Raw Strings are JSON Objects (the raw bytes are stored in an array for the key “raw”). The Ruby String can be created by this module method.
static VALUE mString_Extend_json_create(VALUE self, VALUE o)
{
VALUE ary;
Check_Type(o, T_HASH);
ary = rb_hash_aref(o, rb_str_new2("raw"));
return rb_funcall(ary, i_pack, 1, rb_str_new2("C*"));
}