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129 lines
4.2 KiB
129 lines
4.2 KiB
const EthQuery = require('ethjs-query')
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const {
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hexToBn,
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BnMultiplyByFraction,
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bnToHex,
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} = require('../../lib/util')
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const { addHexPrefix } = require('ethereumjs-util')
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const SIMPLE_GAS_COST = '0x5208' // Hex for 21000, cost of a simple send.
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/**
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tx-gas-utils are gas utility methods for Transaction manager
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its passed ethquery
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and used to do things like calculate gas of a tx.
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@param {Object} provider - A network provider.
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*/
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class TxGasUtil {
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constructor (provider) {
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this.query = new EthQuery(provider)
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}
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/**
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@param txMeta {Object} - the txMeta object
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@returns {object} the txMeta object with the gas written to the txParams
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*/
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async analyzeGasUsage (txMeta) {
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const block = await this.query.getBlockByNumber('latest', false)
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let estimatedGasHex
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try {
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estimatedGasHex = await this.estimateTxGas(txMeta, block.gasLimit)
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} catch (err) {
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const simulationFailed = (
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err.message.includes('Transaction execution error.') ||
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err.message.includes('gas required exceeds allowance or always failing transaction')
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)
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if (simulationFailed) {
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txMeta.simulationFails = true
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return txMeta
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}
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}
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this.setTxGas(txMeta, block.gasLimit, estimatedGasHex)
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return txMeta
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}
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/**
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Estimates the tx's gas usage
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@param txMeta {Object} - the txMeta object
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@param blockGasLimitHex {string} - hex string of the block's gas limit
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@returns {string} the estimated gas limit as a hex string
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*/
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async estimateTxGas (txMeta, blockGasLimitHex) {
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const txParams = txMeta.txParams
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// check if gasLimit is already specified
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txMeta.gasLimitSpecified = Boolean(txParams.gas)
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// if it is, use that value
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if (txMeta.gasLimitSpecified) {
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return txParams.gas
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}
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// if recipient has no code, gas is 21k max:
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const recipient = txParams.to
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const hasRecipient = Boolean(recipient)
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let code
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if (recipient) code = await this.query.getCode(recipient)
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if (hasRecipient && (!code || code === '0x')) {
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txParams.gas = SIMPLE_GAS_COST
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txMeta.simpleSend = true // Prevents buffer addition
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return SIMPLE_GAS_COST
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}
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// if not, fall back to block gasLimit
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const blockGasLimitBN = hexToBn(blockGasLimitHex)
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const saferGasLimitBN = BnMultiplyByFraction(blockGasLimitBN, 19, 20)
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txParams.gas = bnToHex(saferGasLimitBN)
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// run tx
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return await this.query.estimateGas(txParams)
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}
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/**
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Writes the gas on the txParams in the txMeta
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@param txMeta {Object} - the txMeta object to write to
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@param blockGasLimitHex {string} - the block gas limit hex
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@param estimatedGasHex {string} - the estimated gas hex
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*/
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setTxGas (txMeta, blockGasLimitHex, estimatedGasHex) {
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txMeta.estimatedGas = addHexPrefix(estimatedGasHex)
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const txParams = txMeta.txParams
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// if gasLimit was specified and doesnt OOG,
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// use original specified amount
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if (txMeta.gasLimitSpecified || txMeta.simpleSend) {
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txMeta.estimatedGas = txParams.gas
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return
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}
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// if gasLimit not originally specified,
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// try adding an additional gas buffer to our estimation for safety
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const recommendedGasHex = this.addGasBuffer(txMeta.estimatedGas, blockGasLimitHex)
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txParams.gas = recommendedGasHex
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return
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}
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/**
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Adds a gas buffer with out exceeding the block gas limit
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@param initialGasLimitHex {string} - the initial gas limit to add the buffer too
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@param blockGasLimitHex {string} - the block gas limit
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@returns {string} the buffered gas limit as a hex string
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*/
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addGasBuffer (initialGasLimitHex, blockGasLimitHex) {
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const initialGasLimitBn = hexToBn(initialGasLimitHex)
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const blockGasLimitBn = hexToBn(blockGasLimitHex)
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const upperGasLimitBn = blockGasLimitBn.muln(0.9)
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const bufferedGasLimitBn = initialGasLimitBn.muln(1.5)
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// if initialGasLimit is above blockGasLimit, dont modify it
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if (initialGasLimitBn.gt(upperGasLimitBn)) return bnToHex(initialGasLimitBn)
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// if bufferedGasLimit is below blockGasLimit, use bufferedGasLimit
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if (bufferedGasLimitBn.lt(upperGasLimitBn)) return bnToHex(bufferedGasLimitBn)
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// otherwise use blockGasLimit
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return bnToHex(upperGasLimitBn)
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}
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}
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module.exports = TxGasUtil
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