content: /*
   * 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.
   */
  // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  package accord.utils;
  
  import java.nio.ByteBuffer;
  
  import static accord.utils.BitUtils.readLeastSignificantBytes;
  import static accord.utils.BitUtils.writeMostSignificantBytes;
  
  /**
   * Borrows idea from
   * https://developers.google.com/protocol-buffers/docs/encoding#varints
   */
  public class VIntCoding
  {
      /**
       * Throw when attempting to decode a vint and the output type
       * doesn't have enough space to fit the value that was decoded
       */
      public static class VIntOutOfRangeException extends RuntimeException
      {
          public final long value;
  
          private VIntOutOfRangeException(long value)
          {
              super(value + " is out of range for a 32-bit integer");
              this.value = value;
          }
      }
  
      public static long readUnsignedVInt(ByteBuffer in)
      {
          byte firstByte = in.get();
          if (firstByte >= 0)
              return firstByte;
  
          int extraBytes = VIntCoding.numberOfExtraBytesToRead(firstByte);
          long retval = readLeastSignificantBytes(extraBytes, in);
          // remove the non-value bits from the first byte
          firstByte &= VIntCoding.firstByteValueMask(extraBytes);
          // shift the first byte up to its correct position
          retval |= (long) firstByte << (extraBytes * 8);
          return retval;
  
      }
  
      /**
       * Computes size of an unsigned vint that starts at readerIndex of the provided ByteBuf.
       *
       * @return -1 if there are not enough bytes in the input to calculate the size; else, the vint unsigned value size in bytes.
       */
      public static int sizeOfUnsignedVInt(ByteBuffer input, int readerIndex)
      {
          return sizeOfUnsignedVInt(input, readerIndex, input.limit());
      }
      public static int sizeOfUnsignedVInt(ByteBuffer input, int readerIndex, int readerLimit)
      {
          if (readerIndex >= readerLimit)
              return -1;
  
          int firstByte = input.get(readerIndex);
          return 1 + ((firstByte >= 0) ? 0 : numberOfExtraBytesToRead(firstByte));
      }
  
      public static long readVInt(ByteBuffer input)
      {
          return decodeZigZag64(readUnsignedVInt(input));
      }
  
      /**
       * Read up to a 32-bit integer.
       *
       * This method assumes the original integer was written using {@link #writeUnsignedVInt32(int, ByteBuffer)}
       * or similar that doesn't zigzag encodes the vint.
       *
       * @throws VIntOutOfRangeException If the vint doesn't fit into a 32-bit integer
       */
      public static int readUnsignedVInt32(ByteBuffer input)
      {
          return checkedCast(readUnsignedVInt(input));
      }
  
      // & this with the first byte to give the value part for a given extraBytesToRead encoded in the byte
      public static int firstByteValueMask(int extraBytesToRead)
      {
          // by including the known 0bit in the mask, we can use this for encodeExtraBytesToRead
          return 0xff >> extraBytesToRead;
      }
  
      public static int encodeExtraBytesToRead(int extraBytesToRead)
      {
          // because we have an extra bit in the value mask, we just need to invert it
          return ~firstByteValueMask(extraBytesToRead);
      }
  
      public static int numberOfExtraBytesToRead(int firstByte)
      {
          // we count number of set upper bits; so if we simply invert all of the bits, we're golden
          // this is aided by the fact that we only work with negative numbers, so when upcast to an int all
          // of the new upper bits are also set, so by inverting we set all of them to zero
          return Integer.numberOfLeadingZeros(~firstByte) - 24;
      }
  
      public static void writeUnsignedVInt(long value, ByteBuffer output)
      {
          int size = VIntCoding.sizeOfUnsignedVInt(value);
          if (size == 1)
          {
              output.put((byte)value);
          }
          else if (size < 9)
          {
              int shift = (8 - size) << 3;
              int extraBytes = size - 1;
              long mask = (long)VIntCoding.encodeExtraBytesToRead(extraBytes) << 56;
              long register = (value << shift) | mask;
              writeMostSignificantBytes(register, size, output);
          }
          else
          {
              output.put((byte)0xff);
              output.putLong(value);
          }
      }
  
      public static void writeUnsignedVInt32(int value, ByteBuffer output)
      {
          writeUnsignedVInt((long)value, output);
      }
  
      public static void writeVInt(long value, ByteBuffer output)
      {
          writeUnsignedVInt(encodeZigZag64(value), output);
      }
  
      public static void writeVInt32(int value, ByteBuffer output)
      {
          writeVInt((long)value, output);
      }
  
      /**
       * Decode a ZigZag-encoded 64-bit value.  ZigZag encodes signed integers
       * into values that can be efficiently encoded with varint.  (Otherwise,
       * negative values must be sign-extended to 64 bits to be varint encoded,
       * thus always taking 10 bytes on the wire.)
       *
       * @param n An unsigned 64-bit integer, stored in a signed int because
       *          Java has no explicit unsigned support.
       * @return A signed 64-bit integer.
       */
      public static long decodeZigZag64(final long n)
      {
          return (n >>> 1) ^ -(n & 1);
      }
  
      /**
       * Encode a ZigZag-encoded 64-bit value.  ZigZag encodes signed integers
       * into values that can be efficiently encoded with varint.  (Otherwise,
       * negative values must be sign-extended to 64 bits to be varint encoded,
       * thus always taking 10 bytes on the wire.)
       *
       * @param n A signed 64-bit integer.
       * @return An unsigned 64-bit integer, stored in a signed int because
       *         Java has no explicit unsigned support.
       */
      public static long encodeZigZag64(final long n)
      {
          // Note:  the right-shift must be arithmetic
          return (n << 1) ^ (n >> 63);
      }
  
      /** Compute the number of bytes that would be needed to encode a varint. */
      public static int sizeOfVInt(final long param)
      {
          return sizeOfUnsignedVInt(encodeZigZag64(param));
      }
  
      /** Compute the number of bytes that would be needed to encode an unsigned varint. */
      public static int sizeOfUnsignedVInt(final long value)
      {
          int magnitude = Long.numberOfLeadingZeros(value | 1); // | with 1 to ensure magntiude <= 63, so (63 - 1) / 7 <= 8
          // the formula below is hand-picked to match the original 9 - ((magnitude - 1) / 7)
          return (639 - magnitude * 9) >> 6;
      }
  
      public static int checkedCast(long value)
      {
          int result = (int)value;
          if ((long)result != value)
              throw new VIntOutOfRangeException(value);
          return result;
      }
  }
  