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cache.go
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cache.go
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package main
import (
"fmt"
"time"
"github.com/bbailey1024/geohash"
)
const (
LATMAX = 90.0
LATMIN = -90.0
LNGMAX = 180.0
LNGMIN = -180.0
)
type Cache struct {
Timer int
Geo *Geocache
Search *Searchcache
Quit chan struct{}
Done chan struct{}
}
type Searchcache struct {
List []SearchFields
}
type SearchFields struct {
MMSI int `json:"mmsi"`
Name string `json:"name"`
LatLon []float64 `json:"latlon"`
}
type Geocache struct {
List []GeoMMSI
LastUpdate int64
}
type GeoMMSI struct {
MMSI int
Geohash uint64
}
func NewCache(t int) *Cache {
return &Cache{
Timer: t,
Geo: NewGeocache(),
Search: NewSearchcache(),
Quit: make(chan struct{}),
Done: make(chan struct{}),
}
}
func NewSearchcache() *Searchcache {
return &Searchcache{
List: []SearchFields{},
}
}
func NewGeocache() *Geocache {
return &Geocache{
List: []GeoMMSI{},
LastUpdate: 0,
}
}
func (c *Cache) Run(s *Ships) {
// Generate every second for the first five seconds.
for i := 0; i < 5; i++ {
c.Geo.Generate(s)
c.Search.Generate(s)
time.Sleep(time.Second * 1)
}
ticker := time.NewTicker(time.Duration(c.Timer) * time.Second)
for {
select {
case <-ticker.C:
c.Geo.Generate(s)
c.Search.Generate(s)
case <-c.Quit:
c.Done <- struct{}{}
return
}
}
}
func (sc *Searchcache) Generate(s *Ships) {
s.StateLock.RLock()
defer s.StateLock.RUnlock()
searchList := make([]SearchFields, 0, len(s.State))
for mmsi, ship := range s.State {
searchList = append(searchList, SearchFields{
MMSI: mmsi,
Name: ship.Name,
LatLon: ship.LatLon,
})
}
sc.List = searchList
}
func (gc *Geocache) Generate(s *Ships) {
s.StateLock.RLock()
defer s.StateLock.RUnlock()
geoSortedMMSI := make([]GeoMMSI, 0, len(s.State))
for mmsi, state := range s.State {
geoSortedMMSI = append(geoSortedMMSI, GeoMMSI{MMSI: mmsi, Geohash: state.Geohash})
}
gc.LastUpdate = time.Now().Unix()
quickSortGeohash(geoSortedMMSI, 0, len(geoSortedMMSI))
gc.List = geoSortedMMSI
}
func (gc *Geocache) BinarySearch(bbox [2][2]float64) (int, int, error) {
if len(gc.List) == 0 {
return 0, 0, fmt.Errorf("geocache list is empty, binary search cannot be performed")
}
bboxHashSW := geohash.EncodeInt(bbox[0][0], bbox[0][1])
bboxHashNE := geohash.EncodeInt(bbox[1][0], bbox[1][1])
begin := gc.binarySearchSW(bboxHashSW)
end := gc.binarySearchNE(bboxHashNE)
return begin, end, nil
}
func (gc *Geocache) binarySearchSW(bboxSW uint64) int {
mid := len(gc.List) / 2
top := len(gc.List)
begin := 0
for {
if gc.List[mid].Geohash >= bboxSW {
if mid-1 < 0 || gc.List[mid-1].Geohash < bboxSW {
begin = mid
break
}
top = mid
mid = mid / 2
} else {
if mid+1 >= len(gc.List) || gc.List[mid+1].Geohash > bboxSW {
begin = mid + 1 // Does this break things? Should it just be mid?
break
}
mid = mid + ((top - mid) / 2)
}
}
return begin
}
func (gc *Geocache) binarySearchNE(bboxNE uint64) int {
mid := len(gc.List) / 2
top := len(gc.List)
end := 0
for {
if gc.List[mid].Geohash < bboxNE {
if mid+1 >= len(gc.List) || gc.List[mid+1].Geohash > bboxNE {
end = mid
break
}
mid = mid + ((top - mid) / 2)
} else {
if mid-1 < 0 || gc.List[mid-1].Geohash < bboxNE {
end = mid - 1
break
}
top = mid
mid = mid / 2
}
}
return end
}
func quickSortGeohash(list []GeoMMSI, begin int, end int) {
// End sorting partition branch when finished.
if begin-end == 0 {
return
}
pivot := end - 1
swap := begin
for i := begin; i < pivot; i++ {
if list[i].Geohash < list[pivot].Geohash {
list[i], list[swap] = list[swap], list[i]
swap++
}
}
list[pivot], list[swap] = list[swap], list[pivot]
quickSortGeohash(list, begin, swap)
quickSortGeohash(list, swap+1, end)
}