/*
 * 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.hadoop.hbase.client;

import edu.umd.cs.findbugs.annotations.CheckForNull;
import java.io.DataInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.exceptions.DeserializationException;
import org.apache.hadoop.hbase.util.ByteArrayHashKey;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.HashKey;
import org.apache.hadoop.hbase.util.JenkinsHash;
import org.apache.hadoop.hbase.util.MD5Hash;
import org.apache.hadoop.io.DataInputBuffer;
import org.apache.hadoop.io.IOUtils;
import org.apache.yetus.audience.InterfaceAudience;

import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
import org.apache.hadoop.hbase.shaded.protobuf.generated.HBaseProtos;

/**
 * Information about a region. A region is a range of keys in the whole keyspace of a table, an
 * identifier (a timestamp) for differentiating between subset ranges (after region split) and a
 * replicaId for differentiating the instance for the same range and some status information about
 * the region. The region has a unique name which consists of the following fields:
 * <ul>
 * <li>tableName : The name of the table</li>
 * <li>startKey : The startKey for the region.</li>
 * <li>regionId : A timestamp when the region is created.</li>
 * <li>replicaId : An id starting from 0 to differentiate replicas of the same region range but
 * hosted in separated servers. The same region range can be hosted in multiple locations.</li>
 * <li>encodedName : An MD5 encoded string for the region name.</li>
 * </ul>
 * <br>
 * Other than the fields in the region name, region info contains:
 * <ul>
 * <li>endKey : the endKey for the region (exclusive)</li>
 * <li>split : Whether the region is split</li>
 * <li>offline : Whether the region is offline</li>
 * </ul>
 */
@InterfaceAudience.Public
public interface RegionInfo extends Comparable<RegionInfo> {

  /**
   * Separator used to demarcate the encodedName in a region name in the new format. See description
   * on new format above.
   */
  @InterfaceAudience.Private
  int ENC_SEPARATOR = '.';

  @InterfaceAudience.Private
  int MD5_HEX_LENGTH = 32;

  @InterfaceAudience.Private
  int DEFAULT_REPLICA_ID = 0;

  /**
   * to keep appended int's sorted in string format. Only allows 2 bytes to be sorted for replicaId.
   */
  @InterfaceAudience.Private
  String REPLICA_ID_FORMAT = "%04X";

  @InterfaceAudience.Private
  byte REPLICA_ID_DELIMITER = (byte) '_';

  @InterfaceAudience.Private
  String INVALID_REGION_NAME_FORMAT_MESSAGE = "Invalid regionName format";

  @InterfaceAudience.Private
  Comparator<RegionInfo> COMPARATOR = (RegionInfo lhs, RegionInfo rhs) -> {
    if (rhs == null) {
      return 1;
    }

    // Are regions of same table?
    int result = lhs.getTable().compareTo(rhs.getTable());
    if (result != 0) {
      return result;
    }

    // Compare start keys.
    result = Bytes.compareTo(lhs.getStartKey(), rhs.getStartKey());
    if (result != 0) {
      return result;
    }

    // Compare end keys.
    result = Bytes.compareTo(lhs.getEndKey(), rhs.getEndKey());

    if (result != 0) {
      if (lhs.getStartKey().length != 0 && lhs.getEndKey().length == 0) {
        return 1; // this is last region
      }
      if (rhs.getStartKey().length != 0 && rhs.getEndKey().length == 0) {
        return -1; // o is the last region
      }
      return result;
    }

    // regionId is usually milli timestamp -- this defines older stamps
    // to be "smaller" than newer stamps in sort order.
    if (lhs.getRegionId() > rhs.getRegionId()) {
      return 1;
    } else if (lhs.getRegionId() < rhs.getRegionId()) {
      return -1;
    }

    int replicaDiff = lhs.getReplicaId() - rhs.getReplicaId();
    if (replicaDiff != 0) {
      return replicaDiff;
    }

    if (lhs.isOffline() == rhs.isOffline()) {
      return 0;
    }
    if (lhs.isOffline()) {
      return -1;
    }

    return 1;
  };

