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Rearrange gasEstimation for readability
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@nicholasjpaterno
nicholasjpaterno committed Dec 14, 2019
1 parent da66ca6 commit 9c523f7
Showing 1 changed file with 144 additions and 144 deletions.
288 changes: 144 additions & 144 deletions lib/utils/gas/guestimation.js
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@@ -1,157 +1,14 @@
const RuntimeError = require("../runtimeerror");

const { BN } = require("ethereumjs-util");

const bn = (val = 0) => new BN(val);
const STIPEND = bn(2300);

const check = (set) => (opname) => set.has(opname);
const isCall = check(new Set(["CALL", "DELEGATECALL", "STATICCALL", "CALLCODE"]));
const isCallOrCallcode = check(new Set(["CALL", "CALLCODE"]));
const isCreate = check(new Set(["CREATE", "CREATE2"]));
const isTerminator = check(new Set(["STOP", "RETURN", "REVERT", "INVALID", "SELFDESTRUCT"]));

module.exports = async(vm, runArgs, callback) => {
const steps = stepTracker();
vm.on("step", steps.collect);

const Context = (index, fee) => {
const base = index === 0;
let start = index;
let stop = 0;
let cost = bn();
let sixtyFloorths = bn();
const op = steps.ops[index];
const next = steps.ops[index + 1];
const intermediateCost = op.gasLeft.sub(next.gasLeft);
const callingFee = fee || bn();
let compositeContext = false;

function addGas(val) {
// Add to our current context, but accounted for in sixtyfloorths
if (sixtyFloorths.gtn(0)) {
if (val.gte(sixtyFloorths)) {
sixtyFloorths = bn();
} else {
sixtyFloorths.isub(val);
}
}
cost.iadd(val);
}

return {
start: () => start,
stop: () => stop,
setStart: (val) => {
start = val;
compositeContext = true;
},
setStop: (val) => {
stop = val;
},
getCost: () => ({ cost, sixtyFloorths }),
transfer: (ctx) => {
const values = ctx.getCost();
addGas(values.cost);
sixtyFloorths.iadd(values.sixtyFloorths);
},
addSixtyFloorth: (sixtyFloorth) => {
sixtyFloorths.iadd(sixtyFloorth);
},
addRange: (fee = bn()) => {
// only occurs on stack increasing ops
addGas(steps.ops[base || compositeContext ? start : start + 1].gasLeft.sub(steps.ops[stop].gasLeft).add(fee));
},
finalizeRange: () => {
let range;
// if we have a composite context and we are NOT at the final terminator
if (compositeContext && stop !== steps.ops.length - 1) {
range = steps.ops[start].gasLeft.sub(steps.ops[stop - 1].gasLeft);
addGas(range);
const tail = steps.ops[stop - 1].gasLeft.sub(steps.ops[stop].gasLeft);
range = tail.add(intermediateCost);
} else {
range = steps.ops[start].gasLeft.sub(steps.ops[stop].gasLeft);
}
range.isub(callingFee);
addGas(range);
if (isCallOrCallcode(op.opcode.name) && !op.stack[op.stack.length - 3].isZero()) {
cost.iadd(sixtyFloorths);
const innerCost = next.gasLeft.sub(steps.ops[stop - 1].gasLeft);
if (innerCost.gt(STIPEND)) {
sixtyFloorths = cost.divn(63);
} else if (innerCost.lte(STIPEND)) {
sixtyFloorths = STIPEND.sub(innerCost);
}
} else if (stop !== steps.ops.length - 1) {
cost.iadd(sixtyFloorths);
sixtyFloorths = cost.divn(63);
}
}
};
};

const getTotal = () => {
const sysops = steps.systemOps;
const ops = steps.ops;
const opIndex = (cursor) => sysops[cursor].index;
const stack = [];
let cursor = 0;
let context = Context(0);
while (cursor < sysops.length) {
const currentIndex = opIndex(cursor);
const current = ops[currentIndex];
const name = current.opcode.name;
if (isCall(name) || isCreate(name)) {
if (steps.isPrecompile(currentIndex)) {
context.setStop(currentIndex + 1);
context.addRange();
context.setStart(currentIndex + 1);
context.addSixtyFloorth(STIPEND);
} else {
context.setStop(currentIndex);
context.addRange(bn(current.opcode.fee));
stack.push(context);
context = Context(currentIndex, bn(current.opcode.fee)); // setup next context
}
} else if (isTerminator(name)) {
// only on the last operation
context.setStop(currentIndex + 1 < steps.ops.length ? currentIndex + 1 : currentIndex);
context.finalizeRange();
const ctx = stack.pop();
if (ctx) {
ctx.transfer(context);
context = ctx;
context.setStart(currentIndex + 1);
} else {
break;
}
} else {
throw new Error("INVALID OPCODE");
}
cursor++;
}
const gas = context.getCost();
return gas.cost.add(gas.sixtyFloorths);
};

const result = await vm.runTx(runArgs).catch((vmerr) => ({ vmerr }));
const vmerr = result.vmerr;
if (vmerr) {
return callback(vmerr);
} else if (result.execResult.exceptionError) {
const vmerr = RuntimeError.fromResults([runArgs.tx], { results: [result] });
return callback(vmerr, result);
} else if (steps.done()) {
const estimate = result.gasUsed;
result.gasEstimate = estimate;
} else {
const actualUsed = steps.ops[0].gasLeft.sub(steps.ops[steps.ops.length - 1].gasLeft);
const sixtyFloorths = getTotal().sub(actualUsed);
result.gasEstimate = result.gasUsed.add(sixtyFloorths);
}
callback(vmerr, result);
};

