path: root/common/event.go

// Copyright 2018 The dexon-consensus-core Authors
// This file is part of the dexon-consensus-core library.
//
// The dexon-consensus-core library is free software: you can redistribute it
// and/or modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// The dexon-consensus-core library is distributed in the hope that it will be
// useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser
// General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the dexon-consensus-core library. If not, see
// <http://www.gnu.org/licenses/>.

package common

import (
    "container/heap"
    "sync"
    "time"
)

type timeEventFn func(time.Time)

type timeEvent struct {
    t  time.Time
    fn timeEventFn
}

// timeEvents implements a Min-Heap structure.
type timeEvents []timeEvent

func (h timeEvents) Len() int           { return len(h) }
func (h timeEvents) Less(i, j int) bool { return h[i].t.Before(h[j].t) }
func (h timeEvents) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }
func (h *timeEvents) Push(x interface{}) {
    *h = append(*h, x.(timeEvent))
}
func (h *timeEvents) Pop() interface{} {
    old := *h
    n := len(old)
    x := old[n-1]
    *h = old[0 : n-1]
    return x
}

// Event implements the Observer pattern.
type Event struct {
    timeEvents     timeEvents
    timeEventsLock sync.Mutex
}

// NewEvent creates a new event instance.
func NewEvent() *Event {
    te := timeEvents{}
    heap.Init(&te)
    return &Event{
        timeEvents: te,
    }
}

// RegisterTime to get notified on and after specific time.
func (e *Event) RegisterTime(t time.Time, fn timeEventFn) {
    e.timeEventsLock.Lock()
    defer e.timeEventsLock.Unlock()
    heap.Push(&e.timeEvents, timeEvent{
        t:  t,
        fn: fn,
    })
}

// NotifyTime and trigger function callback.
func (e *Event) NotifyTime(t time.Time) {
    fns := func() (fns []timeEventFn) {
        e.timeEventsLock.Lock()
        defer e.timeEventsLock.Unlock()
        if len(e.timeEvents) == 0 {
            return
        }
        for !t.Before(e.timeEvents[0].t) {
            te := heap.Pop(&e.timeEvents).(timeEvent)
            fns = append(fns, te.fn)
            if len(e.timeEvents) == 0 {
                return
            }
        }
        return
    }()
    for _, fn := range fns {
        fn(t)
    }
}