Returns the value from a storage position at a given address, or in other words, returns the state of the contract's storage, which may not be exposed via the contract's methods.
Parameters
- DATA, 20 Bytes - Address of the storage.
- QUANTITY - Integer of the position in the storage.
- QUANTITY|TAG - Integer block number, or the string "latest", "earliest" or "pending", see the default block parameter.
Returns
DATA - The value at this storage position.
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 straight forward:
Request
curl --location --request POST 'https://scroll-alpha.unifra.io/v1/your-api-key' \
--header 'Content-Type: application/json' \
--data-raw '{
"jsonrpc":"2.0",
"method":"eth_getStorageAt",
"params":["0xE06F3c8076dcf99Bc7b9f7a552fE9D18e4c5e85c", "0x0", "latest"],
"id":1
}'Result
{
"jsonrpc": "2.0",
"id": 1,
"result": "0x0000000000000000000000000000000000000000000000000000000000000000"
}Retrieving an element of the map is harder. The position of an element in the map is calculated with:
keccack(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 geth console which comes with the web3 library can be used to make the calculation:
> var key = "000000000000000000000000391694e7e0b0cce554cb130d723a9d27458f9298" + "0000000000000000000000000000000000000000000000000000000000000001"
undefined
> web3.sha3(key, {"encoding": "hex"})
"0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9"Now to fetch the storage:
Request
curl https://eth-mainnet.unifra.io/v1/your-api-key \
-X POST \
-H "Content-Type: application/json" \
-d '{"jsonrpc":"2.0", "method": "eth_getStorageAt", "params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9", "latest"], "id": 1}'Result
{
"jsonrpc": "2.0",
"id": 1,
"result": "0x000000000000000000000000000000000000000000000000000000000000162e"
}