先看看最熱門的幾個ERC-20的token
前五名是
1.USDT Tether USD
2.BNB Binance 幣安幣
3.LEO Bitfinex LEO Token
4.LINK ChainLink Token
5.HT Huobi Token
然後來看看源碼
1.USDT Tether USD 451行
2.BNB Binance 幣安幣 150行
3.LEO Bitfinex LEO Token 734行
4.LINK ChainLink Token 299行
5.HT Huobi Token 127行
BNB和HT是最少的
就來看看BNB和HT吧
BNB
https://etherscan.io/address/0xB8c77482e45F1F44dE1745F52C74426C631bDD52#code
/**
*Submitted for verification at Etherscan.io on 2017-07-06
*/
pragma solidity ^0.4.8;
/**
* Math operations with safety checks
*/
contract SafeMath {
function safeMul(uint256 a, uint256 b) internal returns (uint256) {
uint256 c = a * b;
assert(a == 0 || c / a == b);
return c;
}
function safeDiv(uint256 a, uint256 b) internal returns (uint256) {
assert(b > 0);
uint256 c = a / b;
assert(a == b * c + a % b);
return c;
}
function safeSub(uint256 a, uint256 b) internal returns (uint256) {
assert(b <= a);
return a - b;
}
function safeAdd(uint256 a, uint256 b) internal returns (uint256) {
uint256 c = a + b;
assert(c>=a && c>=b);
return c;
}
function assert(bool assertion) internal {
if (!assertion) {
throw;
}
}
}
contract BNB is SafeMath{
string public name;
string public symbol;
uint8 public decimals;
uint256 public totalSupply;
address public owner;
/* This creates an array with all balances */
mapping (address => uint256) public balanceOf;
mapping (address => uint256) public freezeOf;
mapping (address => mapping (address => uint256)) public allowance;
/* This generates a public event on the blockchain that will notify clients */
event Transfer(address indexed from, address indexed to, uint256 value);
/* This notifies clients about the amount burnt */
event Burn(address indexed from, uint256 value);
/* This notifies clients about the amount frozen */
event Freeze(address indexed from, uint256 value);
/* This notifies clients about the amount unfrozen */
event Unfreeze(address indexed from, uint256 value);
/* Initializes contract with initial supply tokens to the creator of the contract */
function BNB(
uint256 initialSupply,
string tokenName,
uint8 decimalUnits,
string tokenSymbol
) {
balanceOf[msg.sender] = initialSupply; // Give the creator all initial tokens
totalSupply = initialSupply; // Update total supply
name = tokenName; // Set the name for display purposes
symbol = tokenSymbol; // Set the symbol for display purposes
decimals = decimalUnits; // Amount of decimals for display purposes
owner = msg.sender;
}
/* Send coins */
function transfer(address _to, uint256 _value) {
if (_to == 0x0) throw; // Prevent transfer to 0x0 address. Use burn() instead
if (_value <= 0) throw;
if (balanceOf[msg.sender] < _value) throw; // Check if the sender has enough
if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
balanceOf[msg.sender] = SafeMath.safeSub(balanceOf[msg.sender], _value); // Subtract from the sender
balanceOf[_to] = SafeMath.safeAdd(balanceOf[_to], _value); // Add the same to the recipient
Transfer(msg.sender, _to, _value); // Notify anyone listening that this transfer took place
}
/* Allow another contract to spend some tokens in your behalf */
function approve(address _spender, uint256 _value)
returns (bool success) {
if (_value <= 0) throw;
allowance[msg.sender][_spender] = _value;
return true;
}
/* A contract attempts to get the coins */
function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
if (_to == 0x0) throw; // Prevent transfer to 0x0 address. Use burn() instead
if (_value <= 0) throw;
if (balanceOf[_from] < _value) throw; // Check if the sender has enough
if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
if (_value > allowance[_from][msg.sender]) throw; // Check allowance
balanceOf[_from] = SafeMath.safeSub(balanceOf[_from], _value); // Subtract from the sender
balanceOf[_to] = SafeMath.safeAdd(balanceOf[_to], _value); // Add the same to the recipient
allowance[_from][msg.sender] = SafeMath.safeSub(allowance[_from][msg.sender], _value);
Transfer(_from, _to, _value);
return true;
}
function burn(uint256 _value) returns (bool success) {
if (balanceOf[msg.sender] < _value) throw; // Check if the sender has enough
if (_value <= 0) throw;
balanceOf[msg.sender] = SafeMath.safeSub(balanceOf[msg.sender], _value); // Subtract from the sender
totalSupply = SafeMath.safeSub(totalSupply,_value); // Updates totalSupply
Burn(msg.sender, _value);
return true;
}
function freeze(uint256 _value) returns (bool success) {
if (balanceOf[msg.sender] < _value) throw; // Check if the sender has enough
if (_value <= 0) throw;
balanceOf[msg.sender] = SafeMath.safeSub(balanceOf[msg.sender], _value); // Subtract from the sender
freezeOf[msg.sender] = SafeMath.safeAdd(freezeOf[msg.sender], _value); // Updates totalSupply
Freeze(msg.sender, _value);