  /**
   * Returns Return a short, printable name for this region (usually encoded name) for us logging.
   */
  String getShortNameToLog();

  /** Returns the regionId. */
  long getRegionId();

  /**
   * @return the regionName as an array of bytes.
   * @see #getRegionNameAsString()
   */
  byte[] getRegionName();

  /** Returns Region name as a String for use in logging, etc. */
  String getRegionNameAsString();

  /** Returns the encoded region name. */
  String getEncodedName();

  /** Returns the encoded region name as an array of bytes. */
  byte[] getEncodedNameAsBytes();

  /** Returns the startKey. */
  byte[] getStartKey();

  /** Returns the endKey. */
  byte[] getEndKey();

  /** Returns current table name of the region */
  TableName getTable();

  /** Returns returns region replica id */
  int getReplicaId();

  /** Returns True if has been split and has daughters. */
  boolean isSplit();

  /**
   * @return True if this region is offline.
   * @deprecated since 3.0.0 and will be removed in 4.0.0
   * @see <a href="https://issues.apache.org/jira/browse/HBASE-25210">HBASE-25210</a>
   */
  @Deprecated
  boolean isOffline();

  /**
   * @return True if this is a split parent region.
   * @deprecated since 3.0.0 and will be removed in 4.0.0, Use {@link #isSplit()} instead.
   * @see <a href="https://issues.apache.org/jira/browse/HBASE-25210">HBASE-25210</a>
   */
  @Deprecated
  boolean isSplitParent();

  /** Returns true if this region is a meta region. */
  boolean isMetaRegion();

  /**
   * @return true if the given inclusive range of rows is fully contained by this region. For
   *         example, if the region is foo,a,g and this is passed ["b","c"] or ["a","c"] it will
   *         return true, but if this is passed ["b","z"] it will return false.
   * @throws IllegalArgumentException if the range passed is invalid (ie. end &lt; start)
   */
  boolean containsRange(byte[] rangeStartKey, byte[] rangeEndKey);

  /** Returns true if the given row falls in this region. */
  boolean containsRow(byte[] row);

  /**
   * Does region name contain its encoded name?
   * @param regionName region name
   * @return boolean indicating if this a new format region name which contains its encoded name.
   */
  @InterfaceAudience.Private
  static boolean hasEncodedName(final byte[] regionName) {
    // check if region name ends in ENC_SEPARATOR
    return (regionName.length >= 1)
      && (regionName[regionName.length - 1] == RegionInfo.ENC_SEPARATOR);
  }

  /** Returns the encodedName */
  @InterfaceAudience.Private
  static String encodeRegionName(final byte[] regionName) {
    String encodedName;
    if (hasEncodedName(regionName)) {
      // region is in new format:
      // <tableName>,<startKey>,<regionIdTimeStamp>/encodedName/
      encodedName =
        Bytes.toString(regionName, regionName.length - MD5_HEX_LENGTH - 1, MD5_HEX_LENGTH);
    } else {
      // old format region name. First hbase:meta region also
      // use this format.EncodedName is the JenkinsHash value.
      HashKey<byte[]> key = new ByteArrayHashKey(regionName, 0, regionName.length);
      int hashVal = Math.abs(JenkinsHash.getInstance().hash(key, 0));
      encodedName = String.valueOf(hashVal);
    }
    return encodedName;
  }

  @InterfaceAudience.Private
  static String getRegionNameAsString(byte[] regionName) {
    return getRegionNameAsString(null, regionName);
  }

  @InterfaceAudience.Private
  static String getRegionNameAsString(@CheckForNull RegionInfo ri, byte[] regionName) {
    if (RegionInfo.hasEncodedName(regionName)) {
      // new format region names already have their encoded name.
      return Bytes.toStringBinary(regionName);
    }

    // old format. regionNameStr doesn't have the region name.
    if (ri == null) {
      return Bytes.toStringBinary(regionName) + "." + RegionInfo.encodeRegionName(regionName);
    } else {
      return Bytes.toStringBinary(regionName) + "." + ri.getEncodedName();
    }
  }

