// Returns the slice to which any down-resolution data should be written for the given higher-res block coord.
func (d *Data) getLoresCache(v dvid.VersionID, block dvid.IZYXString) ([]byte, error) {
// Setup the octant buffer and block cache.
downresBlock, err := block.Downres()
if err != nil {
return nil, fmt.Errorf("unable to downres labelblk %q block: %v\n", d.DataName(), err)
}
var chunkPt dvid.ChunkPoint3d
chunkPt, err = block.ToChunkPoint3d()
if err != nil {
return nil, err
}
// determine which down-res sector (0-7 where it's x, then y, then z ordering) in 2x2x2 block
// the given block will sit.
nx := chunkPt[0] % 2
ny := chunkPt[1] % 2
nz := chunkPt[2] % 2
sector := (nz * 4) + (ny * 2) + nx
// Get the sector slice from the octant corresponding to the downres block coord.
// Initialize blockCache if necessary.
d.vcache_mu.Lock()
defer d.vcache_mu.Unlock()
var bc blockCache
if d.vcache == nil {
d.vcache = make(map[dvid.VersionID]blockCache)
} else {
var found bool
bc, found = d.vcache[v]
if !found {
bc = nil
}
}
if bc == nil {
bc = make(blockCache)
d.vcache[v] = bc
}
// Get the relevant slice.
oct := bc[downresBlock]
if oct[sector] == nil {
nbytes := d.BlockSize().Prod() // actually / 8 (downres 2^3) then * 8 bytes for label
oct[sector] = make([]byte, nbytes)
}
d.vcache[v][downresBlock] = oct
return oct[sector], nil
}
