path: root/core/utils.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 core

import (
    "errors"
    "fmt"
    "os"
    "sort"
    "time"

    "github.com/dexon-foundation/dexon-consensus-core/common"
)

var (
    debug = false
    // ErrEmptyTimestamps would be reported if Block.timestamps is empty.
    ErrEmptyTimestamps = errors.New("timestamp vector should not be empty")
)

func init() {
    if os.Getenv("DEBUG") != "" {
        debug = true
    }
}

// Debugf is like fmt.Printf, but only output when we are in debug mode.
func Debugf(format string, args ...interface{}) {
    if debug {
        fmt.Printf(format, args...)
    }
}

// Debugln is like fmt.Println, but only output when we are in debug mode.
func Debugln(args ...interface{}) {
    if debug {
        fmt.Println(args)
    }
}

func interpoTime(t1 time.Time, t2 time.Time, sep int) []time.Time {
    if sep == 0 {
        return []time.Time{}
    }
    if t1.After(t2) {
        return interpoTime(t2, t1, sep)
    }
    timestamps := make([]time.Time, sep)
    duration := t2.Sub(t1)
    period := time.Duration(
        (duration.Nanoseconds() / int64(sep+1))) * time.Nanosecond
    prevTime := t1
    for idx := range timestamps {
        prevTime = prevTime.Add(period)
        timestamps[idx] = prevTime
    }
    return timestamps
}

func getMedianTime(timestamps []time.Time) (t time.Time, err error) {
    if len(timestamps) == 0 {
        err = ErrEmptyTimestamps
        return
    }
    tscopy := make([]time.Time, 0, len(timestamps))
    for _, ts := range timestamps {
        tscopy = append(tscopy, ts)
    }
    sort.Sort(common.ByTime(tscopy))
    if len(tscopy)%2 == 0 {
        t1 := tscopy[len(tscopy)/2-1]
        t2 := tscopy[len(tscopy)/2]
        t = interpoTime(t1, t2, 1)[0]
    } else {
        t = tscopy[len(tscopy)/2]
    }
    return
}

func removeFromSortedUint32Slice(xs []uint32, x uint32) []uint32 {
    indexToRemove := sort.Search(len(xs), func(idx int) bool {
        return xs[idx] >= x
    })
    if indexToRemove == len(xs) || xs[indexToRemove] != x {
        // This value is not found.
        return xs
    }
    return append(xs[:indexToRemove], xs[indexToRemove+1:]...)
}