Improve BeaconState safe accessors
And fix a bug in the compact committees accessor.
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0c3fdcd57c
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5a7903a377
@ -221,42 +221,29 @@ pub fn process_final_updates<T: EthSpec>(
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// Update start shard.
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state.start_shard = state.next_epoch_start_shard(spec)?;
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// This is a hack to allow us to update index roots and slashed balances for the next epoch.
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//
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// The indentation here is to make it obvious where the weird stuff happens.
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{
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state.slot += 1;
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// Set active index root
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let index_epoch = next_epoch + spec.activation_exit_delay;
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let indices_list = VariableList::<usize, T::ValidatorRegistryLimit>::from(
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state.get_active_validator_indices(index_epoch),
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);
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state.set_active_index_root(
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index_epoch,
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Hash256::from_slice(&indices_list.tree_hash_root()),
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spec,
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)?;
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// Reset slashings
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state.set_slashings(next_epoch, 0)?;
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// Set randao mix
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state.set_randao_mix(next_epoch, *state.get_randao_mix(current_epoch)?)?;
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state.slot -= 1;
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}
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// Set active index root
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let index_epoch = next_epoch + spec.activation_exit_delay;
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let indices_list = VariableList::<usize, T::ValidatorRegistryLimit>::from(
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state.get_active_validator_indices(index_epoch),
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);
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state.set_active_index_root(
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index_epoch,
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Hash256::from_slice(&indices_list.tree_hash_root()),
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spec,
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)?;
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// Set committees root
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// Note: we do this out-of-order w.r.t. to the spec, because we don't want the slot to be
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// incremented. It's safe because the updates to slashings and the RANDAO mix (above) don't
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// affect this.
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state.set_compact_committee_root(
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next_epoch,
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get_compact_committees_root(state, RelativeEpoch::Next, spec)?,
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spec,
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)?;
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// Reset slashings
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state.set_slashings(next_epoch, 0)?;
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// Set randao mix
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state.set_randao_mix(next_epoch, *state.get_randao_mix(current_epoch)?)?;
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// Set historical root accumulator
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if next_epoch.as_u64() % (T::SlotsPerHistoricalRoot::to_u64() / T::slots_per_epoch()) == 0 {
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let historical_batch = state.historical_batch();
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@ -60,6 +60,22 @@ pub enum Error {
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SszTypesError(ssz_types::Error),
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}
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/// Control whether an epoch-indexed field can be indexed at the next epoch or not.
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#[derive(Debug, PartialEq, Clone, Copy)]
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enum AllowNextEpoch {
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True,
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False,
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}
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impl AllowNextEpoch {
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fn upper_bound_of(self, current_epoch: Epoch) -> Epoch {
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match self {
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AllowNextEpoch::True => current_epoch + 1,
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AllowNextEpoch::False => current_epoch,
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}
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}
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}
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/// The state of the `BeaconChain` at some slot.
