179 lines
7.0 KiB
Nim
179 lines
7.0 KiB
Nim
# beacon_chain
|
|
# Copyright (c) 2018-2020 Status Research & Development GmbH
|
|
# Licensed and distributed under either of
|
|
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
|
|
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
|
|
# at your option. This file may not be copied, modified, or distributed except according to those terms.
|
|
|
|
# Uncategorized helper functions from the spec
|
|
|
|
{.push raises: [Defect].}
|
|
|
|
import
|
|
# Standard lib
|
|
std/[math, tables],
|
|
# Third-party
|
|
stew/endians2,
|
|
# Internal
|
|
./datatypes, ./digest, ./crypto, ../ssz/merkleization
|
|
|
|
type
|
|
# This solves an ambiguous identifier Error in some contexts
|
|
# (other candidate is nativesockets.Domain)
|
|
Domain = datatypes.Domain
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#integer_squareroot
|
|
func integer_squareroot*(n: SomeInteger): SomeInteger =
|
|
# Return the largest integer ``x`` such that ``x**2 <= n``.
|
|
doAssert n >= 0'u64
|
|
|
|
var
|
|
x = n
|
|
y = (x + 1) div 2
|
|
while y < x:
|
|
x = y
|
|
y = (x + n div x) div 2
|
|
x
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#compute_epoch_at_slot
|
|
func compute_epoch_at_slot*(slot: Slot|uint64): Epoch =
|
|
# Return the epoch number at ``slot``.
|
|
(slot div SLOTS_PER_EPOCH).Epoch
|
|
|
|
template epoch*(slot: Slot): Epoch =
|
|
compute_epoch_at_slot(slot)
|
|
|
|
template isEpoch*(slot: Slot): bool =
|
|
(slot mod SLOTS_PER_EPOCH) == 0
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#compute_start_slot_at_epoch
|
|
func compute_start_slot_at_epoch*(epoch: Epoch): Slot =
|
|
# Return the start slot of ``epoch``.
|
|
(epoch * SLOTS_PER_EPOCH).Slot
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#is_active_validator
|
|
func is_active_validator*(validator: Validator, epoch: Epoch): bool =
|
|
### Check if ``validator`` is active
|
|
validator.activation_epoch <= epoch and epoch < validator.exit_epoch
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#get_active_validator_indices
|
|
func get_active_validator_indices*(state: BeaconState, epoch: Epoch):
|
|
seq[ValidatorIndex] =
|
|
# Return the sequence of active validator indices at ``epoch``.
|
|
for idx, val in state.validators:
|
|
if is_active_validator(val, epoch):
|
|
result.add idx.ValidatorIndex
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#get_current_epoch
|
|
func get_current_epoch*(state: BeaconState): Epoch =
|
|
# Return the current epoch.
|
|
doAssert state.slot >= GENESIS_SLOT, $state.slot
|
|
compute_epoch_at_slot(state.slot)
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#get_randao_mix
|
|
func get_randao_mix*(state: BeaconState,
|
|
epoch: Epoch): Eth2Digest =
|
|
## Returns the randao mix at a recent ``epoch``.
|
|
state.randao_mixes[epoch mod EPOCHS_PER_HISTORICAL_VECTOR]
|
|
|
|
func bytes_to_uint64*(data: openarray[byte]): uint64 =
|
|
doAssert data.len == 8
|
|
|
|
# Little-endian data representation
|
|
result = 0
|
|
for i in countdown(7, 0):
|
|
result = result * 256 + data[i]
|
|
|
|
# Have 1, 4, and 8-byte versions. Spec only defines 8-byte version, but useful
|
|
# to check invariants on rest.
|
|
func uint_to_bytes8*(x: uint64): array[8, byte] =
|
|
x.toBytesLE()
