219 lines
5.4 KiB
Go
219 lines
5.4 KiB
Go
// Copyright 2009 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 path implements utility routines for manipulating slash-separated
|
|
// paths.
|
|
package path
|
|
|
|
import (
|
|
"strings"
|
|
)
|
|
|
|
// A lazybuf is a lazily constructed path buffer.
|
|
// It supports append, reading previously appended bytes,
|
|
// and retrieving the final string. It does not allocate a buffer
|
|
// to hold the output until that output diverges from s.
|
|
type lazybuf struct {
|
|
s string
|
|
buf []byte
|
|
w int
|
|
}
|
|
|
|
func (b *lazybuf) index(i int) byte {
|
|
if b.buf != nil {
|
|
return b.buf[i]
|
|
}
|
|
return b.s[i]
|
|
}
|
|
|
|
func (b *lazybuf) append(c byte) {
|
|
if b.buf == nil {
|
|
if b.w < len(b.s) && b.s[b.w] == c {
|
|
b.w++
|
|
return
|
|
}
|
|
b.buf = make([]byte, len(b.s))
|
|
copy(b.buf, b.s[:b.w])
|
|
}
|
|
b.buf[b.w] = c
|
|
b.w++
|
|
}
|
|
|
|
func (b *lazybuf) string() string {
|
|
if b.buf == nil {
|
|
return b.s[:b.w]
|
|
}
|
|
return string(b.buf[:b.w])
|
|
}
|
|
|
|
// Clean returns the shortest path name equivalent to path
|
|
// by purely lexical processing. It applies the following rules
|
|
// iteratively until no further processing can be done:
|
|
//
|
|
// 1. Replace multiple slashes with a single slash.
|
|
// 2. Eliminate each . path name element (the current directory).
|
|
// 3. Eliminate each inner .. path name element (the parent directory)
|
|
// along with the non-.. element that precedes it.
|
|
// 4. Eliminate .. elements that begin a rooted path:
|
|
// that is, replace "/.." by "/" at the beginning of a path.
|
|
//
|
|
// The returned path ends in a slash only if it is the root "/".
|
|
//
|
|
// If the result of this process is an empty string, Clean
|
|
// returns the string ".".
|
|
//
|
|
// See also Rob Pike, ``Lexical File Names in Plan 9 or
|
|
// Getting Dot-Dot Right,''
|
|
// http://plan9.bell-labs.com/sys/doc/lexnames.html
|
|
func Clean(path string) string {
|
|
if path == "" {
|
|
return "."
|
|
}
|
|
|
|
rooted := path[0] == '/'
|
|
n := len(path)
|
|
|
|
// Invariants:
|
|
// reading from path; r is index of next byte to process.
|
|
// writing to buf; w is index of next byte to write.
|
|
// dotdot is index in buf where .. must stop, either because
|
|
// it is the leading slash or it is a leading ../../.. prefix.
|
|
out := lazybuf{s: path}
|
|
r, dotdot := 0, 0
|
|
if rooted {
|
|
out.append('/')
|
|
r, dotdot = 1, 1
|
|
}
|
|
|
|
for r < n {
|
|
switch {
|
|
case path[r] == '/':
|
|
// empty path element
|
|
r++
|
|
case path[r] == '.' && (r+1 == n || path[r+1] == '/'):
|
|
// . element
|
|
r++
|
|
case path[r] == '.' && path[r+1] == '.' && (r+2 == n || path[r+2] == '/'):
|
|
// .. element: remove to last /
|
|
r += 2
|
|
switch {
|
|
case out.w > dotdot:
|
|
// can backtrack
|
|
out.w--
|
|
for out.w > dotdot && out.index(out.w) != '/' {
|
|
out.w--
|
|
}
|
|
case !rooted:
|
|
// cannot backtrack, but not rooted, so append .. element.
|
|
if out.w > 0 {
|
|
out.append('/')
|
|
}
|
|
out.append('.')
|
|
out.append('.')
|
|
dotdot = out.w
|
|
}
|
|
default:
|
|
// real path element.
|
|
// add slash if needed
|
|
if rooted && out.w != 1 || !rooted && out.w != 0 {
|
|
out.append('/')
|
|
}
|
|
// copy element
|
|
for ; r < n && path[r] != '/'; r++ {
|
|
out.append(path[r])
|
|
}
|
|
}
|
|
}
|
|
|
|
// Turn empty string into "."
|
|
if out.w == 0 {
|
|
return "."
|
|
}
|
|
|
|
return out.string()
|
|
}
|
|
|
|
// Split splits path immediately following the final slash.
|
|
// separating it into a directory and file name component.
|
|
// If there is no slash path, Split returns an empty dir and
|
|
// file set to path.
|
|
// The returned values have the property that path = dir+file.
|
|
func Split(path string) (dir, file string) {
|
|
i := strings.LastIndex(path, "/")
|
|
return path[:i+1], path[i+1:]
|
|
}
|
|
|
|
// Join joins any number of path elements into a single path, adding a
|
|
// separating slash if necessary. The result is Cleaned; in particular,
|
|
// all empty strings are ignored.
|
|
func Join(elem ...string) string {
|
|
for i, e := range elem {
|
|
if e != "" {
|
|
return Clean(strings.Join(elem[i:], "/"))
|
|
}
|
|
}
|
|
return ""
|
|
}
|
|
|
|
// Ext returns the file name extension used by path.
|
|
// The extension is the suffix beginning at the final dot
|
|
// in the final slash-separated element of path;
|
|
// it is empty if there is no dot.
|
|
func Ext(path string) string {
|
|
for i := len(path) - 1; i >= 0 && path[i] != '/'; i-- {
|
|
if path[i] == '.' {
|
|
return path[i:]
|
|
}
|
|
}
|
|
return ""
|
|
}
|
|
|
|
// Base returns the last element of path.
|
|
// Trailing slashes are removed before extracting the last element.
|
|
// If the path is empty, Base returns ".".
|
|
// If the path consists entirely of slashes, Base returns "/".
|
|
func Base(path string) string {
|
|
if path == "" {
|
|
return "."
|
|
}
|
|
// Strip trailing slashes.
|
|
for len(path) > 0 && path[len(path)-1] == '/' {
|
|
path = path[0 : len(path)-1]
|
|
}
|
|
// Find the last element
|
|
if i := strings.LastIndex(path, "/"); i >= 0 {
|
|
path = path[i+1:]
|
|
}
|
|
// If empty now, it had only slashes.
|
|
if path == "" {
|
|
return "/"
|
|
}
|
|
return path
|
|
}
|
|
|
|
// IsAbs returns true if the path is absolute.
|
|
func IsAbs(path string) bool {
|
|
return len(path) > 0 && path[0] == '/'
|
|
}
|
|
|
|
// Dir returns all but the last element of path, typically the path's directory.
|
|
// After dropping the final element using Split, the path is Cleaned and trailing
|
|
// slashes are removed.
|
|
// If the path is empty, Dir returns ".".
|
|
// If the path consists entirely of slashes followed by non-slash bytes, Dir
|
|
// returns a single slash. In any other case, the returned path does not end in a
|
|
// slash.
|
|
func Dir(path string) string {
|
|
dir, _ := Split(path)
|
|
dir = Clean(dir)
|
|
last := len(dir) - 1
|
|
if last > 0 && dir[last] == '/' {
|
|
dir = dir[:last]
|
|
}
|
|
if dir == "" {
|
|
dir = "."
|
|
}
|
|
return dir
|
|
}
|