+++ /dev/null
-// Copyright 2011 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package vfs
-
-import (
- "fmt"
- "io"
- "os"
- pathpkg "path"
- "sort"
- "strings"
- "time"
-)
-
-// Setting debugNS = true will enable debugging prints about
-// name space translations.
-const debugNS = false
-
-// A NameSpace is a file system made up of other file systems
-// mounted at specific locations in the name space.
-//
-// The representation is a map from mount point locations
-// to the list of file systems mounted at that location. A traditional
-// Unix mount table would use a single file system per mount point,
-// but we want to be able to mount multiple file systems on a single
-// mount point and have the system behave as if the union of those
-// file systems were present at the mount point.
-// For example, if the OS file system has a Go installation in
-// c:\Go and additional Go path trees in d:\Work1 and d:\Work2, then
-// this name space creates the view we want for the godoc server:
-//
-// NameSpace{
-// "/": {
-// {old: "/", fs: OS(`c:\Go`), new: "/"},
-// },
-// "/src/pkg": {
-// {old: "/src/pkg", fs: OS(`c:\Go`), new: "/src/pkg"},
-// {old: "/src/pkg", fs: OS(`d:\Work1`), new: "/src"},
-// {old: "/src/pkg", fs: OS(`d:\Work2`), new: "/src"},
-// },
-// }
-//
-// This is created by executing:
-//
-// ns := NameSpace{}
-// ns.Bind("/", OS(`c:\Go`), "/", BindReplace)
-// ns.Bind("/src/pkg", OS(`d:\Work1`), "/src", BindAfter)
-// ns.Bind("/src/pkg", OS(`d:\Work2`), "/src", BindAfter)
-//
-// A particular mount point entry is a triple (old, fs, new), meaning that to
-// operate on a path beginning with old, replace that prefix (old) with new
-// and then pass that path to the FileSystem implementation fs.
-//
-// If you do not explicitly mount a FileSystem at the root mountpoint "/" of the
-// NameSpace like above, Stat("/") will return a "not found" error which could
-// break typical directory traversal routines. In such cases, use NewNameSpace()
-// to get a NameSpace pre-initialized with an emulated empty directory at root.
-//
-// Given this name space, a ReadDir of /src/pkg/code will check each prefix
-// of the path for a mount point (first /src/pkg/code, then /src/pkg, then /src,
-// then /), stopping when it finds one. For the above example, /src/pkg/code
-// will find the mount point at /src/pkg:
-//
-// {old: "/src/pkg", fs: OS(`c:\Go`), new: "/src/pkg"},
-// {old: "/src/pkg", fs: OS(`d:\Work1`), new: "/src"},
-// {old: "/src/pkg", fs: OS(`d:\Work2`), new: "/src"},
-//
-// ReadDir will when execute these three calls and merge the results:
-//
-// OS(`c:\Go`).ReadDir("/src/pkg/code")
-// OS(`d:\Work1').ReadDir("/src/code")
-// OS(`d:\Work2').ReadDir("/src/code")
-//
-// Note that the "/src/pkg" in "/src/pkg/code" has been replaced by
-// just "/src" in the final two calls.
-//
-// OS is itself an implementation of a file system: it implements
-// OS(`c:\Go`).ReadDir("/src/pkg/code") as ioutil.ReadDir(`c:\Go\src\pkg\code`).
-//
-// Because the new path is evaluated by fs (here OS(root)), another way
-// to read the mount table is to mentally combine fs+new, so that this table:
-//
-// {old: "/src/pkg", fs: OS(`c:\Go`), new: "/src/pkg"},
-// {old: "/src/pkg", fs: OS(`d:\Work1`), new: "/src"},
-// {old: "/src/pkg", fs: OS(`d:\Work2`), new: "/src"},
-//
-// reads as:
-//
-// "/src/pkg" -> c:\Go\src\pkg
-// "/src/pkg" -> d:\Work1\src
-// "/src/pkg" -> d:\Work2\src
-//
-// An invariant (a redundancy) of the name space representation is that
-// ns[mtpt][i].old is always equal to mtpt (in the example, ns["/src/pkg"]'s
-// mount table entries always have old == "/src/pkg"). The 'old' field is
-// useful to callers, because they receive just a []mountedFS and not any
-// other indication of which mount point was found.
-//
-type NameSpace map[string][]mountedFS
-
-// A mountedFS handles requests for path by replacing
-// a prefix 'old' with 'new' and then calling the fs methods.
-type mountedFS struct {
- old string
- fs FileSystem
- new string
-}
-
-// hasPathPrefix reports whether x == y or x == y + "/" + more.
