README
¶
encoding/wkb 
This package provides encoding and decoding of WKB data. The interface is defined as:
func Marshal(geom orb.Geometry, byteOrder ...binary.ByteOrder) ([]byte, error)
func MustMarshal(geom orb.Geometry, byteOrder ...binary.ByteOrder) []byte
func NewEncoder(w io.Writer) *Encoder
func (e *Encoder) SetByteOrder(bo binary.ByteOrder)
func (e *Encoder) Encode(geom orb.Geometry) error
func Unmarshal(b []byte) (orb.Geometry, error)
func NewDecoder(r io.Reader) *Decoder
func (d *Decoder) Decode() (orb.Geometry, error)
Reading and Writing to a SQL database
This package provides wrappers for orb.Geometry types that implement
sql.Scanner and driver.Value. For example:
row := db.QueryRow("SELECT ST_AsBinary(point_column) FROM postgis_table")
var p orb.Point
err := row.Scan(wkb.Scanner(&p))
db.Exec("INSERT INTO table (point_column) VALUES (?)",
wkb.Value(p))
If you don't know the type of the geometry try something like
s := wkb.Scanner(nil)
err := row.Scan(&s)
switch g := s.Geometry.(type) {
case orb.Point:
case orb.LineString:
}
Scanning directly from MySQL columns is supported. By default MySQL returns geometry data as WKB but prefixed with a 4 byte SRID. To support this, if the data is not valid WKB, the code will strip the first 4 bytes, the SRID, and try again. This works for most use cases.
Documentation
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Overview ¶
Package wkb is for decoding ESRI's Well Known Binary (WKB) format sepcification at https://en.wikipedia.org/wiki/Well-known_text_representation_of_geometry#Well-known_binary
Index ¶
- Variables
- func Marshal(geom orb.Geometry, byteOrder ...binary.ByteOrder) ([]byte, error)
- func MustMarshal(geom orb.Geometry, byteOrder ...binary.ByteOrder) []byte
- func Unmarshal(data []byte) (orb.Geometry, error)
- func Value(g orb.Geometry) driver.Valuer
- type Decoder
- type Encoder
- type GeometryScanner
Constants ¶
This section is empty.
Variables ¶
var ( // ErrUnsupportedDataType is returned by Scan methods when asked to scan // non []byte data from the database. This should never happen // if the driver is acting appropriately. ErrUnsupportedDataType = errors.New("wkb: scan value must be []byte") // ErrNotWKB is returned when unmarshalling WKB and the data is not valid. ErrNotWKB = errors.New("wkb: invalid data") // ErrIncorrectGeometry is returned when unmarshalling WKB data into the wrong type. // For example, unmarshaling linestring data into a point. ErrIncorrectGeometry = errors.New("wkb: incorrect geometry") // ErrUnsupportedGeometry is returned when geometry type is not supported by this lib. ErrUnsupportedGeometry = errors.New("wkb: unsupported geometry") )
var DefaultByteOrder binary.ByteOrder = binary.LittleEndian
DefaultByteOrder is the order used for marshalling or encoding is none is specified.
Functions ¶
func MustMarshal ¶
MustMarshal will encode the geometry and panic on error. Currently there is no reason to error during geometry marshalling.
Types ¶
type Decoder ¶
type Decoder struct {
// contains filtered or unexported fields
}
Decoder can decoder WKB geometry off of the stream.
type Encoder ¶
type Encoder struct {
// contains filtered or unexported fields
}
An Encoder will encode a geometry as WKB to the writer given at creation time.
func NewEncoder ¶
NewEncoder creates a new Encoder for the given writer.
func (*Encoder) SetByteOrder ¶
SetByteOrder will override the default byte order set when the encoder was created.
type GeometryScanner ¶
type GeometryScanner struct {
Geometry orb.Geometry
Valid bool // Valid is true if the geometry is not NULL
// contains filtered or unexported fields
}
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
} else {
// NULL value
}
func Scanner ¶
func Scanner(g interface{}) *GeometryScanner
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
}
Scanning directly from MySQL columns is supported. By default MySQL returns geometry data as WKB but prefixed with a 4 byte SRID. To support this, if the data is not valid WKB, the code will strip the first 4 bytes and try again. This works for most use cases.
func (*GeometryScanner) Scan ¶
func (s *GeometryScanner) Scan(d interface{}) error
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.
Source Files