State Machine

Blockchain development can be model as a State Machine.

The set of all the functions deployed on chain is the State token_transfer Function (STF) of a State Machine.

The State Machine comes with the basic concepts, an Input is applied to the Current State, under the rule of State token_transfer Function to transit the Current State into a New State.

State Machine

Here is an example, let's assume we have a Current State of block number 100:

{
   Alice's USDC Balace: 50,
   Bob's USDC Balace: 200,
}

While in the block 100, Bob is sending a transaction to move USDC balance from Bob to Alice:

{"p": "zen", "f": "token_transfer", "a": ["USDC", "Alice", 100]}

The token_transfer function is accepting the transaction as the Input of State Machine, outputs a New State:

{
   Alice's USDC Balace: 150,
   Bob's USDC Balace: 100,
}

As an example, we can take a look how the token_transfer STF is written in python:

def token_transfer(info, args):
    sender = info['sender']
    tick = args['a'][0]
    receiver = args['a'][1].lower()
    value = int(args['a'][2])
    assert value > 0

    sender_balance = get(tick, 'balance', 0, sender)
    assert sender_balance >= value
    sender_balance -= value
    put(sender, tick, 'balance', sender_balance, sender)
    receiver_balance = get(tick, 'balance', 0, receiver)
    receiver_balance += value
    put(receiver, tick, 'balance', receiver_balance, receiver)

This is a very basic function, we use get and put API calls here. For the security reason, we should do more check for the arguments.