content: /*
   * 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 |= (1 << 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();
      }
  }
  