Presentation format encoding

RFC 4034 specifies the presentation format of the DNSKEY public key,
RRSIG signature, and DS digest fields (base64, base64, and hexadecimal).
With this change, when fields are represented as such, the package will
use the corresponding encoding.

index.js

@@ -894,10 +894,7 @@ rdnskey.encode = function (key, buf, offset) {
   if (!offset) offset = 0
   const oldOffset = offset
 
-  const keydata = key.key
-  if (!Buffer.isBuffer(keydata)) {
-    throw new Error('Key must be a Buffer')
-  }
+  const keydata = Buffer.from(key.key, 'base64')
 
   offset += 2 // Leave space for length
   buf.writeUInt16BE(key.flags, offset)
@@ -940,7 +937,7 @@ rdnskey.decode = function (buf, offset) {
 rdnskey.decode.bytes = 0
 
 rdnskey.encodingLength = function (key) {
-  return 6 + Buffer.byteLength(key.key)
+  return 6 + Buffer.byteLength(key.key, 'base64')
 }
 
 const rrrsig = exports.rrsig = {}
@@ -950,10 +947,7 @@ rrrsig.encode = function (sig, buf, offset) {
   if (!offset) offset = 0
   const oldOffset = offset
 
-  const signature = sig.signature
-  if (!Buffer.isBuffer(signature)) {
-    throw new Error('Signature must be a Buffer')
-  }
+  const signature = Buffer.from(sig.signature, 'base64')
 
   offset += 2 // Leave space for length
   buf.writeUInt16BE(types.toType(sig.typeCovered), offset)
@@ -1016,7 +1010,7 @@ rrrsig.decode.bytes = 0
 rrrsig.encodingLength = function (sig) {
   return 20 +
     name.encodingLength(sig.signersName) +
-    Buffer.byteLength(sig.signature)
+    Buffer.byteLength(sig.signature, 'base64')
 }
 
 const rrp = exports.rp = {}
@@ -1267,10 +1261,7 @@ rds.encode = function (digest, buf, offset) {
   if (!offset) offset = 0
   const oldOffset = offset
 
-  const digestdata = digest.digest
-  if (!Buffer.isBuffer(digestdata)) {
-    throw new Error('Digest must be a Buffer')
-  }
+  const digestdata = Buffer.from(digest.digest, 'hex')
 
   offset += 2 // Leave space for length
   buf.writeUInt16BE(digest.keyTag, offset)
@@ -1311,7 +1302,7 @@ rds.decode = function (buf, offset) {
 rds.decode.bytes = 0
 
 rds.encodingLength = function (digest) {
-  return 6 + Buffer.byteLength(digest.digest)
+  return 6 + Buffer.byteLength(digest.digest, 'hex')
 }
 
 const rsshfp = exports.sshfp = {}