Get ERC20 token balance by GetStorageRanges on Snap Protocol

[suhoangson]

Hi Everyone,
I want to use GetStorageRanges in Snap Protocol https://github.com/ethereum/devp2p/blob/master/caps/snap.md#getstorageranges-0x02 for get balance of ERC20 token from Peer (i do not want to use RCP).
Based on my understanding, balance of ERC20 token is stored in storage slots
I check with USDT token: 0xdAC17F958D2ee523a2206206994597C13D831ec7
My account holder: 0xC0fcFAd6a5db86F566102B8a7115823068a93c50
Current my USDT balance on Metamask is: 7.45433 USDT
I checked on this tool: https://github.com/vocdoni/storage-proofs-eth-go/blob/master/examples/verify-top-50-erc20/main.go with USDT token and my account above
=>The result: my USDT balance was stored in slot 2, slot hash is: 0xc83ac632ddd978600e673c3064377a289fc7b6beba2050e1c1b0c5905a89fb9e

Based on above result, my code is:

......
func GetMapSlot(holder common.Address, position int) [32]byte {
	return crypto.Keccak256Hash(
		common.LeftPadBytes(holder[:], 32),
		common.LeftPadBytes(big.NewInt(int64(position)).Bytes(), 32),
	)
}
func main(){
                token_addr:=common.HexToAddress("0xdAC17F958D2ee523a2206206994597C13D831ec7") //USDT 
		token_hash:=crypto.Keccak256Hash(token_addr[:])
		fmt.Println("1. USDT Token hash: ",token_hash)

		account_addr:=common.HexToAddress("0xC0fcFAd6a5db86F566102B8a7115823068a93c50") //holder address
		start_slot_hash:=GetMapSlot(account_addr,2)
		fmt.Println("2. Start slot hash: ",common.Hash(start_slot_hash).Hex())
		end_slot_hash:=start_slot_hash
		
		//StateRoot: just pick a latest block on etherscan.io
		root_hash:=common.HexToHash("0xe87f3c92bbeadc3963c747fd039e390d4f3e0f0f9e6491302b96d20b284db0a0") 
               
               /* 
                    .....
                   create a peer connection as this example:  https://github.com/ethereum/go-ethereum/blob/master/cmd/devp2p/internal/ethtest/conn.go
               */ 
 	       // write request
	       req := &snap.GetStorageRangesPacket{
		      ID:               uint64(rand.Int63()),
		      Root:           root_hash,
		      Accounts:    []common.Hash{token_hash},
	 	      Origin:         start_slot_hash[:],
		      Limit:           end_slot_hash[:],
		      Bytes:          4000,
	       }
	       msg, err := conn.snapRequest(snap.GetStorageRangesMsg, req)
	       if err != nil {
		      return
	       }
	       res, ok := msg.(*snap.StorageRangesPacket)
	       if !ok {
		      return
	       }
               for _, slots := range res.Slots {
                      for j := 0; j < len(slots); j++ {
                            slot_hash:=slots[j].Hash
                            balance:=new(big.Int).SetBytes(slots[j].Body)
	                    fmt.Println("3. Slot hash from Peer: ",slot_hash)
	                    fmt.Println("4. Balance from Peer: ",balance)
                      }
               }
}

After i excuted above code, the result is:

1. USDT Token hash:              0xab14d68802a763f7db875346d03fbf86f137de55814b191c069e721f47474733
2. Start slot hash:             0xc83ac632ddd978600e673c3064377a289fc7b6beba2050e1c1b0c5905a89fb9e 
3. Slot hash from Peer:          0xc83ac7360fc812328443907c5af92c510beeec16180b33b60783bada4d36ecf5 
4. Balance from Peer:            18642526367207907463194928586398753164376467531168130810352671025274013872029695;

Slot hash (3) return from Peer is difference with (2) and blance (4) from Peer also difference with my current USDT balance. What is wrong in my code?