distribution/registry/storage/layerhandler.go

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package storage
import (
"fmt"
"net/http"
"github.com/docker/distribution"
storagedriver "github.com/docker/distribution/registry/storage/driver"
)
// LayerHandler provides middleware for serving the contents of a Layer.
type LayerHandler interface {
// Resolve returns an http.Handler which can serve the contents of a given
// Layer if possible, or nil and an error when unsupported. This may
// directly serve the contents of the layer or issue a redirect to another
// URL hosting the content.
Resolve(layer distribution.Layer) (http.Handler, error)
}
// LayerHandlerInitFunc is the type of a LayerHandler factory function and is
// used to register the contsructor for different LayerHandler backends.
type LayerHandlerInitFunc func(storageDriver storagedriver.StorageDriver, options map[string]interface{}) (LayerHandler, error)
var layerHandlers map[string]LayerHandlerInitFunc
// RegisterLayerHandler is used to register an LayerHandlerInitFunc for
// a LayerHandler backend with the given name.
func RegisterLayerHandler(name string, initFunc LayerHandlerInitFunc) error {
if layerHandlers == nil {
layerHandlers = make(map[string]LayerHandlerInitFunc)
}
if _, exists := layerHandlers[name]; exists {
return fmt.Errorf("name already registered: %s", name)
}
layerHandlers[name] = initFunc
return nil
}
// GetLayerHandler constructs a LayerHandler
// with the given options using the named backend.
func GetLayerHandler(name string, options map[string]interface{}, storageDriver storagedriver.StorageDriver) (LayerHandler, error) {
if layerHandlers != nil {
if initFunc, exists := layerHandlers[name]; exists {
return initFunc(storageDriver, options)
}
}
return nil, fmt.Errorf("no layer handler registered with name: %s", name)
}