From ccde149531d740ff3c9e47658fae88a96080a405 Mon Sep 17 00:00:00 2001 From: James Shubin Date: Thu, 22 Feb 2024 12:29:47 -0500 Subject: [PATCH] Add new relpath filesystem This new filesystem implements a relative filesystem modifier which can be useful for converting between absolute filesystems rooted at / and relative ones. This is particularly useful when interfacing with the golang embed package. --- relpath.go | 216 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 216 insertions(+) create mode 100644 relpath.go diff --git a/relpath.go b/relpath.go new file mode 100644 index 00000000..91ae6622 --- /dev/null +++ b/relpath.go @@ -0,0 +1,216 @@ +// Copyright (C) 2024+ James Shubin +// Written by James Shubin +// This filesystem implementation is based on the afero.BasePathFs code. +package afero + +import ( + "io/fs" + "os" + "path/filepath" + "strings" + "time" +) + +var ( + _ Lstater = (*RelPathFs)(nil) + _ fs.ReadDirFile = (*RelPathFile)(nil) + _ fs.ReadDirFile = readDirFile{} +) + +// RelPathFs removes a prefix from all operations to a given path within an Fs. +// The given file name to the operations on this Fs will have a prefix removed +// before calling the base Fs. +// +// When initializing it with "/", a call to `/foo` turns into `foo`. +// +// Note that it does not clean the error messages on return, so you may reveal +// the real path on errors. +type RelPathFs struct { + source Fs + + prefix string +} + +type RelPathFile struct { + File + + prefix string +} + +func (obj *RelPathFile) Name() string { + sourcename := obj.File.Name() + //return strings.TrimPrefix(sourcename, filepath.Clean(obj.prefix)) + return filepath.Clean(obj.prefix) + sourcename // add prefix back on +} + +func (obj *RelPathFile) ReadDir(n int) ([]fs.DirEntry, error) { + if rdf, ok := obj.File.(fs.ReadDirFile); ok { + return rdf.ReadDir(n) + } + return readDirFile{obj.File}.ReadDir(n) +} + +// NewRelPathFs creates a new RelPathFs. +func NewRelPathFs(source Fs, prefix string) Fs { + return &RelPathFs{source: source, prefix: prefix} +} + +// on a file outside the base path it returns the given file name and an error, +// else the given file with the base path removed +func (obj *RelPathFs) RealPath(name string) (string, error) { + if name == "/" { + return ".", nil // special trim + } + if name == "" { + return filepath.Clean(name), nil // returns a single period + } + path := filepath.Clean(name) // actual path + prefix := filepath.Clean(obj.prefix) // is often a / and we trim it off + + //if strings.HasPrefix(path, prefix) { // redundant + path = strings.TrimPrefix(path, prefix) + //} + + return path, nil +} + +func (obj *RelPathFs) Chtimes(name string, atime, mtime time.Time) (err error) { + if name, err = obj.RealPath(name); err != nil { + return &os.PathError{Op: "chtimes", Path: name, Err: err} + } + return obj.source.Chtimes(name, atime, mtime) +} + +func (obj *RelPathFs) Chmod(name string, mode os.FileMode) (err error) { + if name, err = obj.RealPath(name); err != nil { + return &os.PathError{Op: "chmod", Path: name, Err: err} + } + return obj.source.Chmod(name, mode) +} + +func (obj *RelPathFs) Chown(name string, uid, gid int) (err error) { + if name, err = obj.RealPath(name); err != nil { + return &os.PathError{Op: "chown", Path: name, Err: err} + } + return obj.source.Chown(name, uid, gid) +} + +func (obj *RelPathFs) Name() string { + return "RelPathFs" +} + +func (obj *RelPathFs) Stat(name string) (fi os.FileInfo, err error) { + if name, err = obj.RealPath(name); err != nil { + return nil, &os.PathError{Op: "stat", Path: name, Err: