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-rw-r--r--app/scripts/lib/tx-utils.js87
1 files changed, 87 insertions, 0 deletions
diff --git a/app/scripts/lib/tx-utils.js b/app/scripts/lib/tx-utils.js
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+const async = require('async')
+const EthQuery = require('eth-query')
+const ethUtil = require('ethereumjs-util')
+const BN = ethUtil.BN
+
+/*
+tx-utils are utility methods for Transaction manager
+its passed a provider and that is passed to ethquery
+and used to do things like calculate gas of a tx.
+*/
+
+module.exports = class txProviderUtils {
+ constructor (provider) {
+ this.provider = provider
+ this.query = new EthQuery(provider)
+ }
+ analyzeGasUsage (txData, cb) {
+ var self = this
+ this.query.getBlockByNumber('latest', true, (err, block) => {
+ if (err) return cb(err)
+ async.waterfall([
+ self.estimateTxGas.bind(self, txData, block.gasLimit),
+ self.checkForTxGasError.bind(self, txData),
+ self.setTxGas.bind(self, txData, block.gasLimit),
+ ], cb)
+ })
+ }
+
+ estimateTxGas (txData, blockGasLimitHex, cb) {
+ const txParams = txData.txParams
+ // check if gasLimit is already specified
+ txData.gasLimitSpecified = Boolean(txParams.gas)
+ // if not, fallback to block gasLimit
+ if (!txData.gasLimitSpecified) {
+ txParams.gas = blockGasLimitHex
+ }
+ // run tx, see if it will OOG
+ this.query.estimateGas(txParams, cb)
+ }
+
+ checkForTxGasError (txData, estimatedGasHex, cb) {
+ txData.estimatedGas = estimatedGasHex
+ // all gas used - must be an error
+ if (estimatedGasHex === txData.txParams.gas) {
+ txData.simulationFails = true
+ }
+ cb()
+ }
+
+ setTxGas (txData, blockGasLimitHex, cb) {
+ const txParams = txData.txParams
+ // if OOG, nothing more to do
+ if (txData.simulationFails) {
+ cb()
+ return
+ }
+ // if gasLimit was specified and doesnt OOG,
+ // use original specified amount
+ if (txData.gasLimitSpecified) {
+ txData.estimatedGas = txParams.gas
+ cb()
+ return
+ }
+ // if gasLimit not originally specified,
+ // try adding an additional gas buffer to our estimation for safety
+ const estimatedGasBn = new BN(ethUtil.stripHexPrefix(txData.estimatedGas), 16)
+ const blockGasLimitBn = new BN(ethUtil.stripHexPrefix(blockGasLimitHex), 16)
+ const estimationWithBuffer = new BN(this.addGasBuffer(estimatedGasBn), 16)
+ // added gas buffer is too high
+ if (estimationWithBuffer.gt(blockGasLimitBn)) {
+ txParams.gas = txData.estimatedGas
+ // added gas buffer is safe
+ } else {
+ const gasWithBufferHex = ethUtil.intToHex(estimationWithBuffer)
+ txParams.gas = gasWithBufferHex
+ }
+ cb()
+ return
+ }
+
+ addGasBuffer (gas) {
+ const gasBuffer = new BN('100000', 10)
+ const bnGas = new BN(ethUtil.stripHexPrefix(gas), 16)
+ const correct = bnGas.add(gasBuffer)
+ return ethUtil.addHexPrefix(correct.toString(16))
+ }
+}