78 lines
1.8 KiB
Go
78 lines
1.8 KiB
Go
package geos
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/*
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#cgo LDFLAGS: -lgeos_c
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#include "geos_c.h"
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#include <stdlib.h>
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#include <stdint.h>
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extern void IndexQueryCallback(void *, void *);
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extern void goIndexSendQueryResult(size_t, void *);
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extern uint32_t *IndexQuery(GEOSContextHandle_t, GEOSSTRtree *, const GEOSGeometry *, uint32_t *);
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extern void IndexAdd(GEOSContextHandle_t, GEOSSTRtree *, const GEOSGeometry *, size_t);
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*/
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import "C"
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import (
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"sync"
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"unsafe"
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)
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// IndexGeom is a struct for indexed geometries used by Index
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// and returned by IndexQuery.
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type IndexGeom struct {
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Geom *Geom
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}
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type Index struct {
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v *C.GEOSSTRtree
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mu *sync.Mutex
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geoms []IndexGeom
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}
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func (this *Geos) CreateIndex() *Index {
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tree := C.GEOSSTRtree_create_r(this.v, 10)
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if tree == nil {
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panic("unable to create tree")
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}
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return &Index{tree, &sync.Mutex{}, []IndexGeom{}}
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}
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// IndexQuery adds a geom to the index with the id.
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func (this *Geos) IndexAdd(index *Index, geom *Geom) {
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index.mu.Lock()
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defer index.mu.Unlock()
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id := len(index.geoms)
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C.IndexAdd(this.v, index.v, geom.v, C.size_t(id))
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index.geoms = append(index.geoms, IndexGeom{geom})
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}
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// IndexQueryGeoms queries the index for intersections with geom.
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func (this *Geos) IndexQueryGeoms(index *Index, geom *Geom) []IndexGeom {
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hits := this.IndexQuery(index, geom)
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var geoms []IndexGeom
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for _, idx := range hits {
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geoms = append(geoms, index.geoms[idx])
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}
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return geoms
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}
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// IndexQuery queries the index for intersections with geom.
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func (this *Geos) IndexQuery(index *Index, geom *Geom) []int {
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index.mu.Lock()
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defer index.mu.Unlock()
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var num C.uint32_t
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r := C.IndexQuery(this.v, index.v, geom.v, &num)
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if r == nil {
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return nil
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}
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hits := (*[2 << 16]C.uint32_t)(unsafe.Pointer(r))[:num]
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defer C.free(unsafe.Pointer(r))
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indices := make([]int, len(hits))
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for i := range hits {
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indices[i] = int(hits[i])
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}
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return indices
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}
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