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