  /**
   * @return Return a String of short, printable names for <code>hris</code> (usually encoded name)
   *         for us logging.
   */
  static String getShortNameToLog(RegionInfo... hris) {
    return getShortNameToLog(Arrays.asList(hris));
  }

  /**
   * @return Return a String of short, printable names for <code>hris</code> (usually encoded name)
   *         for us logging.
   */
  static String getShortNameToLog(final List<RegionInfo> ris) {
    return ris.stream().map(RegionInfo::getEncodedName).collect(Collectors.toList()).toString();
  }

  /**
   * Gets the table name from the specified region name.
   * @param regionName to extract the table name from
   * @return Table name
   */
  @InterfaceAudience.Private
  // This method should never be used. Its awful doing parse from bytes.
  // It is fallback in case we can't get the tablename any other way. Could try removing it.
  // Keeping it Audience Private so can remove at later date.
  static TableName getTable(final byte[] regionName) {
    int offset = -1;
    for (int i = 0; i < regionName.length; i++) {
      if (regionName[i] == HConstants.DELIMITER) {
        offset = i;
        break;
      }
    }
    if (offset <= 0) {
      throw new IllegalArgumentException("offset=" + offset);
    }
    byte[] buff = new byte[offset];
    System.arraycopy(regionName, 0, buff, 0, offset);
    return TableName.valueOf(buff);
  }

  /**
   * Gets the start key from the specified region name.
   * @return Start key.
   */
  static byte[] getStartKey(final byte[] regionName) throws IOException {
    return parseRegionName(regionName)[1];
  }

  /**
   * Figure if the passed bytes represent an encoded region name or not.
   * @param regionName A Region name either encoded or not.
   * @return True if <code>regionName</code> represents an encoded name.
   */
  @InterfaceAudience.Private // For use by internals only.
  public static boolean isEncodedRegionName(byte[] regionName) {
    // If not parseable as region name, presume encoded. TODO: add stringency; e.g. if hex.
    return parseRegionNameOrReturnNull(regionName) == null && regionName.length <= MD5_HEX_LENGTH;
  }

  /**
   * Returns A deserialized {@link RegionInfo} or null if we failed deserialize or passed bytes null
   */
  @InterfaceAudience.Private
  static RegionInfo parseFromOrNull(final byte[] bytes) {
    if (bytes == null) return null;
    return parseFromOrNull(bytes, 0, bytes.length);
  }

  /**
   * Returns A deserialized {@link RegionInfo} or null if we failed deserialize or passed bytes null
   */
  @InterfaceAudience.Private
  static RegionInfo parseFromOrNull(final byte[] bytes, int offset, int len) {
    if (bytes == null || len <= 0) return null;
    try {
      return parseFrom(bytes, offset, len);
    } catch (DeserializationException e) {
      return null;
    }
  }

  /**
   * @param bytes A pb RegionInfo serialized with a pb magic prefix.
   * @return A deserialized {@link RegionInfo}
   */
  @InterfaceAudience.Private
  static RegionInfo parseFrom(final byte[] bytes) throws DeserializationException {
    if (bytes == null) return null;
    return parseFrom(bytes, 0, bytes.length);
  }

  /**
   * @param bytes  A pb RegionInfo serialized with a pb magic prefix.
   * @param offset starting point in the byte array
   * @param len    length to read on the byte array
   * @return A deserialized {@link RegionInfo}
   */
  @InterfaceAudience.Private
  static RegionInfo parseFrom(final byte[] bytes, int offset, int len)
    throws DeserializationException {
    if (ProtobufUtil.isPBMagicPrefix(bytes, offset, len)) {
      int pblen = ProtobufUtil.lengthOfPBMagic();
      try {
        HBaseProtos.RegionInfo.Builder builder = HBaseProtos.RegionInfo.newBuilder();
        ProtobufUtil.mergeFrom(builder, bytes, pblen + offset, len - pblen);
        HBaseProtos.RegionInfo ri = builder.build();
        return ProtobufUtil.toRegionInfo(ri);
      } catch (IOException e) {
        throw new DeserializationException(e);
      }
    } else {
      throw new DeserializationException("PB encoded RegionInfo expected");
    }
  }

