do not encode partial or invalid code points to utf8
do not encode partial or invalid code points to utf8

kawanet/buffer,LiuDeng/buffer,jessetane/buffer,loon3/buffer,LinusU/buffer,LiuDeng/buffer,btd/buffer,btd/buffer,beni55/buffer,SAGV/buffer,kawanet/buffer,LinusU/buffer,SAGV/buffer,feross/buffer,beni55/buffer,feross/buffer,nolanlawson/buffer,feross/buffer,nolanlawson/buffer,loon3/buffer