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nimbus-eth2/beacon_chain/spec/helpers.nim

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# beacon_chain
# Copyright (c) 2018-2022 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
when (NimMajor, NimMinor) < (1, 4):
{.push raises: [Defect].}
else:
{.push raises: [].}
import
# Standard lib
std/[algorithm, math, sets, tables, times],
# Status libraries
stew/[bitops2, byteutils, endians2, objects, saturation_arith],
chronicles,
eth/eip1559, eth/common/[eth_types, eth_types_rlp],
# Internal
./datatypes/[phase0, altair, bellatrix],
"."/[eth2_merkleization, forks, ssz_codec]
# TODO although eth2_merkleization already exports ssz_codec, *sometimes* code
# fails to compile if the export is not done here also
export
forks, eth2_merkleization, ssz_codec
type
ExecutionBlockHeader = eth_types.BlockHeader
FinalityCheckpoints* = object
justified*: Checkpoint
finalized*: Checkpoint
func shortLog*(v: FinalityCheckpoints): auto =
(
justified: shortLog(v.justified),
finalized: shortLog(v.finalized)
)
chronicles.formatIt FinalityCheckpoints: it.shortLog
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/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/consensus-specs/blob/v1.2.0/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
func is_exited_validator*(validator: Validator, epoch: Epoch): bool =
## Check if ``validator`` is exited
validator.exit_epoch <= epoch
func is_withdrawable_validator*(validator: Validator, epoch: Epoch): bool =
epoch >= validator.withdrawable_epoch
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/phase0/beacon-chain.md#get_active_validator_indices
iterator get_active_validator_indices*(state: ForkyBeaconState, epoch: Epoch):
ValidatorIndex =
for vidx in state.validators.vindices:
if is_active_validator(state.validators[vidx], epoch):
yield vidx
func get_active_validator_indices*(state: ForkyBeaconState, epoch: Epoch):
seq[ValidatorIndex] =
## Return the sequence of active validator indices at ``epoch``.
var res = newSeqOfCap[ValidatorIndex](state.validators.len)
for vidx in get_active_validator_indices(state, epoch):
res.add vidx
res
func get_active_validator_indices_len*(state: ForkyBeaconState, epoch: Epoch):
uint64 =
for vidx in state.validators.vindices:
if is_active_validator(state.validators.item(vidx), epoch):
inc result
func get_active_validator_indices_len*(
state: ForkedHashedBeaconState; epoch: Epoch): uint64 =
withState(state):
get_active_validator_indices_len(forkyState.data, epoch)
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/phase0/beacon-chain.md#get_current_epoch
func get_current_epoch*(state: ForkyBeaconState): Epoch =
## Return the current epoch.
state.slot.epoch
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/phase0/beacon-chain.md#get_current_epoch
func get_current_epoch*(state: ForkedHashedBeaconState): Epoch =
## Return the current epoch.
withState(state): get_current_epoch(forkyState.data)
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/phase0/beacon-chain.md#get_previous_epoch
func get_previous_epoch*(
state: ForkyBeaconState | ForkedHashedBeaconState): Epoch =
## Return the previous epoch (unless the current epoch is ``GENESIS_EPOCH``).
get_previous_epoch(get_current_epoch(state))
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/phase0/beacon-chain.md#get_randao_mix
func get_randao_mix*(state: ForkyBeaconState, 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
uint64.fromBytesLE(data)
func uint_to_bytes*(x: uint64): array[8, byte] = toBytesLE(x)
func uint_to_bytes*(x: uint32): array[4, byte] = toBytesLE(x)
func uint_to_bytes*(x: uint16): array[2, byte] = toBytesLE(x)
func uint_to_bytes*(x: uint8): array[1, byte] = toBytesLE(x)
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/phase0/beacon-chain.md#compute_domain