  static boolean isMD5Hash(String encodedRegionName) {
    if (encodedRegionName.length() != MD5_HEX_LENGTH) {
      return false;
    }

    for (int i = 0; i < encodedRegionName.length(); i++) {
      char c = encodedRegionName.charAt(i);
      if (!((c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f') || (c >= '0' && c <= '9'))) {
        return false;
      }
    }
    return true;
  }

  /**
   * Check whether two regions are adjacent; i.e. lies just before or just after in a table.
   * @return true if two regions are adjacent
   */
  static boolean areAdjacent(RegionInfo regionA, RegionInfo regionB) {
    if (regionA == null || regionB == null) {
      throw new IllegalArgumentException("Can't check whether adjacent for null region");
    }
    if (!regionA.getTable().equals(regionB.getTable())) {
      return false;
    }
    RegionInfo a = regionA;
    RegionInfo b = regionB;
    if (Bytes.compareTo(a.getStartKey(), b.getStartKey()) > 0) {
      a = regionB;
      b = regionA;
    }
    return Bytes.equals(a.getEndKey(), b.getStartKey());
  }

  /**
   * @return This instance serialized as protobuf w/ a magic pb prefix.
   * @see #parseFrom(byte[])
   */
  static byte[] toByteArray(RegionInfo ri) {
    byte[] bytes = ProtobufUtil.toRegionInfo(ri).toByteArray();
    return ProtobufUtil.prependPBMagic(bytes);
  }

  /**
   * Use logging.
   * @param encodedRegionName The encoded regionname.
   * @return <code>hbase:meta</code> if passed <code>1028785192</code> else returns
   *         <code>encodedRegionName</code>
   */
  static String prettyPrint(final String encodedRegionName) {
    if (encodedRegionName.equals("1028785192")) {
      return encodedRegionName + "/hbase:meta";
    }
    return encodedRegionName;
  }

  /**
   * Make a region name of passed parameters.
   * @param startKey  Can be null
   * @param regionid  Region id (Usually timestamp from when region was created).
   * @param newFormat should we create the region name in the new format (such that it contains its
   *                  encoded name?).
   * @return Region name made of passed tableName, startKey and id
   */
  static byte[] createRegionName(final TableName tableName, final byte[] startKey,
    final long regionid, boolean newFormat) {
    return createRegionName(tableName, startKey, Long.toString(regionid), newFormat);
  }

  /**
   * Make a region name of passed parameters.
   * @param startKey  Can be null
   * @param id        Region id (Usually timestamp from when region was created).
   * @param newFormat should we create the region name in the new format (such that it contains its
   *                  encoded name?).
   * @return Region name made of passed tableName, startKey and id
   */
  static byte[] createRegionName(final TableName tableName, final byte[] startKey, final String id,
    boolean newFormat) {
    return createRegionName(tableName, startKey, Bytes.toBytes(id), newFormat);
  }

  /**
   * Make a region name of passed parameters.
   * @param startKey  Can be null
   * @param regionid  Region id (Usually timestamp from when region was created).
   * @param newFormat should we create the region name in the new format (such that it contains its
   *                  encoded name?).
   * @return Region name made of passed tableName, startKey, id and replicaId
   */
  static byte[] createRegionName(final TableName tableName, final byte[] startKey,
    final long regionid, int replicaId, boolean newFormat) {
    return createRegionName(tableName, startKey, Bytes.toBytes(Long.toString(regionid)), replicaId,
      newFormat);
  }

  /**
   * Make a region name of passed parameters.
   * @param startKey  Can be null
   * @param id        Region id (Usually timestamp from when region was created).
   * @param newFormat should we create the region name in the new format (such that it contains its
   *                  encoded name?).
   * @return Region name made of passed tableName, startKey and id
   */
  static byte[] createRegionName(final TableName tableName, final byte[] startKey, final byte[] id,
    boolean newFormat) {
    return createRegionName(tableName, startKey, id, DEFAULT_REPLICA_ID, newFormat);
  }

