{dataBlocks: 6, onDisks: 12, offDisks: 0, blocksize: int64(blockSizeV2), data: int64(2 * blockSizeV2), offset: 512, length: int64(blockSizeV2) + 8*1024, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},           // 30

	{dataBlocks: 5, disks: 10, offDisks: 3, badDisks: 1, badStaleDisks: 0, blocksize: int64(blockSizeV2), size: oneMiByte, algorithm: DefaultBitrotAlgorithm, shouldFail: false},  // 3

					testReadFrom{fileOps{
						int64(1e10 - blockSize),
						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
						int64(1e10 - blockSize),
						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
						int64(1e10 - blockSize),
						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
						int64(1e10 - blockSize),

	{dataBlocks: 4, onDisks: 8, offDisks: 2, blocksize: int64(blockSizeV2), data: oneMiByte, offset: 2, algorithm: DefaultBitrotAlgorithm, shouldFail: false, shouldFailQuorum: false},                 // 2

	}
	w := metacacheWriter{
		mw:        nil,
		blockSize: blockSize,
	}
	w.creator = func() error {
		s2w := s2.NewWriter(out, s2.WriterBlockSize(blockSize), s2.WriterConcurrency(2))
		w.mw = msgp.NewWriter(s2w)
		w.creator = nil
		if err := w.mw.WriteByte(metacacheStreamVersion); err != nil {
			return err
		}

		w.closer = func() (err error) {
			defer func() {
				cerr := s2w.Close()

// Erasure - erasure encoding details.
type Erasure struct {
	encoder                  func() reedsolomon.Encoder
	dataBlocks, parityBlocks int
	blockSize                int64
}

// NewErasure creates a new ErasureStorage.
func NewErasure(ctx context.Context, dataBlocks, parityBlocks int, blockSize int64) (e Erasure, err error) {
	// Check the parameters for sanity now.
	if dataBlocks <= 0 || parityBlocks < 0 {

			blockLength = e.blockSize - blockOffset
		case block == endBlock:
			blockOffset = 0
			blockLength = (offset + length) % e.blockSize
		default:
			blockOffset = 0
			blockLength = e.blockSize
		}
		if blockLength == 0 {
			break
		}

		var err error
		bufs, err = reader.Read(bufs)
		if len(bufs) > 0 {
			// Set only if there are be enough data for reconstruction.

)

// blockPadding computes the number of bytes needed to pad offset up to the
// nearest block edge where 0 <= n < blockSize.
func blockPadding(offset int64) (n int64) {
	return -offset & (blockSize - 1)
}

var zeroBlock block

type block [blockSize]byte

// Convert block to any number of formats.
func (b *block) toV7() *headerV7       { return (*headerV7)(b) }

	fd := f.Fd()
	_, err := unix.FcntlInt(fd, unix.F_NOCACHE, 0)
	return err
}

// AlignedBlock - pass through to directio implementation.
func AlignedBlock(blockSize int) []byte {
	return directio.AlignedBlock(blockSize)

type erasureTestSetup struct {
	dataBlocks   int
	parityBlocks int
	blockSize    int64
	diskPaths    []string
	disks        []StorageAPI
}

// Returns an initialized setup for erasure tests.
func newErasureTestSetup(tb testing.TB, dataBlocks int, parityBlocks int, blockSize int64) (*erasureTestSetup, error) {
	diskPaths := make([]string, dataBlocks+parityBlocks)