SEP206: Manipulate Native Token as a SEP20 Token
This SEP proposes a method to manipulate the native token, i.e., BCH, through a pseudo smart contract with SEP20 interface.
On Ethereum, the developers of DApp have always a pain: ETH is not an ERC20 token. And the methods to manipulate ETH and ERC20 tokens are totally different. There are two ways to alleviate this problem:
- 1.
- 2.Write two sets of logic in smart contracts to support ETH and ERC20 seperately.
These methods are neither perfect.
On smartBCH, a psuedo smart contract can help you manipulate BCH directly. This smart contract is psuedo because it is not implemented by EVM bytecode. Instead, it is supported natively in the full client, smartbchd. So it can do a thing that no other smart contracts can do: moving BCH. It has a predefined address: 10001, like the precompiled contracts.
This pseudo contract has a SEP20 interface, it can be called as if it is SEP20 smart contract.
This proposal specifies the behavior of functions in this psuedo smart contract, such that developers can use it correctly.
This SEP has been implemented since genesis.
NOTES:
- The following specifications use syntax from Solidity 0.5.16 (or above)
- The following methods must be invoked through
callorstaticall,delegatecallandcallcodeare not allowed. - The allowance granted by
ownertospenderis stored at the slot whose location is calculated asuint(sha256(abi.encodePacked(uint(owner), uint(spender)). The size of this slot is not required to be 32-byte long and you can NOT read its value witheth_getStorageAt.
5.1.1.1 name
function name() external view returns (string)
- Returns "BCH".
5.1.1.2 symbol
function symbol() external view returns (string)
- Returns "BCH".
5.1.1.3 decimals
function decimals() external view returns (uint8)
- Returns 18.
5.1.1.4 totalSupply
function totalSupply() external view returns (uint256)
- Returns 2.1E25.
- NOTE - Most of the BCH tokens of smartBCH will be locked in a smart contract, which is be controlled by the gateway keepers.
5.1.1.5 balanceOf
function balanceOf(address _owner) external view returns (uint256 balance)
- Returns the BCH balance of another account with address
_owner. - Returns the same value as the
eth_getBalancefunction in Web3 API.
5.1.1.6 transfer
function transfer(address _to, uint256 _value) external returns (bool success)
- Transfers
_valueamount of BCH to address_to, and fire the Transfer event. The function throws if the message caller’s account balance does not have enough tokens to spend.
5.1.1.7 transferFrom
function transferFrom(address _from, address _to, uint256 _value) external returns (bool success)
- Transfers
_valueamount of BCH from address_fromto address_to, and fires the Transfer event. - The function throws unless the
_fromaccount has deliberately authorized the sender of the message via allowance control.
5.1.1.8 approve
function approve(address _spender, uint256 _value) external returns (bool success)
- Allows
_spenderto withdraw from your account multiple times, up to the_valueamount of BCH. If this function is called again it overwrites the current allowance with_value.
5.1.1.9 allowance
function allowance(address _owner, address _spender) external view returns (uint256 remaining)
- Returns the amount which
_spenderis still allowed to withdraw from_owner.
5.1.1.10 increaseAllowance
function increaseAllowance(address _spender, uint256 _delta) external returns (bool success)
- Increases the amount which
_spenderis still allowed to withdraw from you.
5.1.1.11 decreaseAllowance
function decreaseAllowance(address _spender, uint256 _delta) external returns (bool success)
- Decreases the amount which
_spenderis still allowed to withdraw from you.
5.1.2.1 Transfer
event Transfer(address indexed _from, address indexed _to, uint256 _value)
- It's triggerred when tokens are transferred, including zero value transfers.
5.1.2.2 Approval
event Approval(address indexed _owner, address indexed _spender, uint256 _value)
- It's triggerred on any successful call to
approve(address _spender, uint256 _value),increaseAllowance(address _spender, uint256 _delta)ordecreaseAllowance(address _spender, uint256 _delta).
Calling these functions costs fixed gas, as is shown below:
- name: 3000
- symbol: 3000
- decimals: 1000
- totalSupply: 1000
- balanceOf: 20000
- transfer: 32000
- transferFrom: 40000
- approve: 25000
- allowance: 20000
- increaseAllowance: 31000
- decreaseAllowance: 31000