  /**
   * Make a region name of passed parameters.
   * @param startKey  Can be null
   * @param id        Region id (Usually timestamp from when region was created).
   * @param newFormat should we create the region name in the new format
   * @return Region name made of passed tableName, startKey, id and replicaId
   */
  static byte[] createRegionName(final TableName tableName, final byte[] startKey, final byte[] id,
    final int replicaId, boolean newFormat) {
    int len = tableName.getName().length + 2 + id.length + (startKey == null ? 0 : startKey.length);
    if (newFormat) {
      len += MD5_HEX_LENGTH + 2;
    }
    byte[] replicaIdBytes = null;
    // Special casing: replicaId is only appended if replicaId is greater than
    // 0. This is because all regions in meta would have to be migrated to the new
    // name otherwise
    if (replicaId > 0) {
      // use string representation for replica id
      replicaIdBytes = Bytes.toBytes(String.format(REPLICA_ID_FORMAT, replicaId));
      len += 1 + replicaIdBytes.length;
    }

    byte[] b = new byte[len];

    int offset = tableName.getName().length;
    System.arraycopy(tableName.getName(), 0, b, 0, offset);
    b[offset++] = HConstants.DELIMITER;
    if (startKey != null && startKey.length > 0) {
      System.arraycopy(startKey, 0, b, offset, startKey.length);
      offset += startKey.length;
    }
    b[offset++] = HConstants.DELIMITER;
    System.arraycopy(id, 0, b, offset, id.length);
    offset += id.length;

    if (replicaIdBytes != null) {
      b[offset++] = REPLICA_ID_DELIMITER;
      System.arraycopy(replicaIdBytes, 0, b, offset, replicaIdBytes.length);
      offset += replicaIdBytes.length;
    }

    if (newFormat) {
      //
      // Encoded name should be built into the region name.
      //
      // Use the region name thus far (namely, <tablename>,<startKey>,<id>_<replicaId>)
      // to compute a MD5 hash to be used as the encoded name, and append
      // it to the byte buffer.
      //
      String md5Hash = MD5Hash.getMD5AsHex(b, 0, offset);
      byte[] md5HashBytes = Bytes.toBytes(md5Hash);

      if (md5HashBytes.length != MD5_HEX_LENGTH) {
        System.out.println(
          "MD5-hash length mismatch: Expected=" + MD5_HEX_LENGTH + "; Got=" + md5HashBytes.length);
      }

      // now append the bytes '.<encodedName>.' to the end
      b[offset++] = ENC_SEPARATOR;
      System.arraycopy(md5HashBytes, 0, b, offset, MD5_HEX_LENGTH);
      offset += MD5_HEX_LENGTH;
      b[offset] = ENC_SEPARATOR;
    }

    return b;
  }

  /**
   * Creates a RegionInfo object for MOB data.
   * @param tableName the name of the table
   * @return the MOB {@link RegionInfo}.
   */
  static RegionInfo createMobRegionInfo(TableName tableName) {
    // Skipping reference to RegionInfoBuilder in this class.
    return new MutableRegionInfo(tableName, Bytes.toBytes(".mob"), HConstants.EMPTY_END_ROW, false,
      0, DEFAULT_REPLICA_ID, false);
  }

  /**
   * Separate elements of a regionName.
   * @return Array of byte[] containing tableName, startKey and id OR null if not parseable as a
   *         region name.
   * @throws IOException if not parseable as regionName.
   */
  static byte[][] parseRegionName(final byte[] regionName) throws IOException {
    byte[][] result = parseRegionNameOrReturnNull(regionName);
    if (result == null) {
      throw new IOException(
        INVALID_REGION_NAME_FORMAT_MESSAGE + ": " + Bytes.toStringBinary(regionName));
    }
    return result;
  }

