important change to regrank interface, need some more test

python/xgboost_python.cpp

@@ -1,12 +1,41 @@
 #include "xgboost_python.h"
+#include "../regrank/xgboost_regrank.h"
+#include "../regrank/xgboost_regrank_data.h"
 
-void* XGDMatrixCreate(void){
-    return NULL;
-}
-void XGDMatrixFree(void *handle){
-}
-void XGDMatrixLoad(void *handle, const char *fname){
-}
-void XGDMatrixSaveBinary( void *handle, const char *fname ){
-}
+namespace xgboost{
+    namespace python{
+        class DMatrix: public regrank::DMatrix{
+        public:
+            // whether column is initialized
+            bool init_col_;
+        public:
+            DMatrix(void){
+                init_col_ = false;
+            }            
+            ~DMatrix(void){}
+        public:            
+            inline void Load(const char *fname, bool silent){
+                this->CacheLoad(fname, silent);
+                init_col_ = this->data.HaveColAccess();
+            }
+        };
+    };
+};
+
+using namespace xgboost::python;
+
+extern "C"{
+    void* XGDMatrixCreate(void){
+        return new DMatrix();
+    }
+    void XGDMatrixFree(void *handle){
+        delete static_cast<DMatrix*>(handle);
+    }
+    void XGDMatrixLoad(void *handle, const char *fname, int silent){
+        static_cast<DMatrix*>(handle)->Load(fname, silent!=0);
+    }
+    void XGDMatrixSaveBinary(void *handle, const char *fname, int silent){
+        static_cast<DMatrix*>(handle)->SaveBinary(fname, silent!=0);
+    }
+};