mirror of https://github.com/tidwall/tile38.git
125 lines
3.2 KiB
Go
125 lines
3.2 KiB
Go
package geojson
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import (
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"encoding/binary"
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"math"
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"strconv"
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"unsafe"
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"github.com/tidwall/gjson"
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"github.com/tidwall/tile38/geojson/geo"
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"github.com/tidwall/tile38/geojson/poly"
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)
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const sizeofPosition = 24 // (X,Y,Z) * 8
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// Position is a simple point
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type Position poly.Point
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func pointPositions(positions []Position) []poly.Point {
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return *(*[]poly.Point)(unsafe.Pointer(&positions))
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}
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func polyPositions(positions []Position) poly.Polygon {
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return *(*poly.Polygon)(unsafe.Pointer(&positions))
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}
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func polyMultiPositions(positions [][]Position) []poly.Polygon {
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return *(*[]poly.Polygon)(unsafe.Pointer(&positions))
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}
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func polyExteriorHoles(positions [][]Position) (exterior poly.Polygon, holes []poly.Polygon) {
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switch len(positions) {
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case 0:
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case 1:
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exterior = polyPositions(positions[0])
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default:
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exterior = polyPositions(positions[0])
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holes = polyMultiPositions(positions[1:])
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}
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return
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}
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func appendPositionJSON(json []byte, p Position, isCordZ bool) []byte {
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json = strconv.AppendFloat(json, p.X, 'f', -1, 64)
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json = append(json, ',')
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json = strconv.AppendFloat(json, p.Y, 'f', -1, 64)
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if isCordZ {
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json = append(json, ',')
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json = strconv.AppendFloat(json, p.Z, 'f', -1, 64)
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}
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return json
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}
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const earthRadius = 6371e3
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func toRadians(deg float64) float64 { return deg * math.Pi / 180 }
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func toDegrees(rad float64) float64 { return rad * 180 / math.Pi }
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// DistanceTo calculates the distance to a position
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func (p Position) DistanceTo(position Position) float64 {
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return geo.DistanceTo(p.Y, p.X, position.Y, position.X)
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}
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// Destination calculates a new position based on the distance and bearing.
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func (p Position) Destination(meters, bearingDegrees float64) Position {
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lat, lon := geo.DestinationPoint(p.Y, p.X, meters, bearingDegrees)
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return Position{X: lon, Y: lat, Z: 0}
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}
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func fillPosition(coords gjson.Result) (Position, error) {
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var p Position
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v := coords.Array()
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switch len(v) {
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case 0:
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return p, errInvalidNumberOfPositionValues
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case 1:
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if v[0].Type != gjson.Number {
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return p, errInvalidPositionValue
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}
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return p, errInvalidNumberOfPositionValues
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}
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for i := 0; i < len(v); i++ {
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if v[i].Type != gjson.Number {
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return p, errInvalidPositionValue
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}
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}
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p.X = v[0].Float()
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p.Y = v[1].Float()
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if len(v) > 2 {
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p.Z = v[2].Float()
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} else {
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p.Z = nilz
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}
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return p, nil
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}
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func fillPositionBytes(b []byte, isCordZ bool) (Position, []byte, error) {
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var p Position
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if len(b) < 8 {
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return p, b, errNotEnoughData
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}
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p.X = math.Float64frombits(binary.LittleEndian.Uint64(b))
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b = b[8:]
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if len(b) < 8 {
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return p, b, errNotEnoughData
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}
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p.Y = math.Float64frombits(binary.LittleEndian.Uint64(b))
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b = b[8:]
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if isCordZ {
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if len(b) < 8 {
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return p, b, errNotEnoughData
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}
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p.Z = math.Float64frombits(binary.LittleEndian.Uint64(b))
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b = b[8:]
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} else {
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p.Z = nilz
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}
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return p, b, nil
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}
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// ExternalJSON is the simple json representation of the position used for external applications.
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func (p Position) ExternalJSON() string {
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if p.Z != 0 {
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return `{"lat":` + strconv.FormatFloat(p.Y, 'f', -1, 64) + `,"lon":` + strconv.FormatFloat(p.X, 'f', -1, 64) + `,"z":` + strconv.FormatFloat(p.Z, 'f', -1, 64) + `}`
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}
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return `{"lat":` + strconv.FormatFloat(p.Y, 'f', -1, 64) + `,"lon":` + strconv.FormatFloat(p.X, 'f', -1, 64) + `}`
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}
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