[#303] user: Make user.ID a [20]byte array

Signed-off-by: Ekaterina Lebedeva <ekaterina.lebedeva@yadro.com>

user/id.go

@@ -12,9 +12,9 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/util"
 )
 
-const idSize = 25
+const idSizeFull = 25
 
-var zeroSlice = bytes.Repeat([]byte{0}, idSize)
+var zeroSlice = bytes.Repeat([]byte{0}, 20)
 
 // ID identifies users of the FrostFS system.
 //
@@ -25,7 +25,7 @@ var zeroSlice = bytes.Repeat([]byte{0}, idSize)
 // so it MUST be initialized using some modifying function (e.g. SetScriptHash,
 // IDFromKey, etc.).
 type ID struct {
-	w []byte
+	w [20]byte
 }
 
 // ReadFromV2 reads ID from the refs.OwnerID message. Returns an error if
@@ -33,22 +33,7 @@ type ID struct {
 //
 // See also WriteToV2.
 func (x *ID) ReadFromV2(m refs.OwnerID) error {
-	w := m.GetValue()
-	if len(w) != idSize {
-		return fmt.Errorf("invalid length %d, expected %d", len(w), idSize)
-	}
-
-	if w[0] != address.NEO3Prefix {
-		return fmt.Errorf("invalid prefix byte 0x%X, expected 0x%X", w[0], address.NEO3Prefix)
-	}
-
-	if !bytes.Equal(w[21:], hash.Checksum(w[:21])) {
-		return errors.New("checksum mismatch")
-	}
-
-	x.w = w
-
-	return nil
+	return x.setUserID(m.GetValue())
 }
 
 // WriteToV2 writes ID to the refs.OwnerID message.
@@ -56,25 +41,17 @@ func (x *ID) ReadFromV2(m refs.OwnerID) error {
 //
 // See also ReadFromV2.
 func (x ID) WriteToV2(m *refs.OwnerID) {
-	m.SetValue(x.w)
+	m.SetValue(x.WalletBytes())
 }
 
 // SetScriptHash forms user ID from wallet address scripthash.
 func (x *ID) SetScriptHash(scriptHash util.Uint160) {
-	if cap(x.w) < idSize {
-		x.w = make([]byte, idSize)
-	} else if len(x.w) < idSize {
-		x.w = x.w[:idSize]
-	}
-
-	x.w[0] = address.Prefix
-	copy(x.w[1:], scriptHash.BytesBE())
-	copy(x.w[21:], hash.Checksum(x.w[:21]))
+	copy(x.w[:], scriptHash.BytesBE())
 }
 
 // ScriptHash calculates and returns script hash of ID.
 func (x *ID) ScriptHash() util.Uint160 {
-	res, _ := util.Uint160DecodeBytesBE(x.w[1:21])
+	res, _ := util.Uint160DecodeBytesBE(x.w[:])
 	return res
 }
 
@@ -84,14 +61,18 @@ func (x *ID) ScriptHash() util.Uint160 {
 //
 // See also Neo3 wallet docs.
 func (x ID) WalletBytes() []byte {
-	return x.w
+	v := make([]byte, idSizeFull)
+	v[0] = address.Prefix
+	copy(v[1:], x.w[:])
+	copy(v[21:], hash.Checksum(v[:21]))
+	return v
 }
 
 // EncodeToString encodes ID into FrostFS API V2 protocol string.
 //
 // See also DecodeString.
 func (x ID) EncodeToString() string {
-	return base58.Encode(x.w)
+	return base58.Encode(x.WalletBytes())
 }
 
 // DecodeString decodes FrostFS API V2 protocol string. Returns an error
@@ -101,14 +82,11 @@ func (x ID) EncodeToString() string {
 //
 // See also EncodeToString.
 func (x *ID) DecodeString(s string) error {
-	var err error
-
-	x.w, err = base58.Decode(s)
+	w, err := base58.Decode(s)
 	if err != nil {
 		return fmt.Errorf("decode base58: %w", err)
 	}
-
-	return nil
+	return x.setUserID(w)
 }
 
 // String implements fmt.Stringer.
@@ -122,10 +100,28 @@ func (x ID) String() string {
 
 // Equals defines a comparison relation between two ID instances.
 func (x ID) Equals(x2 ID) bool {
-	return bytes.Equal(x.w, x2.w)
+	return bytes.Equal(x.w[:], x2.w[:])
 }
 
 // IsEmpty returns True, if ID is empty value.
 func (x ID) IsEmpty() bool {
-	return bytes.Equal(zeroSlice, x.w)
+	return bytes.Equal(zeroSlice, x.w[:])
+}
+
+func (x *ID) setUserID(w []byte) error {
+	if len(w) != idSizeFull {
+		return fmt.Errorf("invalid length %d, expected %d", len(w), idSizeFull)
+	}
+
+	if w[0] != address.NEO3Prefix {
+		return fmt.Errorf("invalid prefix byte 0x%X, expected 0x%X", w[0], address.NEO3Prefix)
+	}
+
+	if !bytes.Equal(w[21:], hash.Checksum(w[:21])) {
+		return errors.New("checksum mismatch")
+	}
+
+	copy(x.w[:], w[1:21])
+
+	return nil
 }