move plugin to util

util/plugin/default.go

@@ -0,0 +1,72 @@
+// Package plugin provides the ability to load plugins
+package plugin
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	pg "plugin"
+	"strings"
+	"text/template"
+)
+
+type plugin struct{}
+
+// Load loads a plugin created with `go build -buildmode=plugin`
+func (p *plugin) Load(path string) (*Config, error) {
+	plugin, err := pg.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	s, err := plugin.Lookup("Plugin")
+	if err != nil {
+		return nil, err
+	}
+	pl, ok := s.(*Config)
+	if !ok {
+		return nil, errors.New("could not cast Plugin object")
+	}
+	return pl, nil
+}
+
+// Generate creates a go file at the specified path.
+// You must use `go build -buildmode=plugin`to build it.
+func (p *plugin) Generate(path string, c *Config) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	t, err := template.New(c.Name).Parse(tmpl)
+	if err != nil {
+		return err
+	}
+	return t.Execute(f, c)
+}
+
+// Build generates a dso plugin using the go command `go build -buildmode=plugin`
+func (p *plugin) Build(path string, c *Config) error {
+	path = strings.TrimSuffix(path, ".so")
+
+	// create go file in tmp path
+	temp := os.TempDir()
+	base := filepath.Base(path)
+	goFile := filepath.Join(temp, base+".go")
+
+	// generate .go file
+	if err := p.Generate(goFile, c); err != nil {
+		return err
+	}
+	// remove .go file
+	defer os.Remove(goFile)
+
+	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil && !os.IsExist(err) {
+		return fmt.Errorf("Failed to create dir %s: %v", filepath.Dir(path), err)
+	}
+	cmd := exec.Command("go", "build", "-buildmode=plugin", "-o", path+".so", goFile)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}