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slot_epoch.go
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slot_epoch.go
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package helpers
import (
"fmt"
"time"
stateTrie "github.com/prysmaticlabs/prysm/beacon-chain/state"
"github.com/prysmaticlabs/prysm/shared/params"
"github.com/prysmaticlabs/prysm/shared/roughtime"
)
// SlotToEpoch returns the epoch number of the input slot.
//
// Spec pseudocode definition:
// def compute_epoch_of_slot(slot: Slot) -> Epoch:
// """
// Return the epoch number of ``slot``.
// """
// return Epoch(slot // SLOTS_PER_EPOCH)
func SlotToEpoch(slot uint64) uint64 {
return slot / params.BeaconConfig().SlotsPerEpoch
}
// CurrentEpoch returns the current epoch number calculated from
// the slot number stored in beacon state.
//
// Spec pseudocode definition:
// def get_current_epoch(state: BeaconState) -> Epoch:
// """
// Return the current epoch.
// """
// return compute_epoch_of_slot(state.slot)
func CurrentEpoch(state *stateTrie.BeaconState) uint64 {
return SlotToEpoch(state.Slot())
}
// PrevEpoch returns the previous epoch number calculated from
// the slot number stored in beacon state. It alswo checks for
// underflow condition.
//
// Spec pseudocode definition:
// def get_previous_epoch(state: BeaconState) -> Epoch:
// """`
// Return the previous epoch (unless the current epoch is ``GENESIS_EPOCH``).
// """
// current_epoch = get_current_epoch(state)
// return GENESIS_EPOCH if current_epoch == GENESIS_EPOCH else Epoch(current_epoch - 1)
func PrevEpoch(state *stateTrie.BeaconState) uint64 {
currentEpoch := CurrentEpoch(state)
if currentEpoch == 0 {
return 0
}
return currentEpoch - 1
}
// NextEpoch returns the next epoch number calculated form
// the slot number stored in beacon state.
func NextEpoch(state *stateTrie.BeaconState) uint64 {
return SlotToEpoch(state.Slot()) + 1
}
// StartSlot returns the first slot number of the
// current epoch.
//
// Spec pseudocode definition:
// def compute_start_slot_of_epoch(epoch: Epoch) -> Slot:
// """
// Return the start slot of ``epoch``.
// """
// return Slot(epoch * SLOTS_PER_EPOCH
func StartSlot(epoch uint64) uint64 {
return epoch * params.BeaconConfig().SlotsPerEpoch
}
// IsEpochStart returns true if the given slot number is an epoch starting slot
// number.
func IsEpochStart(slot uint64) bool {
return slot%params.BeaconConfig().SlotsPerEpoch == 0
}
// IsEpochEnd returns true if the given slot number is an epoch ending slot
// number.
func IsEpochEnd(slot uint64) bool {
return IsEpochStart(slot + 1)
}
// SlotsSinceEpochStarts returns number of slots since the start of the epoch.
func SlotsSinceEpochStarts(slot uint64) uint64 {
return slot - StartSlot(SlotToEpoch(slot))
}
// Allow for slots "from the future" within a certain tolerance.
const timeShiftTolerance = 10 // ms
// VerifySlotTime validates the input slot is not from the future.
func VerifySlotTime(genesisTime uint64, slot uint64) error {
slotTime := genesisTime + slot*params.BeaconConfig().SecondsPerSlot
currentTime := uint64(roughtime.Now().Unix())
if slotTime > currentTime+timeShiftTolerance {
return fmt.Errorf("could not process slot from the future, slot time %d > current time %d", slotTime, currentTime)
}
return nil
}
// SlotsSince computes the number of time slots that have occurred since the given timestamp.
func SlotsSince(time time.Time) uint64 {
return uint64(roughtime.Since(time).Seconds()) / params.BeaconConfig().SecondsPerSlot
}
// RoundUpToNearestEpoch rounds up the provided slot value to the nearest epoch.
func RoundUpToNearestEpoch(slot uint64) uint64 {
if slot%params.BeaconConfig().SlotsPerEpoch != 0 {
slot -= slot % params.BeaconConfig().SlotsPerEpoch
slot += params.BeaconConfig().SlotsPerEpoch
}
return slot
}