distribution/storagedriver/base/base.go
Stephen J Day f265a29f24 Move shared checks to base storage driver
This changeset moves common checks from driver implementations into base
package. The Base type can be embedded in a driver implementation, ensuring
that incoming arguments are checked for validity.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
2015-02-03 17:05:50 -08:00

141 lines
4.3 KiB
Go

// Package base provides a base implementation of the storage driver that can
// be used to implement common checks. The goal is to increase the amount of
// code sharing.
//
// The canonical approach to use this class is to embed in the exported driver
// struct such that calls are proxied through this implementation. First,
// declare the internal driver, as follows:
//
// type driver struct { ... internal ...}
//
// The resulting type should implement StorageDriver such that it can be the
// target of a Base struct. The exported type can then be declared as follows:
//
// type Driver struct {
// Base
// }
//
// Because Driver embeds Base, it effectively implements Base. If the driver
// needs to intercept a call, before going to base, Driver should implement
// that method. Effectively, Driver can intercept calls before coming in and
// driver implements the actual logic.
//
// To further shield the embed from other packages, it is recommended to
// employ a private embed struct:
//
// type baseEmbed struct {
// base.Base
// }
//
// Then, declare driver to embed baseEmbed, rather than Base directly:
//
// type Driver struct {
// baseEmbed
// }
//
// The type now implements StorageDriver, proxying through Base, without
// exporting an unnessecary field.
package base
import (
"io"
"github.com/docker/distribution/storagedriver"
)
// Base provides a wrapper around a storagedriver implementation that provides
// common path and bounds checking.
type Base struct {
storagedriver.StorageDriver
}
// GetContent wraps GetContent of underlying storage driver.
func (base *Base) GetContent(path string) ([]byte, error) {
if !storagedriver.PathRegexp.MatchString(path) {
return nil, storagedriver.InvalidPathError{Path: path}
}
return base.StorageDriver.GetContent(path)
}
// PutContent wraps PutContent of underlying storage driver.
func (base *Base) PutContent(path string, content []byte) error {
if !storagedriver.PathRegexp.MatchString(path) {
return storagedriver.InvalidPathError{Path: path}
}
return base.StorageDriver.PutContent(path, content)
}
// ReadStream wraps ReadStream of underlying storage driver.
func (base *Base) ReadStream(path string, offset int64) (io.ReadCloser, error) {
if offset < 0 {
return nil, storagedriver.InvalidOffsetError{Path: path, Offset: offset}
}
if !storagedriver.PathRegexp.MatchString(path) {
return nil, storagedriver.InvalidPathError{Path: path}
}
return base.StorageDriver.ReadStream(path, offset)
}
// WriteStream wraps WriteStream of underlying storage driver.
func (base *Base) WriteStream(path string, offset int64, reader io.Reader) (nn int64, err error) {
if offset < 0 {
return 0, storagedriver.InvalidOffsetError{Path: path, Offset: offset}
}
if !storagedriver.PathRegexp.MatchString(path) {
return 0, storagedriver.InvalidPathError{Path: path}
}
return base.StorageDriver.WriteStream(path, offset, reader)
}
// Stat wraps Stat of underlying storage driver.
func (base *Base) Stat(path string) (storagedriver.FileInfo, error) {
if !storagedriver.PathRegexp.MatchString(path) {
return nil, storagedriver.InvalidPathError{Path: path}
}
return base.StorageDriver.Stat(path)
}
// List wraps List of underlying storage driver.
func (base *Base) List(path string) ([]string, error) {
if !storagedriver.PathRegexp.MatchString(path) && path != "/" {
return nil, storagedriver.InvalidPathError{Path: path}
}
return base.StorageDriver.List(path)
}
// Move wraps Move of underlying storage driver.
func (base *Base) Move(sourcePath string, destPath string) error {
if !storagedriver.PathRegexp.MatchString(sourcePath) {
return storagedriver.InvalidPathError{Path: sourcePath}
} else if !storagedriver.PathRegexp.MatchString(destPath) {
return storagedriver.InvalidPathError{Path: destPath}
}
return base.StorageDriver.Move(sourcePath, destPath)
}
// Delete wraps Delete of underlying storage driver.
func (base *Base) Delete(path string) error {
if !storagedriver.PathRegexp.MatchString(path) {
return storagedriver.InvalidPathError{Path: path}
}
return base.StorageDriver.Delete(path)
}
// URLFor wraps URLFor of underlying storage driver.
func (base *Base) URLFor(path string, options map[string]interface{}) (string, error) {
if !storagedriver.PathRegexp.MatchString(path) {
return "", storagedriver.InvalidPathError{Path: path}
}
return base.StorageDriver.URLFor(path, options)
}