star/mget/range.go

package mget

import "sort"

type Range struct {
	Min uint64 `json:"min"`
	Max uint64 `json:"max"`
}
type SortRange []Range

func (s SortRange) Len() int           { return len(s) }
func (s SortRange) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }
func (s SortRange) Less(i, j int) bool { return s[i].Min < s[j].Min }

func uniformRange(rg []Range) ([]Range, error) {
	newRg := make([]Range, 0, len(rg))
	sort.Sort(SortRange(rg))
	var last *Range = nil
	for _, v := range rg {
		if last != nil && v.Min <= last.Max+1 {
			if last.Max <= v.Max {
				last.Max = v.Max
			}
			continue
		}
		newRg = append(newRg, v)
		last = &newRg[len(newRg)-1]
	}
	return newRg, nil
}

func singleSubRange(origin []Range, v Range) []Range {
	newRg := make([]Range, 0)
	sort.Sort(SortRange(origin))
	for i := 0; i < len(origin); i++ {
		ori := origin[i]
		res := make([]Range, 0)
		shouldAdd := true
		for j := 0; j < 1; j++ {
			if v.Min <= ori.Min && v.Max >= ori.Max {
				shouldAdd = false
				break
			}
			if v.Max < ori.Min {
				continue
			}
			if v.Min > ori.Max {
				break
			}
			ur1 := Range{
				Min: ori.Min,
				Max: v.Min - 1,
			}
			if v.Min == 0 {
				ur1.Min = 1
				ur1.Max = 0
			}
			ur2 := Range{
				Min: v.Max + 1,
				Max: ori.Max,
			}
			if ur1.Max >= ur1.Min {
				res = append(res, ur1)
			}
			if ur2.Max >= ur2.Min {
				res = append(res, ur2)
			}
		}
		if len(res) == 0 && shouldAdd {
			res = append(res, ori)
		}
		newRg = append(newRg, res...)
	}
	return newRg
}

func subRange(origin, rg []Range) []Range {
	sort.Sort(SortRange(rg))
	sort.Sort(SortRange(origin))
	for _, v := range rg {
		origin = singleSubRange(origin, v)
	}
	return origin
}