return true;
}
function unfreeze(uint256 _value) returns (bool success) {
if (freezeOf[msg.sender] < _value) throw; // Check if the sender has enough
if (_value <= 0) throw;
freezeOf[msg.sender] = SafeMath.safeSub(freezeOf[msg.sender], _value); // Subtract from the sender
balanceOf[msg.sender] = SafeMath.safeAdd(balanceOf[msg.sender], _value);
Unfreeze(msg.sender, _value);
return true;
}
// transfer balance to owner
function withdrawEther(uint256 amount) {
if(msg.sender != owner)throw;
owner.transfer(amount);
}
// can accept ether
function() payable {
}
}
然後是HT
https://etherscan.io/address/0x6f259637dcd74c767781e37bc6133cd6a68aa161#code
/**
*Submitted for verification at Etherscan.io on 2018-02-27
*/
pragma solidity 0.4.19;
contract Token {
/// @return total amount of tokens
function totalSupply() constant returns (uint supply) {}
/// @param _owner The address from which the balance will be retrieved
/// @return The balance
function balanceOf(address _owner) constant returns (uint balance) {}
/// @notice send `_value` token to `_to` from `msg.sender`
/// @param _to The address of the recipient
/// @param _value The amount of token to be transferred
/// @return Whether the transfer was successful or not
function transfer(address _to, uint _value) returns (bool success) {}
/// @notice send `_value` token to `_to` from `_from` on the condition it is approved by `_from`
/// @param _from The address of the sender
/// @param _to The address of the recipient
/// @param _value The amount of token to be transferred
/// @return Whether the transfer was successful or not
function transferFrom(address _from, address _to, uint _value) returns (bool success) {}
/// @notice `msg.sender` approves `_addr` to spend `_value` tokens
/// @param _spender The address of the account able to transfer the tokens
/// @param _value The amount of wei to be approved for transfer
/// @return Whether the approval was successful or not
function approve(address _spender, uint _value) returns (bool success) {}
/// @param _owner The address of the account owning tokens
/// @param _spender The address of the account able to transfer the tokens
/// @return Amount of remaining tokens allowed to spent
function allowance(address _owner, address _spender) constant returns (uint remaining) {}
event Transfer(address indexed _from, address indexed _to, uint _value);
event Approval(address indexed _owner, address indexed _spender, uint _value);
}
contract RegularToken is Token {
function transfer(address _to, uint _value) returns (bool) {
//Default assumes totalSupply can't be over max (2^256 - 1).
if (balances[msg.sender] >= _value && balances[_to] + _value >= balances[_to]) {
balances[msg.sender] -= _value;
balances[_to] += _value;
Transfer(msg.sender, _to, _value);
return true;
} else { return false; }
}
function transferFrom(address _from, address _to, uint _value) returns (bool) {
if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && balances[_to] + _value >= balances[_to]) {
balances[_to] += _value;
balances[_from] -= _value;
allowed[_from][msg.sender] -= _value;
Transfer(_from, _to, _value);
return true;
} else { return false; }
}
function balanceOf(address _owner) constant returns (uint) {
return balances[_owner];
}
function approve(address _spender, uint _value) returns (bool) {
allowed[msg.sender][_spender] = _value;
Approval(msg.sender, _spender, _value);
return true;
}
function allowance(address _owner, address _spender) constant returns (uint) {
return allowed[_owner][_spender];
}
mapping (address => uint) balances;
mapping (address => mapping (address => uint)) allowed;
uint public totalSupply;
}
contract UnboundedRegularToken is RegularToken {
uint constant MAX_UINT = 2**256 - 1;
/// @dev ERC20 transferFrom, modified such that an allowance of MAX_UINT represents an unlimited amount.
/// @param _from Address to transfer from.
/// @param _to Address to transfer to.
/// @param _value Amount to transfer.
/// @return Success of transfer.
function transferFrom(address _from, address _to, uint _value)
public
returns (bool)
{
uint allowance = allowed[_from][msg.sender];
if (balances[_from] >= _value
&& allowance >= _value
&& balances[_to] + _value >= balances[_to]
) {
balances[_to] += _value;
balances[_from] -= _value;
if (allowance < MAX_UINT) {
allowed[_from][msg.sender] -= _value;
}
Transfer(_from, _to, _value);
return true;
} else {
return false;
}
}
}
contract HBToken is UnboundedRegularToken {
uint public totalSupply = 5*10**26;
uint8 constant public decimals = 18;
string constant public name = "HuobiToken";
string constant public symbol = "HT";
function HBToken() {
balances[msg.sender] = totalSupply;
Transfer(address(0), msg.sender, totalSupply);
}
}