & ~mask);
}
}
/**
* Checks whether a bit at the given index is set.
*
* @param index bit index
* @return true if set, false otherwise
*/
public boolean isBitSet(int index) {
int byteIndex = index / 8;
if (byteIndex >= bytes.length) {
return false;
}
int bitIndex = index % 8;
int mask = 1 << bitIndex;
return (bytes[byteIndex] & mask) != 0;
}
/** Performs a non-destructive bit-wise "and" of this bit field with another one. */
public BitField and(BitField other) {
int size = Math.min(bytes.length, other.bytes.length);
byte[] result = new byte[size];
for (int i = 0; i < size; i++) {
result[i] = (byte) (bytes[i] & other.bytes[i]);
}
return new BitField(result);
}
/**
* Performs a non-destructive bit-wise merge of this bit field and another one.
*
* @param other the other bit field
* @return this bit field
*/
public BitField or(BitField other) {
byte[] largerArray, smallerArray;
if (bytes.length < other.bytes.length) {
largerArray = other.bytes;
smallerArray = bytes;
} else {
largerArray = bytes;
smallerArray = other.bytes;
}
// Start out with a copy of the larger of the two arrays.
byte[] result = Arrays.copyOf(largerArray, largerArray.length);
for (int i = 0; i < smallerArray.length; i++) {
result[i] |= smallerArray[i];
}
return new BitField(result);
}
/**
* Compares two bit fields for equality.
*
* @param obj another object
* @return true if the other object is a bit field with the same bits set
*/
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (!(obj instanceof BitField)) {
return false;
}
return Arrays.equals(bytes, ((BitField) obj).bytes);
}
/**
* Compare a BitField object with an array of bytes
*
* @param other a byte array to compare to
* @return true if the underlying byte array is equal to the given byte array
*/
public boolean equals(byte[] other) {
return Arrays.equals(bytes, other);
}
@Override
public int hashCode() {
return Arrays.hashCode(bytes);
}
public int countBitsSet() {
int count = 0;
for (byte b : bytes) {
// JAVA doesn't have the concept of unsigned byte; need to & with 255
// to avoid exception of IndexOutOfBoundException when b < 0.
count += BIT_COUNT_LOOKUP[0xFF & b];
}
return count;
}
public BitField not() {
byte[] invertedBytes = new byte[bytes.length];
for (int i = 0; i < bytes.length; i++) {
invertedBytes[i] = Integer.valueOf(~bytes[i]).byteValue();
}
return new BitField(invertedBytes);
}
public int sizeInBits() {
return bytes.length * 8;
}
public boolean any() {
for (int i = 0; i < bytes.length; i++) {
if (bytes[i] != (byte) 0) {
return true;
}
}
return false;
}
}
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