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