Support Modrinth modpack fileSize field and sha512 hash

core/hash.go

@@ -15,34 +15,76 @@ import (
 )
 
 // GetHashImpl gets an implementation of hash.Hash for the given hash type string
-func GetHashImpl(hashType string) (hash.Hash, HashStringer, error) {
+func GetHashImpl(hashType string) (HashStringer, error) {
 	switch strings.ToLower(hashType) {
 	case "sha1":
-		return sha1.New(), hexStringer{}, nil
+		return hexStringer{sha1.New()}, nil
 	case "sha256":
-		return sha256.New(), hexStringer{}, nil
+		return hexStringer{sha256.New()}, nil
 	case "sha512":
-		return sha512.New(), hexStringer{}, nil
+		return hexStringer{sha512.New()}, nil
 	case "md5":
-		return md5.New(), hexStringer{}, nil
-	case "murmur2":
-		return murmur2.New(), numberStringer{}, nil
+		return hexStringer{md5.New()}, nil
+	case "murmur2": // TODO: change to something indicating that this is the CF variant
+		return number32As64Stringer{murmur2.New()}, nil
+	case "length-bytes": // TODO: only used internally for now; should not be saved
+		return number64Stringer{&LengthHasher{}}, nil
 	}
-	return nil, nil, fmt.Errorf("hash implementation %s not found", hashType)
+	return nil, fmt.Errorf("hash implementation %s not found", hashType)
 }
 
 type HashStringer interface {
+	hash.Hash
 	HashToString([]byte) string
 }
 
-type hexStringer struct{}
+type hexStringer struct {
+	hash.Hash
+}
 
 func (hexStringer) HashToString(data []byte) string {
 	return hex.EncodeToString(data)
 }
 
-type numberStringer struct{}
+type number32As64Stringer struct {
+	hash.Hash
+}
 
-func (numberStringer) HashToString(data []byte) string {
+func (number32As64Stringer) HashToString(data []byte) string {
 	return strconv.FormatUint(uint64(binary.BigEndian.Uint32(data)), 10)
 }
+
+type number64Stringer struct {
+	hash.Hash
+}
+
+func (number64Stringer) HashToString(data []byte) string {
+	return strconv.FormatUint(binary.BigEndian.Uint64(data), 10)
+}
+
+type LengthHasher struct {
+	length uint64
+}
+
+func (h *LengthHasher) Write(p []byte) (n int, err error) {
+	h.length += uint64(len(p))
+	return len(p), nil
+}
+
+func (h *LengthHasher) Sum(b []byte) []byte {
+	ext := append(b, make([]byte, 8)...)
+	binary.BigEndian.PutUint64(ext, h.length)
+	return ext
+}
+
+func (h *LengthHasher) Size() int {
+	return 8
+}
+
+func (h *LengthHasher) BlockSize() int {
+	return 1
+}
+
+func (h *LengthHasher) Reset() {
+	h.length = 0
+}