Simple token contract

The contract essentially proxies token holder requests, parallely updating balances map. In this way, it works similar to transfering extra currency, but with ability to add custom logic on transfers.

It also supports bouncing token transfers (which is useful in DEXes).

Also there is silent transfers, primary for wallet contracts which don't support the notifications.

allowance mechanism isn't implemented, because it's just an alternative to notify-on-transfer interface. It might be more convinient in synchronous Ethereum model, but is totally inconvinient for asynchronous TON architecture.

The code is structured in a way to make it easier to modify the reference token implementation.

Token requests and responses

As per func/scheme.tlb.

Transfer

transfer#4034a3c0 query_id:uint64
    reciever:MsgAddrSmpl amount:Extra body:Any = Request;

Regular token transfer. Sends a notification to receiver contract, which carries all of the remaining message value and indicated body. After receiving a response, sends the remaining toncoins to the original sender.

Recv_transfer

recv_transfer#0x5fb163bd query_id:uint64
    sender:MsgAddrSmpl amount:Extra body:Any = Request;

A notification of regular transfer. The receiver contract (e.g. a decentralized exchange) may perform some action based on the sender, amount and body and expected to send a response (with the same query_id), carring remaining message value. If such query is bounced, or a 0xffffffff op returned, token contract processes a rollback.

Confirm_transfer

confirm_transfer#0xbc85eb11 query_id:uint64
    reciever:MsgAddrSmpl change:Extra body:Any = Response;

A confirmation of receiving a transfer notification. The token contract resends body and remaining value to the original request sender. Also reciever can return some change of token.

Transfer_ok

transfer_ok#0x9f94a9c5 query_id:uint64
    reciever:MsgAddrSmpl change:Extra body:Any = Response;

Notification of a successful regular transfer.

Transfer_fail

transfer_fail#0xbed2072b query_id:uint64
    reciever:MsgAddrSmpl change:Extra = Response;

Notification of a failed and rolled back regular transfer.

Silent_transfer

silent_transfer#0x333cd134 query_id:uint64
    reciever:MsgAddrSmpl amount:Extra = Request;

Just change balances map without sending a notification. Primary for transfers on user wallet contracts which don't support notifications.

Silent_transfer_ok

silent_transfer_ok#0xb48aba01 query_id:uint64 = Response;

Silent transfer confirmation.