dragonfly/server: Make block hashes more dynamic to avoid registry co…

…llisions (#918)

cmd/blockhash/main.go

@@ -8,7 +8,6 @@ import (
 	"golang.org/x/tools/go/packages"
 	"io"
 	"log"
-	"math/bits"
 	"os"
 	"sort"
 	"strconv"
@@ -54,14 +53,14 @@ func procPackage(pkg *packages.Package, w io.Writer) {
 	b.sortNames()
 
 	b.writePackage(w)
-	i := b.writeConstants(w)
+	b.writeConstants(w)
 	b.writeNextHash(w)
-	b.writeMethods(w, i)
+	b.writeMethods(w)
 }
 
 var (
 	packageFormat = "// Code generated by cmd/blockhash; DO NOT EDIT.\n\npackage %v\n\n"
-	methodFormat  = "\n// Hash ...\nfunc (%v%v) Hash() uint64 {\n\treturn %v\n}\n"
+	methodFormat  = "\nfunc (%v%v) Hash() (uint64, uint64) {\n\treturn %v, %v\n}\n"
 	constFormat   = "\thash%v"
 )
 
@@ -91,16 +90,18 @@ func (b *hashBuilder) writePackage(w io.Writer) {
 	if _, err := fmt.Fprintf(w, packageFormat, b.pkg.Name); err != nil {
 		log.Fatalln(err)
 	}
+	if _, err := fmt.Fprintf(w, "import \"github.com/df-mc/dragonfly/server/world\"\n\n"); err != nil {
+		log.Fatalln(err)
+	}
 }
 
 // writeConstants writes hash constants for every block to a file.
-func (b *hashBuilder) writeConstants(w io.Writer) (bitSize int) {
+func (b *hashBuilder) writeConstants(w io.Writer) {
 	if _, err := fmt.Fprintln(w, "const ("); err != nil {
 		log.Fatalln(err)
 	}
 
-	var i uint64
-	for _, name := range b.names {
+	for i, name := range b.names {
 		c := constFormat
 		if i == 0 {
 			c += " = iota"
@@ -109,14 +110,11 @@ func (b *hashBuilder) writeConstants(w io.Writer) (bitSize int) {
 		if _, err := fmt.Fprintf(w, c+"\n", name); err != nil {
 			log.Fatalln(err)
 		}
-		i++
 	}
 
 	if _, err := fmt.Fprintln(w, "\thashCustomBlockBase\n)"); err != nil {
 		log.Fatalln(err)
 	}
-
-	return bits.Len64(i)
 }
 
 func (b *hashBuilder) writeNextHash(w io.Writer) {
@@ -134,12 +132,12 @@ func (b *hashBuilder) writeNextHash(w io.Writer) {
 	}
 }
 
-func (b *hashBuilder) writeMethods(w io.Writer, baseBits int) {
+func (b *hashBuilder) writeMethods(w io.Writer) {
 	for _, name := range b.names {
 		fields := b.blockFields[name]
 
-		h := "hash" + name
-		bitSize := baseBits
+		var h string
+		var bitSize int
 
 		fun := b.funcs[name]
 		var recvName string
@@ -185,27 +183,36 @@ func (b *hashBuilder) writeMethods(w io.Writer, baseBits int) {
 				}
 
 				if bitSize > 64 {
-					log.Println("Hash size of block properties of", name, "exceeds", 64-baseBits, "bits. Please look at this manually.")
+					log.Println("Hash size of block properties of", name, "exceeds 64 bits. Please look at this manually.")
 				} else {
-					h += " | " + str + "<<" + strconv.Itoa(bitSize)
+					if h == "" {
+						h += str
+					} else {
+						h += " | " + str
+					}
+					if bitSize > 0 {
+						h += "<<" + strconv.Itoa(bitSize)
+					}
 				}
 				bitSize += v
 			}
 		}
-		if bitSize == baseBits {
+		if bitSize == 0 {
 			// No need to have a receiver name if we don't use any of the fields of the block.
 			recvName = ""
 		}
 
 		if recvName != "" {
 			recvName += " "
 		}
+		if h == "" {
+			h = "0"
+		}
 
-		if _, err := fmt.Fprintf(w, methodFormat, recvName, name, h); err != nil {
+		if _, err := fmt.Fprintf(w, methodFormat, recvName, name, "hash"+name, h); err != nil {
 			log.Fatalln(err)
 		}
 	}
-	log.Println("Assuming int size of 8 bits at most for all int fields: Make sure this is valid for all blocks.")
 }
 
 func (b *hashBuilder) ftype(structName, s string, expr ast.Expr, directives map[string]string) (string, int) {
@@ -227,7 +234,7 @@ func (b *hashBuilder) ftype(structName, s string, expr ast.Expr, directives map[
 	case "int":
 		return "uint64(" + s + ")", 8
 	case "Block":
-		return s + ".Hash()", 16
+		return "world.BlockHash(" + s + ")", 32
 	case "Attachment":
 		if _, ok := directives["facing_only"]; ok {
 			log.Println("Found directive: 'facing_only'")