evm

v0.1.14

evm v0.1.14 EVM.MachineState

Module for tracking the current machine state, which is roughly equivilant to the VM state for an executing contract.

This is most often seen as µ in the Yellow Paper.

Link to this section Summary

Types

memory()
program_counter()
t()

Functions

maybe_set_active_words(machine_state, last_word)

After a memory operation, we may have incremented the total number of active words. This function takes a memory offset accessed and updates the machine state accordingly

move_program_counter(machine_state, operation_metadata, inputs)

Increments the program counter

pop_n(machine_state, n)

Pops n values off the stack

push(machine_state, value)

Push a values onto the stack

subtract_gas(machine_state, exec_env)

Returns a new execution environment less the amount of gas specified

Link to this section Types

Link to this type memory() 
memory() :: binary
Link to this type program_counter() 
program_counter() :: integer
Link to this type t() 
t() :: %EVM.MachineState{active_words: integer, gas: EVM.Gas.t, memory: memory, previously_active_words: term, program_counter: program_counter, stack: EVM.Stack.t}

Link to this section Functions

Link to this function maybe_set_active_words(machine_state, last_word) 
maybe_set_active_words(t, EVM.val) :: t

After a memory operation, we may have incremented the total number of active words. This function takes a memory offset accessed and updates the machine state accordingly.

Examples 

iex> %EVM.MachineState{active_words: 2} |> EVM.MachineState.maybe_set_active_words(1)
%EVM.MachineState{active_words: 2}

iex> %EVM.MachineState{active_words: 2} |> EVM.MachineState.maybe_set_active_words(3)
%EVM.MachineState{active_words: 3}

iex> %EVM.MachineState{active_words: 2} |> EVM.MachineState.maybe_set_active_words(1)
%EVM.MachineState{active_words: 2}
Link to this function move_program_counter(machine_state, operation_metadata, inputs) 
move_program_counter(EVM.MachineState.t, EVM.Operation.Metadata.t, [EVM.val]) :: EVM.MachineState.t

Increments the program counter

Examples 

iex> EVM.MachineState.move_program_counter(%EVM.MachineState{program_counter: 9}, EVM.Operation.metadata(:add), [1, 1])
%EVM.MachineState{program_counter: 10}
Link to this function pop_n(machine_state, n) 
pop_n(EVM.MachineState.t, integer) :: {EVM.MachineState.t, [EVM.val]}

Pops n values off the stack

Examples 

iex> EVM.MachineState.pop_n(%EVM.MachineState{stack: [1, 2, 3]}, 2)
{[1 ,2], %EVM.MachineState{stack: [3]}}
Link to this function push(machine_state, value) 
push(EVM.MachineState.t, EVM.val) :: EVM.MachineState.t

Push a values onto the stack

Examples 

iex> EVM.MachineState.push(%EVM.MachineState{stack: [2, 3]}, 1)
%EVM.MachineState{stack: [1, 2, 3]}
Link to this function subtract_gas(machine_state, exec_env) 
subtract_gas(EVM.MachineState.t, ExecEnv.t) :: EVM.MachineState.t

Returns a new execution environment less the amount of gas specified.

Examples 

iex> machine_state = %EVM.MachineState{gas: 10, stack: [1, 1], program_counter: 0}
iex> exec_env = %EVM.ExecEnv{machine_code: <<EVM.Operation.metadata(:add).id>>}
iex> EVM.MachineState.subtract_gas(machine_state, exec_env)
%EVM.MachineState{gas: 7, stack: [1, 1]}