Mercurial > gemma
view pkg/imports/wkb.go @ 5520:05db984d3db1
Improve performance of bottleneck area calculation
Avoid buffer calculations by replacing them with simple distance comparisons
and calculate the boundary of the result geometry only once per iteration.
In some edge cases with very large numbers of iterations, this reduced
the runtime of a bottleneck import by a factor of more than twenty.
author | Tom Gottfried <tom@intevation.de> |
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date | Thu, 21 Oct 2021 19:50:39 +0200 |
parents | 41a67619c170 |
children | 6270951dda28 |
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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" "gemma.intevation.de/gemma/pkg/wkb" ) type ( pointSlice []float64 lineSlice [][]float64 multiLineSlice []lineSlice polygonSlice [][][]float64 multiPolygonSlice []polygonSlice ) func newPointFeature(newProperties func() interface{}) func() (string, interface{}) { return func() (string, interface{}) { return "Point", newProperties() } } func newMultiLineFeature( newProperties func() interface{}, ) func() (string, interface{}) { return func() (string, interface{}) { return "MultiLineString", newProperties() } } func (ls lineSlice) toWKB(buf *bytes.Buffer) { binary.Write(buf, binary.LittleEndian, wkb.NDR) binary.Write(buf, binary.LittleEndian, wkb.LineString) binary.Write(buf, binary.LittleEndian, uint32(len(ls))) for _, c := range ls { var lat, lon float64 if len(c) > 0 { lat = c[0] } if len(c) > 1 { lon = c[1] } binary.Write(buf, binary.LittleEndian, math.Float64bits(lat)) binary.Write(buf, binary.LittleEndian, math.Float64bits(lon)) } } func (ls lineSlice) asWKB() []byte { size := 1 + 4 + 4 + len(ls)*(2*8) buf := bytes.NewBuffer(make([]byte, 0, size)) ls.toWKB(buf) return buf.Bytes() } func (ls lineSlice) LinearRingGeom() wkb.LinearRingGeom { lr := make(wkb.LinearRingGeom, len(ls)) for i, v := range ls { lr[i].X = v[0] lr[i].Y = v[1] } return lr } func (mls multiLineSlice) asWKB() []byte { size := 1 + 4 + 4 for _, ls := range mls { size += 1 + 4 + 4 + len(ls)*(2*8) } buf := bytes.NewBuffer(make([]byte, 0, size)) binary.Write(buf, binary.LittleEndian, wkb.NDR) binary.Write(buf, binary.LittleEndian, wkb.MultiLineString) binary.Write(buf, binary.LittleEndian, uint32(len(mls))) for _, ls := range mls { ls.toWKB(buf) } return buf.Bytes() } func (p pointSlice) asWKB() []byte { size := 1 + 4 + 2*8 buf := bytes.NewBuffer(make([]byte, 0, size)) binary.Write(buf, binary.LittleEndian, wkb.NDR) binary.Write(buf, binary.LittleEndian, wkb.Point) var lat, lon float64 if len(p) > 0 { lat = p[0] } if len(p) > 1 { lon = p[1] } binary.Write(buf, binary.LittleEndian, math.Float64bits(lat)) binary.Write(buf, binary.LittleEndian, math.Float64bits(lon)) return buf.Bytes() } func (ps polygonSlice) asWKB() []byte { if ps == nil { return nil } // pre-calculate size to avoid reallocations. size := 1 + 4 + 4 for _, ring := range ps { size += 4 + len(ring)*2*8 } buf := bytes.NewBuffer(make([]byte, 0, size)) binary.Write(buf, binary.LittleEndian, wkb.NDR) binary.Write(buf, binary.LittleEndian, wkb.Polygon) binary.Write(buf, binary.LittleEndian, uint32(len(ps))) for _, ring := range ps { binary.Write(buf, binary.LittleEndian, uint32(len(ring))) for _, v := range ring { var lat, lon float64 if len(v) > 0 { lat = v[0] } if len(v) > 1 { lon = v[1] } binary.Write(buf, binary.LittleEndian, math.Float64bits(lat)) binary.Write(buf, binary.LittleEndian, math.Float64bits(lon)) } } return buf.Bytes() } func shapeToPolygon(s shp.Shape) (polygonSlice, 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) polygonSlice { out := make(polygonSlice, 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([][]float64, howMany) vertices := make([]float64, 2*howMany) for j := int32(0); j < howMany; j, pos = j+1, pos+1 { p := &points[pos] vertex := vertices[j*2 : j*2+2] vertex[0], vertex[1] = p.X, p.Y line[j] = vertex } out[i] = line } return out } func (ps polygonSlice) MultiPolygonGeom() wkb.MultiPolygonGeom { var mp wkb.MultiPolygonGeom var curr wkb.PolygonGeom for _, r := range ps { lr := lineSlice(r).LinearRingGeom() // A counter clockwise ring starts a new polygon. if lr.CCW() { if len(curr) > 0 { mp = append(mp, curr) curr = wkb.PolygonGeom{} } } curr = append(curr, lr) } if len(curr) > 0 { mp = append(mp, curr) } return mp }