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backend.go
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backend.go
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/*
* knoxite
* Copyright (c) 2016-2017, Christian Muehlhaeuser <muesli@gmail.com>
*
* For license see LICENSE
*/
package knoxite
import (
"errors"
"net/url"
"path/filepath"
"strings"
)
// BackendFactory is used to initialize a new backend.
type BackendFactory interface {
NewBackend(url url.URL) (Backend, error)
Protocols() []string
}
// Backend is used to store and access data.
type Backend interface {
// Location returns the type and location of the repository
Location() string
// Protocols returns the Protocol Schemes supported by this backend
Protocols() []string
// Description returns a user-friendly description for this backend
Description() string
// Close the backend
Close() error
// AvailableSpace returns the free space in bytes on this backend
AvailableSpace() (uint64, error)
// LoadChunk loads a single Chunk
LoadChunk(shasum string, part, totalParts uint) ([]byte, error)
// StoreChunk stores a single Chunk
StoreChunk(shasum string, part, totalParts uint, data []byte) (uint64, error)
// DeleteChunk deletes a single Chunk
DeleteChunk(shasum string, part, totalParts uint) error
// LoadSnapshot loads a snapshot
LoadSnapshot(id string) ([]byte, error)
// SaveSnapshot stores a snapshot
SaveSnapshot(id string, data []byte) error
// LoadChunkIndex loads the chunk-index
LoadChunkIndex() ([]byte, error)
// SaveChunkIndex stores the chunk-index
SaveChunkIndex(data []byte) error
// InitRepository creates a new repository
InitRepository() error
// LoadRepository reads the metadata for a repository
LoadRepository() ([]byte, error)
// SaveRepository stores the metadata for a repository
SaveRepository(data []byte) error
}
// Error declarations.
var (
ErrRepositoryExists = errors.New("repository seems to already exist")
ErrInvalidRepositoryURL = errors.New("invalid repository url specified")
ErrAvailableSpaceUnknown = errors.New("available space is unknown or undefined")
ErrAvailableSpaceUnlimited = errors.New("available space is unlimited")
ErrInvalidUsername = errors.New("username wrong or missing")
backends = []BackendFactory{}
)
// RegisterStorageBackend needs to be called by storage backends to register
// themselves.
func RegisterStorageBackend(factory BackendFactory) {
backends = append(backends, factory)
}
func newBackendFromProtocol(url url.URL) (Backend, error) {
for _, backend := range backends {
for _, p := range backend.Protocols() {
if p == url.Scheme {
return backend.NewBackend(url)
}
}
}
return nil, ErrInvalidRepositoryURL
}
// BackendFromURL returns the matching backend for path.
func BackendFromURL(path string) (Backend, error) {
if !strings.Contains(path, "://") {
if !filepath.IsAbs(path) {
var err error
path, err = filepath.Abs(path)
if err != nil {
return nil, err
}
}
if !strings.HasPrefix(path, "/") {
path = "/" + path
}
path = "file://" + path
}
u, err := url.Parse(path)
if err != nil {
return nil, err
}
return newBackendFromProtocol(*u)
}