merged @pwmckenna's fix for 53bit numbers

Author: themasch

lib/encode.js

@@ -33,7 +33,7 @@ encode._encode = function( buffers, data ) {
         : encode.dict( buffers, data )
       break
   }
-  
+
 }
 
 var buff_e = new Buffer('e')
@@ -46,14 +46,13 @@ encode.bytes = function( buffers, data ) {
 }
 
 encode.number = function( buffers, data ) {
-  
-  var maxLo = 4294967295
+  var maxLo = 0x80000000
   var hi = ( data / maxLo ) << 0
   var lo = ( data % maxLo  ) << 0
   var val = hi * maxLo + lo
-  
+
   buffers.push( new Buffer( 'i' + val + 'e' ))
-  
+
   if( val !== data && !encode._floatConversionDetected ) {
     encode._floatConversionDetected = true
     console.warn(
@@ -62,7 +61,7 @@ encode.number = function( buffers, data ) {
     )
     console.trace()
   }
-  
+
 }
 
 encode.dict = function( buffers, data ) {

test/encode.test.js

@@ -2,6 +2,10 @@ var assert = require("assert");
 var bencode = require('./lib.js');
 
 describe("bencode", function() {
+
+  // prevent the warning showing up in the test
+  bencode.encode._floatConversionDetected = true
+
   describe("#encode()", function() {
     it('should always return a Buffer', function() {
       assert.ok(Buffer.isBuffer(bencode.encode({})), "its not a buffer for empty dicts");
@@ -36,17 +40,42 @@ describe("bencode", function() {
     it('should be able to encode a negative float (as int)', function() {
       assert.equal(bencode.encode(-123.5), 'i-123e');
     })
-    it('should be able to encode a positive 64 bit int', function() {
-      assert.equal(bencode.encode(4777722361), 'i4777722361e');
+    it('should be able to safely encode numbers between -/+ 2 ^ 53 (as ints)', function() {
+      assert.equal(bencode.encode(0), 'i' + 0 + 'e');
+
+      var JAVASCRIPT_INT_BITS = 53;
+      var MAX_JAVASCRIPT_INT = Math.pow(2, JAVASCRIPT_INT_BITS);
+
+      for (var exp = 1; exp < JAVASCRIPT_INT_BITS; ++exp) {
+        var val = Math.pow(2, exp);
+        // try the positive and negative
+        assert.equal(bencode.encode(val), 'i' + val + 'e');
+        assert.equal(bencode.encode(-val), 'i-' + val + 'e');
+
+        // try the value, one above and one below, both positive and negative
+        var above = val + 1;
+        var below = val - 1;
+
+        assert.equal(bencode.encode(above), 'i' + above + 'e');
+        assert.equal(bencode.encode(-above), 'i-' + above + 'e');
+
+        assert.equal(bencode.encode(below), 'i' + below + 'e');
+        assert.equal(bencode.encode(-below), 'i-' + below + 'e');
+      }
+      assert.equal(bencode.encode(MAX_JAVASCRIPT_INT), 'i' + MAX_JAVASCRIPT_INT + 'e');
+      assert.equal(bencode.encode(-MAX_JAVASCRIPT_INT), 'i-' + MAX_JAVASCRIPT_INT + 'e');
+    });
+    it('should be able to encode a previously problematice 64 bit int', function() {
+      assert.equal(bencode.encode(2433088826), 'i' + 2433088826 + 'e');
     })
     it('should be able to encode a negative 64 bit int', function() {
-      assert.equal(bencode.encode(-4777722361), 'i-4777722361e');
+      assert.equal(bencode.encode(-0xffffffff), 'i-' + 0xffffffff + 'e');
     })
     it('should be able to encode a positive 64 bit float (as int)', function() {
-      assert.equal(bencode.encode(4777722361.5), 'i4777722361e');
+      assert.equal(bencode.encode(0xffffffff + 0.5), 'i' + 0xffffffff + 'e');
     })
     it('should be able to encode a negative 64 bit float (as int)', function() {
-      assert.equal(bencode.encode(-4777722361.5), 'i-4777722361e');
+      assert.equal(bencode.encode(-0xffffffff - 0.5), 'i-' + 0xffffffff + 'e');
     })
     it('should be able to encode a string', function() {
       assert.equal(bencode.encode("asdf"), '4:asdf');