feat: add compact protobuf format (#76)

* docs: document .createFromProtobuf and .marshal
* fix: lint
* test: verify .marshal() does it's job

src/index.js

@@ -8,6 +8,7 @@ const mh = require('multihashes')
 const cryptoKeys = require('libp2p-crypto/src/keys')
 const assert = require('assert')
 const withIs = require('class-is')
+const { PeerIdProto } = require('./proto')
 
 class PeerId {
   constructor (id, privKey, pubKey) {
@@ -67,6 +68,15 @@ class PeerId {
     }
   }
 
+  // Return the protobuf version of the peer-id
+  marshal (excludePriv) {
+    return PeerIdProto.encode({
+      id: this.toBytes(),
+      pubKey: this.marshalPubKey(),
+      privKey: excludePriv ? null : this.marshalPrivKey()
+    })
+  }
+
   toPrint () {
     let pid = this.toB58String()
     // All sha256 nodes start with Qm
@@ -232,6 +242,49 @@ exports.createFromJSON = async (obj) => {
   return new PeerIdWithIs(id, privKey, pub)
 }
 
+exports.createFromProtobuf = async (buf) => {
+  if (typeof buf === 'string') {
+    buf = Buffer.from(buf, 'hex')
+  }
+
+  let { id, privKey, pubKey } = PeerIdProto.decode(buf)
+
+  privKey = privKey ? await cryptoKeys.unmarshalPrivateKey(privKey) : false
+  pubKey = pubKey ? await cryptoKeys.unmarshalPublicKey(pubKey) : false
+
+  let pubDigest
+  let privDigest
+
+  if (privKey) {
+    privDigest = await computeDigest(privKey.public)
+  }
+
+  if (pubKey) {
+    pubDigest = await computeDigest(pubKey)
+  }
+
+  if (privKey) {
+    if (pubKey) {
+      if (!privDigest.equals(pubDigest)) {
+        throw new Error('Public and private key do not match')
+      }
+    }
+    return new PeerIdWithIs(privDigest, privKey, privKey.public)
+  }
+
+  // TODO: val id and pubDigest
+
+  if (pubKey) {
+    return new PeerIdWithIs(pubDigest, null, pubKey)
+  }
+
+  if (id) {
+    return new PeerIdWithIs(id)
+  }
+
+  throw new Error('Protobuf did not contain any usable key material')
+}
+
 exports.isPeerId = (peerId) => {
   return Boolean(typeof peerId === 'object' &&
     peerId._id &&

src/proto.js

@@ -0,0 +1,12 @@
+'use strict'
+
+const protons = require('protons')
+module.exports = protons(`
+
+message PeerIdProto {
+  required bytes id = 1;
+  bytes pubKey = 2;
+  bytes privKey = 3;
+}
+
+`)