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klay_getStorageAt
Returns the value from a storage position at a given address.
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" |
Type | Description |
|---|---|
DATA | The value at this storage position.s. |
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"}
Last modified 1yr ago