code: @DoesServiceRequest
      public final int downloadRangeToByteArray(final long offset, final Long length, final byte[] buffer,
              final int bufferOffset, final AccessCondition accessCondition, FileRequestOptions options,
              OperationContext opContext) throws StorageException {
  
          Utility.assertNotNull("buffer", buffer);
  
          if (length != null) {
              if (length + bufferOffset > buffer.length) {
                  throw new IndexOutOfBoundsException();
              }
          }
  
          if (opContext == null) {
              opContext = new OperationContext();
          }
  
          opContext.initialize();
  
          return this.downloadRangeInternal(offset, length, buffer, bufferOffset, accessCondition, options, opContext);
      }
docs: Downloads a range of bytes from the file to the given byte buffer, using the specified request options and
  operation context.
  
  @param offset
  A <code>long</code> which represents the byte offset to use as the starting point for the source.
  @param length
  A <code>Long</code> which represents the number of bytes to read or <code>null</code>.
  @param buffer
  A <code>byte</code> array which represents the buffer to which the file bytes are downloaded.
  @param bufferOffset
  An <code>int</code> which represents the byte offset to use as the starting point for the target.
  @param accessCondition
  An {@link AccessCondition} object that represents the access conditions for the file.
  @param options
  A {@link FileRequestOptions} object that specifies any additional options for the request. Specifying
  <code>null</code> will use the default request options from the associated service client (
  {@link CloudFileClient}).
  @param opContext
  An {@link OperationContext} object that represents the context for the current operation. This object
  is used to track requests to the storage service, and to provide additional runtime information about
  the operation.
  
  @throws StorageException
  If a storage service error occurred.