type Write interface {
    Org() uint64
    Len() uint64
    Write(b io.WriterAt) error
    String() string
}

type Patch []Write

func Conflict(p1, p2 Patch) (c1, c2 []Write) {
    i, j := 0, 0
    w1, w2 := p1[0], p2[0]
    org1, org2 := w1.Org(), w2.Org()
    end1, end2 := org1 + w1.Len(), org2 + w2.Len()
    for {
        if org1 >= org2 && org1 < end2 || org2 >= org1 && org2 < end1 {
            c1 = append(c1, w1)
            c2 = append(c2, w2)
        }
        if end1 < end2 {
            i++
            if i >= len(p1) {
                return
            }
            w1 = p1[i]
            org1 = w1.Org()
            end1 = org1 + w1.Len()
        } else if end1 > end2 {
            j++
            if j >= len(p2) {
                return
            }
            w2 = p2[j]
            org2 = w2.Org()
            end2 = org2 + w2.Len()
        } else {
            i++
            j++
            if i >= len(p1) || j >= len(p2) {
                return
            }
            w1, w2 = p1[i], p2[j]
            org1, org2 = w1.Org(), w2.Org()
            end1, end2 = org1 + w1.Len(), org2 + w2.Len()
        }
    }
    return
}