mirror of
https://gitlab.com/pulsechaincom/prysm-pulse.git
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99 lines
3.8 KiB
Go
99 lines
3.8 KiB
Go
package helpers
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import (
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"github.com/pkg/errors"
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"github.com/prysmaticlabs/prysm/beacon-chain/cache"
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pb "github.com/prysmaticlabs/prysm/proto/beacon/p2p/v1"
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"github.com/prysmaticlabs/prysm/shared/bytesutil"
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"github.com/prysmaticlabs/prysm/shared/hashutil"
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"github.com/prysmaticlabs/prysm/shared/params"
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)
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var currentEpochSeed = cache.NewSeedCache()
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// ErrInvalidStateLatestActiveIndexRoots is returned when the state active
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// index root count does not match the expected EpochsPerHistoricalVector.
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var ErrInvalidStateLatestActiveIndexRoots = errors.New("state does not have correct number of latest active index roots")
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// Seed returns the randao seed used for shuffling of a given epoch.
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//
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// Spec pseudocode definition:
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// def get_seed(state: BeaconState, epoch: Epoch) -> Hash:
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// """
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// Return the seed at ``epoch``.
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// """
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// mix = get_randao_mix(state, Epoch(epoch + EPOCHS_PER_HISTORICAL_VECTOR - MIN_SEED_LOOKAHEAD - 1)) #Avoid underflow
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// active_index_root = state.active_index_roots[epoch % EPOCHS_PER_HISTORICAL_VECTOR]
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// return hash(mix + active_index_root + int_to_bytes(epoch, length=32))
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func Seed(state *pb.BeaconState, epoch uint64) ([32]byte, error) {
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seed, err := currentEpochSeed.SeedInEpoch(epoch)
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if err != nil {
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return [32]byte{}, errors.Wrap(err, "could not retrieve total balance from cache")
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}
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if seed != nil {
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return bytesutil.ToBytes32(seed), nil
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}
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// See https://github.com/ethereum/eth2.0-specs/pull/1296 for
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// rationale on why offset has to look down by 1.
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lookAheadEpoch := epoch + params.BeaconConfig().EpochsPerHistoricalVector -
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params.BeaconConfig().MinSeedLookahead - 1
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// Check that the state has the correct latest active index roots or
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// randao mix may panic for index out of bounds.
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if uint64(len(state.ActiveIndexRoots)) != params.BeaconConfig().EpochsPerHistoricalVector {
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return [32]byte{}, ErrInvalidStateLatestActiveIndexRoots
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}
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randaoMix := RandaoMix(state, lookAheadEpoch)
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indexRoot := ActiveIndexRoot(state, epoch)
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th := append(randaoMix, indexRoot...)
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th = append(th, bytesutil.Bytes32(epoch)...)
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seed32 := hashutil.Hash(th)
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if err := currentEpochSeed.AddSeed(&cache.SeedByEpoch{
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Epoch: epoch,
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Seed: seed32[:],
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}); err != nil {
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return [32]byte{}, errors.Wrap(err, "could not save active balance for cache")
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}
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return seed32, nil
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}
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// ActiveIndexRoot returns the index root of a given epoch.
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//
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// Spec pseudocode definition:
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// def get_active_index_root(state: BeaconState,
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// epoch: Epoch) -> Bytes32:
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// """
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// Return the index root at a recent ``epoch``.
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// ``epoch`` expected to be between
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// (current_epoch - LATEST_ACTIVE_INDEX_ROOTS_LENGTH + ACTIVATION_EXIT_DELAY, current_epoch + ACTIVATION_EXIT_DELAY].
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// """
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// return state.latest_active_index_roots[epoch % LATEST_ACTIVE_INDEX_ROOTS_LENGTH]
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func ActiveIndexRoot(state *pb.BeaconState, epoch uint64) []byte {
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newRootLength := len(state.ActiveIndexRoots[epoch%params.BeaconConfig().EpochsPerHistoricalVector])
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newRoot := make([]byte, newRootLength)
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copy(newRoot, state.ActiveIndexRoots[epoch%params.BeaconConfig().EpochsPerHistoricalVector])
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return newRoot
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}
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// RandaoMix returns the randao mix (xor'ed seed)
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// of a given slot. It is used to shuffle validators.
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//
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// Spec pseudocode definition:
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// def get_randao_mix(state: BeaconState, epoch: Epoch) -> Hash:
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// """
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// Return the randao mix at a recent ``epoch``.
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// """
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// return state.randao_mixes[epoch % EPOCHS_PER_HISTORICAL_VECTOR]
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func RandaoMix(state *pb.BeaconState, epoch uint64) []byte {
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newMixLength := len(state.RandaoMixes[epoch%params.BeaconConfig().EpochsPerHistoricalVector])
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newMix := make([]byte, newMixLength)
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copy(newMix, state.RandaoMixes[epoch%params.BeaconConfig().EpochsPerHistoricalVector])
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return newMix
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}
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