initial commit

internal/block_states.go

@@ -0,0 +1,53 @@
+package internal
+
+import (
+	"fmt"
+	"github.com/df-mc/worldupgrader/blockupgrader"
+	"sort"
+	"strings"
+	"unsafe"
+)
+
+// StateHash is a struct that may be used as a map key for block states. It contains the name of the block state
+// and an encoded version of the properties.
+type StateHash struct {
+	Name, Properties string
+}
+
+// HashState produces a hash for the block properties held by the blockState.
+func HashState(state blockupgrader.BlockState) StateHash {
+	if state.Properties == nil {
+		return StateHash{Name: state.Name}
+	}
+	keys := make([]string, 0, len(state.Properties))
+	for k := range state.Properties {
+		keys = append(keys, k)
+	}
+	sort.Slice(keys, func(i, j int) bool {
+		return keys[i] < keys[j]
+	})
+
+	var b strings.Builder
+	for _, k := range keys {
+		switch v := state.Properties[k].(type) {
+		case bool:
+			if v {
+				b.WriteByte(1)
+			} else {
+				b.WriteByte(0)
+			}
+		case uint8:
+			b.WriteByte(v)
+		case int32:
+			a := *(*[4]byte)(unsafe.Pointer(&v))
+			b.Write(a[:])
+		case string:
+			b.WriteString(v)
+		default:
+			// If block encoding is broken, we want to find out as soon as possible. This saves a lot of time
+			// debugging in-game.
+			panic(fmt.Sprintf("invalid block property type %T for property %v", v, k))
+		}
+	}
+	return StateHash{Name: state.Name, Properties: b.String()}
+}