/// <summary>
/// Return the committee assignment in the ``epoch`` for ``validator_index``.
/// ``assignment`` returned is a tuple of the following form:
/// * ``assignment[0]`` is the list of validators in the committee
/// * ``assignment[1]`` is the index to which the committee is assigned
/// * ``assignment[2]`` is the slot at which the committee is assigned
/// Return None if no assignment.
/// </summary>
public CommitteeAssignment GetCommitteeAssignment(BeaconState state, Epoch epoch, ValidatorIndex validatorIndex)
{
Epoch nextEpoch = _beaconStateAccessor.GetCurrentEpoch(state) + Epoch.One;
if (epoch > nextEpoch)
{
throw new ArgumentOutOfRangeException(nameof(epoch), epoch,
$"Committee epoch cannot be greater than next epoch {nextEpoch}.");
}
TimeParameters timeParameters = _timeParameterOptions.CurrentValue;
Slot startSlot = _beaconChainUtility.ComputeStartSlotOfEpoch(epoch);
ulong endSlot = startSlot + timeParameters.SlotsPerEpoch;
for (Slot slot = startSlot; slot < endSlot; slot += Slot.One)
{
ulong committeeCount = _beaconStateAccessor.GetCommitteeCountAtSlot(state, slot);
for (CommitteeIndex index = CommitteeIndex.Zero;
index < new CommitteeIndex(committeeCount);
index += CommitteeIndex.One)
{
IReadOnlyList <ValidatorIndex> committee =
_beaconStateAccessor.GetBeaconCommittee(state, slot, index);
if (committee.Contains(validatorIndex))
{
CommitteeAssignment committeeAssignment = new CommitteeAssignment(committee, index, slot);
return(committeeAssignment);
}
}
}
return(CommitteeAssignment.None);
}
public async Task <Attestation> NewAttestationAsync(BlsPublicKey validatorPublicKey,
bool proofOfCustodyBit, Slot slot, CommitteeIndex index,
CancellationToken cancellationToken)
{
Root head = await _store.GetHeadAsync().ConfigureAwait(false);
BeaconBlock headBlock = (await _store.GetSignedBlockAsync(head).ConfigureAwait(false)).Message;
BeaconState parentState = await _store.GetBlockStateAsync(head).ConfigureAwait(false);
// Clone state (will mutate) and process outstanding slots
BeaconState headState = BeaconState.Clone(parentState);
_beaconStateTransition.ProcessSlots(headState, slot);
// Set attestation_data.index = index where index is the index associated with the validator's committee.
ValidatorIndex?validatorIndex = FindValidatorIndexByPublicKey(headState, validatorPublicKey);
if (validatorIndex == null)
{
throw new Exception($"Can not find validator index for public key {validatorPublicKey}");
}
// TODO: May need a more efficient way to try and find the committee and position within the committee.
// Some of this may already be cached in Validator Assignments (generally stable for an epoch),
// but not with the index within the committee. Easy enough to extend and use the same cache.
IReadOnlyList <ValidatorIndex> committee =
_beaconStateAccessor.GetBeaconCommittee(headState, headState.Slot, index);
int committeeSize = committee.Count;
int?committeeMemberIndexOfValidator = null;
for (int committeeMemberIndex = 0; committeeMemberIndex < committee.Count; committeeMemberIndex++)
{
if (committee[committeeMemberIndex] == validatorIndex)
{
committeeMemberIndexOfValidator = committeeMemberIndex;
break;
}
}
if (committeeMemberIndexOfValidator == null)
{
throw new Exception($"Validator index {validatorIndex} is not a member of committee {index}");
}
Root beaconBlockRoot = _cryptographyService.HashTreeRoot(headBlock);
Checkpoint source = headState.CurrentJustifiedCheckpoint;
Epoch currentEpoch = _beaconStateAccessor.GetCurrentEpoch(headState);
Slot startSlot = _beaconChainUtility.ComputeStartSlotOfEpoch(currentEpoch);
Root epochBoundaryBlockRoot;
if (startSlot == headState.Slot)
{
epochBoundaryBlockRoot = beaconBlockRoot;
}
else
{
epochBoundaryBlockRoot = _beaconStateAccessor.GetBlockRootAtSlot(headState, startSlot);
}
Checkpoint target = new Checkpoint(currentEpoch, epochBoundaryBlockRoot);
AttestationData attestationData = new AttestationData(slot, index, beaconBlockRoot, source, target);
var aggregationBits = new BitArray(committeeSize);
aggregationBits.Set(committeeMemberIndexOfValidator.Value, true);
var attestation = new Attestation(aggregationBits, attestationData, BlsSignature.Zero);
return(attestation);
}
