Mercurial > gemma
view pkg/wkb/data.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> |
---|---|
date | Thu, 21 Oct 2021 19:50:39 +0200 |
parents | 0ddb308fed37 |
children | 1222b777f51f |
line wrap: on
line source
// 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] } }