-func hasPathPrefix(x, y string) bool {
- return x == y || strings.HasPrefix(x, y) && (strings.HasSuffix(y, "/") || strings.HasPrefix(x[len(y):], "/"))
-}
-
-// translate translates path for use in m, replacing old with new.
-//
-// mountedFS{"/src/pkg", fs, "/src"}.translate("/src/pkg/code") == "/src/code".
-func (m mountedFS) translate(path string) string {
- path = pathpkg.Clean("/" + path)
- if !hasPathPrefix(path, m.old) {
- panic("translate " + path + " but old=" + m.old)
- }
- return pathpkg.Join(m.new, path[len(m.old):])
-}
-
-func (NameSpace) String() string {
- return "ns"
-}
-
-// Fprint writes a text representation of the name space to w.
-func (ns NameSpace) Fprint(w io.Writer) {
- fmt.Fprint(w, "name space {\n")
- var all []string
- for mtpt := range ns {
- all = append(all, mtpt)
- }
- sort.Strings(all)
- for _, mtpt := range all {
- fmt.Fprintf(w, "\t%s:\n", mtpt)
- for _, m := range ns[mtpt] {
- fmt.Fprintf(w, "\t\t%s %s\n", m.fs, m.new)
- }
- }
- fmt.Fprint(w, "}\n")
-}
-
-// clean returns a cleaned, rooted path for evaluation.
-// It canonicalizes the path so that we can use string operations
-// to analyze it.
-func (NameSpace) clean(path string) string {
- return pathpkg.Clean("/" + path)
-}
-
-type BindMode int
-
-const (
- BindReplace BindMode = iota
- BindBefore
- BindAfter
-)
-
-// Bind causes references to old to redirect to the path new in newfs.
-// If mode is BindReplace, old redirections are discarded.
-// If mode is BindBefore, this redirection takes priority over existing ones,
-// but earlier ones are still consulted for paths that do not exist in newfs.
-// If mode is BindAfter, this redirection happens only after existing ones
-// have been tried and failed.
-func (ns NameSpace) Bind(old string, newfs FileSystem, new string, mode BindMode) {
- old = ns.clean(old)
- new = ns.clean(new)
- m := mountedFS{old, newfs, new}
- var mtpt []mountedFS
- switch mode {
- case BindReplace:
- mtpt = append(mtpt, m)
- case BindAfter:
- mtpt = append(mtpt, ns.resolve(old)...)
- mtpt = append(mtpt, m)
- case BindBefore:
- mtpt = append(mtpt, m)
- mtpt = append(mtpt, ns.resolve(old)...)
- }
-
- // Extend m.old, m.new in inherited mount point entries.
- for i := range mtpt {
- m := &mtpt[i]
- if m.old != old {
- if !hasPathPrefix(old, m.old) {
- // This should not happen. If it does, panic so
- // that we can see the call trace that led to it.
- panic(fmt.Sprintf("invalid Bind: old=%q m={%q, %s, %q}", old, m.old, m.fs.String(), m.new))
- }
- suffix := old[len(m.old):]
- m.old = pathpkg.Join(m.old, suffix)
- m.new = pathpkg.Join(m.new, suffix)
- }
- }
-
- ns[old] = mtpt
-}
-
-// resolve resolves a path to the list of mountedFS to use for path.
-func (ns NameSpace) resolve(path string) []mountedFS {
- path = ns.clean(path)
- for {
- if m := ns[path]; m != nil {
- if debugNS {
- fmt.Printf("resolve %s: %v\n", path, m)
- }
- return m
- }
- if path == "/" {
- break
- }
- path = pathpkg.Dir(path)
- }
- return nil
-}
-
-// Open implements the FileSystem Open method.
-func (ns NameSpace) Open(path string) (ReadSeekCloser, error) {
- var err error
- for _, m := range ns.resolve(path) {
- if debugNS {
- fmt.Printf("tx %s: %v\n", path, m.translate(path))
- }
- tp := m.translate(path)
- r, err1 := m.fs.Open(tp)
- if err1 == nil {
- return r, nil
- }
- // IsNotExist errors in overlay FSes can mask real errors in
- // the underlying FS, so ignore them if there is another error.
- if err == nil || os.IsNotExist(err) {
- err = err1
- }
- }
- if err == nil {
- err = &os.PathError{Op: "open", Path: path, Err: os.ErrNotExist}
- }
- return nil, err
-}
-
-// stat implements the FileSystem Stat and Lstat methods.