  /**
   * Separate elements of a regionName. Region name is of the format:
   * <code>tablename,startkey,regionIdTimestamp[_replicaId][.encodedName.]</code>. Startkey can
   * contain the delimiter (',') so we parse from the start and then parse from the end.
   * @return Array of byte[] containing tableName, startKey and id OR null if not parseable as a
   *         region name.
   */
  static byte[][] parseRegionNameOrReturnNull(final byte[] regionName) {
    int offset = -1;
    for (int i = 0; i < regionName.length; i++) {
      if (regionName[i] == HConstants.DELIMITER) {
        offset = i;
        break;
      }
    }
    if (offset == -1) {
      return null;
    }
    byte[] tableName = new byte[offset];
    System.arraycopy(regionName, 0, tableName, 0, offset);
    offset = -1;

    int endOffset = regionName.length;
    // check whether regionName contains encodedName
    if (
      regionName.length > MD5_HEX_LENGTH + 2 && regionName[regionName.length - 1] == ENC_SEPARATOR
        && regionName[regionName.length - MD5_HEX_LENGTH - 2] == ENC_SEPARATOR
    ) {
      endOffset = endOffset - MD5_HEX_LENGTH - 2;
    }

    // parse from end
    byte[] replicaId = null;
    int idEndOffset = endOffset;
    for (int i = endOffset - 1; i > 0; i--) {
      if (regionName[i] == REPLICA_ID_DELIMITER) { // replicaId may or may not be present
        replicaId = new byte[endOffset - i - 1];
        System.arraycopy(regionName, i + 1, replicaId, 0, endOffset - i - 1);
        idEndOffset = i;
        // do not break, continue to search for id
      }
      if (regionName[i] == HConstants.DELIMITER) {
        offset = i;
        break;
      }
    }
    if (offset == -1) {
      return null;
    }
    byte[] startKey = HConstants.EMPTY_BYTE_ARRAY;
    if (offset != tableName.length + 1) {
      startKey = new byte[offset - tableName.length - 1];
      System.arraycopy(regionName, tableName.length + 1, startKey, 0,
        offset - tableName.length - 1);
    }
    byte[] id = new byte[idEndOffset - offset - 1];
    System.arraycopy(regionName, offset + 1, id, 0, idEndOffset - offset - 1);
    byte[][] elements = new byte[replicaId == null ? 3 : 4][];
    elements[0] = tableName;
    elements[1] = startKey;
    elements[2] = id;
    if (replicaId != null) {
      elements[3] = replicaId;
    }
    return elements;
  }

  /**
   * Serializes given RegionInfo's as a byte array. Use this instead of
   * {@link RegionInfo#toByteArray(RegionInfo)} when writing to a stream and you want to use the pb
   * mergeDelimitedFrom (w/o the delimiter, pb reads to EOF which may not be what you want).
   * {@link #parseDelimitedFrom(byte[], int, int)} can be used to read back the instances.
   * @param infos RegionInfo objects to serialize
   * @return This instance serialized as a delimited protobuf w/ a magic pb prefix.
   */
  static byte[] toDelimitedByteArray(RegionInfo... infos) throws IOException {
    byte[][] bytes = new byte[infos.length][];
    int size = 0;
    for (int i = 0; i < infos.length; i++) {
      bytes[i] = toDelimitedByteArray(infos[i]);
      size += bytes[i].length;
    }

    byte[] result = new byte[size];
    int offset = 0;
    for (byte[] b : bytes) {
      System.arraycopy(b, 0, result, offset, b.length);
      offset += b.length;
    }
    return result;
  }

  /**
   * Use this instead of {@link RegionInfo#toByteArray(RegionInfo)} when writing to a stream and you
   * want to use the pb mergeDelimitedFrom (w/o the delimiter, pb reads to EOF which may not be what
   * you want).
   * @return This instance serialized as a delimied protobuf w/ a magic pb prefix.
   */
  static byte[] toDelimitedByteArray(RegionInfo ri) throws IOException {
    return ProtobufUtil.toDelimitedByteArray(ProtobufUtil.toRegionInfo(ri));
  }

