wip internal tx decoding

raw-trace-decoder.js

function deriveGas(stack) {
  const gasHexString = stack[stack.length - 1]
  return parseInt(gasHexString, 16)
}

function deriveAddress(stack) {
  const addressRaw = stack[stack.length - 2]
  return `0x${addressRaw.slice(24)}`
}

function deriveInput(op, stack, memoryArr) {
  let inputStart
  let inputLen
  // 1 byte is two chars
  if (op === 'DELEGATECALL') {
    inputStart = parseInt(stack[stack.length - 3], 16) * 2
    inputLen = parseInt(stack[stack.length - 4], 16) * 2
  } else {
    inputStart = parseInt(stack[stack.length - 4], 16) * 2
    inputLen = parseInt(stack[stack.length - 5], 16) * 2
  }

  const memory = memoryArr.join('')
  return `0x${memory.slice(inputStart, inputStart + inputLen)}`
}

function deriveValue(op, stack, lastValue) {
  if (op === 'DELEGATECALL') return lastValue
  return parseInt(stack[stack.length - 3], 16)
}

function decodeRawTrace({ op, stack, memory }, lastValue) {
  if (op !== 'CALL' && op !== 'DELEGATECALL' && op !== 'CALLCODE') {
    throw Error(`op code not supported [${op}]`)
  }

  const gas = deriveGas(stack)
  const to = deriveAddress(stack)
  const input = deriveInput(op, stack, memory)
  const value = deriveValue(op, stack, lastValue)

  return { gas, to, input, value, type: op }
}

function decodeInternalTransactions(traces, firstValue) {
  let lastValue = firstValue
  const internalTransactions = traces.map((trace) => {
    const internalTransaction = decodeRawTrace(trace, lastValue)
    if (trace.op !== 'DELEGATECALL') {
      lastValue = internalTransaction.value
    }
    return internalTransaction
  })
  return internalTransactions
}