witnet-solidity-bridge

witnet/witnet-solidity-bridge is an open source implementation of an API that enables Solidity smart contract developers to harness the full power of the Witnet Decentralized Oracle Network.

This repository provides several deployable contracts:

• WitnetParserLib, helper library useful for parsing Witnet-solved results to previously posted Witnet Data Requests.
• WitnetProxy, a delegate-proxy contract that routes Witnet Data Requests to a currently active WitnetRequestBoard implementation.
• Multiple implementations of the WitnetRequestBoard interface (WRB), which declares all required functionality to relay encapsulated Witnet Data Requests from an EVM compatible chain to the Witnet mainnet, as well as to relay Witnet-solved results back to Ethereum.

The repository also provides:

• UsingWitnet, an inheritable abstract contract that injects methods for conveniently interacting with the WRB.
• WitnetRequest, used as a means to encapsulate unmodifiable Witnet Data Requests.
• WitnetRequestBase, useful as a base contract to implement your own modifiable Witnet Data Requests.

WitnetProxy

WitnetProxy is an upgradable delegate-proxy contract that routes Witnet Data Requests coming from a UsingWitnet-inheriting contract to a currently active WitnetRequestBoard implementation.

To find the entry-point address of the latest deployed version of the WitnetRequestBoard contract in every supported chain, please visit the Witnet Data Feeds Explorer.

IWitnetRequest

Used as a means to encapsulate Witnet Data Requests, that can eventually be posted to a WitnetRequestBoard implementation. The bytecode() of a IWitnetRequest must be constructed from the CBOR-encoded serialization of a Witnet Data Request. The IWitnetRequest interface defines two methods:

• bytecode():

  • Description:
    • Returns Witnet Data Request as a CBOR-encoded bytes.

• hash():

  • Description:
    • Returns SHA256 hash of Witnet Data Request as CBOR-encoded bytes.

WitnetRequestBoard

From the point of view of a UsingWitnet contract, any given WitnetRequestBoard will always support the following interfaces:

• IWitnetRequestBoardEvents
• IWitnetRequestBoardRequestor
• IWitnetRequestBoardView

IWitnetRequestBoardEvents:

• Event PostedRequest(uint256 queryId, address from):

  • Description:
    • Emitted when a Witnet Data Request is posted to the WRB.
  • Arguments:
    • queryId: the query id assigned to this new posting.
    • from: the address from which the Witnet Data Request was posted.

• Event PostedResult(uint256 queryId, address from):

  • Description:
    • Emitted when a Witnet-solved result is reported to the WRB.
  • Arguments:
    • queryId: the id of the query the result refers to.
    • from: the address from which the result was reported.

• Event DeletedQuery(uint256 queryId, address from):

  • Description:
    • Emitted when all data related to given query is deleted from the WRB.
  • Arguments:
    • queryId: the id of the query that has been deleted.
    • from: the address from which the result was reported.

IWitnetRequestBoardRequestor:

• postRequest(IWitnetRequest _request):

  • Description:
    • Posts a Witnet Data Request into the WRB in the expectation that it will be eventually relayed and resolved by the Witnet decentralized oracle network, with msg.value as reward.
  • Inputs:
    • _request: the actual IWitnetRequest contract address which provided the Witnet Data Request bytecode.
  • Returns:
    • _id: the unique identifier of the data request.

• upgradeReward(uint256 _id):

  • Description: increments the reward of a Witnet data request by adding more value to it. The new data request reward will be increased by msg.value.
  • Inputs:
    • _id: the unique identifier of a previously posted Witnet data request.

• deleteQuery(uint256 _id):

  • Description:
    • Retrieves copy of all Witnet-provided data related to a previously posted request, removing the whole query from the WRB storage.
  • Inputs:
    • _id: the unique identifier of a previously posted Witnet data request.
  • Returns:
    • The Witnet-solved result of the given data request, as CBOR-encoded bytes.

IWitnetRequestBoardView:

• estimateReward(uint256 _gasPrice):

  • Description:
    • Estimates the minimal amount of reward needed to post a Witnet data request into the WRB, for a given gas price.
  • Inputs:
    • _gasPrice: the gas price for which we need to calculate the rewards.

• getNextQueryId():

  • Description:
    • Returns next query id to be generated by the Witnet Request Board.

• getQueryData(uint256 _queryId):

  • Description:
    • Gets the whole Witnet.Query record related to a previously posted Witnet Data Request.
  • Inputs:
    • _queryId: the unique identifier of the query.

