Mercurial > gemma
view pkg/imports/polygon.go @ 1646:a0982c38eac0
Import queue: Implemented email notifications.
author | Sascha L. Teichmann <sascha.teichmann@intevation.de> |
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date | Thu, 20 Dec 2018 15:33:29 +0100 |
parents | 20c98c2964f7 |
children |
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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) 2018 by via donau // – Österreichische Wasserstraßen-Gesellschaft mbH // Software engineering by Intevation GmbH // // Author(s): // * Sascha L. Teichmann <sascha.teichmann@intevation.de> package imports import ( "bytes" "encoding/binary" "fmt" "math" shp "github.com/jonas-p/go-shp" ) type ( point struct { X float64 Y float64 } lineString []point polygon []lineString ) const ( wkbNDR byte = 1 wkbPolygon uint32 = 3 ) func shapeToPolygon(s shp.Shape) (polygon, error) { switch p := s.(type) { case *shp.Polygon: return toPolygon(p.NumParts, p.Parts, p.Points), nil case *shp.PolygonZ: return toPolygon(p.NumParts, p.Parts, p.Points), nil case *shp.PolygonM: return toPolygon(p.NumParts, p.Parts, p.Points), nil } return nil, fmt.Errorf("Unsupported shape type %T", s) } func toPolygon(numParts int32, parts []int32, points []shp.Point) polygon { out := make(polygon, numParts) var pos int32 for i := range out { var howMany int32 if i+1 >= len(parts) { howMany = int32(len(points)) - pos } else { howMany = parts[i+1] - parts[i] } line := make(lineString, howMany) for j := int32(0); j < howMany; j, pos = j+1, pos+1 { p := &points[pos] line[j] = point{p.X, p.Y} } out[i] = line } return out } func (p polygon) asWKB() []byte { if p == nil { return nil } // pre-calculate size to avoid reallocations. size := 1 + 4 + 4 for _, ring := range p { size += 4 + len(ring)*2*8 } buf := bytes.NewBuffer(make([]byte, 0, size)) binary.Write(buf, binary.LittleEndian, wkbNDR) binary.Write(buf, binary.LittleEndian, wkbPolygon) binary.Write(buf, binary.LittleEndian, uint32(len(p))) for _, ring := range p { binary.Write(buf, binary.LittleEndian, uint32(len(ring))) for _, v := range ring { binary.Write(buf, binary.LittleEndian, math.Float64bits(v.X)) binary.Write(buf, binary.LittleEndian, math.Float64bits(v.Y)) } } return buf.Bytes() }