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annotate pkg/wkb/data.go @ 4296:95786a675d70

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WIP: Started with downloading stretches as ESRI shapes. GET /api/data/stretch/shape/{stretch}
author Sascha L. Teichmann <sascha.teichmann@intevation.de>
date Fri, 30 Aug 2019 18:34:27 +0200
parents
children 8b730ee6f17b
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rev   line source
4296
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Sascha L. Teichmann <sascha.teichmann@intevation.de>
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1 // This is Free Software under GNU Affero General Public License v >= 3.0
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2 // without warranty, see README.md and license for details.
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3 //
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4 // SPDX-License-Identifier: AGPL-3.0-or-later
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5 // License-Filename: LICENSES/AGPL-3.0.txt
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6 //
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7 // Copyright (C) 2019 by via donau
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8 // – Österreichische Wasserstraßen-Gesellschaft mbH
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9 // Software engineering by Intevation GmbH
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10 //
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11 // Author(s):
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12 // * Sascha L. Teichmann <sascha.teichmann@intevation.de>
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13
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14 package wkb
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15
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16 import (
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17 "bytes"
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18 "encoding/binary"
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19 "fmt"
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20 "log"
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21 )
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22
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23 type (
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24 PointGeom struct {
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25 X float64
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26 Y float64
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27 }
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28 LinearRingGeom []PointGeom
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29 PolygonGeom []LinearRingGeom
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30 MultiPolygonGeom []PolygonGeom
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31 )
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32
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33 func (mpg *MultiPolygonGeom) FromWKB(data []byte) error {
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34 r := bytes.NewReader(data)
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35
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36 endian, err := r.ReadByte()
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37
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38 var order binary.ByteOrder
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39
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40 switch {
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41 case err != nil:
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42 return err
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43 case endian == NDR:
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44 order = binary.LittleEndian
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45 case endian == XDR:
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46 order = binary.BigEndian
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47 default:
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48 return fmt.Errorf("unknown byte order %x", endian)
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49 }
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50
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51 var geomType uint32
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52 err = binary.Read(r, order, &geomType)
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53
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54 switch {
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55 case err != nil:
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56 return err
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57 case geomType != MultiPolygon:
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58 return fmt.Errorf("unknown geometry type %x", geomType)
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59 }
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60
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61 var numPolygons int32
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62 if err := binary.Read(r, order, &numPolygons); err != nil {
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63 return err
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64 }
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65 log.Printf("info: num polygons: %d\n", numPolygons)
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66
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67 polygons := make([]PolygonGeom, numPolygons)
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68
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69 // TODO: Parse the polygons.
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70
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71 *mpg = polygons
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72 return nil
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73 }