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const ethUtil = require('ethereumjs-util')
const Transaction = require('ethereumjs-tx')
const normalize = require('eth-sig-util').normalize
const BN = ethUtil.BN
/*
tx-utils are utility methods for Transaction manager
its passed ethquery
and used to do things like calculate gas of a tx.
*/
module.exports = class txProvideUtils {
constructor (ethQuery) {
this.query = ethQuery
}
async analyzeGasUsage (txMeta) {
const block = await this.query.getBlockByNumber('latest', true)
const estimatedGasHex = await this.estimateTxGas(txMeta, block.gasLimit)
this.setTxGas(txMeta, block.gasLimit, estimatedGasHex)
return txMeta
}
async estimateTxGas (txMeta, blockGasLimitHex) {
const txParams = txMeta.txParams
// check if gasLimit is already specified
txMeta.gasLimitSpecified = Boolean(txParams.gas)
// if not, fallback to block gasLimit
if (!txMeta.gasLimitSpecified) {
const blockGasLimitBN = hexToBn(blockGasLimitHex)
const saferGasLimitBN = BnMultiplyByFraction(blockGasLimitBN, 19, 20)
txParams.gas = bnToHex(saferGasLimitBN)
}
// run tx, see if it will OOG
return this.query.estimateGas(txParams)
}
setTxGas (txMeta, blockGasLimitHex, estimatedGasHex) {
txMeta.estimatedGas = estimatedGasHex
const txParams = txMeta.txParams
// if gasLimit was specified and doesnt OOG,
// use original specified amount
if (txMeta.gasLimitSpecified) {
txMeta.estimatedGas = txParams.gas
return
}
// if gasLimit not originally specified,
// try adding an additional gas buffer to our estimation for safety
const recommendedGasHex = this.addGasBuffer(txMeta.estimatedGas, blockGasLimitHex)
txParams.gas = recommendedGasHex
return
}
addGasBuffer (initialGasLimitHex, blockGasLimitHex) {
const initialGasLimitBn = hexToBn(initialGasLimitHex)
const blockGasLimitBn = hexToBn(blockGasLimitHex)
const upperGasLimitBn = blockGasLimitBn.muln(0.9)
const bufferedGasLimitBn = initialGasLimitBn.muln(1.5)
// if initialGasLimit is above blockGasLimit, dont modify it
if (initialGasLimitBn.gt(upperGasLimitBn)) return bnToHex(initialGasLimitBn)
// if bufferedGasLimit is below blockGasLimit, use bufferedGasLimit
if (bufferedGasLimitBn.lt(upperGasLimitBn)) return bnToHex(bufferedGasLimitBn)
// otherwise use blockGasLimit
return bnToHex(upperGasLimitBn)
}
// builds ethTx from txParams object
buildEthTxFromParams (txParams) {
// normalize values
txParams.to = normalize(txParams.to)
txParams.from = normalize(txParams.from)
txParams.value = normalize(txParams.value)
txParams.data = normalize(txParams.data)
txParams.gas = normalize(txParams.gas || txParams.gasLimit)
txParams.gasPrice = normalize(txParams.gasPrice)
txParams.nonce = normalize(txParams.nonce)
// build ethTx
log.info(`Prepared tx for signing: ${JSON.stringify(txParams)}`)
const ethTx = new Transaction(txParams)
return ethTx
}
publishTransaction (rawTx) {
return this.query.sendRawTransaction(rawTx)
}
validateTxParams (txParams) {
return new Promise((resolve, reject) => {
if (('value' in txParams) && txParams.value.indexOf('-') === 0) {
reject(new Error(`Invalid transaction value of ${txParams.value} not a positive number.`))
} else {
resolve()
}
})
}
sufficientBalance (txParams, hexBalance) {
const balance = hexToBn(hexBalance)
const value = hexToBn(txParams.value)
const gasLimit = hexToBn(txParams.gas)
const gasPrice = hexToBn(txParams.gasPrice)
const maxCost = value.add(gasLimit.mul(gasPrice))
return balance.gte(maxCost)
}
}
// util
function bnToHex (inputBn) {
return ethUtil.addHexPrefix(inputBn.toString(16))
}
function hexToBn (inputHex) {
return new BN(ethUtil.stripHexPrefix(inputHex), 16)
}
function BnMultiplyByFraction (targetBN, numerator, denominator) {
const numBN = new BN(numerator)
const denomBN = new BN(denominator)
return targetBN.mul(numBN).div(denomBN)
}
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