• getQueryStatus(uint256 _queryId):

  • Description:
    • Gets current status of the given query.
  • Inputs:
    • _queryId: the unique identifier of the query.

• readRequest(uint256 _queryId):

  • Description:
    • Retrieves the whole Witnet.Request record referred to a previously posted Witnet Data Request.
  • Inputs:
    • _queryId: the unique identifier of the query.

• readRequestBytecode(uint256 _queryId):

  • Description:
    • Retrieves the serialized bytecode of a previously posted Witnet Data Request.
  • Inputs:
    • _queryId: the unique identifier of the query.
  • Returns:
    • The Witnet Data Request bytecode, serialized as bytes.

• readRequestGasPrice(uint256 _queryId):

  • Description:
    • Retrieves the gas price that any assigned reporter will have to pay when reporting result to the referred query.
  • Inputs:
    • _queryId: the unique identifier of the query.

• readRequestReward(uint256 _queryId):

  • Description:
    • Retrieves the reward currently set for the referred query.
  • Inputs:
    • _queryId: the unique identifier of the query.

• readResponse(uint256 _queryId):

  • Description:
    • Retrieves the whole Witnet.Response record referred to a previously posted Witnet Data Request. Fails it the query has not been solved yet.
  • Inputs:
    • _queryId: the unique identifier of the query.

• readResponseTimestamp(uint256 _queryId):

  • Description:
    • Retrieves the timestamp in which the result to the referred query was solved by the Witnet DON.
  • Inputs:
    • _queryId: the unique identifier of a previously posted Witnet data request.

• readResponseDrTxHash(uint256 _queryId):

  • Description:
    • Retrieves the hash of the Witnet transaction hash that actually solved the referred query.
  • Inputs:
    • _queryId: the unique identifier of the query.

• readResponseReporter(uint256 _queryId):

  • Description:
    • Retrieves the address from which the result to the referred query was actually reported.
  • Inputs:
    • _queryId: the unique identifier of a previously posted Witnet data request.

• readResponseResult(uint256 _queryId):

  • Description:
    • Retrieves the Witnet-provided CBOR-bytes result to the referred query. Fails it the query has not been solved yet.
  • Inputs:
    • _queryId: the unique identifier of the query.
  • Returns:
    • The Witnet-provided result to the given query, as CBOR-encoded bytes.

UsingWitnet base contract

The UsingWitnet contract injects the following internal methods into the contracts inheriting from it:

• _witnetEstimateReward():

  • Description:
    • Estimates the reward amount, considering current transaction's gas price.
  • Returns:
    • The reward to be included when either posting a new request, or upgrading the reward of a previously posted one.

• _witnetEstimateReward(uint256 _gasPrice):

  • Description:
    • Estimates the reward amount, considering the given gas price is used when either posting or upgrading a request.
  • Inputs:
    • _gasPrice: the gas price for which we want to retrieve the estimation.
  • Returns:
    • The reward to be included when either posting a new request, or upgrading the reward of a previously posted one.

• _witnetPostRequest(IWitnetRequest _request):

  • Description:
    • Method to be called for posting Witnet data request into the WRB, with provided msg.value as reward.
  • Inputs:
    • _request: the Witnet request contract address that provides the Witnet Data Request encoded bytecode.
  • Returns:
    • The unique identifier of the Witnet data request just posted to the WRB.

• _witnetUpgradeReward():

  • Description:
    • Increments the reward of a previously posted Witnet data request by adding more value to it. The new request reward will be increased by msg.value.
  • Inputs:
    • _id: the unique identifier of a previously posted Witnet data request.

• _witnetCheckResultAvailability():

  • Description:
    • Checks if a Witnet data request has already been solved by Witnet network.
  • Inputs:
    • _id: the unique identifier of a previously posted Witnet data request.
  • Returns:
    • A boolean telling whether the Witnet data request has been already solved, or not.

• _witnetReadResult(uint256 _id):

  • Description:
    • Retrieves the Witnet-solved result of a previously posted Witnet data request.
  • Inputs:
    • _id: the unique identifier of a previously posted Witnet data request.
  • Returns:
    • The Witnet-solved result of the given data request, as CBOR-encoded bytes.

