karma/contracts/karma-ERC20.sol

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2021-04-29 19:43:03 +00:00
// Copyright [2021] - [2021], [Shaun Reed] and [Karma] contributors
// SPDX-License-Identifier: MIT
pragma solidity >= 0.8.0;
// ----------------------------------------------------------------------------
// Import ERC Token Standard #20 Interface
// ETH EIP repo: https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md
// ----------------------------------------------------------------------------
import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
// ----------------------------------------------------------------------------
// SourceCoin Contract
// ----------------------------------------------------------------------------
contract Karma is IERC20
{
string public name;
string public symbol;
uint8 public decimals; // 18 decimals is the strongly suggested default, avoid changing it
uint256 public _totalSupply;
// Balances for each account; A hashmap using wallet address as key and uint as value
mapping(address => uint) balances;
// Owner of account approves the transfer of an amount to another account
mapping(address => mapping(address => uint)) allowed;
/**
* Constrctor function
*
* Initializes contract with initial supply tokens to the creator of the contract
*/
constructor()
{
name = "Karma"; // Name of the token
symbol = "KRMA"; // Abbreviation of the token
decimals = 18; // Number of decimals that can be used to split token
// FORMAT: <SUPPLY><DECIMALS>
// Where SUPPLY is the number of coins in base 10 decimal notation
// And DECIMALS is a trailing number of 0's; Count must match `decimals` value set above
// 1000 000 000 000000000000000000 == 1 billion total supply;
// + trailing 0's represent the 18 decimal locations that can be used to send fractions
_totalSupply = 1000000000000000000000000000;
// Set the remaining balance of the contract owner to the total supply
balances[msg.sender] = _totalSupply; // msg.sender is the calling address for this constructor
// Transfer the total supply to the contract owner on initialization
emit Transfer(address(0), msg.sender, _totalSupply); // address(0) is used to represent a new TX
}
// Get the total circulating supply of the token
function totalSupply() public override view returns (uint)
{
// By subtracting from tokens held at address(0), we provide an address to 'burn' the supply
return _totalSupply - balances[address(0)]; // Subtract from tokens held at address(0)
}
// Get the token balance for account `tokenOwner`
function balanceOf(address tokenOwner) public override view returns (uint balance)
{
return balances[tokenOwner]; // Return the balance of the owner's address
}
/// @param tokenOwner The address of the account owning tokens
/// @param spender The address of the account able to transfer the tokens
/// returns Amount of remaining tokens allowed to spent
function allowance(address tokenOwner, address spender) public override view returns (uint remaining)
{
return allowed[tokenOwner][spender];
}
// Allow `spender` to withdraw from your account, multiple times, up to the `tokens`
// If this function is called again it overwrites the current allowance with _value.
function approve(address spender, uint tokens) public override returns (bool success)
{
allowed[msg.sender][spender] = tokens;
emit Approval(msg.sender, spender, tokens);
return true;
}
// Transfer the balance from owner's account to another account
function transfer(address to, uint tokens) public override returns (bool success)
{
balances[msg.sender] = balances[msg.sender] - tokens;
balances[to] = balances[to] + tokens;
emit Transfer(msg.sender, to, tokens);
return true;
}
// Send `tokens` amount of tokens from address `from` to address `to`
// The transferFrom method is used for a withdraw workflow, allowing contracts to send
// tokens on your behalf, for example to "deposit" to a contract address and/or to charge
// fees in sub-currencies; the command should fail unless the _from account has
// deliberately authorized the sender of the message via some mechanism; we propose
// these standardized APIs for approval:
function transferFrom(address from, address to, uint tokens) public override returns (bool success)
{
balances[from] = balances[from] - tokens;
allowed[from][msg.sender] = allowed[from][msg.sender] - tokens;
balances[to] = balances[to] - tokens;
emit Transfer(from, to, tokens);
return true;
}
}