func compute_domain*(
domain_type: DomainType,
fork_version: Version,
genesis_validators_root: Eth2Digest = ZERO_HASH): Eth2Domain =
## Return the domain for the ``domain_type`` and ``fork_version``.
#
# TODO Can't be used as part of a const/static expression:
# https://github.com/nim-lang/Nim/issues/15952
# https://github.com/nim-lang/Nim/issues/19969
let fork_data_root =
compute_fork_data_root(fork_version, genesis_validators_root)
result[0..3] = domain_type.data
result[4..31] = fork_data_root.data.toOpenArray(0, 27)
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/phase0/beacon-chain.md#get_domain
func get_domain*(
fork: Fork,
domain_type: DomainType,
epoch: Epoch,
genesis_validators_root: Eth2Digest): Eth2Domain =
## 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: ForkyBeaconState, domain_type: DomainType, epoch: Epoch): Eth2Domain =
## 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/consensus-specs/blob/v1.2.0/specs/phase0/beacon-chain.md#compute_signing_root
func compute_signing_root*(ssz_object: auto, domain: Eth2Domain): 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/consensus-specs/blob/v1.2.0/specs/phase0/beacon-chain.md#get_seed
func get_seed*(state: ForkyBeaconState, 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] = domain_type.data
seed_input[4..11] = uint_to_bytes(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)
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/altair/beacon-chain.md#add_flag
func add_flag*(flags: ParticipationFlags, flag_index: int): ParticipationFlags =
let flag = ParticipationFlags(1'u8 shl flag_index)
flags or flag
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/altair/beacon-chain.md#has_flag
func has_flag*(flags: ParticipationFlags, flag_index: int): bool =
let flag = ParticipationFlags(1'u8 shl flag_index)
(flags and flag) == flag
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/altair/light-client/sync-protocol.md#is_sync_committee_update
template is_sync_committee_update*(update: SomeLightClientUpdate): bool =
when update is SomeLightClientUpdateWithSyncCommittee:
not isZeroMemory(update.next_sync_committee_branch)
else:
false
# https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.3/specs/altair/light-client/sync-protocol.md#is_finality_update
template is_finality_update*(update: SomeLightClientUpdate): bool =
when update is SomeLightClientUpdateWithFinality:
not isZeroMemory(update.finality_branch)
else:
false
# https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.3/specs/altair/light-client/sync-protocol.md#is_next_sync_committee_known
template is_next_sync_committee_known*(store: LightClientStore): bool =
not isZeroMemory(store.next_sync_committee)
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/altair/light-client/sync-protocol.md#get_safety_threshold
func get_safety_threshold*(store: LightClientStore): uint64 =
max(
store.previous_max_active_participants,
store.current_max_active_participants
) div 2
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/altair/light-client/sync-protocol.md#is_better_update
type LightClientUpdateMetadata* = object
attested_slot*, finalized_slot*, signature_slot*: Slot
has_sync_committee*, has_finality*: bool
num_active_participants*: uint64
func toMeta*(update: SomeLightClientUpdate): LightClientUpdateMetadata =
var meta {.noinit.}: LightClientUpdateMetadata
meta.attested_slot =
update.attested_header.slot
meta.finalized_slot =
when update is SomeLightClientUpdateWithFinality:
update.finalized_header.slot
else:
GENESIS_SLOT
meta.signature_slot =
update.signature_slot
meta.has_sync_committee =
when update is SomeLightClientUpdateWithSyncCommittee:
not update.next_sync_committee_branch.isZeroMemory
else:
false
meta.has_finality =
when update is SomeLightClientUpdateWithFinality:
not update.finality_branch.isZeroMemory
else:
false
meta.num_active_participants =
countOnes(update.sync_aggregate.sync_committee_bits).uint64
meta
func is_better_data*(new_meta, old_meta: LightClientUpdateMetadata): bool =
# Compare supermajority (> 2/3) sync committee participation
const max_active_participants = SYNC_COMMITTEE_SIZE.uint64
let
new_has_supermajority =
new_meta.num_active_participants * 3 >= max_active_participants * 2
old_has_supermajority =
old_meta.num_active_participants * 3 >= max_active_participants * 2
if new_has_supermajority != old_has_supermajority:
return new_has_supermajority > old_has_supermajority
if not new_has_supermajority:
if new_meta.num_active_participants != old_meta.num_active_participants:
return new_meta.num_active_participants > old_meta.num_active_participants
# Compare presence of relevant sync committee
let
new_has_relevant_sync_committee = new_meta.has_sync_committee and
new_meta.attested_slot.sync_committee_period ==
new_meta.signature_slot.sync_committee_period
old_has_relevant_sync_committee = old_meta.has_sync_committee and
old_meta.attested_slot.sync_committee_period ==
