eth_getStorageAt 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
.
Copy 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 Postman
Copy curl https://ethereum.api.watchdata.io/node/jsonrpc?api_key=your_api_key
-X POST \
-d '{"jsonrpc":"2.0", "method": "eth_getStorageAt", "params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x0", "latest"], "id": 1}'
Copy URL: https: //ethereum.api.watchdata.io/node/jsonrpc?api_key=your_api_key
RequestType: POST
Body:
{
"jsonrpc" : "2.0" ,
"method" : "eth_getStorageAt" ,
"params" : [ "0x295a70b2de5e3953354a6a8344e616ed314d7251" , "0x0" , "latest" ] ,
"id" : 1
}
Result
Copy {
"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:
Copy keccack ( LeftPad32 (key , 0 ) , LeftPad32 (map position , 0 ))
This means to retrieve the storage on pos1[β0x391694e7e0b0cce554cb130d723a9d27458f9298β]
we need to calculate the position with:
Copy keccak(decodeHex("000000000000000000000000391694e7e0b0cce554cb130d723a9d27458f9298" + "0000000000000000000000000000000000000000000000000000000000000001"))
The geth console which comes with the web3 library can be used to make the calculation:
Copy > var key = "000000000000000000000000391694e7e0b0cce554cb130d723a9d27458f9298" + "0000000000000000000000000000000000000000000000000000000000000001"
undefined
> web3.sha3( key, { "encoding" : "hex" } )
"0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9"
Now to fetch the storage:
Request example
Curl Postman
Copy curl https://ethereum.api.watchdata.io/node/jsonrpc?api_key=your_api_key
-X POST \
-d '{"jsonrpc":"2.0", "method": "eth_getStorageAt", "params": ["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9", "latest"], "id": 1}'
Copy URL: https: //ethereum.api.watchdata.io/node/jsonrpc?api_key=your_api_key
RequestType: POST
Body:
{
"jsonrpc" : "2.0" ,
"method" : "eth_getStorageAt" ,
"params":["0x295a70b2de5e3953354a6a8344e616ed314d7251", "0x6661e9d6d8b923d5bbaab1b96e1dd51ff6ea2a93520fdc9eb75d059238b8c5e9", "latest"],
"id" : 1
}
Result
Copy {
"jsonrpc" : "2.0" ,
"id" : 1 ,
"result" : "0x000000000000000000000000000000000000000000000000000000000000162e"
}