150 lines
2.8 KiB
Go
150 lines
2.8 KiB
Go
package ogr
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/*
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#cgo LDFLAGS: -lgdal
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#include "ogr_api.h"
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#include "cpl_error.h"
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#include "cpl_conv.h"
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*/
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import "C"
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import (
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"fmt"
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"imposm3/geom/geos"
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"strings"
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"unsafe"
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)
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func init() {
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C.OGRRegisterAll()
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}
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type DataSource struct {
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v C.OGRDataSourceH
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}
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type Layer struct {
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v C.OGRLayerH
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}
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type OgrError struct {
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message string
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}
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func (e *OgrError) Error() string {
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return e.message
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}
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func lastOgrError(fallback string) error {
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msg := C.CPLGetLastErrorMsg()
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if msg == nil {
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return &OgrError{fallback}
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}
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str := C.GoString(msg)
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if str == "" {
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return &OgrError{fallback}
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}
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return &OgrError{str}
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}
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func Open(name string) (*DataSource, error) {
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namec := C.CString(name)
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defer C.free(unsafe.Pointer(namec))
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ds := C.OGROpen(namec, 0, nil)
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if ds == nil {
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return nil, lastOgrError("failed to open")
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}
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return &DataSource{ds}, nil
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}
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func (ds *DataSource) Layer() (*Layer, error) {
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layer := C.OGR_DS_GetLayer(ds.v, 0)
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if layer == nil {
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return nil, lastOgrError("failed to get layer 0")
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}
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return &Layer{layer}, nil
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}
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func (ds *DataSource) Query(query string) (*Layer, error) {
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// create select query if it is only a where statement
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if !strings.HasPrefix(strings.ToLower(query), "select") {
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layer, err := ds.Layer()
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if err != nil {
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return nil, err
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}
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layerDef := C.OGR_L_GetLayerDefn(layer.v)
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name := C.OGR_FD_GetName(layerDef)
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query = fmt.Sprintf("SELECT * FROM %s WHERE %s", C.GoString(name), query)
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}
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queryc := C.CString(query)
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defer C.free(unsafe.Pointer(queryc))
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layer := C.OGR_DS_ExecuteSQL(ds.v, queryc, nil, nil)
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if layer == nil {
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return nil, lastOgrError("unable to execute query '" + query + "'")
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}
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return &Layer{layer}, nil
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}
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func (layer *Layer) Wkts() chan string {
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wkts := make(chan string)
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go func() {
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defer close(wkts)
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C.OGR_L_ResetReading(layer.v)
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for {
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feature := C.OGR_L_GetNextFeature(layer.v)
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if feature == nil {
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break
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}
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geom := C.OGR_F_GetGeometryRef(feature)
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var res *C.char
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C.OGR_G_ExportToWkt(geom, &res)
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wkts <- C.GoString(res)
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C.CPLFree(unsafe.Pointer(res))
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C.OGR_F_Destroy(feature)
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}
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}()
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return wkts
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}
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func (layer *Layer) Wkbs() chan []byte {
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wkbs := make(chan []byte)
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go func() {
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defer close(wkbs)
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C.OGR_L_ResetReading(layer.v)
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for {
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feature := C.OGR_L_GetNextFeature(layer.v)
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if feature == nil {
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break
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}
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geom := C.OGR_F_GetGeometryRef(feature)
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size := C.OGR_G_WkbSize(geom)
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buf := make([]byte, size)
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C.OGR_G_ExportToWkb(geom, C.wkbNDR, (*C.uchar)(&buf[0]))
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wkbs <- buf
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C.OGR_F_Destroy(feature)
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}
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}()
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return wkbs
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}
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func (layer *Layer) Geoms() chan *geos.Geom {
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geoms := make(chan *geos.Geom)
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go func() {
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defer close(geoms)
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g := geos.NewGeos()
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defer g.Finish()
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wkbs := layer.Wkbs()
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for wkb := range wkbs {
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geom := g.FromWkb(wkb)
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geoms <- geom
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}
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}()
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return geoms
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}
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