Token Fee

ACS8 - Transaction Resource Token Fee Standard#

ACS8 is a transaction fee standard similar to ACS1, but it charges the called contract rather than the user. The fee charged includes four specified tokens: WRITE, READ, NET, and TRAFFIC.

When a contract inherits from ACS8, each transaction within this contract incurs charges in these four resource tokens.

Interface#

The acs8.proto file defines the following method:

Methods#

Method Name	Request Type	Response Type	Description
BuyResourceToken	acs8.BuyResourceTokenInput	google.protobuf.Empty	Buys one of the four resource tokens. Consumes ELF balance in the contract account.

Types#

acs8.BuyResourceTokenInput

Field	Type	Description
symbol	string	The symbol of the token to buy.
amount	int64	The amount of token to buy.
pay_limit	int64	Limit of cost; buying is abandoned if exceeded. 0 means no limit.

Usage#

Contracts inheriting ACS1 use a pre-plugin transaction called ChargeTransactionFees for transaction fee charging. ACS8 introduces a similar post-plugin transaction called ChargeResourceToken, which charges resource tokens based on actual transaction consumption.

The ChargeResourceToken implementation involves calculating token amounts using polynomial coefficients stored in CalculateFeeCoefficients defined in token_contract.proto. Each resource token has a polynomial for fee calculation, which determines the cost based on transaction consumption.

1public override Empty ChargeResourceToken(ChargeResourceTokenInput input)
2{
3    Context.LogDebug(() => string.Format("Start executing ChargeResourceToken.{0}", input));
4    if (input.Equals(new ChargeResourceTokenInput()))
5    {
6        return new Empty();
7    }
8    var bill = new TransactionFeeBill();
9    foreach (var pair in input.CostDic)
10    {
11        Context.LogDebug(() => string.Format("Charging {0} {1} tokens.", pair.Value, pair.Key));
12        var existingBalance = GetBalance(Context.Sender, pair.Key);
13        Assert(existingBalance >= pair.Value,
14            string.Format("Insufficient resource of {0}. Need balance: {1}; Current balance: {2}.", pair.Key, pair.Value, existingBalance));
15        bill.FeesMap.Add(pair.Key, pair.Value);
16    }
17    foreach (var pair in bill.FeesMap)
18    {
19        Context.Fire(new ResourceTokenCharged
20        {
21            Symbol = pair.Key,
22            Amount = pair.Value,
23            ContractAddress = Context.Sender
24        });
25        if (pair.Value == 0)
26        {
27            Context.LogDebug(() => string.Format("Maybe incorrect charged resource fee of {0}: it's 0.", pair.Key));
28        }
29    }
30    return new Empty();
31}

Additionally, contracts cannot execute methods if they lack sufficient resource token balance. To enforce this, a pre-plugin transaction CheckResourceToken, similar to ACS5, verifies the contract's resource token balance before method execution.

1public override Empty CheckResourceToken(Empty input)
2{
3    foreach (var symbol in Context.Variables.GetStringArray(TokenContractConstants.PayTxFeeSymbolListName))
4    {
5        var balance = GetBalance(Context.Sender, symbol);
6        var owningBalance = State.OwningResourceToken[Context.Sender][symbol];
7        Assert(balance > owningBalance,
8            string.Format("Contract balance of {0} token is not enough. Owning {1}.", symbol, owningBalance));
9    }
10    return new Empty();
11}

Edited on: 15 July 2024 05:52:51 GMT+0