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points.go
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points.go
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package geo
import (
"encoding/json"
"fmt"
"strconv"
"strings"
)
// pointsEqual compares two slices of points.
func pointsEqual(p1, p2 [][3]float64) bool {
if len(p1) != len(p2) {
return false
}
for i, vertex := range p1 {
if vertex[0] != p2[i][0] {
return false
}
if vertex[1] != p2[i][1] {
return false
}
}
return true
}
// pointsContain returns true if the
func pointsContain(pts [][3]float64, pt [3]float64) bool {
if len(pts) < 2 {
return false
}
for i, vertex := range pts {
if vertex[0] == pt[0] && vertex[1] == pt[1] {
return true
}
if i == 0 {
continue
}
if segmentContains(vertex, pts[i-1], pt) {
return true
}
}
return false
}
// pointsMarshalJSON converts a list of points to JSON.
func pointsMarshalJSON(points [][3]float64, prefix, suffix string) []byte {
s := prefix
for i, point := range points {
if i == 0 {
s += "[" + strconv.FormatFloat(point[0], 'f', -1, 64) + ","
s += strconv.FormatFloat(point[1], 'f', -1, 64) + "]"
} else {
s += ",[" + strconv.FormatFloat(point[0], 'f', -1, 64) + ","
s += strconv.FormatFloat(point[1], 'f', -1, 64) + "]"
}
}
return []byte(s + suffix)
}
// pointsScan scans a list of points from Well Known Text.
// The points should look like this: X0 Y0,X1 Y1,X2 Y2.
// It is also acceptable to have leading and trailing parens, these will be stripped.
// Examples:
// * (X0 Y0,X1 Y1,X2 Y2
// * X0 Y0,X1 Y1,X2 Y2)
// * (X0 Y0,X1 Y1,X2 Y2)
func pointsScan(s string) ([][3]float64, error) {
// Trim leading and trailing parens.
leadingIdx := 0
for s[leadingIdx] == '(' {
leadingIdx++
}
s = s[leadingIdx:]
trailingIdx := len(s)
if trailingIdx > 0 {
for s[trailingIdx-1] == ')' {
trailingIdx--
}
s = s[:trailingIdx]
}
// At this point s should look like this:
// x x, x x, x x, ...
// Where x is a float.
points := [][3]float64{}
for _, coords := range strings.Split(s, ",") {
var (
pair = [3]float64{}
xy = strings.Split(strings.TrimSpace(coords), " ")
)
if len(xy) != 2 {
return nil, fmt.Errorf("could not scan points from %s (xy=%s)", s, xy)
}
for i, val := range xy {
f, err := strconv.ParseFloat(val, 64)
if err != nil {
return nil, err
}
pair[i] = f
}
points = append(points, pair)
}
return points, nil
}
// pointsScanPrefix scans a string form points, and expects the given prefix.
func pointsScanPrefix(s, prefix, typeName string) ([][3]float64, error) {
if len(s) <= len(prefix) {
return nil, fmt.Errorf("could not scan %s from %s", typeName, s)
}
return pointsScan(s[len(prefix):])
}
// pointsString converts a slice of points to Well Known Text.
func pointsString(points [][3]float64) string {
s := "("
s += strconv.FormatFloat(points[0][0], 'f', -1, 64)
s += " " + strconv.FormatFloat(points[0][1], 'f', -1, 64)
for _, coord := range points[1:] {
s += ", " + strconv.FormatFloat(coord[0], 'f', -1, 64)
s += " " + strconv.FormatFloat(coord[1], 'f', -1, 64)
}
return s + ")"
}
// pointsUnmarshal unmarshals a slice of points
func pointsUnmarshal(data []byte, expectedType string) ([][3]float64, error) {
g := geometry{}
// Never fails because data is always valid JSON.
_ = json.Unmarshal(data, &g)
if expected, got := expectedType, g.Type; expected != got {
return nil, fmt.Errorf("expected type %s, got %s", expected, got)
}
pts := [][3]float64{}
if err := json.Unmarshal(g.Coordinates, &pts); err != nil {
return nil, err
}
return pts, nil
}