handle varInts better

lib/bufferreader.js

@@ -70,7 +70,7 @@ BufferReader.prototype.readVarInt = function() {
     case 0xFE:
       return this.readUInt32LE();
     case 0xFF:
-      return this.readUInt64LEBN().toNumber();
+      throw new Error('number too large to retain precision - use readVarIntBN');
     default:
       return first;
   }

lib/bufferwriter.js

@@ -56,7 +56,6 @@ BufferWriter.prototype.writeUInt64BEBN = function(bn) {
   return this;
 };
 
-//TODO: What if n is so large that it loses precision?
 BufferWriter.prototype.writeUInt64LEBN = function(bn) {
   var buf = bn.toBuffer({size: 8});
   var reversebuf = new Buffer(Array.apply(new Array(), buf).reverse());
@@ -76,7 +75,6 @@ BufferWriter.prototype.writeVarIntBN = function(bn) {
   return this;
 };
 
-//TODO: What if n is so large that it loses precision?
 BufferWriter.varIntBuf = function(n) {
   var buf = undefined;
   if (n < 253) {

test/test.bufferreader.js

@@ -1,3 +1,4 @@
+var BufferWriter = require('../lib/bufferwriter');
 var BufferReader = require('../lib/bufferreader');
 var should = require('chai').should();
 
@@ -156,10 +157,12 @@ describe('BufferReader', function() {
       br.readVarInt().should.equal(50000);
     });
 
-    it('should read a 9 byte varint', function() {
+    it('should throw an error on a 9 byte varint', function() {
       var buf = Buffer.concat([new Buffer([255]), new Buffer('ffffffffffffffff', 'hex')]);
       var br = new BufferReader(buf);
-      br.readVarInt().should.equal(Math.pow(2, 64));
+      (function() {
+        br.readVarInt();
+      }).should.throw('number too large to retain precision - use readVarIntBN');
     });
 
   });

test/test.bufferwriter.js

@@ -1,4 +1,5 @@
 var BufferWriter = require('../lib/bufferwriter');
+var BufferReader = require('../lib/bufferreader');
 var BN = require('../lib/bn');
 var should = require('chai').should();
 
@@ -120,6 +121,15 @@ describe('BufferWriter', function() {
       bw.concat().length.should.equal(9);
     });
 
+    it('should read back the same value it wrote for a 9 byte varInt', function() {
+      var bw = new BufferWriter();
+      var n = Math.pow(2, 53);
+      n.should.equal(n + 1); //javascript number precision limit
+      bw.writeVarInt(n);
+      var br = new BufferReader(bw.concat());
+      br.readVarIntBN().toNumber().should.equal(n);
+    });
+
   });
 
   describe('#writeVarIntBN', function() {