-func (ns NameSpace) stat(path string, f func(FileSystem, string) (os.FileInfo, error)) (os.FileInfo, error) {
- var err error
- for _, m := range ns.resolve(path) {
- fi, err1 := f(m.fs, m.translate(path))
- if err1 == nil {
- return fi, nil
- }
- if err == nil {
- err = err1
- }
- }
- if err == nil {
- err = &os.PathError{Op: "stat", Path: path, Err: os.ErrNotExist}
- }
- return nil, err
-}
-
-func (ns NameSpace) Stat(path string) (os.FileInfo, error) {
- return ns.stat(path, FileSystem.Stat)
-}
-
-func (ns NameSpace) Lstat(path string) (os.FileInfo, error) {
- return ns.stat(path, FileSystem.Lstat)
-}
-
-// dirInfo is a trivial implementation of os.FileInfo for a directory.
-type dirInfo string
-
-func (d dirInfo) Name() string { return string(d) }
-func (d dirInfo) Size() int64 { return 0 }
-func (d dirInfo) Mode() os.FileMode { return os.ModeDir | 0555 }
-func (d dirInfo) ModTime() time.Time { return startTime }
-func (d dirInfo) IsDir() bool { return true }
-func (d dirInfo) Sys() interface{} { return nil }
-
-var startTime = time.Now()
-
-// ReadDir implements the FileSystem ReadDir method. It's where most of the magic is.
-// (The rest is in resolve.)
-//
-// Logically, ReadDir must return the union of all the directories that are named
-// by path. In order to avoid misinterpreting Go packages, of all the directories
-// that contain Go source code, we only include the files from the first,
-// but we include subdirectories from all.
-//
-// ReadDir must also return directory entries needed to reach mount points.
-// If the name space looks like the example in the type NameSpace comment,
-// but c:\Go does not have a src/pkg subdirectory, we still want to be able
-// to find that subdirectory, because we've mounted d:\Work1 and d:\Work2
-// there. So if we don't see "src" in the directory listing for c:\Go, we add an
-// entry for it before returning.
-//
-func (ns NameSpace) ReadDir(path string) ([]os.FileInfo, error) {
- path = ns.clean(path)
-
- // List matching directories and determine whether any of them contain
- // Go files.
- var (
- dirs [][]os.FileInfo
- goDirIndex = -1
- readDirErr error
- )
-
- for _, m := range ns.resolve(path) {
- dir, err := m.fs.ReadDir(m.translate(path))
- if err != nil {
- if readDirErr == nil {
- readDirErr = err
- }
- continue
- }
-
- dirs = append(dirs, dir)
-
- if goDirIndex < 0 {
- for _, f := range dir {
- if !f.IsDir() && strings.HasSuffix(f.Name(), ".go") {
- goDirIndex = len(dirs) - 1
- break
- }
- }
- }
- }
-
- // Build a list of files and subdirectories. If a directory contains Go files,
- // only include files from that directory. Otherwise, include files from
- // all directories. Include subdirectories from all directories regardless
- // of whether Go files are present.
- haveName := make(map[string]bool)
- var all []os.FileInfo
- for i, dir := range dirs {
- for _, f := range dir {
- name := f.Name()
- if !haveName[name] && (f.IsDir() || goDirIndex < 0 || goDirIndex == i) {
- all = append(all, f)
- haveName[name] = true
- }
- }
- }
-
- // Add any missing directories needed to reach mount points.
- for old := range ns {
- if hasPathPrefix(old, path) && old != path {
- // Find next element after path in old.
- elem := old[len(path):]
- elem = strings.TrimPrefix(elem, "/")
- if i := strings.Index(elem, "/"); i >= 0 {
- elem = elem[:i]
- }
- if !haveName[elem] {
- haveName[elem] = true
- all = append(all, dirInfo(elem))
- }
- }
- }
-
- if len(all) == 0 {
- return nil, readDirErr
- }
-
- sort.Sort(byName(all))
- return all, nil
-}
-
-// RootType returns the RootType for the given path in the namespace.
-func (ns NameSpace) RootType(path string) RootType {
- // We resolve the given path to a list of mountedFS and then return
- // the root type for the filesystem which contains the path.
- for _, m := range ns.resolve(path) {
- _, err := m.fs.ReadDir(m.translate(path))
- // Found a match, return the filesystem's root type
- if err == nil {
- return m.fs.RootType(path)
- }
- }
- return ""
-}
-
-// byName implements sort.Interface.
-type byName []os.FileInfo
-
-func (f byName) Len() int { return len(f) }
-func (f byName) Less(i, j int) bool { return f[i].Name() < f[j].Name() }
-func (f byName) Swap(i, j int) { f[i], f[j] = f[j], f[i] }
projects / dotfiles / .git / blobdiff