VM Actor Interface

• State reliable
• Theory Audit wip
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• section-systems.filecoin_vm.actor

As mentioned above, Actors are the Filecoin equivalent of smart contracts in the Ethereum Virtual Machine. As such, Actors are very central components of the system. Any change to the current state of the Filecoin blockchain has to be triggered through an actor method invocation.

This sub-section describes the interface between Actors and the Filecoin Virtual Machine. This means that most of what is described below does not strictly belong to the VM. Instead it is logic that sits on the interface between the VM and Actors logic.

There are eleven (11) types of builtin Actors in total, not all of which interact with the VM. Some Actors do not invoke changes to the StateTree of the blockchain and therefore, do not need to have an interface to the VM. We discuss the details of all System Actors later on in the System Actors subsection.

The actor address is a stable address generated by hashing the sender’s public key and a creation nonce. It should be stable across chain re-organizations. The actor ID address on the other hand, is an auto-incrementing address that is compact but can change in case of chain re-organizations. That being said, after being created, actors should use an actor address.

package builtin

import (
	addr "github.com/filecoin-project/go-address"
)

// Addresses for singleton system actors.
var (
	// Distinguished AccountActor that is the source of system implicit messages.
	SystemActorAddr           = mustMakeAddress(0)
	InitActorAddr             = mustMakeAddress(1)
	RewardActorAddr           = mustMakeAddress(2)
	CronActorAddr             = mustMakeAddress(3)
	StoragePowerActorAddr     = mustMakeAddress(4)
	StorageMarketActorAddr    = mustMakeAddress(5)
	VerifiedRegistryActorAddr = mustMakeAddress(6)
	// Distinguished AccountActor that is the destination of all burnt funds.
	BurntFundsActorAddr = mustMakeAddress(99)
)

const FirstNonSingletonActorId = 100

func mustMakeAddress(id uint64) addr.Address {
	address, err := addr.NewIDAddress(id)
	if err != nil {
		panic(err)
	}
	return address
}

The ActorState structure is composed of the actor’s balance, in terms of tokens held by this actor, as well as a group of state methods used to query, inspect and interact with chain state.