Fantom-foundation/go-lachesis

package temporary

import (
    "fmt"
)

type ringbuf struct {
    Min    uint64
    offset int
    count  int
    seq    [5]*pair // len is a max count
}

func (r *ringbuf) Get(num uint64) *pair {
    i := int(num - r.Min)
    if num < r.Min || i >= r.count {
        return nil
    }

    i = (i + r.offset) % len(r.seq)
    return r.seq[i]
}

func (r *ringbuf) Set(num uint64, val *pair) {
    if r.count >= len(r.seq) {
        panic("no space")
    }

    if r.count == 0 {
        r.Min = num
    }

    i := int(num - r.Min)
    if i != r.count {
        panic(fmt.Sprintf("sequence is broken (set %d to %+v)", num, r))
    }

    i = (i + r.offset) % len(r.seq)
    r.seq[i] = val
    r.count++
}

func (r *ringbuf) Del(num uint64) {
    if num != r.Min {
        panic(fmt.Sprintf("sequence is broken (del %d from %+v)", num, r))
    }

    r.Min++
    r.offset = (r.offset + 1) % len(r.seq)
    r.count--
}