eth_getStorageAt - Polygon

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

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 example

Curl

curl https://polygon.api.watchdata.io/node/jsonrpc?api_key=your_api_key
-X POST \
-d '{"jsonrpc":"2.0", "method": "eth_getStorageAt", "params": ["0xa53d90b608c930cb8cdff22048dc942708c4f263", "0x0", "latest"], "id": 1}'

Postman

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 example

Curl

curl https://polygon.api.watchdata.io/node/jsonrpc?api_key=your_api_key
-X POST \
-d '{"jsonrpc":"2.0", "method": "eth_getStorageAt", "params": ["0xa53d90b608c930cb8cdff22048dc942708c4f263", "0x4acde13c82106a719dbe4751fccb70dee8df86975dd387db9f0c85745005c518", "latest"], "id": 1}'

Postman

Result

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": "0x0000000000000000000000000000000000000000000000000000000000000000"
}