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reading.go
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reading.go
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package ewkb
import (
"encoding/binary"
"errors"
"math"
"github.com/kcasctiv/go-ewkb/geo"
)
func readHeader(data []byte) (header, binary.ByteOrder, int) {
byteOrder := getBinaryByteOrder(data[0])
offset := 1
wkbType := byteOrder.Uint32(data[offset:])
var h header
h.byteOrder = data[0]
h.wkbType = wkbType
offset += 4
if (wkbType & sridFlag) == sridFlag {
h.srid = int32(byteOrder.Uint32(data[offset:]))
offset += 4
}
return h, byteOrder, offset
}
type readPointFunc func(b []byte, byteOrder binary.ByteOrder) (geo.Point, int, error)
func getReadPointFunc(wkbType uint32) readPointFunc {
if (wkbType & zFlag) == zFlag {
if (wkbType & mFlag) == mFlag {
return readPointZM
}
return readPointZ
}
if (wkbType & mFlag) == mFlag {
return readPointM
}
return readPoint
}
func readPoint(b []byte, byteOrder binary.ByteOrder) (geo.Point, int, error) {
if len(b) < 16 {
return nil, 0, errors.New("out of range")
}
x := math.Float64frombits(byteOrder.Uint64(b))
y := math.Float64frombits(byteOrder.Uint64(b[8:]))
return geo.NewPoint(x, y), 16, nil
}
func readPointZ(b []byte, byteOrder binary.ByteOrder) (geo.Point, int, error) {
if len(b) < 24 {
return nil, 0, errors.New("out of range")
}
x := math.Float64frombits(byteOrder.Uint64(b))
y := math.Float64frombits(byteOrder.Uint64(b[8:]))
z := math.Float64frombits(byteOrder.Uint64(b[16:]))
return geo.NewPointZ(x, y, z), 24, nil
}
func readPointM(b []byte, byteOrder binary.ByteOrder) (geo.Point, int, error) {
if len(b) < 24 {
return nil, 0, errors.New("out of range")
}
x := math.Float64frombits(byteOrder.Uint64(b))
y := math.Float64frombits(byteOrder.Uint64(b[8:]))
m := math.Float64frombits(byteOrder.Uint64(b[16:]))
return geo.NewPointM(x, y, m), 24, nil
}
func readPointZM(b []byte, byteOrder binary.ByteOrder) (geo.Point, int, error) {
if len(b) < 32 {
return nil, 0, errors.New("out of range")
}
x := math.Float64frombits(byteOrder.Uint64(b))
y := math.Float64frombits(byteOrder.Uint64(b[8:]))
z := math.Float64frombits(byteOrder.Uint64(b[16:]))
m := math.Float64frombits(byteOrder.Uint64(b[24:]))
return geo.NewPointZM(x, y, z, m), 32, nil
}
func readMultiPoint(
b []byte, byteOrder binary.ByteOrder,
readFunc readPointFunc) (geo.MultiPoint, int, error) {
if len(b) < 4 {
return nil, 0, errors.New("out of range")
}
mplen := int(byteOrder.Uint32(b))
points := make([]geo.Point, mplen)
var err error
var n int
offset := 4
for idx := 0; idx < mplen; idx++ {
points[idx], n, err = readFunc(b[offset:], byteOrder)
if err != nil {
return nil, 0, err
}
offset += n
}
return geo.NewMultiPoint(points), offset, nil
}
func readPolygon(b []byte, byteOrder binary.ByteOrder,
readFunc readPointFunc) (geo.Polygon, int, error) {
if len(b) < 4 {
return nil, 0, errors.New("out of range")
}
plen := int(byteOrder.Uint32(b))
rings := make([]geo.MultiPoint, plen)
var err error
var n int
offset := 4
for idx := 0; idx < plen; idx++ {
rings[idx], n, err = readMultiPoint(b[offset:], byteOrder, readFunc)
if err != nil {
return nil, 0, err
}
offset += n
}
return geo.NewPolygon(rings), offset, nil
}
func readMultiLine(
b []byte, byteOrder binary.ByteOrder, readFunc readPointFunc,
) (geo.MultiLine, int, error) {
if len(b) < 4 {
return nil, 0, errors.New("out of range")
}
plen := int(byteOrder.Uint32(b))
lines := make([]geo.MultiPoint, plen)
var err error
var n int
var h header
var bo binary.ByteOrder
offset := 4
for idx := 0; idx < plen; idx++ {
h, bo, n = readHeader(b[offset:])
if h.Type() != LineType {
return nil, 0, errors.New("not expected geometry type")
}
offset += n
lines[idx], n, err = readMultiPoint(
b[offset:], bo,
getReadPointFunc(h.wkbType),
)
if err != nil {
return nil, 0, err
}
offset += n
}
return geo.NewMultiLine(lines), offset, nil
}
func readMultiPolygon(b []byte, byteOrder binary.ByteOrder,
readFunc readPointFunc) (geo.MultiPolygon, int, error) {
if len(b) < 4 {
return nil, 0, errors.New("out of range")
}
mplen := int(byteOrder.Uint32(b))
pols := make([]geo.Polygon, mplen)
var err error
var n int
offset := 4
for idx := 0; idx < mplen; idx++ {
pols[idx], n, err = readPolygon(b[offset:], byteOrder, readFunc)
if err != nil {
return nil, 0, err
}
offset += n
}
return geo.NewMultiPolygon(pols), offset, nil
}
func readCollection(b []byte, byteOrder binary.ByteOrder) ([]Geometry, int, error) {
clen := byteOrder.Uint32(b)
offset := 4
geoms := make([]Geometry, clen)
var n int
var err error
for idx := 0; idx < len(geoms); idx++ {
h1, byteOrder1, offset1 := readHeader(b[offset:])
offset += offset1
switch h1.Type() {
case PointType:
point := Point{header: h1}
point.point, n, err = getReadPointFunc(h1.wkbType)(b[offset:], byteOrder1)
geoms[idx] = &point
case LineType:
line := LineString{header: h1}
line.mp, n, err = readMultiPoint(b[offset:], byteOrder1, getReadPointFunc(h1.wkbType))
geoms[idx] = &line
case PolygonType:
poly := Polygon{header: h1}
poly.poly, n, err = readPolygon(b[offset:], byteOrder1, getReadPointFunc(h1.wkbType))
geoms[idx] = &poly
case MultiPointType:
mpoint := MultiPoint{header: h1}
mpoint.mp, n, err = readMultiPoint(b[offset:], byteOrder1, getReadPointFunc(h1.wkbType))
geoms[idx] = &mpoint
case MultiLineType:
mline := MultiLineString{header: h1}
mline.ml, n, err = readMultiLine(b[offset:], byteOrder1, getReadPointFunc(h1.wkbType))
geoms[idx] = &mline
case MultiPolygonType:
mpoly := MultiPolygon{header: h1}
mpoly.mp, n, err = readMultiPolygon(b[offset:], byteOrder1, getReadPointFunc(h1.wkbType))
geoms[idx] = &mpoly
default:
return nil, 0, errors.New("not expected geometry type")
}
if err != nil {
return nil, 0, err
}
offset += n
}
return geoms, offset, nil
}