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utils.js
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utils.js
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const abi = require('ethereumjs-abi');
const util = require('ethereumjs-util');
const BN = require('bn.js')
//============================================================================
// PUBLIC FUNCTIONS
//============================================================================
const constructPaymentMessage = async function (contractAddress, balance) {
return abi.soliditySHA3(
["address", "uint256"],
[new BN(contractAddress, 16), balance]
);
}
const signMessage = async function (web3, message, accountAddress) {
return await web3.eth.sign(
accountAddress,
`0x${message.toString("hex")}`
);
}
const isValidSignature = async function (contractAddress, balance, signature, expectedSigner) {
let message = await constructPaymentMessage(contractAddress, balance);
let prefixedMessage = await prefixed(message);
let signer = await recoverSigner(prefixedMessage, signature);
return signer.toLowerCase() === util.stripHexPrefix(expectedSigner).toLowerCase();
}
const getEvent = async function (event, result) {
for (let i = 0; i < result.logs.length; i++) {
const log = result.logs[i];
if (log.event === event) {
return log;
}
}
return undefined;
}
const assertFail = async function (promise, message) {
try {
await promise;
assert(false);
} catch (e) {
if (e.name == 'AssertionError') {
if (message)
assert(false, message);
else
assert(false);
}
}
}
//============================================================================
// INTERNAL FUNCTIONS
//============================================================================
async function prefixed(hash) {
return abi.soliditySHA3(
["string", "bytes32"],
["\x19Ethereum Signed Message:\n32", hash]
);
}
async function recoverSigner(message, signature) {
let split = util.fromRpcSig(signature);
let publicKey = util.ecrecover(message, split.v, split.r, split.s);
let signer = util.pubToAddress(publicKey).toString("hex");
return signer;
}
module.exports = {
constructPaymentMessage,
signMessage,
isValidSignature,
getEvent,
assertFail
}