if offset < 0 || length < 0 {
		return -1, errInvalidArgument
	}
	if offset+length > totalLength {
		return -1, errInvalidArgument
	}

	if length == 0 {
		return 0, nil
	}

	reader := newParallelReader(readers, e, offset, totalLength)
	if len(prefer) == len(readers) {

}

// ShardFileSize - returns final erasure size from original size.
func (e *Erasure) ShardFileSize(totalLength int64) int64 {
	if totalLength == 0 {
		return 0
	}
	if totalLength == -1 {
		return -1
	}
	numShards := totalLength / e.blockSize
	lastBlockSize := totalLength % e.blockSize
	lastShardSize := ceilFrac(lastBlockSize, int64(e.dataBlocks))
	return numShards*e.ShardSize() + lastShardSize
}

	buf.WriteByte(7)
	buf.Write([]byte{0, 4})
	buf.WriteString("Cont")

	header := buf.Bytes()
	headerLength := len(header)
	payloadLength := 0
	totalLength := totalByteLength(headerLength, payloadLength)

	buf = new(bytes.Buffer)
	binary.Write(buf, binary.BigEndian, uint32(totalLength))
	binary.Write(buf, binary.BigEndian, uint32(headerLength))
	prelude := buf.Bytes()
	binary.Write(buf, binary.BigEndian, crc32.ChecksumIEEE(prelude))

//	          return string(b)
//	}
//
// for example, the following is true:
//
// f(NewDummyDataGen(100, 0)) == f(NewDummyDataGen(50, 0)) + f(NewDummyDataGen(50, 50))
func NewDummyDataGen(totalLength, skipOffset int64) io.ReadSeeker {
	if totalLength < 0 {
		panic("Negative length passed to DummyDataGen!")
	}
	if skipOffset < 0 {
		panic("Negative rotations are not allowed")
	}

	skipOffset %= int64(len(alphabets))