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/*
* Copyright (C) 2017 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.internal.util;
import android.annotation.Nullable;
import android.text.TextUtils;
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.util.Objects;
import java.util.UUID;
import java.util.function.IntFunction;
/**
* A utility class for handling unsigned integers and unsigned arithmetics, as well as syntactic
* sugar methods for {@link ByteBuffer}. Useful for networking and packet manipulations.
* {@hide}
*/
public final class BitUtils {
private BitUtils() {}
public static boolean maskedEquals(long a, long b, long mask) {
return (a & mask) == (b & mask);
}
public static boolean maskedEquals(byte a, byte b, byte mask) {
return (a & mask) == (b & mask);
}
public static boolean maskedEquals(byte[] a, byte[] b, @Nullable byte[] mask) {
if (a == null || b == null) return a == b;
Preconditions.checkArgument(a.length == b.length, "Inputs must be of same size");
if (mask == null) return Arrays.equals(a, b);
Preconditions.checkArgument(a.length == mask.length, "Mask must be of same size as inputs");
for (int i = 0; i < mask.length; i++) {
if (!maskedEquals(a[i], b[i], mask[i])) return false;
}
return true;
}
public static boolean maskedEquals(UUID a, UUID b, @Nullable UUID mask) {
if (mask == null) {
return Objects.equals(a, b);
}
return maskedEquals(a.getLeastSignificantBits(), b.getLeastSignificantBits(),
mask.getLeastSignificantBits())
&& maskedEquals(a.getMostSignificantBits(), b.getMostSignificantBits(),
mask.getMostSignificantBits());
}
public static int[] unpackBits(long val) {
int size = Long.bitCount(val);
int[] result = new int[size];
int index = 0;
int bitPos = 0;
while (val != 0) {
if ((val & 1) == 1) result[index++] = bitPos;
val = val >>> 1;
bitPos++;
}
return result;
}
public static long packBits(int[] bits) {
long packed = 0;
for (int b : bits) {
packed |= (1L << b);
}
return packed;
}
public static int uint8(byte b) {
return b & 0xff;
}
public static int uint16(short s) {
return s & 0xffff;
}
public static int uint16(byte hi, byte lo) {
return ((hi & 0xff) << 8) | (lo & 0xff);
}
public static long uint32(int i) {
return i & 0xffffffffL;
}
public static int bytesToBEInt(byte[] bytes) {
return (uint8(bytes[0]) << 24)
+ (uint8(bytes[1]) << 16)
+ (uint8(bytes[2]) << 8)
+ (uint8(bytes[3]));
}
public static int bytesToLEInt(byte[] bytes) {
return Integer.reverseBytes(bytesToBEInt(bytes));
}
public static int getUint8(ByteBuffer buffer, int position) {
return uint8(buffer.get(position));
}
public static int getUint16(ByteBuffer buffer, int position) {
return uint16(buffer.getShort(position));
}
public static long getUint32(ByteBuffer buffer, int position) {
return uint32(buffer.getInt(position));
}
public static void put(ByteBuffer buffer, int position, byte[] bytes) {
final int original = buffer.position();
buffer.position(position);
buffer.put(bytes);
buffer.position(original);
}
public static boolean isBitSet(long flags, int bitIndex) {
return (flags & bitAt(bitIndex)) != 0;
}
public static long bitAt(int bitIndex) {
return 1L << bitIndex;
}
public static String flagsToString(int flags, IntFunction<String> getFlagName) {
StringBuilder builder = new StringBuilder();
int count = 0;
while (flags != 0) {
final int flag = 1 << Integer.numberOfTrailingZeros(flags);
flags &= ~flag;
if (count > 0) builder.append(", ");
builder.append(getFlagName.apply(flag));
count++;
}
TextUtils.wrap(builder, "[", "]");
return builder.toString();
}
/**
* Converts long to byte array
*/
public static byte[] toBytes(long l) {
return ByteBuffer.allocate(8).putLong(l).array();
}
/**
* 0b01000 -> 0b01111
*/
public static int flagsUpTo(int lastFlag) {
return lastFlag <= 0 ? 0 : lastFlag | flagsUpTo(lastFlag >> 1);
}
/**
* 0b00010, 0b01000 -> 0b01110
*/
public static int flagsWithin(int firstFlag, int lastFlag) {
return (flagsUpTo(lastFlag) & ~flagsUpTo(firstFlag)) | firstFlag;
}
}
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