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klay_getStorageAt

Returns the value from a storage position at a given address.

Parameters

Type
Description
20-byte DATA
Address of the storage.
QUANTITY
Integer of the position in the storage.
QUANTITY | TAG | HASH
Integer or hexadecimal block number, or the string "earliest", "latest" or "pending"

Return Value

Type
Description
DATA
The value at this storage position.s.

Example

Calculating the correct position depends on the storage to retrieve. Consider the following contract deployed at 0x295a70b2de5e3953354a6a8344e616ed314d7251 by address 0x391694e7e0b0cce554cb130d723a9d27458f9298.
contract Storage {
uint pos0;
mapping(address => uint) pos1;
​
function Storage() {
pos0 = 1234;
pos1[msg.sender] = 5678;
}
}
Retrieving the value of pos0 is straightforward:
curl -H "Content-Type: application/json" --data '{"jsonrpc":"2.0", "method": "klay_getStorageAt", "params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x0", "latest"], "id": 1}' http://klaytn.blockpi.network/v1/rpc/your-api-key
​
{"jsonrpc":"2.0","id":1,"result":"0x00000000000000000000000000000000000000000000000000000000000004d2"}
Retrieving an element of the map is harder. The position of an element in the map is calculated with:
keccak(LeftPad32(key, 0), LeftPad32(map position, 0))
This means to retrieve the storage on pos1["0x391694e7e0b0cce554cb130d723a9d27458f9298"] we need to calculate the position with:
keccak(decodeHex("000000000000000000000000391694e7e0b0cce554cb130d723a9d27458f9298" + "0000000000000000000000000000000000000000000000000000000000000001"))
The Klaytn console which comes with the klay library can be used to make the calculation
> var key = "000000000000000000000000391694e7e0b0cce554cb130d723a9d27458f9298" + "0000000000000000000000000000000000000000000000000000000000000001"
undefined
> klay.sha3(key, {"encoding": "hex"})
"0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9"
Now to fetch the storage:
curl -H "Content-Type: application/json" --data '{"jsonrpc":"2.0", "method": "klay_getStorageAt", "params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9", "latest"], "id": 1}' http://klaytn.blockpi.network/v1/rpc/your-api-key
​
{"jsonrpc":"2.0","id":1,"result":"0x000000000000000000000000000000000000000000000000000000000000162e"}