Fix exception in separated packages

lib/composer.js

@@ -107,8 +107,8 @@ pro.reset = function() {
 // read length part of package
 pro._readLength = function(data, offset, end) {
   var b, i, length = this.length, finish;
-  for(i=0; i<end; i++) {
-    b = data.readUInt8(i + offset);
+  for(i=offset; i<end; i++) {
+    b = data.readUInt8(i);
     length *= LEFT_SHIFT_BITS;    // left shift only within 32 bits
     length += (b & 0x7f);
 
@@ -133,7 +133,7 @@ pro._readLength = function(data, offset, end) {
     this.left = this.length;
     this.buf = new Buffer(this.length);
   }
-  return i + offset;
+  return i;
 };
 
 // read data part of package

test/composer-test.js

@@ -104,4 +104,32 @@ describe('#Composer', function() {
     // should come here
     should.be.ok(false);
   });
+
+  it('should compose and decompose the separated packages', function (done) {
+      var src1 = 'hello';
+      var src2 = 'world' + new Array(127).join(".");
+      var comp1 = new Composer();
+      var comp2 = new Composer();
+
+      var res1 = comp1.compose(src1);
+      var res2 = comp1.compose(src2);
+
+      // assumeed that packets are separated by TCP.
+      var packet1 = Buffer.concat([res1, res2.slice(0, 1)]);
+      var packet2 = res2.slice(1);
+
+      var first = true;
+      comp2.on('data', function (data) {
+          var str = data.toString('utf-8');
+          if (first) {
+              str.should.equal(src1);
+              first = false;
+          } else {
+              str.should.equal(src2);
+              done();
+          }
+      });
+      comp2.feed(packet1);
+      comp2.feed(packet2);
+  });
 });