refactor storage format and bpe handling; add redirecting bpe support and utility function for next largest number

level/section.go

@@ -42,6 +42,7 @@ func MakeBiomeFormat(version string) StorageFormat {
 func MakeBlockFormat(version string) StorageFormat {
 	directBpe := uint8(math.Ceil(math.Log2(float64(len(data.BlocksForVersion(version))))))
 	return StorageFormat{
+		RedirectingBpes: []uint8{1, 2, 3},
 		AvailableBpes:   []uint8{0, 4, 5, 6, 7, 8, directBpe},
 		BiggestDirect:   true,
 		Len:             BlocksPerChunkSection,

level/storage.go

@@ -6,9 +6,12 @@ import (
 	"io"
 	"math"
 	"slices"
+
+	"github.com/admin-else/strom/util"
 )
 
 type StorageFormat struct {
+	RedirectingBpes []uint8 // block bpe 1 2 3 redirect to 4
 	AvailableBpes   []uint8
 	BiggestDirect   bool
 	Len             int32
@@ -33,24 +36,16 @@ func (r StorageFormat) Import(data []uint64, bpe uint8, palette []int32) (s *Sto
 	s.resize(bpe)
 
 	if !slices.Contains(r.AvailableBpes, bpe) {
-		var newBpe uint8
-		for _, newBpe = range r.AvailableBpes {
-			if bpe <= newBpe {
-				break
+		if !slices.Contains(r.RedirectingBpes, bpe) {
+			err = NoAvailableBpeErr
+			return
 		}
-		}
-		var tmps *Storage
-		tmps, err = StorageFormat{
-			AvailableBpes: []uint8{bpe},
-			BiggestDirect: false,
-			Len:           r.Len,
-		}.ImportDataDirect(data)
-		if err != nil {
+		var found bool
+		bpe, found = util.GetNextLargestNumberSlice(bpe, r.AvailableBpes)
+		if !found {
+			err = NoAvailableBpeErr
 			return
 		}
-		tmps.resize(newBpe)
-		data = tmps.data
-		bpe = newBpe
 	}
 	if bpe == 0 && len(palette) != 1 {
 		err = Bpe0PalletMustBeLenOneErr

util/slices.go

@@ -85,3 +85,12 @@ func SliceRange[T Numeric](s, e T) (ret []T) {
 func IsLastElement[T comparable](s []T, e T) bool {
 	return len(s) > 0 && s[len(s)-1] == e
 }
+
+func GetNextLargestNumberSlice[T Numeric](a T, s []T) (ret T, found bool) {
+	for _, v := range s {
+		if v > a {
+			return v, true
+		}
+	}
+	return
+}