dotcloud/docker

package layer // import "github.com/docker/docker/layer"

import (
    "errors"
)

// Getter is an interface to get the path to a layer on the host.
type Getter interface {
    // GetLayerPath gets the path for the layer. This is different from Get()
    // since that returns an interface to account for unmountable layers.
    GetLayerPath(id string) (string, error)
}

// GetLayerPath returns the path to a layer
func GetLayerPath(s Store, layer ChainID) (string, error) {
    ls, ok := s.(*layerStore)
    if !ok {
        return "", errors.New("unsupported layer store")
    }
    ls.layerL.Lock()
    defer ls.layerL.Unlock()

    rl, ok := ls.layerMap[layer]
    if !ok {
        return "", ErrLayerDoesNotExist
    }

    if layerGetter, ok := ls.driver.(Getter); ok {
        return layerGetter.GetLayerPath(rl.cacheID)
    }
    path, err := ls.driver.Get(rl.cacheID, "")
    if err != nil {
        return "", err
    }

    if err := ls.driver.Put(rl.cacheID); err != nil {
        return "", err
    }

    return path, nil
}

func (ls *layerStore) mountID(name string) string {
    // windows has issues if container ID doesn't match mount ID
    return name
}