|
|
|
|
func uint_to_bytes4*(x: uint64): array[4, byte] =
|
|
doAssert x < 2'u64^32
|
|
|
|
# Little-endian data representation
|
|
result[0] = ((x shr 0) and 0xff).byte
|
|
result[1] = ((x shr 8) and 0xff).byte
|
|
result[2] = ((x shr 16) and 0xff).byte
|
|
result[3] = ((x shr 24) and 0xff).byte
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#compute_fork_data_root
|
|
func compute_fork_data_root(current_version: Version,
|
|
genesis_validators_root: Eth2Digest): Eth2Digest =
|
|
# Return the 32-byte fork data root for the ``current_version`` and
|
|
# ``genesis_validators_root``.
|
|
# This is used primarily in signature domains to avoid collisions across
|
|
# forks/chains.
|
|
hash_tree_root(ForkData(
|
|
current_version: current_version,
|
|
genesis_validators_root: genesis_validators_root
|
|
))
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#compute_fork_digest
|
|
func compute_fork_digest*(current_version: Version,
|
|
genesis_validators_root: Eth2Digest): ForkDigest =
|
|
# Return the 4-byte fork digest for the ``current_version`` and
|
|
# ``genesis_validators_root``.
|
|
# This is a digest primarily used for domain separation on the p2p layer.
|
|
# 4-bytes suffices for practical separation of forks/chains.
|
|
array[4, byte](result)[0..3] =
|
|
compute_fork_data_root(
|
|
current_version, genesis_validators_root).data.toOpenArray(0, 3)
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#compute_domain
|
|
func compute_domain*(
|
|
domain_type: DomainType,
|
|
fork_version: Version,
|
|
genesis_validators_root: Eth2Digest = ZERO_HASH): Domain =
|
|
# Return the domain for the ``domain_type`` and ``fork_version``.
|
|
let fork_data_root =
|
|
compute_fork_data_root(fork_version, genesis_validators_root)
|
|
result[0..3] = uint_to_bytes4(domain_type.uint64)
|
|
result[4..31] = fork_data_root.data[0..27]
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#get_domain
|
|
func get_domain*(
|
|
fork: Fork, domain_type: DomainType, epoch: Epoch, genesis_validators_root: Eth2Digest): Domain =
|
|
## Return the signature domain (fork version concatenated with domain type)
|
|
## of a message.
|
|
let fork_version =
|
|
if epoch < fork.epoch:
|
|
fork.previous_version
|
|
else:
|
|
fork.current_version
|
|
compute_domain(domain_type, fork_version, genesis_validators_root)
|
|
|
|
func get_domain*(
|
|
state: BeaconState, domain_type: DomainType, epoch: Epoch): Domain =
|
|
## Return the signature domain (fork version concatenated with domain type)
|
|
## of a message.
|
|
get_domain(state.fork, domain_type, epoch, state.genesis_validators_root)
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.11.3/specs/phase0/beacon-chain.md#compute_signing_root
|
|
func compute_signing_root*(ssz_object: auto, domain: Domain): Eth2Digest =
|
|
# Return the signing root of an object by calculating the root of the
|
|
# object-domain tree.
|
|
let domain_wrapped_object = SigningData(
|
|
object_root: hash_tree_root(ssz_object),
|
|
domain: domain
|
|
)
|
|
hash_tree_root(domain_wrapped_object)
|
|
|
|
# https://github.com/ethereum/eth2.0-specs/blob/v0.12.2/specs/phase0/beacon-chain.md#get_seed
|
|
func get_seed*(state: BeaconState, epoch: Epoch, domain_type: DomainType): Eth2Digest =
|
|
# Return the seed at ``epoch``.
|
|
|
|
var seed_input : array[4+8+32, byte]
|
|
|
|
# Detect potential underflow
|
|
static:
|
|
doAssert EPOCHS_PER_HISTORICAL_VECTOR > MIN_SEED_LOOKAHEAD
|
|
|
|
seed_input[0..3] = uint_to_bytes4(domain_type.uint64)
|
|
seed_input[4..11] = uint_to_bytes8(epoch.uint64)
|
|
seed_input[12..43] =
|
|
get_randao_mix(state, # Avoid underflow
|
|
epoch + EPOCHS_PER_HISTORICAL_VECTOR - MIN_SEED_LOOKAHEAD - 1).data
|
|
eth2digest(seed_input)
|