120 lines
3.2 KiB
Go
120 lines
3.2 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package fs
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import (
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"path/filepath"
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"strings"
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)
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// TrimTrailingSlashes trims any trailing slashes.
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//
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// The returned boolean indicates whether any changes were made.
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//
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//go:nosplit
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func TrimTrailingSlashes(dir string) (trimmed string, changed bool) {
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// Trim the trailing slash, except for root.
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for len(dir) > 1 && dir[len(dir)-1] == '/' {
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dir = dir[:len(dir)-1]
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changed = true
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}
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return dir, changed
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}
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// SplitLast splits the given path into a directory and a file.
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//
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// The "absoluteness" of the path is preserved, but dir is always stripped of
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// trailing slashes.
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//
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//go:nosplit
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func SplitLast(path string) (dir, file string) {
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path, _ = TrimTrailingSlashes(path)
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if path == "" {
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return ".", "."
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} else if path == "/" {
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return "/", "."
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}
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var slash int // Last location of slash in path.
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for slash = len(path) - 1; slash >= 0 && path[slash] != '/'; slash-- {
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}
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switch {
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case slash < 0:
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return ".", path
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case slash == 0:
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// Directory of the form "/foo", or just "/". We need to
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// preserve the first slash here, since it indicates an
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// absolute path.
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return "/", path[1:]
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default:
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// Drop the trailing slash.
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dir, _ = TrimTrailingSlashes(path[:slash])
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return dir, path[slash+1:]
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}
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}
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// SplitFirst splits the given path into a first directory and the remainder.
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//
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// If remainder is empty, then the path is a single element.
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//
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//go:nosplit
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func SplitFirst(path string) (current, remainder string) {
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path, _ = TrimTrailingSlashes(path)
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if path == "" {
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return ".", ""
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}
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var slash int // First location of slash in path.
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for slash = 0; slash < len(path) && path[slash] != '/'; slash++ {
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}
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switch {
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case slash >= len(path):
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return path, ""
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case slash == 0:
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// See above.
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return "/", path[1:]
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default:
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current = path[:slash]
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remainder = path[slash+1:]
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// Strip redundant slashes.
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for len(remainder) > 0 && remainder[0] == '/' {
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remainder = remainder[1:]
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}
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return current, remainder
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}
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}
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// IsSubpath checks whether the first path is a (strict) descendent of the
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// second. If it is a subpath, then true is returned along with a clean
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// relative path from the second path to the first. Otherwise false is
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// returned.
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func IsSubpath(subpath, path string) (string, bool) {
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cleanPath := filepath.Clean(path)
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cleanSubpath := filepath.Clean(subpath)
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// Add a trailing slash to the path if it does not already have one.
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if len(cleanPath) == 0 || cleanPath[len(cleanPath)-1] != '/' {
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cleanPath += "/"
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}
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if cleanPath == cleanSubpath {
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// Paths are equal, thus not a strict subpath.
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return "", false
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}
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if strings.HasPrefix(cleanSubpath, cleanPath) {
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return strings.TrimPrefix(cleanSubpath, cleanPath), true
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}
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return "", false
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}
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