I tried to add a native java method in Openjdk 7; I built the Openjdk 7 over windows XP using Microsoft VS2010.

Before adding the method in Openjdk I tried it in Microsoft VS2010 as follow:
The code of my method is: 

void test (obj* from, int count){
 
 __asm{
	 mov esi, from  ; 
         mov ecx, count ;
         lo: 
            cmp ecx, 0;
            jl doni;
	     add dword ptr [esi + ecx * 8], 10
        sub ecx,1 
	 jmp lo;
        doni: ;
      }
}

Where obj* is an array of objects

obj.cpp

#include "stdafx.h"
#include "obj.hpp"
#include <iostream> 
 
using namespace std;
 
 
obj:: obj(int x, int y) {
   this->x =x;
   this->y =y;
   }
 
obj:: obj (){}
 
int obj::getX(){return x;}
int obj::getY(){return y;}

obj.hpp 

#include <iostream> 
using namespace std;
 
class obj
{
public:
    obj();
    obj (int x, int y);
    int getX(); 
    int getY(); 
private: 
  int x,y;
};

When I execute this procedure in Microsoft VS2010 it works very well.
For example: we have an array of object obj* T :
(1,1) (2,2) (3,3) after the call of test (T,2) the result will be:
(2,1) (3,2) (4,3)

The problem:

When I add this procedure in openJDK7 “openjdk\hotspot\src\os_cpu\windows_x86\vm\ copy_windows_x86.inline.hpp” with the following code: (oop is an ordinary object in JVM)


 void test (oop* from, int count){
 __asm{
         mov esi, from  ; 
         mov ecx, count ;
         lo: 
            cmp ecx, 0;
            jl doni;
	     add dword ptr [esi + ecx * 8], 10
        sub ecx,1 
	 jmp lo;
        doni: ;
      }
}
I call this procedure from:
“openjdk\hotspot\src\share\vm\oops\objArrayKlass.c pp

void objArrayKlass::test1(arrayOop s,int src_pos int length, TRAPS) {
 
         	  oop*  src = objArrayOop(s)->obj_at_addr<oop>(src_pos);
  		  Copy::test2(src,length);
              }

It does not work; the problem is the mode addressing of the object in the heap of JVM.
The size of object in C++ or Microsoft VS2010 is not the same as the size of Java object.
I want of change the ligne :

add dword ptr [esi + ecx * 8], 10

to be able to get the right address of object in memory and change it

I note that when a use an array of primitive type it works very well in openJdk.
For example, an array of integer in

“openjdk\hotspot\src\share\vm\oops\typeArrayKlass. cpp”

void typeArrayKlass::test1(arrayOop s, int src_pos, int length, TRAPS) {
      int l2es = log2_element_size();
      int ihs = array_header_in_bytes() / wordSize;
 
      char* src = (char*) ((oop*)s + ihs) + ((size_t)src_pos << l2es);
       Copy::test2((jint*)src,(size_t)length << l2es); 
 
    }