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

REQUEST

POST https://SliceLedger-rpc.com
Content-Type: application/json

REQUEST PARAMS

  • ADDRESS [required] - a string representing the address (20 bytes) of the storage
  • STORAGE POSITION [required] - a hex code of the position in the storage
  • BLOCK PARAMETER [required] - an integer block number, or the string "latest", "earliest" or "pending", see the default block parameter

EXAMPLE

## JSON-RPC over HTTPS POST
curl https://SliceLedger-rpc.com \
-X POST \
-H "Content-Type: application/json" \
-d '{"jsonrpc":"2.0","method":"eth_getStorageAt","params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9", "0x65a8db"],"id":1}'
## JSON-RPC over WSS
wscat -c ws://SliceLedger-rpc.com
>{"jsonrpc":"2.0","method":"eth_getStorageAt","params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9", "0x65a8db"],"id":1}

RESPONSE

RESULT FIELDS

  • STORAGE VALUE - a hex code of the integer indicating the value of the storage position at the provided address

BODY

{
"jsonrpc": "2.0",
"id": 1,
"result": "0x0000000000000000000000000000000000000000000000000000000000000000"
}
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://SliceLedger-rpc.com \
-X POST \
-H "Content-Type: application/json" \
-d '{"jsonrpc":"2.0", "method": "eth_getStorageAt", "params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251
{
"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 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://SliceLedger-rpc.com \
-X POST \
-H "Content-Type: application/json" \
-d '{"jsonrpc":"2.0", "method": "eth_getStorageAt", "params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9", "0x65a8db"], "id": 1}'
{
"jsonrpc": "2.0",
"id": 1,
"result": "0x000000000000000000000000000000000000000000000000000000000000162e"
}
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Outline
REQUEST
RESPONSE