fixed C# bytebuffer put methods

net/FlatBuffers/ByteBuffer.cs

@@ -35,13 +35,18 @@ namespace FlatBuffers
 
         public byte[] Data { get { return _buffer; } }
 
-        public ByteBuffer(byte[] buffer)
+        public ByteBuffer(byte[] buffer) : this(buffer, 0) { }
+
+        public ByteBuffer(byte[] buffer, int pos)
         {
             _buffer = buffer;
-            _pos = 0;
+            _pos = pos;
         }
 
-        public int Position { get { return _pos; } }
+        public int Position {
+            get { return _pos; }
+            set { _pos = value; }
+        }
 
         // Pre-allocated helper arrays for convertion.
         private float[] floathelper = new[] { 0.0f };
@@ -92,7 +97,6 @@ namespace FlatBuffers
                     _buffer[offset + count - 1 - i] = (byte)(data >> i * 8);
                 }
             }
-            _pos = offset;
         }
 
         protected ulong ReadLittleEndian(int offset, int count)
@@ -129,14 +133,12 @@ namespace FlatBuffers
         {
             AssertOffsetAndLength(offset, sizeof(sbyte));
             _buffer[offset] = (byte)value;
-            _pos = offset;
         }
 
         public void PutByte(int offset, byte value)
         {
             AssertOffsetAndLength(offset, sizeof(byte));
             _buffer[offset] = value;
-            _pos = offset;
         }
 
         // this method exists in order to conform with Java ByteBuffer standards

net/FlatBuffers/FlatBufferBuilder.cs

@@ -75,8 +75,8 @@ namespace FlatBuffers
 
             Buffer.BlockCopy(oldBuf, 0, newBuf, newBufSize - oldBufSize,
                              oldBufSize);
-
-            _bb = new ByteBuffer(newBuf);
+            _bb = new ByteBuffer(newBuf, newBufSize);
+            System.Diagnostics.Debug.WriteLine(_bb.Position);
         }
 
         // Prepare to write an element of `size` after `additional_bytes`
@@ -359,6 +359,7 @@ namespace FlatBuffers
         {
             Prep(_minAlign, sizeof(int));
             AddOffset(rootTable);
+            _bb.Position = _space;
         }
 
         public ByteBuffer DataBuffer { get { return _bb; } }
@@ -387,7 +388,7 @@ namespace FlatBuffers
              {
                 AddByte((byte)fileIdentifier[i]);
              }
-             AddOffset(rootTable);
+             Finish(rootTable);
         }