keys: rework nep-2/wif encoding without bytes.Buffer

It doesn't make any sense here and the length check was just a dead code.

Signed-off-by: Roman Khimov <roman@nspcc.ru>

pkg/crypto/keys/nep2.go

@@ -67,17 +67,13 @@ func NEP2Encrypt(priv *PrivateKey, passphrase string, params ScryptParams) (s st
 		return s, err
 	}
 
-	buf := new(bytes.Buffer)
+	var buf = make([]byte, 0, len(nepHeader)+1+len(addrHash)+len(encrypted))
-	buf.Write(nepHeader)
+	buf = append(buf, nepHeader...)
-	buf.WriteByte(nepFlag)
+	buf = append(buf, nepFlag)
-	buf.Write(addrHash)
+	buf = append(buf, addrHash...)
-	buf.Write(encrypted)
+	buf = append(buf, encrypted...)
 
-	if buf.Len() != 39 {
+	return base58.CheckEncode(buf), nil
-		return s, fmt.Errorf("invalid buffer length: expecting 39 bytes got %d", buf.Len())
-	}
-
-	return base58.CheckEncode(buf.Bytes()), nil
 }
 
 // NEP2Decrypt decrypts an encrypted key using the given passphrase

pkg/crypto/keys/wif.go

@@ -1,7 +1,6 @@
 package keys
 
 import (
-	"bytes"
 	"fmt"
 
 	"github.com/nspcc-dev/neo-go/pkg/encoding/base58"
@@ -36,14 +35,14 @@ func WIFEncode(key []byte, version byte, compressed bool) (s string, err error)
 		return s, fmt.Errorf("invalid private key length: %d", len(key))
 	}
 
-	buf := new(bytes.Buffer)
+	var buf = make([]byte, 0, 1+len(key)+1)
-	buf.WriteByte(version)
+	buf = append(buf, version)
-	buf.Write(key)
+	buf = append(buf, key...)
 	if compressed {
-		buf.WriteByte(0x01)
+		buf = append(buf, 0x01)
 	}
 
-	s = base58.CheckEncode(buf.Bytes())
+	s = base58.CheckEncode(buf)
 	return
 }