nimbus-eth2/beacon_chain/beacon_clock.nim

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# beacon_chain
# Copyright (c) 2018-2021 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.
{.push raises: [Defect].}
import
chronos, chronicles,
./spec/datatypes
from times import Time, getTime, fromUnix, `<`, `-`, inNanoseconds
export chronos.Duration, Moment, now
type
BeaconClock* = object
## The beacon clock represents time as it passes on a beacon chain. Beacon
## time is locked to unix time, starting at a particular offset set during
## beacon chain instantiation.
##
## Time on the beacon chain determines what actions should be taken and
## which blocks are valid - in particular, blocks are not valid if they
## come from the future as seen from the local clock.
##
## https://github.com/ethereum/eth2.0-specs/blob/v1.0.1/specs/phase0/fork-choice.md#fork-choice
##
# TODO consider NTP and network-adjusted timestamps as outlined here:
# https://ethresear.ch/t/network-adjusted-timestamps/4187
genesis: Time
BeaconTime* = distinct Duration ## Nanoseconds from beacon genesis time
GetWallTimeFn* = proc(): BeaconTime {.gcsafe, raises: [Defect].}
proc init*(T: type BeaconClock, genesis_time: uint64): T =
# ~290 billion years into the future
doAssert genesis_time <= high(int64).uint64
let
unixGenesis = fromUnix(genesis_time.int64)
# GENESIS_SLOT offsets slot time, but to simplify calculations, we apply that
# offset to genesis instead of applying it at every time conversion
unixGenesisOffset = times.seconds(int(GENESIS_SLOT * SECONDS_PER_SLOT))
T(genesis: unixGenesis - unixGenesisOffset)
template `<`*(a, b: BeaconTime): bool =
Duration(a) < Duration(b)
template `<=`*(a, b: BeaconTime): bool =
Duration(a) <= Duration(b)
template `+`*(t: BeaconTime, offset: Duration): BeaconTime =
BeaconTime(Duration(t) + offset)
template `-`*(t: BeaconTime, offset: Duration): BeaconTime =
BeaconTime(nanoseconds(nanoseconds(Duration(t)) - nanoseconds(offset)))
template `-`*(a, b: BeaconTime): Duration =
nanoseconds(nanoseconds(Duration(a)) - nanoseconds(Duration(b)))
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func toSlot*(t: BeaconTime): tuple[afterGenesis: bool, slot: Slot] =
let ti = seconds(Duration(t))
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if ti >= 0:
(true, Slot(uint64(ti) div SECONDS_PER_SLOT))
else:
(false, Slot(uint64(-ti) div SECONDS_PER_SLOT))
func slotOrZero*(time: BeaconTime): Slot =
let exSlot = time.toSlot
if exSlot.afterGenesis: exSlot.slot
else: Slot(0)
func toBeaconTime*(c: BeaconClock, t: Time): BeaconTime =
BeaconTime(nanoseconds(inNanoseconds(t - c.genesis)))
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func toSlot*(c: BeaconClock, t: Time): tuple[afterGenesis: bool, slot: Slot] =
c.toBeaconTime(t).toSlot()
func toBeaconTime*(s: Slot, offset = Duration()): BeaconTime =
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# BeaconTime/Duration stores nanoseconds, internally
const maxSlot = (not 0'u64 div 2 div SECONDS_PER_SLOT div 1_000_000_000).Slot
var slot = s
if slot > maxSlot:
slot = maxSlot
BeaconTime(seconds(int64(uint64(slot) * SECONDS_PER_SLOT)) + offset)
proc now*(c: BeaconClock): BeaconTime =
## Current time, in slots - this may end up being less than GENESIS_SLOT(!)
toBeaconTime(c, getTime())
proc fromNow*(c: BeaconClock, t: BeaconTime): tuple[inFuture: bool, offset: Duration] =
let now = c.now()
if t > now:
(true, t - now)
else:
(false, now - t)
proc fromNow*(c: BeaconClock, slot: Slot): tuple[inFuture: bool, offset: Duration] =
c.fromNow(slot.toBeaconTime())
func saturate*(d: tuple[inFuture: bool, offset: Duration]): Duration =
if d.inFuture: d.offset else: seconds(0)
proc addTimer*(fromNow: Duration, cb: CallbackFunc, udata: pointer = nil) =
discard setTimer(Moment.now() + fromNow, cb, udata)
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func shortLog*(d: Duration): string =
$d
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func toFloatSeconds*(d: Duration): float =
float(milliseconds(d)) / 1000.0
func `$`*(v: BeaconTime): string = $(Duration v)
func shortLog*(v: BeaconTime): string = $(Duration v)
chronicles.formatIt Duration: $it
chronicles.formatIt BeaconTime: $(Duration it)