  /**
   * Parses an RegionInfo instance from the passed in stream. Presumes the RegionInfo was serialized
   * to the stream with {@link #toDelimitedByteArray(RegionInfo)}.
   * @return An instance of RegionInfo.
   */
  static RegionInfo parseFrom(final DataInputStream in) throws IOException {
    // I need to be able to move back in the stream if this is not a pb
    // serialization so I can do the Writable decoding instead.
    int pblen = ProtobufUtil.lengthOfPBMagic();
    byte[] pbuf = new byte[pblen];
    if (in.markSupported()) { // read it with mark()
      in.mark(pblen);
    }

    // assumption: if Writable serialization, it should be longer than pblen.
    IOUtils.readFully(in, pbuf, 0, pblen);
    if (ProtobufUtil.isPBMagicPrefix(pbuf)) {
      return ProtobufUtil.toRegionInfo(HBaseProtos.RegionInfo.parseDelimitedFrom(in));
    } else {
      throw new IOException("PB encoded RegionInfo expected");
    }
  }

  /**
   * Parses all the RegionInfo instances from the passed in stream until EOF. Presumes the
   * RegionInfo's were serialized to the stream with oDelimitedByteArray()
   * @param bytes  serialized bytes
   * @param offset the start offset into the byte[] buffer
   * @param length how far we should read into the byte[] buffer
   * @return All the RegionInfos that are in the byte array. Keeps reading till we hit the end.
   */
  static List<RegionInfo> parseDelimitedFrom(final byte[] bytes, final int offset, final int length)
    throws IOException {
    if (bytes == null) {
      throw new IllegalArgumentException("Can't build an object with empty bytes array");
    }
    List<RegionInfo> ris = new ArrayList<>();
    try (DataInputBuffer in = new DataInputBuffer()) {
      in.reset(bytes, offset, length);
      while (in.available() > 0) {
        RegionInfo ri = parseFrom(in);
        ris.add(ri);
      }
    }
    return ris;
  }

  /** Returns True if this is first Region in Table */
  default boolean isFirst() {
    return Bytes.equals(getStartKey(), HConstants.EMPTY_START_ROW);
  }

  /** Returns True if this is last Region in Table */
  default boolean isLast() {
    return Bytes.equals(getEndKey(), HConstants.EMPTY_END_ROW);
  }

  /**
   * @return True if region is next, adjacent but 'after' this one.
   * @see #isAdjacent(RegionInfo)
   * @see #areAdjacent(RegionInfo, RegionInfo)
   */
  default boolean isNext(RegionInfo after) {
    return getTable().equals(after.getTable()) && Bytes.equals(getEndKey(), after.getStartKey());
  }

  /**
   * @return True if region is adjacent, either just before or just after this one.
   * @see #isNext(RegionInfo)
   */
  default boolean isAdjacent(RegionInfo other) {
    return getTable().equals(other.getTable()) && areAdjacent(this, other);
  }

  /** Returns True if RegionInfo is degenerate... if startKey > endKey. */
  default boolean isDegenerate() {
    return !isLast() && Bytes.compareTo(getStartKey(), getEndKey()) > 0;
  }

  /**
   * @return True if an overlap in region range.
   * @see #isDegenerate()
   */
  default boolean isOverlap(RegionInfo other) {
    if (other == null) {
      return false;
    }
    if (!getTable().equals(other.getTable())) {
      return false;
    }
    int startKeyCompare = Bytes.compareTo(getStartKey(), other.getStartKey());
    if (startKeyCompare == 0) {
      return true;
    }
    if (startKeyCompare < 0) {
      if (isLast()) {
        return true;
      }
      return Bytes.compareTo(getEndKey(), other.getStartKey()) > 0;
    }
    if (other.isLast()) {
      return true;
    }
    return Bytes.compareTo(getStartKey(), other.getEndKey()) < 0;
  }

  default int compareTo(RegionInfo other) {
    return RegionInfo.COMPARATOR.compare(this, other);
  }
}