diff options
Diffstat (limited to 'src/internal/filepathlite/path.go')
-rw-r--r-- | src/internal/filepathlite/path.go | 262 |
1 files changed, 255 insertions, 7 deletions
diff --git a/src/internal/filepathlite/path.go b/src/internal/filepathlite/path.go index b452987b6be..e3daa447d97 100644 --- a/src/internal/filepathlite/path.go +++ b/src/internal/filepathlite/path.go @@ -1,26 +1,274 @@ -// Copyright 2022 The Go Authors. All rights reserved. +// Copyright 2024 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 filepathlite manipulates operating-system file paths. +// Package filepathlite implements a subset of path/filepath, +// only using packages which may be imported by "os". +// +// Tests for these functions are in path/filepath. package filepathlite import ( "errors" + "internal/stringslite" "io/fs" + "slices" ) var errInvalidPath = errors.New("invalid path") +// 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 { + path string + buf []byte + w int + volAndPath string + volLen int +} + +func (b *lazybuf) index(i int) byte { + if b.buf != nil { + return b.buf[i] + } + return b.path[i] +} + +func (b *lazybuf) append(c byte) { + if b.buf == nil { + if b.w < len(b.path) && b.path[b.w] == c { + b.w++ + return + } + b.buf = make([]byte, len(b.path)) + copy(b.buf, b.path[:b.w]) + } + b.buf[b.w] = c + b.w++ +} + +func (b *lazybuf) prepend(prefix ...byte) { + b.buf = slices.Insert(b.buf, 0, prefix...) + b.w += len(prefix) +} + +func (b *lazybuf) string() string { + if b.buf == nil { + return b.volAndPath[:b.volLen+b.w] + } + return b.volAndPath[:b.volLen] + string(b.buf[:b.w]) +} + +// Clean is filepath.Clean. +func Clean(path string) string { + originalPath := path + volLen := volumeNameLen(path) + path = path[volLen:] + if path == "" { + if volLen > 1 && IsPathSeparator(originalPath[0]) && IsPathSeparator(originalPath[1]) { + // should be UNC + return FromSlash(originalPath) + } + return originalPath + "." + } + rooted := IsPathSeparator(path[0]) + + // 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. + n := len(path) + out := lazybuf{path: path, volAndPath: originalPath, volLen: volLen} + r, dotdot := 0, 0 + if rooted { + out.append(Separator) + r, dotdot = 1, 1 + } + + for r < n { + switch { + case IsPathSeparator(path[r]): + // empty path element + r++ + case path[r] == '.' && (r+1 == n || IsPathSeparator(path[r+1])): + // . element + r++ + case path[r] == '.' && path[r+1] == '.' && (r+2 == n || IsPathSeparator(path[r+2])): + // .. element: remove to last separator + r += 2 + switch { + case out.w > dotdot: + // can backtrack + out.w-- + for out.w > dotdot && !IsPathSeparator(out.index(out.w)) { + out.w-- + } + case !rooted: + // cannot backtrack, but not rooted, so append .. element. + if out.w > 0 { + out.append(Separator) + } + 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(Separator) + } + // copy element + for ; r < n && !IsPathSeparator(path[r]); r++ { + out.append(path[r]) + } + } + } + + // Turn empty string into "." + if out.w == 0 { + out.append('.') + } + + postClean(&out) // avoid creating absolute paths on Windows + return FromSlash(out.string()) +} + +// IsLocal is filepath.IsLocal. +func IsLocal(path string) bool { + return isLocal(path) +} + +func unixIsLocal(path string) bool { + if IsAbs(path) || path == "" { + return false + } + hasDots := false + for p := path; p != ""; { + var part string + part, p, _ = stringslite.Cut(p, "/") + if part == "." || part == ".." { + hasDots = true + break + } + } + if hasDots { + path = Clean(path) + } + if path == ".." || stringslite.HasPrefix(path, "../") { + return false + } + return true +} + // Localize is filepath.Localize. -// -// It is implemented in this package to avoid a dependency cycle -// between os and file/filepath. -// -// Tests for this function are in path/filepath. func Localize(path string) (string, error) { if !fs.ValidPath(path) { return "", errInvalidPath } return localize(path) } + +// ToSlash is filepath.ToSlash. +func ToSlash(path string) string { + if Separator == '/' { + return path + } + return replaceStringByte(path, Separator, '/') +} + +// FromSlash is filepath.ToSlash. +func FromSlash(path string) string { + if Separator == '/' { + return path + } + return replaceStringByte(path, '/', Separator) +} + +func replaceStringByte(s string, old, new byte) string { + if stringslite.IndexByte(s, old) == -1 { + return s + } + n := []byte(s) + for i := range n { + if n[i] == old { + n[i] = new + } + } + return string(n) +} + +// Split is filepath.Split. +func Split(path string) (dir, file string) { + vol := VolumeName(path) + i := len(path) - 1 + for i >= len(vol) && !IsPathSeparator(path[i]) { + i-- + } + return path[:i+1], path[i+1:] +} + +// Ext is filepath.Ext. +func Ext(path string) string { + for i := len(path) - 1; i >= 0 && !IsPathSeparator(path[i]); i-- { + if path[i] == '.' { + return path[i:] + } + } + return "" +} + +// Base is filepath.Base. +func Base(path string) string { + if path == "" { + return "." + } + // Strip trailing slashes. + for len(path) > 0 && IsPathSeparator(path[len(path)-1]) { + path = path[0 : len(path)-1] + } + // Throw away volume name + path = path[len(VolumeName(path)):] + // Find the last element + i := len(path) - 1 + for i >= 0 && !IsPathSeparator(path[i]) { + i-- + } + if i >= 0 { + path = path[i+1:] + } + // If empty now, it had only slashes. + if path == "" { + return string(Separator) + } + return path +} + +// Dir is filepath.Dir. +func Dir(path string) string { + vol := VolumeName(path) + i := len(path) - 1 + for i >= len(vol) && !IsPathSeparator(path[i]) { + i-- + } + dir := Clean(path[len(vol) : i+1]) + if dir == "." && len(vol) > 2 { + // must be UNC + return vol + } + return vol + dir +} + +// VolumeName is filepath.VolumeName. +func VolumeName(path string) string { + return FromSlash(path[:volumeNameLen(path)]) +} + +// VolumeNameLen returns the length of the leading volume name on Windows. +// It returns 0 elsewhere. +func VolumeNameLen(path string) int { + return volumeNameLen(path) +} |