buffer: slow buffer copy compatibility fix

Fix issue where SlowBuffers couldn't be passed as target to Buffer
copy().

Also included checks to see if Argument parameters are defined before
assigning their values. This offered ~3x's performance gain.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index 70c9c80876..d808dbf978 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -402,10 +402,10 @@ Handle<Value> Buffer::Copy(const Arguments &args) {
   Local<Object> target = args[0]->ToObject();
   char* target_data = Buffer::Data(target);
   size_t target_length = Buffer::Length(target);
-  size_t target_start = args[1]->Uint32Value();
-  size_t source_start = args[2]->Uint32Value();
-  size_t source_end = args[3]->IsUint32() ? args[3]->Uint32Value()
-                                          : source->length_;
+  size_t target_start = args[1]->IsUndefined() ? 0 : args[1]->Uint32Value();
+  size_t source_start = args[2]->IsUndefined() ? 0 : args[2]->Uint32Value();
+  size_t source_end = args[3]->IsUndefined() ? source->length_
+                                              : args[3]->Uint32Value();
 
   if (source_end < source_start) {
     return ThrowException(Exception::Error(String::New(