TRC-20：波场上的同质化代币标准

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

// 注意：TVM 与 Solidity 兼容，但请务必在波场上进行测试。
// 这是一个最小化示例，省略了高级安全模式。

[contract](https://onekey.so/blog/zh-CN/ecosystem/what-is-a-smart-contract/) ExampleTRC20 {
    string public name = "Example Token";
    string public symbol = "EXM";
    uint8 public decimals = 6; // 波场代币通常使用 6 位小数以兼容 USDT
    uint256 public totalSupply;

    mapping(address => uint256) private _balance;
    mapping(address => mapping(address => uint256)) private _allowance;

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    constructor(uint256 initialSupply) {
        _mint(msg.sender, initialSupply);
    }

    function balanceOf(address account) external view returns (uint256) {
        return _balance[account];
    }

    function transfer(address to, uint256 amount) external returns (bool) {
        _transfer(msg.sender, to, amount);
        return true;
    }

    function allowance(address owner, address spender) external view returns (uint256) {
        return _allowance[owner][spender];
    }

    function approve(address spender, uint256 amount) external returns (bool) {
        _allowance[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(address from, address to, uint256 amount) external returns (bool) {
        uint256 allowed = _allowance[from][msg.sender];
        require(allowed >= amount, "Allowance exceeded");
        _allowance[from][msg.sender] = allowed - amount;
        _transfer(from, to, amount);
        return true;
    }

    // 可选的铸造/销毁功能（在生产环境中，请明确访问控制）
    function _mint(address to, uint256 amount) internal {
        totalSupply += amount;
        _balance[to] += amount;
        emit Transfer(address(0), to, amount);
    }

    function _burn(address from, uint256 amount) internal {
        require(_balance[from] >= amount, "Insufficient balance");
        _balance[from] -= amount;
        totalSupply -= amount;
        emit Transfer(from, address(0), amount);
    }

    function _transfer([address](https://onekey.so/blog/zh-CN/ecosystem/what-is-a-crypto-wallet-address/) from, [address](https://onekey.so/blog/zh-CN/ecosystem/what-is-a-crypto-wallet-address/) to, uint256 amount) internal {
        require(_balance[from] >= amount, "Insufficient balance");
        require(to != [address](https://onekey.so/blog/zh-CN/ecosystem/what-is-a-crypto-wallet-address/)(0), "Invalid recipient");
        _balance[from] -= amount;
        _balance[to] += amount;
        emit Transfer(from, to, amount);
    }
}