Reference → QRNG

As of January 1, 2025, API3 will no longer be supporting the QRNG service. Learn more

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AirnodeRrpV0.sol

A requester (smart contract) uses the function makeFullRequest() from the AirnodeRrpV0.sol contract (by way of RrpRequesterV0.sol) to request, then receive, a quantum random number. See Understanding QRNG.

1. The requester "requests" the quantum random number and gets a requestId in return.

2. When the quantum random number is generated, it is fulfilled to a callback function in the requester.

The code snippets on this page are extracted from the QRNGExample.sol contract. See it for completeness.

airnode.makeFullRequest()

pragma solidity 0.8.9;
import "@api3/airnode-protocol/contracts/rrp/requesters/RrpRequesterV0.sol";
...
event RequestedUint256(bytes32 indexed requestId);
...
mapping(bytes32 => bool) public expectingRequestWithIdToBeFulfilled;
...
function makeRequestUint256() external {
   bytes32 requestId = airnodeRrp.makeFullRequest(
      airnode,                      // address airnode
      endpointIdUint256,            // bytes32 endpointId
      address(this),                // address sponsor
      sponsorWallet,                // address sponsorWallet
      address(this),                // address fulfillAddress
      this.fulfillUint256.selector, // bytes4 fulfillFunctionId
      ""                            // bytes calldata parameters
   );
   expectingRequestWithIdToBeFulfilled[requestId] = true;
   emit RequestedUint256(requestId);
}

Parameters

• address airnode: Address of the Airnode to use. See the Chains page for a list of address on different chains.
• bytes32 endpointId: Endpoint ID known by the Airnode that will map to an API provider call (allowed to be bytes32(0)).
• address sponsor: Sponsor address, usually the requester's contract address.
• address sponsorWallet: Sponsor wallet that is used to fulfill the request.
• address fulfillAddress: Address that will be called to fulfill, usually requester's contract address.
• bytes4 fulfillFunctionId: Signature of the function that will be called to fulfill.
• bytes calldata parameters: There are no parameters QRNG endpoints require.

See the QrngExample.sol contract as an example on how to populate the parameters using its setRequestParameters() function. Setting parameter values once on the requester contract is useful as these parameter values usually do not change.

Returns

• requestId: The request will be assigned an ID for future reference and will also be part of the callback to the fulfillment function.

Callback

Once Airnode receives an RRP request, it will immediately return a requestId to the requester. Airnode then uses the parameters of the request to gather the random number from the appropriate API provider. Then it will callback to the requester with the requestId and the data. The callback is made using the request parameter this.fulfillUint256.selector. Below is an example callback within a requester.

...
event ReceivedUint256(bytes32 indexed requestId, uint256 response);
...
mapping(bytes32 => bool) public expectingRequestWithIdToBeFulfilled;
...
function fulfillUint256(bytes32 requestId, bytes calldata data)
        external
        onlyAirnodeRrp
    {
        require(
            expectingRequestWithIdToBeFulfilled[requestId],
            "Request ID not known"
        );
        expectingRequestWithIdToBeFulfilled[requestId] = false;
        uint256 qrngUint256 = abi.decode(data, (uint256));
        // Do what you want with `qrngUint256` here...
        emit ReceivedUint256(requestId, qrngUint256);
    }

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