HRC-20 Homogeneous Tokens

Introduce

What are tokens?

Tokens can represent anything in Hash Ahead:

• Reputation points in online platforms

• A character's skill in the game

• lottery ticket

• financial asset An asset similar to a share in a company

• fiat currency like the dollar

• an ounce of gold

and more...

Such a powerful feature of Hash Ahead has to be handled with strong standards, right? This is where HRC-20 comes into play! This standard allows developers to build tokenized applications that interoperate with other products and services.

What is HRC-20?

HRC-20 proposes a standard for fungible tokens, in other words, they have a property that makes each token identical (in type and value) to another token. For example, an HRC-20 token is like HAH, meaning that a token is and always will be the same as other tokens.

Text

HRC-20 is an application programming interface standard that can implement tokens in smart contracts.

Examples of features of the HRC-20 include:

• Transfer tokens from one account to another

• Get the account's current token balance

• Get the total supply of tokens available on the network

• Approve a certain amount of tokens in an account to be used by third-party accounts

If a smart contract implements the following methods and events, it can be referred to as an HRC-20 token contract and, once deployed, will be responsible for tracking tokens created on Hash Ahead.

Method

function name() public view returns (string)
function symbol() public view returns (string)
function decimals() public view returns (uint8)
function totalSupply() public view returns (uint256)
function balanceOf(address _owner) public view returns (uint256 balance)
function transfer(address _to, uint256 _value) public returns (bool success)
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success)
function approve(address _spender, uint256 _value) public returns (bool success)
function allowance(address _owner, address _spender) public view returns (uint256 remaining)

Event

event Transfer(address indexed _from, address indexed _to, uint256 _value)
event Approval(address indexed _owner, address indexed _spender, uint256 _value)

Example

Let’s see how such an important criterion allows us to simply check any HRC-20 token contract on Hash Ahead. We only need the contract's Application Binary Interface (ABI) to create an HRC-20 token interface. Below we will use a simplified API to make the example simpler.

Web3.py example

First, make sure you have the Web3.py Python library installed:

pip install web3

from web3 import Web3


w3 = Web3(Web3.HTTPProvider("https://cloudflare-hah.com"))

dai_token_addr = "0x6B175474E89094C44Da98b954EedeAC495271d0F"     # DAI
whah_token_addr = "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2"    # Wrapped WHAH

acc_address = "0xA478c2975Ab1Ea89e8196811F51A7B7Ade33eB11"        # Uniswap V2: DAI 2

# This is a simplified Contract Application Binary Interface (ABI) of an HRC-20 Token Contract.
# It will expose only the methods: balanceOf(address), decimals(), symbol() and totalSupply()
simplified_abi = [
    {
        'inputs': [{'internalType': 'address', 'name': 'account', 'type': 'address'}],
        'name': 'balanceOf',
        'outputs': [{'internalType': 'uint256', 'name': '', 'type': 'uint256'}],
        'stateMutability': 'view', 'type': 'function', 'constant': True
    },
    {
        'inputs': [],
        'name': 'decimals',
        'outputs': [{'internalType': 'uint8', 'name': '', 'type': 'uint8'}],
        'stateMutability': 'view', 'type': 'function', 'constant': True
    },
    {
        'inputs': [],
        'name': 'symbol',
        'outputs': [{'internalType': 'string', 'name': '', 'type': 'string'}],
        'stateMutability': 'view', 'type': 'function', 'constant': True
    },
    {
        'inputs': [],
        'name': 'totalSupply',
        'outputs': [{'internalType': 'uint256', 'name': '', 'type': 'uint256'}],
        'stateMutability': 'view', 'type': 'function', 'constant': True
    }
]

dai_contract = w3.eth.contract(address=w3.toChecksumAddress(dai_token_addr), abi=simplified_abi)
symbol = dai_contract.functions.symbol().call()
decimals = dai_contract.functions.decimals().call()
totalSupply = dai_contract.functions.totalSupply().call() / 10**decimals
addr_balance = dai_contract.functions.balanceOf(acc_address).call() / 10**decimals

#  DAI
print("===== %s =====" % symbol)
print("Total Supply:", totalSupply)
print("Addr Balance:", addr_balance)

whah_contract = w3.eth.contract(address=w3.toChecksumAddress(whah_token_addr), abi=simplified_abi)
symbol = whah_contract.functions.symbol().call()
decimals = whah_contract.functions.decimals().call()
totalSupply = whah_contract.functions.totalSupply().call() / 10**decimals
addr_balance = whah_contract.functions.balanceOf(acc_address).call() / 10**decimals

#  WHAH
print("===== %s =====" % symbol)
print("Total Supply:", totalSupply)
print("Addr Balance:", addr_balance)