[#176] blobstor: Fix maximum tree depth

Correct the calculation of maximum value of fs tree depth. Fix check
of the max depth overflow in WithShallowDepth function.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/local_object_storage/blobstor/blobstor.go

@@ -61,7 +61,7 @@ func New(opts ...Option) *BlobStor {
 // Depth is reduced to maximum value in case of overflow.
 func WithShallowDepth(depth int) Option {
 	return func(c *cfg) {
-		if depth <= maxDepth {
+		if depth > maxDepth {
 			depth = maxDepth
 		}
 

pkg/local_object_storage/blobstor/fstree.go

@@ -22,7 +22,7 @@ type fsTree struct {
 
 const dirNameLen = 2 // in bytes
 
-var maxDepth = (hex.EncodedLen(sha256.Size) - 1) / dirNameLen
+var maxDepth = (sha256.Size - 1) / dirNameLen
 
 var errFileNotFound = errors.New("file not found")