From db0552874bbca4fc5d64199336d4d52c026d4318 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Wed, 27 Jul 2016 03:59:24 -0700
Subject: [PATCH] bip151: more micro-optimization.

---
 lib/bcoin/bip151.js | 35 ++++++++++++++---------------------
 1 file changed, 14 insertions(+), 21 deletions(-)

diff --git a/lib/bcoin/bip151.js b/lib/bcoin/bip151.js
index 8180f31f..ba150125 100644
--- a/lib/bcoin/bip151.js
+++ b/lib/bcoin/bip151.js
@@ -72,6 +72,8 @@ function BIP151Stream(cipher, key) {
   this.tag = null;
   this.seqHi = 0;
   this.seqLo = 0;
+  this.iv = new Buffer(12);
+  this.iv.fill(0);
 
   this.highWaterMark = 1024 * (1 << 20);
   this.processed = 0;
@@ -92,7 +94,6 @@ utils.inherits(BIP151Stream, EventEmitter);
 
 BIP151Stream.prototype.init = function init(publicKey) {
   var p = bcoin.writer();
-  var iv;
 
   this.publicKey = publicKey;
   this.secret = bcoin.ec.ecdh(this.publicKey, this.privateKey);
@@ -108,10 +109,10 @@ BIP151Stream.prototype.init = function init(publicKey) {
   this.seqHi = 0;
   this.seqLo = 0;
 
-  iv = this.iv();
+  this.update();
 
-  this.chacha.init(this.k1, iv);
-  this.aead.init(this.k2, iv);
+  this.chacha.init(this.k1, this.iv);
+  this.aead.init(this.k2, this.iv);
 
   this.lastRekey = utils.now();
 };
@@ -142,8 +143,6 @@ BIP151Stream.prototype.maybeRekey = function maybeRekey(data) {
  */
 
 BIP151Stream.prototype.rekey = function rekey() {
-  var iv;
-
   assert(this.prk, 'Cannot rekey before initialization.');
 
   // All state is reinitialized
@@ -151,10 +150,8 @@ BIP151Stream.prototype.rekey = function rekey() {
   this.k1 = utils.hash256(this.k1);
   this.k2 = utils.hash256(this.k2);
 
-  iv = this.iv();
-
-  this.chacha.init(this.k1, iv);
-  this.aead.init(this.k2, iv);
+  this.chacha.init(this.k1, this.iv);
+  this.aead.init(this.k2, this.iv);
 };
 
 /**
@@ -165,8 +162,6 @@ BIP151Stream.prototype.rekey = function rekey() {
  */
 
 BIP151Stream.prototype.sequence = function sequence() {
-  var iv;
-
   // Wrap sequence number a la openssh.
   if (++this.seqLo === 0x100000000) {
     this.seqLo = 0;
@@ -174,12 +169,12 @@ BIP151Stream.prototype.sequence = function sequence() {
       this.seqHi = 0;
   }
 
-  iv = this.iv();
+  this.update();
 
   // State of the ciphers is
   // unaltered aside from the iv.
-  this.chacha.init(null, iv);
-  this.aead.init(null, iv);
+  this.chacha.init(null, this.iv);
+  this.aead.init(null, this.iv);
 };
 
 /**
@@ -187,12 +182,10 @@ BIP151Stream.prototype.sequence = function sequence() {
  * @returns {Buffer}
  */
 
-BIP151Stream.prototype.iv = function _iv() {
-  var iv = new Buffer(12);
-  iv.writeUInt32LE(this.seqLo, 0, true);
-  iv.writeUInt32LE(this.seqHi, 4, true);
-  iv.writeUInt32LE(0, 8, true);
-  return iv;
+BIP151Stream.prototype.update = function update() {
+  this.iv.writeUInt32LE(this.seqLo, 0, true);
+  this.iv.writeUInt32LE(this.seqHi, 4, true);
+  return this.iv;
 };
 
 /**