dir.go

// Copyright 2019 Denis Bernard <db047h@gmail.com>
//
// Permission to use, copy, modify, and/or distribute this software for any purpose
// with or without fee is hereby granted, provided that the above copyright notice
// and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
// FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
// OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
// TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
// THIS SOFTWARE.

package ofs

import (
	"os"
	"path"
	"path/filepath"
	"strings"

	"golang.org/x/xerrors"
)

// A Dir implements FileSystem using the native file system restricted to a
// specific directory tree.
//
// While the FileSystem.Open method takes '/'-separated paths, a Dir's string
// value is an absolute path to a directory on the native file system, not a
// URL, so it is separated by filepath.Separator, which isn't necessarily '/'.
//
// It behaves similarly to http.Dir, with the difference that the string value
// must be an absolute path and that ErrNotExist errors are not resolved to the
// first non-existing directory when Open or Create fails.
//
type Dir string

func (d Dir) check(name string) error {
	// error if dir is not absolute
	if dir := string(d); !filepath.IsAbs(dir) {
		return xerrors.Errorf("ofs: dir is not absolute %q", dir)
	}
	// error if using local os' path separators instead of '/'
	if filepath.Separator != '/' && strings.ContainsRune(name, filepath.Separator) {
		return xerrors.Errorf("ofs: invalid character in file path %q", name)
	}
	return nil
}

// Open implements FileSystem.Open.
//
func (d Dir) Open(name string) (File, error) {
	if err := d.check(name); err != nil {
		return nil, err
	}
	return os.Open(filepath.Join(string(d), filepath.FromSlash(path.Clean("/"+name))))
}

// Create implements FileSystem.Create.
//
func (d Dir) Create(name string) (File, error) {
	if err := d.check(name); err != nil {
		return nil, err
	}
	return os.Create(filepath.Join(string(d), filepath.FromSlash(path.Clean("/"+name))))
}