wkb

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:
}

Documentation

Overview

Package wkb is for decoding ESRI's Well Known Binary (WKB) format sepcification at http://edndoc.esri.com/arcsde/9.1/general_topics/wkb_representation.htm

Index

• Variables
• func Marshal(geom orb.Geometry, byteOrder ...binary.ByteOrder) ([]byte, error)
• func MustMarshal(geom orb.Geometry, byteOrder ...binary.ByteOrder) []byte
• func Unmarshal(b []byte) (orb.Geometry, error)
• func Value(g orb.Geometry) driver.Valuer
• type Decoder
  • func NewDecoder(r io.Reader) *Decoder
  • func (d *Decoder) Decode() (orb.Geometry, error)
• type Encoder
  • func NewEncoder(w io.Writer) *Encoder
  • func (e *Encoder) Encode(geom orb.Geometry) error
  • func (e *Encoder) SetByteOrder(bo binary.ByteOrder)
• type GeometryScanner
  • func Scanner(g interface{}) *GeometryScanner
  • func (s *GeometryScanner) Scan(d interface{}) error

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 form marshalling or encoding is none is specified.

Functions

func Marshal

func Marshal(geom orb.Geometry, byteOrder ...binary.ByteOrder) ([]byte, error)

Marshal encodes the geometry with the given byte order.

func MustMarshal

func MustMarshal(geom orb.Geometry, byteOrder ...binary.ByteOrder) []byte

MustMarshal will encode the geometry and panic on error. Currently there is no reason to error during geometry marshalling.

func Unmarshal

func Unmarshal(b []byte) (orb.Geometry, error)

Unmarshal will decode the type into a Geometry.

func Value

func Value(g orb.Geometry) driver.Valuer

Value will create a driver.Valuer that will WKB the geometry into the database query.

Types

type Decoder

type Decoder struct {
	// contains filtered or unexported fields
}

Decoder can decoder WKB geometry off of the stream.

func NewDecoder

func NewDecoder(r io.Reader) *Decoder

NewDecoder will create a new WKB decoder.

func (*Decoder) Decode

func (d *Decoder) Decode() (orb.Geometry, error)

Decode will decode the next geometry off of the steam.

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

func NewEncoder(w io.Writer) *Encoder

NewEncoder creates a new Encoder for the given writer

func (*Encoder) Encode

func (e *Encoder) Encode(geom orb.Geometry) error

Encode will write the geometry encoded as WKB to the given writer.

func (*Encoder) SetByteOrder

func (e *Encoder) SetByteOrder(bo binary.ByteOrder)

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
}

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.