// ComputeTransform determines the block coordinate and beginning + ending voxel points
// for the data corresponding to the given Block.
func (v *Voxels) ComputeTransform(block *storage.TKeyValue, blockSize dvid.Point) (blockBeg, dataBeg, dataEnd dvid.Point, err error) {
	var ptIndex *dvid.IndexZYX
	ptIndex, err = DecodeTKey(block.K)
	if err != nil {
		return
	}

	// Get the bounding voxel coordinates for this block.
	minBlockVoxel := ptIndex.MinPoint(blockSize)
	maxBlockVoxel := ptIndex.MaxPoint(blockSize)

	// Compute the boundary voxel coordinates for the ExtData and adjust
	// to our block bounds.
	minDataVoxel := v.StartPoint()
	maxDataVoxel := v.EndPoint()
	begVolCoord, _ := minDataVoxel.Max(minBlockVoxel)
	endVolCoord, _ := maxDataVoxel.Min(maxBlockVoxel)

	// Adjust the DVID volume voxel coordinates for the data so that (0,0,0)
	// is where we expect this slice/subvolume's data to begin.
	dataBeg = begVolCoord.Sub(v.StartPoint())
	dataEnd = endVolCoord.Sub(v.StartPoint())

	// Compute block coord matching dataBeg
	blockBeg = begVolCoord.Sub(minBlockVoxel)

	return
}

// DecodeTKey returns a spatial index from a image block key.
// TODO: Extend this when necessary to allow any form of spatial indexing like CZYX.
func DecodeTKey(tk storage.TKey) (*dvid.IndexZYX, error) {
	ibytes, err := tk.ClassBytes(keyImageBlock)
	if err != nil {
		return nil, err
	}
	var zyx dvid.IndexZYX
	if err = zyx.IndexFromBytes(ibytes); err != nil {
		return nil, fmt.Errorf("Cannot recover ZYX index from image block key %v: %v\n", tk, err)
	}
	return &zyx, nil
}

func DecodeBlockTKey(tk storage.TKey) (pt dvid.ChunkPoint3d, err error) {
	ibytes, err := tk.ClassBytes(keyBlock)
	if err != nil {
		return
	}
	var idx dvid.IndexZYX
	if err = idx.IndexFromBytes(ibytes); err != nil {
		return
	}
	pt = dvid.ChunkPoint3d(idx)
	return
}

// DecodeTKey returns the components of a tile request based on an imagetile-specific key component.
func DecodeTKey(tk storage.TKey) (tile dvid.ChunkPoint3d, plane dvid.DataShape, scale Scaling, err error) {
	if len(tk) < 21 {
		err = fmt.Errorf("imagetile-specific key component has too few bytes (%d)", len(tk))
		return
	}
	plane, err = dvid.BytesToDataShape(tk[0:dvid.DataShapeBytes])
	if err != nil {
		return
	}
	scale = Scaling(tk[dvid.DataShapeBytes])
	var idx dvid.IndexZYX
	if err = idx.IndexFromBytes(tk[dvid.DataShapeBytes+2:]); err != nil {
		return
	}
	tile = dvid.ChunkPoint3d(idx)
	return
}

// SplitCoarseLabels splits a portion of a label's voxels into a given split label or, if the given split
// label is 0, a new label, which is returned.  The input is a binary sparse volume defined by block
// coordinates and should be the smaller portion of a labeled region-to-be-split.
//
// EVENTS
//
// labels.SplitStartEvent occurs at very start of split and transmits labels.DeltaSplitStart struct.
//
// labels.SplitBlockEvent occurs for every block of a split label and transmits labels.DeltaSplit struct.
//
// labels.SplitEndEvent occurs at end of split and transmits labels.DeltaSplitEnd struct.
//
func (d *Data) SplitCoarseLabels(v dvid.VersionID, fromLabel, splitLabel uint64, r io.ReadCloser) (toLabel uint64, err error) {
	store, err := d.GetOrderedKeyValueDB()
	if err != nil {
		err = fmt.Errorf("Data type labelvol had error initializing store: %v\n", err)
		return
	}
	batcher, ok := store.(storage.KeyValueBatcher)
	if !ok {
		err = fmt.Errorf("Data type labelvol requires batch-enabled store, which %q is not\n", store)
		return
	}

	// Create a new label id for this version that will persist to store
	if splitLabel != 0 {
		toLabel = splitLabel
		dvid.Debugf("Splitting coarse subset of label %d into given label %d ...\n", fromLabel, splitLabel)
	} else {
		toLabel, err = d.NewLabel(v)
		if err != nil {
			return
		}
		dvid.Debugf("Splitting coarse subset of label %d into new label %d ...\n", fromLabel, toLabel)
	}

	evt := datastore.SyncEvent{d.DataUUID(), labels.SplitStartEvent}
	splitOpStart := labels.DeltaSplitStart{fromLabel, toLabel}
	splitOpEnd := labels.DeltaSplitEnd{fromLabel, toLabel}

	// Make sure we can split given current merges in progress
	if err := labels.SplitStart(d.getMergeIV(v), splitOpStart); err != nil {
		return toLabel, err
	}
	defer labels.SplitStop(d.getMergeIV(v), splitOpEnd)

	// Signal that we are starting a split.
	msg := datastore.SyncMessage{labels.SplitStartEvent, v, splitOpStart}
	if err := datastore.NotifySubscribers(evt, msg); err != nil {
		return 0, err
	}

	// Read the sparse volume from reader.
	var splits dvid.RLEs
	splits, err = dvid.ReadRLEs(r)
	if err != nil {
		return
	}
	numBlocks, _ := splits.Stats()

	// Order the split blocks
	splitblks := make(dvid.IZYXSlice, numBlocks)
	n := 0
	for _, rle := range splits {
		p := rle.StartPt()
		run := rle.Length()
		for i := int32(0); i < run; i++ {
			izyx := dvid.IndexZYX{p[0] + i, p[1], p[2]}
			splitblks[n] = izyx.ToIZYXString()
			n++
		}
	}
	sort.Sort(splitblks)

	// Iterate through the split blocks, read the original block and change labels.
	// TODO: Modifications should be transactional since it's GET-PUT, therefore use
	// hash on block coord to direct it to block-specific goroutine; we serialize
	// requests to handle concurrency.
	ctx := datastore.NewVersionedCtx(d, v)
	batch := batcher.NewBatch(ctx)

	var toLabelSize uint64
	for _, splitblk := range splitblks {
		// Get original block
		tk := NewTKey(fromLabel, splitblk)
		val, err := store.Get(ctx, tk)
		if err != nil {
			return toLabel, err
		}
		if val == nil {
			return toLabel, fmt.Errorf("Split block %s is not part of original label %d", splitblk, fromLabel)
		}
		var rles dvid.RLEs
		if err := rles.UnmarshalBinary(val); err != nil {
			return toLabel, fmt.Errorf("Unable to unmarshal RLE for original labels in block %s", splitblk)
		}
		numVoxels, _ := rles.Stats()
		toLabelSize += numVoxels

		// Delete the old block and save the sparse volume but under a new label.
//.........这里部分代码省略.........