Mercurial > gemma
view pkg/wkb/data.go @ 5095:e21cbb9768a2
Prevent duplicate fairway areas
In principal, there can be only one or no fairway area at each point
on the map. Since polygons from real data will often be topologically
inexact, just disallow equal geometries. This will also help to
avoid importing duplicates with concurrent imports, once the history
of fairway dimensions will be preserved.
author | Tom Gottfried <tom@intevation.de> |
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date | Wed, 25 Mar 2020 18:10:02 +0100 |
parents | 0ddb308fed37 |
children | 1222b777f51f |
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// This is Free Software under GNU Affero General Public License v >= 3.0 // without warranty, see README.md and license for details. // // SPDX-License-Identifier: AGPL-3.0-or-later // License-Filename: LICENSES/AGPL-3.0.txt // // Copyright (C) 2019 by via donau // – Österreichische Wasserstraßen-Gesellschaft mbH // Software engineering by Intevation GmbH // // Author(s): // * Sascha L. Teichmann <sascha.teichmann@intevation.de> package wkb import ( "bytes" "encoding/binary" "fmt" "math" ) type ( PointGeom struct { X float64 Y float64 } LinearRingGeom []PointGeom PolygonGeom []LinearRingGeom MultiPolygonGeom []PolygonGeom ) func (mpg MultiPolygonGeom) AsWKB() []byte { size := 1 + 4 + 4 for _, pg := range mpg { size += 1 + 4 + 4 for _, r := range pg { size += 4 + 2*8*len(r) } } buf := bytes.NewBuffer(make([]byte, 0, size)) binary.Write(buf, binary.LittleEndian, NDR) binary.Write(buf, binary.LittleEndian, MultiPolygon) binary.Write(buf, binary.LittleEndian, uint32(len(mpg))) for _, pg := range mpg { binary.Write(buf, binary.LittleEndian, NDR) binary.Write(buf, binary.LittleEndian, Polygon) binary.Write(buf, binary.LittleEndian, uint32(len(pg))) for _, r := range pg { binary.Write(buf, binary.LittleEndian, uint32(len(r))) for _, p := range r { x := math.Float64bits(p.X) y := math.Float64bits(p.Y) binary.Write(buf, binary.LittleEndian, x) binary.Write(buf, binary.LittleEndian, y) } } } return buf.Bytes() } func (mpg *MultiPolygonGeom) FromWKB(data []byte) error { r := bytes.NewReader(data) var order binary.ByteOrder switch endian, err := r.ReadByte(); { case err != nil: return err case endian == NDR: order = binary.LittleEndian case endian == XDR: order = binary.BigEndian default: return fmt.Errorf("unknown byte order %x", endian) } var geomType uint32 switch err := binary.Read(r, order, &geomType); { case err != nil: return err case geomType != MultiPolygon: return fmt.Errorf("unknown geometry type %x", geomType) } var numPolygons uint32 if err := binary.Read(r, order, &numPolygons); err != nil { return err } polygons := make([]PolygonGeom, numPolygons) for i := range polygons { switch endian, err := r.ReadByte(); { case err != nil: return err case endian == NDR: order = binary.LittleEndian case endian == XDR: order = binary.BigEndian default: return fmt.Errorf("unknown byte order %x", endian) } switch err := binary.Read(r, order, &geomType); { case err != nil: return err case geomType != Polygon: return fmt.Errorf("unknown geometry type %x", geomType) } var numRings uint32 if err := binary.Read(r, order, &numRings); err != nil { return err } rings := make([]LinearRingGeom, numRings) for j := range rings { var numPoints uint32 if err := binary.Read(r, order, &numPoints); err != nil { return err } points := make([]PointGeom, numPoints) for k := range points { var x, y uint64 if err := binary.Read(r, order, &x); err != nil { return err } if err := binary.Read(r, order, &y); err != nil { return err } points[k] = PointGeom{ X: math.Float64frombits(x), Y: math.Float64frombits(y), } } rings[j] = points } polygons[i] = rings } *mpg = polygons return nil } func (lr LinearRingGeom) CCW() bool { var sum float64 for i, v1 := range lr { v2 := lr[(i+1)%len(lr)] sum += (v2.X - v1.X) * (v2.Y + v1.Y) } return sum > 0 } func (lr LinearRingGeom) Reverse() { for i, j := 0, len(lr)-1; i < j; i, j = i+1, j-1 { lr[i], lr[j] = lr[j], lr[i] } }