// returns error if totalSize is -1, partSize is 0, partIndex is 0.
func calculatePartSizeFromIdx(ctx context.Context, totalSize int64, partSize int64, partIndex int) (currPartSize int64, err error) {
	if totalSize < -1 {
		return 0, errInvalidArgument
	}
	if partSize == 0 {
		return 0, errPartSizeZero
	}
	if partIndex < 1 {
		return 0, errPartSizeIndex
	}
	if totalSize == -1 {

		}

		erasureInfo := latestMeta.Erasure
		for partIndex := 0; partIndex < len(latestMeta.Parts); partIndex++ {
			partSize := latestMeta.Parts[partIndex].Size
			partActualSize := latestMeta.Parts[partIndex].ActualSize
			partModTime := latestMeta.Parts[partIndex].ModTime
			partNumber := latestMeta.Parts[partIndex].Number
			partIdx := latestMeta.Parts[partIndex].Index
			partChecksums := latestMeta.Parts[partIndex].Checksums

		}
	}

	testCasesFailure := []struct {
		totalSize int64
		partSize  int64
		partIndex int
		err       error
	}{
		// partSize is 0, returns error.
		{10, 0, 1, errPartSizeZero},
		// partIndex is 0, returns error.
		{10, 1, 0, errPartSizeIndex},
		// Total size is -1, returns error.
		{-2, 10, 1, errInvalidArgument},
	}

		// values appropriately.
		d.partEncRelOffset = 0
		d.partDecRelOffset = 0
		d.startSeqNum = 0

		d.partIndex++
		if d.partIndex == len(d.parts) {
			return n1, io.EOF
		}

		err = d.buildDecrypter(d.parts[d.partIndex].Number)
		if err != nil {
			return 0, err
		}

		n1, err = d.decrypter.Read(p[n1:])
		if err != nil {
			return 0, err
		}

func (fi FileInfo) ObjectToPartOffset(ctx context.Context, offset int64) (partIndex int, partOffset int64, err error) {
	if offset == 0 {
		// Special case - if offset is 0, then partIndex and partOffset are always 0.
		return 0, 0, nil
	}
	partOffset = offset
	// Seek until object offset maps to a particular part offset.
	for i, part := range fi.Parts {
		partIndex = i
		// Offset is smaller than size we have reached the proper part offset.

	if err != nil {
		return toObjectErr(err, bucket, object)
	}

	var healOnce sync.Once

	for ; partIndex <= lastPartIndex; partIndex++ {
		if length == totalBytesRead {
			break
		}

		partNumber := fi.Parts[partIndex].Number

		// Save the current part name and size.
		partSize := fi.Parts[partIndex].Size

		partLength := partSize - partOffset