old_meta.signature_slot.sync_committee_period
if new_has_relevant_sync_committee != old_has_relevant_sync_committee:
return new_has_relevant_sync_committee > old_has_relevant_sync_committee
# Compare indication of any finality
if new_meta.has_finality != old_meta.has_finality:
return new_meta.has_finality > old_meta.has_finality
# Compare sync committee finality
if new_meta.has_finality:
let
new_has_sync_committee_finality =
new_meta.finalized_slot.sync_committee_period ==
new_meta.attested_slot.sync_committee_period
old_has_sync_committee_finality =
old_meta.finalized_slot.sync_committee_period ==
old_meta.attested_slot.sync_committee_period
if new_has_sync_committee_finality != old_has_sync_committee_finality:
return new_has_sync_committee_finality > old_has_sync_committee_finality
# Tiebreaker 1: Sync committee participation beyond supermajority
if new_meta.num_active_participants != old_meta.num_active_participants:
return new_meta.num_active_participants > old_meta.num_active_participants
# Tiebreaker 2: Prefer older data (fewer changes to best data)
new_meta.attested_slot < old_meta.attested_slot
template is_better_update*[A, B: SomeLightClientUpdate](
new_update: A, old_update: B): bool =
is_better_data(toMeta(new_update), toMeta(old_update))
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/bellatrix/beacon-chain.md#is_merge_transition_complete
func is_merge_transition_complete*(state: bellatrix.BeaconState): bool =
const defaultExecutionPayloadHeader = default(ExecutionPayloadHeader)
state.latest_execution_payload_header != defaultExecutionPayloadHeader
# https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.3/sync/optimistic.md#helpers
func is_execution_block*(blck: SomeForkyBeaconBlock): bool =
when typeof(blck).toFork >= BeaconBlockFork.Bellatrix:
const defaultExecutionPayload =
default(typeof(blck.body.execution_payload))
blck.body.execution_payload != defaultExecutionPayload
else:
false
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/bellatrix/beacon-chain.md#is_merge_transition_block
func is_merge_transition_block(
state: bellatrix.BeaconState,
body: bellatrix.BeaconBlockBody | bellatrix.TrustedBeaconBlockBody |
bellatrix.SigVerifiedBeaconBlockBody): bool =
const defaultBellatrixExecutionPayload = default(bellatrix.ExecutionPayload)
not is_merge_transition_complete(state) and
body.execution_payload != defaultBellatrixExecutionPayload
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/bellatrix/beacon-chain.md#is_execution_enabled
func is_execution_enabled*(
state: bellatrix.BeaconState,
body: bellatrix.BeaconBlockBody | bellatrix.TrustedBeaconBlockBody |
bellatrix.SigVerifiedBeaconBlockBody): bool =
is_merge_transition_block(state, body) or is_merge_transition_complete(state)
# https://github.com/ethereum/consensus-specs/blob/v1.2.0/specs/bellatrix/beacon-chain.md#compute_timestamp_at_slot
func compute_timestamp_at_slot*(state: ForkyBeaconState, slot: Slot): uint64 =
# Note: This function is unsafe with respect to overflows and underflows.
let slots_since_genesis = slot - GENESIS_SLOT
state.genesis_time + slots_since_genesis * SECONDS_PER_SLOT
proc emptyPayloadToBlockHeader*(payload: ExecutionPayload): ExecutionBlockHeader =
## This function assumes that the payload is empty!
doAssert payload.transactions.len == 0
ExecutionBlockHeader(
parentHash : payload.parent_hash,
ommersHash : EMPTY_UNCLE_HASH,
coinbase : EthAddress payload.fee_recipient.data,
stateRoot : payload.state_root,
txRoot : EMPTY_ROOT_HASH,
receiptRoot : payload.receipts_root,
bloom : payload.logs_bloom.data,
difficulty : default(DifficultyInt),
blockNumber : payload.block_number.u256,
gasLimit : GasInt payload.gas_limit,
gasUsed : GasInt payload.gas_used,
timestamp : fromUnix(int64.saturate payload.timestamp),
extraData : payload.extra_data.asSeq,
mixDigest : payload.prev_randao, # EIP-4399 redefine `mixDigest` -> `prevRandao`
nonce : default(BlockNonce),
fee : some payload.base_fee_per_gas
)
func build_empty_execution_payload*(state: bellatrix.BeaconState): ExecutionPayload =
## Assuming a pre-state of the same slot, build a valid ExecutionPayload
## without any transactions.
let
latest = state.latest_execution_payload_header
timestamp = compute_timestamp_at_slot(state, state.slot)
randao_mix = get_randao_mix(state, get_current_epoch(state))
base_fee = calcEip1599BaseFee(GasInt.saturate latest.gas_limit,
GasInt.saturate latest.gas_used,
latest.base_fee_per_gas)
var payload = ExecutionPayload(
parent_hash: latest.block_hash,
state_root: latest.state_root, # no changes to the state
receipts_root: EMPTY_ROOT_HASH,
block_number: latest.block_number + 1,
prev_randao: randao_mix,
gas_limit: latest.gas_limit, # retain same limit
gas_used: 0, # empty block, 0 gas
timestamp: timestamp,
base_fee_per_gas: base_fee)
payload.block_hash = rlpHash emptyPayloadToBlockHeader(payload)
payload
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