magnacarto/render/mapnik.go

package render

import (
	"bytes"
	"errors"
	"io"
	"net/rpc"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"time"

	"github.com/natefinch/pie"
)

type Mapnik struct {
	client *rpc.Client
}

var mapnikPluginName = "magnacarto-mapnik"

func init() {
	if runtime.GOOS == "windows" {
		mapnikPluginName += ".exe"
	}
}

func NewMapnik() (*Mapnik, error) {
	path, err := exec.LookPath(mapnikPluginName)
	if err != nil {
		path = filepath.Join(filepath.Dir(os.Args[0]), mapnikPluginName)
		path, _ = filepath.Abs(path)
		if _, serr := os.Stat(path); serr != nil {
			return nil, err
		}
	}

	client, err := pie.StartProvider(os.Stderr, path)
	if err != nil {
		return nil, err
	}
	return &Mapnik{client: client}, nil
}

func (m *Mapnik) Is3() (bool, error) {
	if m.client == nil {
		return false, errors.New("mapnik plugin not initialized")
	}
	var is3 bool
	err := m.client.Call("Mapnik.Is3", struct{}{} /* not used */, &is3)
	return is3, err
}

func (m *Mapnik) RegisterFonts(fontDir string) error {
	if m.client == nil {
		return errors.New("mapnik plugin not initialized")
	}
	var tmp interface{}
	err := m.client.Call("Mapnik.RegisterFonts", fontDir, &tmp /* not used */)
	return err
}

func (m *Mapnik) CacheLoadedMap(cacheWaitTimeout time.Duration) error {
	if m.client == nil {
		return errors.New("mapnik plugin not initialized")
	}
	var tmp interface{}
	err := m.client.Call("Mapnik.CacheLoadedMap", cacheWaitTimeout, &tmp /* not used */)
	return err
}

func (m *Mapnik) Close() error {
	if m.client == nil {
		return errors.New("mapnik plugin not initialized")
	}
	return m.client.Close()
}

func (m *Mapnik) Render(mapfile string, dst io.Writer, mapReq Request) error {
	if m.client == nil {
		return errors.New("mapnik plugin not initialized")
	}
	var buf []byte
	err := m.client.Call("Mapnik.Render", struct {
		Mapfile string
		Req     Request
	}{mapfile, mapReq}, &buf)
	if err != nil {
		return err
	}
	_, err = io.Copy(dst, bytes.NewBuffer(buf))
	return err
}