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builtins: implement ST_IsPolygonCW/CCW and ST_ForcePolygonCW/CCW
Release note (sql change): implement the ST_IsPolygonCW, ST_IsPolygonCCW, ST_ForcePolygonCW and ST_ForcePolygonCCW builtins. Release justification: low risk, high benefit changes
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,154 @@ | ||
| // Copyright 2020 The Cockroach Authors. | ||
| // | ||
| // Use of this software is governed by the Business Source License | ||
| // included in the file licenses/BSL.txt. | ||
| // | ||
| // As of the Change Date specified in that file, in accordance with | ||
| // the Business Source License, use of this software will be governed | ||
| // by the Apache License, Version 2.0, included in the file | ||
| // licenses/APL.txt. | ||
|
|
||
| package geomfn | ||
|
|
||
| import ( | ||
| "github.com/cockroachdb/cockroach/pkg/geo" | ||
| "github.com/cockroachdb/errors" | ||
| "github.com/twpayne/go-geom" | ||
| ) | ||
|
|
||
| // Orientation defines an orientation of a shape. | ||
| type Orientation int | ||
|
|
||
| const ( | ||
| // OrientationCW denotes a clockwise orientation. | ||
| OrientationCW Orientation = iota | ||
| // OrientationCCW denotes a counter-clockwise orientation | ||
| OrientationCCW | ||
| ) | ||
|
|
||
| // HasPolygonOrientation checks whether a given Geometry have polygons | ||
| // that matches the given Orientation. | ||
| // Non-Polygon objects | ||
| func HasPolygonOrientation(g geo.Geometry, o Orientation) (bool, error) { | ||
| t, err := g.AsGeomT() | ||
| if err != nil { | ||
| return false, err | ||
| } | ||
| return hasPolygonOrientation(t, o) | ||
| } | ||
|
|
||
| func hasPolygonOrientation(g geom.T, o Orientation) (bool, error) { | ||
| switch g := g.(type) { | ||
| case *geom.Polygon: | ||
| for i := 0; i < g.NumLinearRings(); i++ { | ||
| isCCW := geo.IsLinearRingCCW(g.LinearRing(i)) | ||
| // Interior rings should be the reverse orientation of the exterior ring. | ||
| if i > 0 { | ||
| isCCW = !isCCW | ||
| } | ||
| switch o { | ||
| case OrientationCW: | ||
| if isCCW { | ||
| return false, nil | ||
| } | ||
| case OrientationCCW: | ||
| if !isCCW { | ||
| return false, nil | ||
| } | ||
| default: | ||
| return false, errors.Newf("unexpected orientation: %v", o) | ||
| } | ||
| } | ||
| return true, nil | ||
| case *geom.MultiPolygon: | ||
| for i := 0; i < g.NumPolygons(); i++ { | ||
| if ret, err := hasPolygonOrientation(g.Polygon(i), o); !ret || err != nil { | ||
| return ret, err | ||
| } | ||
| } | ||
| return true, nil | ||
| case *geom.GeometryCollection: | ||
| for i := 0; i < g.NumGeoms(); i++ { | ||
| if ret, err := hasPolygonOrientation(g.Geom(i), o); !ret || err != nil { | ||
| return ret, err | ||
| } | ||
| } | ||
| return true, nil | ||
| case *geom.Point, *geom.MultiPoint, *geom.LineString, *geom.MultiLineString: | ||
| return true, nil | ||
| default: | ||
| return false, errors.Newf("unhandled geometry type: %T", g) | ||
| } | ||
| } | ||
|
|
||
| // ForcePolygonOrientation forces orientations within polygons | ||
| // to be oriented the prescribed way. | ||
| func ForcePolygonOrientation(g geo.Geometry, o Orientation) (geo.Geometry, error) { | ||
| t, err := g.AsGeomT() | ||
| if err != nil { | ||
| return geo.Geometry{}, err | ||
| } | ||
|
|
||
| if err := forcePolygonOrientation(t, o); err != nil { | ||
| return geo.Geometry{}, err | ||
| } | ||
| return geo.MakeGeometryFromGeomT(t) | ||
| } | ||
|
|
||
| func forcePolygonOrientation(g geom.T, o Orientation) error { | ||
| switch g := g.(type) { | ||
| case *geom.Polygon: | ||
| for i := 0; i < g.NumLinearRings(); i++ { | ||
| isCCW := geo.IsLinearRingCCW(g.LinearRing(i)) | ||
| // Interior rings should be the reverse orientation of the exterior ring. | ||
| if i > 0 { | ||
| isCCW = !isCCW | ||
| } | ||
| reverse := false | ||
| switch o { | ||
| case OrientationCW: | ||
| if isCCW { | ||
| reverse = true | ||
| } | ||
| case OrientationCCW: | ||
| if !isCCW { | ||
| reverse = true | ||
| } | ||
| default: | ||
| return errors.Newf("unexpected orientation: %v", o) | ||
| } | ||
|
|
||
| if reverse { | ||
| // Reverse coordinates from both ends. | ||
| // Do this by swapping up to the middle of the array of elements, which guarantees | ||
| // each end get swapped. This works for an odd number of elements as well as | ||
| // the middle element ends swapping with itself, which is ok. | ||
| coords := g.LinearRing(i).FlatCoords() | ||
| for cIdx := 0; cIdx < len(coords)/2; cIdx += g.Stride() { | ||
| for sIdx := 0; sIdx < g.Stride(); sIdx++ { | ||
| coords[cIdx+sIdx], coords[len(coords)-cIdx-g.Stride()+sIdx] = coords[len(coords)-cIdx-g.Stride()+sIdx], coords[cIdx+sIdx] | ||
| } | ||
| } | ||
| } | ||
| } | ||
| return nil | ||
| case *geom.MultiPolygon: | ||
| for i := 0; i < g.NumPolygons(); i++ { | ||
| if err := forcePolygonOrientation(g.Polygon(i), o); err != nil { | ||
| return err | ||
| } | ||
| } | ||
| return nil | ||
| case *geom.GeometryCollection: | ||
| for i := 0; i < g.NumGeoms(); i++ { | ||
| if err := forcePolygonOrientation(g.Geom(i), o); err != nil { | ||
| return err | ||
| } | ||
| } | ||
| return nil | ||
| case *geom.Point, *geom.MultiPoint, *geom.LineString, *geom.MultiLineString: | ||
| return nil | ||
| default: | ||
| return errors.Newf("unhandled geometry type: %T", g) | ||
| } | ||
| } |
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