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eth_getstorageat
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.
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.
DATA
- the value at this storage position.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:curl https://rpc.<REGION>.gateway.fm/v4/gnosis/non-archival/mainnet \
-X POST \
-H "Content-Type: application/json" \
-d '{"jsonrpc":"2.0", "method": "eth_getStorageAt", "params": ["0x75Df5AF045d91108662D8080fD1FEFAd6aA0bb59", "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:
curl https://rpc.gateway.fm/v4/ethereum/mainnet \
-X POST \
-H "Authorization: Bearer <YOUR_API_KEY>" \
-H "Content-Type: application/json" \
-d '{"jsonrpc":"2.0", "method": "eth_getStorageAt", "params": ["0x3f5CE5FBFe3E9af3971dD833D26bA9b5C936f0bE","0x0",14036168 ],"id": 89}'
Result
{
"jsonrpc":"2.0",
"id":89,
"result":"0x0000000000000000000000000000000000000000000000000000000000000000"
}
Last modified 10mo ago