EVM State

The EVM is a state machine. A valid Ethereum program or valid bytecode can manipulate that state.

A specific opcode is an operation that manipulates that state.

Program Counter (pc)

The program counter points to the next opcode that the EVM is going to execute.

Stack / Memory / Storage

All of them are part of the EVM state. And are the areas where the EVM manipulates and stores data.

Program

This is where we store the bytecode of the current program. It can not change during execution, which makes it immutable.

Sender

Address of the account currently executing this program. Equivalent to msg.sender in Solidity.

Gas

We need to keep track how much gas we currently have and how much we already consumed. Most opcodes make the gas counter go down.

Value

How much Ether (wei) this current execution can consume.

Calldata

Is the input to our program.

Flags

We are going to keep track of two flags. The stop_flag and revert_flag. If one of them is True the current execution is going to stop.

Returndata

The EVM can return data after execution. We store this data in return.

Logs

There are several opcodes that emit logs when executed. The result of these logs is saved here.

class State:
    def __init__(self,
                 sender,
                 program,
                 gas,
                 value,
                 calldata=[]):
        self.pc      = 0
        
        self.stack   = Stack()
        self.memory  = Memory()
        self.storage = Storage()
        
        self.sender   = sender
        self.program  = program
        self.gas      = gas
        self.value    = value
        self.calldata = calldata
        
        self.stop_flag   = False
        self.revert_flag = False
        
        self.returndata = []
        self.logs       = []