bufferutils: add varIntBuffer

src/block.js

@@ -120,13 +120,7 @@ Block.prototype.toBuffer = function(headersOnly) {
 
   if (headersOnly || !this.transactions) return buffer
 
-  function varIntBuffer(i) {
+  var txLenBuffer = bufferutils.varIntBuffer(this.transactions.length)
-    var ib = new Buffer(bufferutils.varIntSize(i))
-    bufferutils.writeVarInt(ib, i, 0)
-    return ib
-  }
-
-  var txLenBuffer = varIntBuffer(this.transactions.length)
   var txBuffers = this.transactions.map(function(tx) {
     return tx.toBuffer()
   })

src/bufferutils.js

@@ -159,6 +159,14 @@ function writeVarInt(buffer, number, offset) {
   return size
 }
 
+function varIntBuffer(i) {
+  var size = varIntSize(i)
+  var buffer = new Buffer(size)
+  writeVarInt(buffer, i, 0)
+
+  return buffer
+}
+
 function reverse(buffer) {
   var buffer2 = new Buffer(buffer)
   Array.prototype.reverse.call(buffer2)
@@ -171,6 +179,7 @@ module.exports = {
   readUInt64LE: readUInt64LE,
   readVarInt: readVarInt,
   reverse: reverse,
+  varIntBuffer: varIntBuffer,
   varIntSize: varIntSize,
   writePushDataInt: writePushDataInt,
   writeUInt64LE: writeUInt64LE,

src/message.js

@@ -13,8 +13,7 @@ var ecparams = ecurve.getCurveByName('secp256k1')
 function magicHash(message, network) {
   var magicPrefix = new Buffer(network.magicPrefix)
   var messageBuffer = new Buffer(message)
-  var lengthBuffer = new Buffer(bufferutils.varIntSize(messageBuffer.length))
+  var lengthBuffer = bufferutils.varIntBuffer(messageBuffer.length)
-  bufferutils.writeVarInt(lengthBuffer, messageBuffer.length, 0)
 
   var buffer = Buffer.concat([magicPrefix, lengthBuffer, messageBuffer])
   return crypto.hash256(buffer)

test/bufferutils.js

@@ -88,6 +88,16 @@ describe('bufferutils', function() {
     })
   })
 
+  describe('varIntBuffer', function() {
+    fixtures.valid.forEach(function(f) {
+      it('encodes ' + f.dec + ' correctly', function() {
+        var buffer = bufferutils.varIntBuffer(f.dec)
+
+        assert.equal(buffer.toString('hex'), f.hexVI)
+      })
+    })
+  })
+
   describe('varIntSize', function() {
     fixtures.valid.forEach(function(f) {
       it('determines the varIntSize of ' + f.dec + ' correctly', function() {
@@ -99,7 +109,7 @@ describe('bufferutils', function() {
   })
 
   describe('writePushDataInt', function() {
-    fixtures.valid.forEach(function(f, i) {
+    fixtures.valid.forEach(function(f) {
       if (!f.hexPD) return
 
       it('encodes ' + f.dec + ' correctly', function() {