moby/daemon/graphdriver/plugin.go

package graphdriver

import (
	"fmt"
	"io"
	"path/filepath"

	"github.com/docker/docker/pkg/plugingetter"
)

type pluginClient interface {
	// Call calls the specified method with the specified arguments for the plugin.
	Call(string, interface{}, interface{}) error
	// Stream calls the specified method with the specified arguments for the plugin and returns the response IO stream
	Stream(string, interface{}) (io.ReadCloser, error)
	// SendFile calls the specified method, and passes through the IO stream
	SendFile(string, io.Reader, interface{}) error
}

func lookupPlugin(name, home string, opts []string, pg plugingetter.PluginGetter) (Driver, error) {
	pl, err := pg.Get(name, "GraphDriver", plugingetter.LOOKUP)
	if err != nil {
		return nil, fmt.Errorf("Error looking up graphdriver plugin %s: %v", name, err)
	}
	return newPluginDriver(name, home, opts, pl)
}

func newPluginDriver(name, home string, opts []string, pl plugingetter.CompatPlugin) (Driver, error) {
	proxy := &graphDriverProxy{name, pl.Client(), pl}
	return proxy, proxy.Init(filepath.Join(home, name), opts)
}