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///
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/// Spec v0.8.0
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@ -108,12 +124,12 @@ where
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pub start_shard: u64,
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pub randao_mixes: FixedVector<Hash256, T::EpochsPerHistoricalVector>,
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#[compare_fields(as_slice)]
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active_index_roots: FixedVector<Hash256, T::EpochsPerHistoricalVector>,
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pub active_index_roots: FixedVector<Hash256, T::EpochsPerHistoricalVector>,
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#[compare_fields(as_slice)]
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compact_committees_roots: FixedVector<Hash256, T::EpochsPerHistoricalVector>,
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pub compact_committees_roots: FixedVector<Hash256, T::EpochsPerHistoricalVector>,
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// Slashings
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slashings: FixedVector<u64, T::EpochsPerSlashingsVector>,
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pub slashings: FixedVector<u64, T::EpochsPerSlashingsVector>,
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// Attestations
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pub previous_epoch_attestations: VariableList<PendingAttestation<T>, T::MaxPendingAttestations>,
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@ -459,12 +475,16 @@ impl<T: EthSpec> BeaconState<T> {
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/// Safely obtains the index for `randao_mixes`
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///
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/// Spec v0.8.0
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fn get_randao_mix_index(&self, epoch: Epoch) -> Result<usize, Error> {
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/// Spec v0.8.1
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fn get_randao_mix_index(
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&self,
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epoch: Epoch,
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allow_next_epoch: AllowNextEpoch,
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) -> Result<usize, Error> {
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let current_epoch = self.current_epoch();
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let len = T::EpochsPerHistoricalVector::to_u64();
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if epoch + len > current_epoch && epoch <= current_epoch {
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if current_epoch < epoch + len && epoch <= allow_next_epoch.upper_bound_of(current_epoch) {
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Ok(epoch.as_usize() % len as usize)
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} else {
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Err(Error::EpochOutOfBounds)
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@ -492,7 +512,7 @@ impl<T: EthSpec> BeaconState<T> {
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///
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/// Spec v0.8.1
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pub fn get_randao_mix(&self, epoch: Epoch) -> Result<&Hash256, Error> {
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let i = self.get_randao_mix_index(epoch)?;
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let i = self.get_randao_mix_index(epoch, AllowNextEpoch::False)?;
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Ok(&self.randao_mixes[i])
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}
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@ -500,21 +520,29 @@ impl<T: EthSpec> BeaconState<T> {
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///
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/// Spec v0.8.1
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pub fn set_randao_mix(&mut self, epoch: Epoch, mix: Hash256) -> Result<(), Error> {
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let i = self.get_randao_mix_index(epoch)?;
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let i = self.get_randao_mix_index(epoch, AllowNextEpoch::True)?;
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self.randao_mixes[i] = mix;
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Ok(())
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}
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/// Safely obtains the index for `active_index_roots`, given some `epoch`.
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///
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/// If `allow_next_epoch` is `True`, then we allow an _extra_ one epoch of lookahead.
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///
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/// Spec v0.8.1
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fn get_active_index_root_index(&self, epoch: Epoch, spec: &ChainSpec) -> Result<usize, Error> {
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fn get_active_index_root_index(
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&self,
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epoch: Epoch,
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spec: &ChainSpec,
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allow_next_epoch: AllowNextEpoch,
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) -> Result<usize, Error> {
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let current_epoch = self.current_epoch();
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let lookahead = spec.activation_exit_delay;
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let lookback = self.active_index_roots.len() as u64 - lookahead;
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let epoch_upper_bound = allow_next_epoch.upper_bound_of(current_epoch) + lookahead;
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if epoch + lookback > current_epoch && current_epoch + lookahead >= epoch {
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if current_epoch < epoch + lookback && epoch <= epoch_upper_bound {
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Ok(epoch.as_usize() % self.active_index_roots.len())
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} else {
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Err(Error::EpochOutOfBounds)
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@ -525,7 +553,7 @@ impl<T: EthSpec> BeaconState<T> {
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///
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/// Spec v0.8.1
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pub fn get_active_index_root(&self, epoch: Epoch, spec: &ChainSpec) -> Result<Hash256, Error> {
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let i = self.get_active_index_root_index(epoch, spec)?;
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let i = self.get_active_index_root_index(epoch, spec, AllowNextEpoch::False)?;
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Ok(self.active_index_roots[i])
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}
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@ -538,7 +566,7 @@ impl<T: EthSpec> BeaconState<T> {
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index_root: Hash256,
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spec: &ChainSpec,
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) -> Result<(), Error> {
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let i = self.get_active_index_root_index(epoch, spec)?;
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let i = self.get_active_index_root_index(epoch, spec, AllowNextEpoch::True)?;
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self.active_index_roots[i] = index_root;
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Ok(())
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}
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@ -552,19 +580,17 @@ impl<T: EthSpec> BeaconState<T> {
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/// Safely obtains the index for `compact_committees_roots`, given some `epoch`.
