source: code/trunk/rate.go@ 823

package suika

import (
        "math/rand"
        "time"
)

// backoffer implements a simple exponential backoff.
type backoffer struct {
        min, max, jitter time.Duration
        n                int64
}

func newBackoffer(min, max, jitter time.Duration) *backoffer {
        return &backoffer{min: min, max: max, jitter: jitter}
}

func (b *backoffer) Reset() {
        b.n = 0
}

func (b *backoffer) Next() time.Duration {
        if b.n == 0 {
                b.n = 1
                return 0
        }

        d := time.Duration(b.n) * b.min
        if d > b.max {
                d = b.max
        } else {
                b.n *= 2
        }

        if b.jitter != 0 {
                d += time.Duration(rand.Int63n(int64(b.jitter)))
        }

        return d
}