encoding/ewkb sql.Scanner and driver.Value

Author: paulmach

encoding/ewkb/README.md

@@ -1,6 +1,6 @@
 # encoding/ewkb [![Godoc Reference](https://pkg.go.dev/badge/github.com/paulmach/orb)](https://pkg.go.dev/github.com/paulmach/orb/encoding/ewkb)
 
-This package provides encoding and decoding of extended [WKB](https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry#Format_variations)
+This package provides encoding and decoding of [extended WKB](https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry#Format_variations)
 data. This format includes the SRID in the data. If you don't need the SRID you can use the
 [wkb](../wkb) package for a simpler interface.
 

encoding/ewkb/scanner.go

@@ -0,0 +1,99 @@
+package ewkb
+
+import (
+	"database/sql"
+	"database/sql/driver"
+
+	"github.com/paulmach/orb"
+	"github.com/paulmach/orb/encoding/internal/wkbcommon"
+)
+
+var (
+	_ sql.Scanner  = &GeometryScanner{}
+	_ driver.Value = value{}
+)
+
+// GeometryScanner is a thing that can scan in sql query results.
+// It can be used as a scan destination:
+//
+//	var s wkb.GeometryScanner
+//	err := db.QueryRow("SELECT latlon FROM foo WHERE id=?", id).Scan(&s)
+//	...
+//	if s.Valid {
+//	  // use s.Geometry
+//	  // use s.SRID
+//	} else {
+//	  // NULL value
+//	}
+type GeometryScanner struct {
+	g        interface{}
+	SRID     int
+	Geometry orb.Geometry
+	Valid    bool // Valid is true if the geometry is not NULL
+}
+
+// Scanner will return a GeometryScanner that can scan sql query results.
+// The geometryScanner.Geometry attribute will be set to the value.
+// If g is non-nil, it MUST be a pointer to an orb.Geometry
+// type like a Point or LineString. In that case the value will be written to
+// g and the Geometry attribute.
+//
+//	var p orb.Point
+//	err := db.QueryRow("SELECT latlon FROM foo WHERE id=?", id).Scan(wkb.Scanner(&p))
+//	...
+//	// use p
+//
+// If the value may be null check Valid first:
+//
+//	var point orb.Point
+//	s := wkb.Scanner(&point)
+//	err := db.QueryRow("SELECT latlon FROM foo WHERE id=?", id).Scan(s)
+//	...
+//	if s.Valid {
+//	  // use p
+//	} else {
+//	  // NULL value
+//	}
+func Scanner(g interface{}) *GeometryScanner {
+	return &GeometryScanner{g: g}
+}
+
+// Scan will scan the input []byte data into a geometry.
+// This could be into the orb geometry type pointer or, if nil,
+// the scanner.Geometry attribute.
+func (s *GeometryScanner) Scan(d interface{}) error {
+	s.Geometry = nil
+	s.Valid = false
+
+	g, srid, valid, err := wkbcommon.Scan(s.g, d)
+	if err != nil {
+		return mapCommonError(err)
+	}
+
+	s.Geometry = g
+	s.SRID = srid
+	s.Valid = valid
+
+	return nil
+}
+
+type value struct {
+	srid int
+	v    orb.Geometry
+}
+
+// Value will create a driver.Valuer that will EWKB the geometry into the database query.
+//
+//	db.Exec("INSERT INTO table (point_column) VALUES (?)", ewkb.Value(p, 4326))
+func Value(g orb.Geometry, srid int) driver.Valuer {
+	return value{srid: srid, v: g}
+
+}
+
+func (v value) Value() (driver.Value, error) {
+	val, err := Marshal(v.v, v.srid)
+	if val == nil {
+		return nil, err
+	}
+	return val, err
+}