const stepTracker = () => {
const sysOps = [];
const allOps = [];
Expand Down Expand Up @@ -186,3 +43,146 @@ const stepTracker = () => {
systemOps: sysOps
};
};

const setupContext = (steps) => (index, fee) => {
const base = index === 0;
let start = index;
let stop = 0;
let cost = bn();
let sixtyFloorths = bn();
const op = steps.ops[index];
const next = steps.ops[index + 1];
const intermediateCost = op.gasLeft.sub(next.gasLeft);
const callingFee = fee || bn();
let compositeContext = false;

function addGas(val) {
// Add to our current context, but accounted for in sixtyfloorths
if (sixtyFloorths.gtn(0)) {
if (val.gte(sixtyFloorths)) {
sixtyFloorths = bn();
} else {
sixtyFloorths.isub(val);
}
}
cost.iadd(val);
}

return {
start: () => start,
stop: () => stop,
setStart: (val) => {
start = val;
compositeContext = true;
},
setStop: (val) => {
stop = val;
},
getCost: () => ({ cost, sixtyFloorths }),
transfer: (ctx) => {
const values = ctx.getCost();
addGas(values.cost);
sixtyFloorths.iadd(values.sixtyFloorths);
},
addSixtyFloorth: (sixtyFloorth) => {
sixtyFloorths.iadd(sixtyFloorth);
},
addRange: (fee = bn()) => {
// only occurs on stack increasing ops
addGas(steps.ops[base || compositeContext ? start : start + 1].gasLeft.sub(steps.ops[stop].gasLeft).add(fee));
},
finalizeRange: () => {
let range;
// if we have a composite context and we are NOT at the final terminator
if (compositeContext && stop !== steps.ops.length - 1) {
range = steps.ops[start].gasLeft.sub(steps.ops[stop - 1].gasLeft);
addGas(range);
const tail = steps.ops[stop - 1].gasLeft.sub(steps.ops[stop].gasLeft);
range = tail.add(intermediateCost);
} else {
range = steps.ops[start].gasLeft.sub(steps.ops[stop].gasLeft);
}
range.isub(callingFee);
addGas(range);
if (isCallOrCallcode(op.opcode.name) && !op.stack[op.stack.length - 3].isZero()) {
cost.iadd(sixtyFloorths);
const innerCost = next.gasLeft.sub(steps.ops[stop - 1].gasLeft);
if (innerCost.gt(STIPEND)) {
sixtyFloorths = cost.divn(63);
} else if (innerCost.lte(STIPEND)) {
sixtyFloorths = STIPEND.sub(innerCost);
}
} else if (stop !== steps.ops.length - 1) {
cost.iadd(sixtyFloorths);
sixtyFloorths = cost.divn(63);
}
}
};
};

const getTotal = (steps) => {
const Context = setupContext(steps);
const sysops = steps.systemOps;
const ops = steps.ops;
const opIndex = (cursor) => sysops[cursor].index;
const stack = [];
let cursor = 0;
let context = Context(0);
while (cursor < sysops.length) {
const currentIndex = opIndex(cursor);
const current = ops[currentIndex];
const name = current.opcode.name;
if (isCall(name) || isCreate(name)) {
if (steps.isPrecompile(currentIndex)) {
context.setStop(currentIndex + 1);
context.addRange();
context.setStart(currentIndex + 1);
context.addSixtyFloorth(STIPEND);
} else {
context.setStop(currentIndex);
context.addRange(bn(current.opcode.fee));
stack.push(context);
context = Context(currentIndex, bn(current.opcode.fee)); // setup next context
}
} else if (isTerminator(name)) {
// only on the last operation
context.setStop(currentIndex + 1 < steps.ops.length ? currentIndex + 1 : currentIndex);
context.finalizeRange();
const ctx = stack.pop();
if (ctx) {
ctx.transfer(context);
context = ctx;
context.setStart(currentIndex + 1);
} else {
break;
}
} else {
throw new Error("INVALID OPCODE");
}
cursor++;
}
const gas = context.getCost();
return gas.cost.add(gas.sixtyFloorths);
};

module.exports = async(vm, runArgs, callback) => {
const steps = stepTracker();
vm.on("step", steps.collect);

const result = await vm.runTx(runArgs).catch((vmerr) => ({ vmerr }));
const vmerr = result.vmerr;
if (vmerr) {
return callback(vmerr);
} else if (result.execResult.exceptionError) {
const vmerr = RuntimeError.fromResults([runArgs.tx], { results: [result] });
return callback(vmerr, result);
} else if (steps.done()) {
const estimate = result.gasUsed;
result.gasEstimate = estimate;
} else {
const actualUsed = steps.ops[0].gasLeft.sub(steps.ops[steps.ops.length - 1].gasLeft);
const sixtyFloorths = getTotal(steps).sub(actualUsed);
result.gasEstimate = result.gasUsed.add(sixtyFloorths);
}
callback(vmerr, result);
};

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