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metamask-extension/app/scripts/controllers/transactions/tx-gas-utils.js

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import EthQuery from 'ethjs-query';
import log from 'loglevel';
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import { addHexPrefix } from 'ethereumjs-util';
import { cloneDeep } from 'lodash';
import { hexToBn, BnMultiplyByFraction, bnToHex } from '../../lib/util';
/**
* Result of gas analysis, including either a gas estimate for a successful analysis, or
* debug information for a failed analysis.
*
* @typedef {object} GasAnalysisResult
* @property {string} blockGasLimit - The gas limit of the block used for the analysis
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* @property {string} estimatedGasHex - The estimated gas, in hexadecimal
* @property {object} simulationFails - Debug information about why an analysis failed
*/
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/**
* tx-gas-utils are gas utility methods for Transaction manager
* its passed ethquery
* and used to do things like calculate gas of a tx.
*
* @param {object} provider - A network provider.
*/
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export default class TxGasUtil {
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constructor(provider) {
this.query = new EthQuery(provider);
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}
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/**
* @param {object} txMeta - the txMeta object
* @returns {GasAnalysisResult} The result of the gas analysis
*/
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async analyzeGasUsage(txMeta) {
const block = await this.query.getBlockByNumber('latest', false);
// fallback to block gasLimit
const blockGasLimitBN = hexToBn(block.gasLimit);
const saferGasLimitBN = BnMultiplyByFraction(blockGasLimitBN, 19, 20);
let estimatedGasHex = bnToHex(saferGasLimitBN);
let simulationFails;
try {
estimatedGasHex = await this.estimateTxGas(txMeta);
} catch (error) {
log.warn(error);
simulationFails = {
reason: error.message,
errorKey: error.errorKey,
debug: { blockNumber: block.number, blockGasLimit: block.gasLimit },
};
}
return {
blockGasLimit: block.gasLimit,
estimatedGasHex,
simulationFails,
};
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}
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/**
* Estimates the tx's gas usage
*
* @param {object} txMeta - the txMeta object
* @returns {string} the estimated gas limit as a hex string
*/
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async estimateTxGas(txMeta) {
const txParams = cloneDeep(txMeta.txParams);
// `eth_estimateGas` can fail if the user has insufficient balance for the
// value being sent, or for the gas cost. We don't want to check their
// balance here, we just want the gas estimate. The gas price is removed
// to skip those balance checks. We check balance elsewhere. We also delete
// maxFeePerGas and maxPriorityFeePerGas to support EIP-1559 txs.
delete txParams.gasPrice;
delete txParams.maxFeePerGas;
delete txParams.maxPriorityFeePerGas;
// estimate tx gas requirements
return await this.query.estimateGas(txParams);
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}
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/**
* Adds a gas buffer with out exceeding the block gas limit
*
* @param {string} initialGasLimitHex - the initial gas limit to add the buffer too
* @param {string} blockGasLimitHex - the block gas limit
* @param multiplier
* @returns {string} the buffered gas limit as a hex string
*/
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addGasBuffer(initialGasLimitHex, blockGasLimitHex, multiplier = 1.5) {
const initialGasLimitBn = hexToBn(initialGasLimitHex);
const blockGasLimitBn = hexToBn(blockGasLimitHex);
const upperGasLimitBn = blockGasLimitBn.muln(0.9);
const bufferedGasLimitBn = initialGasLimitBn.muln(multiplier);
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// if initialGasLimit is above blockGasLimit, dont modify it
if (initialGasLimitBn.gt(upperGasLimitBn)) {
return bnToHex(initialGasLimitBn);
}
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// if bufferedGasLimit is below blockGasLimit, use bufferedGasLimit
if (bufferedGasLimitBn.lt(upperGasLimitBn)) {
return bnToHex(bufferedGasLimitBn);
}
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// otherwise use blockGasLimit
return bnToHex(upperGasLimitBn);
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}
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async getBufferedGasLimit(txMeta, multiplier) {
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const { blockGasLimit, estimatedGasHex, simulationFails } =
await this.analyzeGasUsage(txMeta);
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// add additional gas buffer to our estimation for safety
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const gasLimit = this.addGasBuffer(
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addHexPrefix(estimatedGasHex),
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blockGasLimit,
multiplier,
);
return { gasLimit, simulationFails };
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}
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}