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///
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/// Spec v0.8.0
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/// Spec v0.8.1
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fn get_compact_committee_root_index(
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&self,
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epoch: Epoch,
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spec: &ChainSpec,
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allow_next_epoch: AllowNextEpoch,
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) -> Result<usize, Error> {
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let current_epoch = self.current_epoch();
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let len = T::EpochsPerHistoricalVector::to_u64();
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let lookahead = spec.activation_exit_delay;
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let lookback = self.compact_committees_roots.len() as u64 - lookahead;
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if epoch + lookback > current_epoch && current_epoch + lookahead >= epoch {
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Ok(epoch.as_usize() % self.compact_committees_roots.len())
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if current_epoch < epoch + len && epoch <= allow_next_epoch.upper_bound_of(current_epoch) {
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Ok(epoch.as_usize() % len as usize)
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} else {
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Err(Error::EpochOutOfBounds)
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}
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@ -572,26 +598,21 @@ impl<T: EthSpec> BeaconState<T> {
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/// Return the `compact_committee_root` at a recent `epoch`.
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///
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/// Spec v0.8.0
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pub fn get_compact_committee_root(
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&self,
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epoch: Epoch,
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spec: &ChainSpec,
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) -> Result<Hash256, Error> {
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let i = self.get_compact_committee_root_index(epoch, spec)?;
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/// Spec v0.8.1
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pub fn get_compact_committee_root(&self, epoch: Epoch) -> Result<Hash256, Error> {
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let i = self.get_compact_committee_root_index(epoch, AllowNextEpoch::False)?;
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Ok(self.compact_committees_roots[i])
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}
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/// Set the `compact_committee_root` at a recent `epoch`.
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///
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/// Spec v0.8.0
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/// Spec v0.8.1
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pub fn set_compact_committee_root(
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&mut self,
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epoch: Epoch,
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index_root: Hash256,
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spec: &ChainSpec,
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) -> Result<(), Error> {
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let i = self.get_compact_committee_root_index(epoch, spec)?;
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let i = self.get_compact_committee_root_index(epoch, AllowNextEpoch::True)?;
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self.compact_committees_roots[i] = index_root;
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Ok(())
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}
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@ -642,14 +663,19 @@ impl<T: EthSpec> BeaconState<T> {
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/// Safely obtain the index for `slashings`, given some `epoch`.
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///
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/// Spec v0.8.0
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fn get_slashings_index(&self, epoch: Epoch) -> Result<usize, Error> {
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/// Spec v0.8.1
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fn get_slashings_index(
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&self,
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epoch: Epoch,
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allow_next_epoch: AllowNextEpoch,
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) -> Result<usize, Error> {
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// We allow the slashings vector to be accessed at any cached epoch at or before
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// the current epoch.
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if epoch <= self.current_epoch()
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&& epoch + T::EpochsPerSlashingsVector::to_u64() >= self.current_epoch() + 1
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// the current epoch, or the next epoch if `AllowNextEpoch::True` is passed.
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let current_epoch = self.current_epoch();
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if current_epoch < epoch + T::EpochsPerSlashingsVector::to_u64()
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&& epoch <= allow_next_epoch.upper_bound_of(current_epoch)
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{
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Ok((epoch.as_u64() % T::EpochsPerSlashingsVector::to_u64()) as usize)
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Ok(epoch.as_usize() % T::EpochsPerSlashingsVector::to_usize())
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} else {
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Err(Error::EpochOutOfBounds)
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}
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@ -664,17 +690,17 @@ impl<T: EthSpec> BeaconState<T> {
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/// Get the total slashed balances for some epoch.
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///
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/// Spec v0.8.0
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/// Spec v0.8.1
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pub fn get_slashings(&self, epoch: Epoch) -> Result<u64, Error> {
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let i = self.get_slashings_index(epoch)?;
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let i = self.get_slashings_index(epoch, AllowNextEpoch::False)?;
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Ok(self.slashings[i])
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}
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/// Set the total slashed balances for some epoch.
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///
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/// Spec v0.8.0
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/// Spec v0.8.1
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pub fn set_slashings(&mut self, epoch: Epoch, value: u64) -> Result<(), Error> {
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let i = self.get_slashings_index(epoch)?;
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let i = self.get_slashings_index(epoch, AllowNextEpoch::True)?;
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self.slashings[i] = value;
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Ok(())
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}
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