err} + } + return obj.source.Stat(name) +} + +func (obj *RelPathFs) Rename(oldname, newname string) (err error) { + if oldname, err = obj.RealPath(oldname); err != nil { + return &os.PathError{Op: "rename", Path: oldname, Err: err} + } + if newname, err = obj.RealPath(newname); err != nil { + return &os.PathError{Op: "rename", Path: newname, Err: err} + } + return obj.source.Rename(oldname, newname) +} + +func (obj *RelPathFs) RemoveAll(name string) (err error) { + if name, err = obj.RealPath(name); err != nil { + return &os.PathError{Op: "remove_all", Path: name, Err: err} + } + return obj.source.RemoveAll(name) +} + +func (obj *RelPathFs) Remove(name string) (err error) { + if name, err = obj.RealPath(name); err != nil { + return &os.PathError{Op: "remove", Path: name, Err: err} + } + return obj.source.Remove(name) +} + +func (obj *RelPathFs) OpenFile(name string, flag int, mode os.FileMode) (f File, err error) { + if name, err = obj.RealPath(name); err != nil { + return nil, &os.PathError{Op: "openfile", Path: name, Err: err} + } + sourcef, err := obj.source.OpenFile(name, flag, mode) + if err != nil { + return nil, err + } + return &RelPathFile{File: sourcef, prefix: obj.prefix}, nil +} + +func (obj *RelPathFs) Open(name string) (f File, err error) { + if name, err = obj.RealPath(name); err != nil { + return nil, &os.PathError{Op: "open", Path: name, Err: err} + } + sourcef, err := obj.source.Open(name) + if err != nil { + return nil, err + } + return &RelPathFile{File: sourcef, prefix: obj.prefix}, nil +} + +func (obj *RelPathFs) Mkdir(name string, mode os.FileMode) (err error) { + if name, err = obj.RealPath(name); err != nil { + return &os.PathError{Op: "mkdir", Path: name, Err: err} + } + return obj.source.Mkdir(name, mode) +} + +func (obj *RelPathFs) MkdirAll(name string, mode os.FileMode) (err error) { + if name, err = obj.RealPath(name); err != nil { + return &os.PathError{Op: "mkdir", Path: name, Err: err} + } + return obj.source.MkdirAll(name, mode) +} + +func (obj *RelPathFs) Create(name string) (f File, err error) { + if name, err = obj.RealPath(name); err != nil { + return nil, &os.PathError{Op: "create", Path: name, Err: err} + } + sourcef, err := obj.source.Create(name) + if err != nil { + return nil, err + } + return &RelPathFile{File: sourcef, prefix: obj.prefix}, nil +} + +func (obj *RelPathFs) LstatIfPossible(name string) (os.FileInfo, bool, error) { + name, err := obj.RealPath(name) + if err != nil { + return nil, false, &os.PathError{Op: "lstat", Path: name, Err: err} + } + if lstater, ok := obj.source.(Lstater); ok { + return lstater.LstatIfPossible(name) + } + fi, err := obj.source.Stat(name) + return fi, false, err +} + +func (obj *RelPathFs) SymlinkIfPossible(oldname, newname string) error { + oldname, err := obj.RealPath(oldname) + if err != nil { + return &os.LinkError{Op: "symlink", Old: oldname, New: newname, Err: err} + } + newname, err = obj.RealPath(newname) + if err != nil { + return &os.LinkError{Op: "symlink", Old: oldname, New: newname, Err: err} + } + if linker, ok := obj.source.(Linker); ok { + return linker.SymlinkIfPossible(oldname, newname) + } + return &os.LinkError{Op: "symlink", Old: oldname, New: newname, Err: ErrNoSymlink} +} + +func (obj *RelPathFs) ReadlinkIfPossible(name string) (string, error) { + name, err := obj.RealPath(name) + if err != nil { + return "", &os.PathError{Op: "readlink", Path: name, Err: err} + } + if reader, ok := obj.source.(LinkReader); ok { + return reader.ReadlinkIfPossible(name) + } + return "", &os.PathError{Op: "readlink", Path: name, Err: ErrNoReadlink} +}