• _witnetDeleteQuery(uint256 _id):

  • Description:
    • Retrieves the Witnet-solved result (if already available) of a previously posted Witnet request, and removes it from the WRB storage. Works only if this UsingWitnet contract is the one that actually posted the given data request.
  • Inputs:
    • _id: the unique identifier of a previously posted Witnet data request.
  • Returns:
    • The Witnet-solved result of the given data request, as CBOR-encoded bytes.

Besides, your contract will have access to the whole Witnet Request Board functionality by means of the immutable witnet address field.

Usage: harness the power of the Witnet Decentralized Oracle Network

In order to integrate your own smart contracts with the Witnet fully-decentralized blockchain, you just need to inherit from the UsingWitnet abstract contract:

pragma solidity >=0.7.0 <0.9.0;

import "./UsingWitnet.sol";

contract MyContract is UsingWitnet {
  IWitnetRequest myRequest;

  constructor() UsingWitnet(/* here comes the entrypoint address provided by the Witnet Foundation */) {
    // TODO
  }

  function myOwnDrPost() public payable returns (uint256 _drTrackId) {
    _drTrackId = witnetPostRequest{value: msg.value}(myRequest);
  }
}

Please, have a look at the witnet/truffle-box repository to learn how to compose your own IWitnetRequest contracts.

Gas cost benchmark

·------------------------------------------------------------------|---------------------------|-------------|----------------------------·
|               Solc version: 0.8.11+commit.d7f03943               ·  Optimizer enabled: true  ·  Runs: 200  ·  Block limit: 6718946 gas  │
···································································|···························|·············|·····························
|  Methods                                                                                                                                │
·······································|···························|·············|·············|·············|··············|··············
|  Contract                            ·  Method                   ·  Min        ·  Max        ·  Avg        ·  # calls     ·  usd (avg)  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetPriceRouter                   ·  transferOwnership        ·          -  ·          -  ·      31826  ·           1  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetProxy                         ·  upgradeTo                ·          -  ·          -  ·     120348  ·           1  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRandomness                    ·  clone                    ·          -  ·          -  ·     245198  ·           3  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestBoardTrustableDefault  ·  deleteQuery              ·          -  ·          -  ·      32760  ·           5  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestBoardTrustableDefault  ·  destruct                 ·          -  ·          -  ·      13593  ·           2  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestBoardTrustableDefault  ·  initialize               ·          -  ·          -  ·      75083  ·          32  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestBoardTrustableDefault  ·  postRequest              ·     144097  ·     159097  ·     158063  ·          29  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestBoardTrustableDefault  ·  reportResult             ·          -  ·          -  ·      79316  ·          14  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestBoardTrustableDefault  ·  upgradeReward            ·      31322  ·      36505  ·      34777  ·           6  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestRandomness             ·  clone                    ·          -  ·          -  ·     244432  ·           8  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestRandomness             ·  renounceOwnership        ·          -  ·          -  ·      15530  ·           2  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestRandomness             ·  setWitnessingCollateral  ·      72225  ·      72994  ·      72610  ·           4  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestRandomness             ·  setWitnessingFees        ·      64087  ·      74380  ·      69234  ·           4  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestRandomness             ·  setWitnessingQuorum      ·      63945  ·      65838  ·      64892  ·           4  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  WitnetRequestRandomness             ·  transferOwnership        ·          -  ·          -  ·      31057  ·           2  ·          -  │
·······································|···························|·············|·············|·············|··············|··············
|  Deployments                                                     ·                                         ·  % of limit  ·             │
···································································|·············|·············|·············|··············|··············
|  WitnetDecoderLib                                                ·          -  ·          -  ·    2036059  ·      30.3 %  ·          -  │
···································································|·············|·············|·············|··············|··············
|  WitnetParserLib                                                 ·          -  ·          -  ·    2627933  ·      39.1 %  ·          -  │
···································································|·············|·············|·············|··············|··············
|  WitnetProxy                                                     ·          -  ·          -  ·     574794  ·       8.6 %  ·          -  │
···································································|·············|·············|·············|··············|··············
|  WitnetRequestBoardTrustableDefault                              ·          -  ·          -  ·    3745708  ·      55.7 %  ·          -  │
···································································|·············|·············|·············|··············|··············
|  WitnetRequestRandomness                                         ·          -  ·          -  ·    1655828  ·      24.6 %  ·          -  │
·------------------------------------------------------------------|-------------|-------------|-------------|--------------|-------------·

License

witnet-solidity-bridge is published under the MIT license.