static long readDiskRegionID(DataInput dis) throws IOException {
    int bytesToRead = dis.readUnsignedByte();
    if (bytesToRead <= DiskStoreImpl.MAX_RESERVED_DRID
        && bytesToRead >= DiskStoreImpl.MIN_RESERVED_DRID) {
      long result = dis.readByte(); // we want to sign extend this first byte
      bytesToRead--;
      while (bytesToRead > 0) {
        result <<= 8;
        result |= dis.readUnsignedByte(); // no sign extension
        bytesToRead--;
      }
      return result;
    } else {
      return bytesToRead;
    }
  }
Maximum number of bytes used to encode a DiskRegion id.
geode-core/src/main/java/org/apache/geode/internal/cache/DiskInitFile.java