nimbus-eth2/beacon_chain/time.nim

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import
chronos,
spec/[datatypes]
from times import Time, getTime, fromUnix, `<`, `-`
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/v0.6.0/specs/core/0_fork-choice.md#beacon-chain-processing
##
# TODO replace time in chronos with a proper unit type, then this code can
# follow:
# https://github.com/status-im/nim-chronos/issues/15
# TODO consider NTP and network-adjusted timestamps as outlined here:
# https://ethresear.ch/t/network-adjusted-timestamps/4187
genesis: Time
BeaconTime* = distinct int64 ## Seconds from beacon genesis time
proc init*(T: type BeaconClock, state: BeaconState): T =
## Initialize time from a beacon state. The genesis time of a beacon state is
## constant throughout its lifetime, so the state from any slot will do,
## including the genesis state.
let
unixGenesis = fromUnix(state.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)
func toSlot*(t: BeaconTime): Slot =
Slot(uint64(t) div SECONDS_PER_SLOT)
func toBeaconTime*(c: BeaconClock, t: Time): BeaconTime =
doAssert t > c.genesis,
"Cannot represent time before genesis, fix BeaconClock"
BeaconTime(times.seconds(t - c.genesis).uint64)
func toSlot*(c: BeaconClock, t: Time): Slot =
c.toBeaconTime(t).toSlot()
func toBeaconTime*(s: Slot, offset = chronos.seconds(0)): BeaconTime =
BeaconTime(int64(uint64(s) * SECONDS_PER_SLOT) + seconds(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 int64(t) > int64(now):
(true, seconds(int64(t) - int64(now)))
else:
(false, seconds(int64(now) - int64(t)))
proc fromNow*(c: BeaconClock, slot: Slot): tuple[inFuture: bool, offset: Duration] =
c.fromNow(slot.toBeaconTime())
proc 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) =
addTimer(Moment.now() + fromNow, cb, udata)
proc shortLog*(d: Duration): string =
let dd = int64(d.milliseconds())
if dd < 1000:
$dd & "ms"
elif dd < 60 * 1000:
$(dd div 1000) & "s"
elif dd < 60 * 60 * 1000:
let secs = dd div 1000
var tmp = $(secs div 60) & "m"
if (let frac = secs mod 60; frac > 0):
tmp &= $frac & "s"
tmp
else:
let mins = dd div 60 * 1000
var tmp = $(mins div 60) & "h"
if (let frac = mins mod 60; frac > 0):
tmp &= $frac & "m"
tmp