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dex/vendor/github.com/containerd/continuity/fs/path.go

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2020-01-31 09:32:00 +00:00
/*
Copyright The containerd 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 (
"bytes"
"context"
"io"
"os"
"path/filepath"
"github.com/pkg/errors"
)
var (
errTooManyLinks = errors.New("too many links")
)
type currentPath struct {
path string
f os.FileInfo
fullPath string
}
func pathChange(lower, upper *currentPath) (ChangeKind, string) {
if lower == nil {
if upper == nil {
panic("cannot compare nil paths")
}
return ChangeKindAdd, upper.path
}
if upper == nil {
return ChangeKindDelete, lower.path
}
switch i := directoryCompare(lower.path, upper.path); {
case i < 0:
// File in lower that is not in upper
return ChangeKindDelete, lower.path
case i > 0:
// File in upper that is not in lower
return ChangeKindAdd, upper.path
default:
return ChangeKindModify, upper.path
}
}
func directoryCompare(a, b string) int {
l := len(a)
if len(b) < l {
l = len(b)
}
for i := 0; i < l; i++ {
c1, c2 := a[i], b[i]
if c1 == filepath.Separator {
c1 = byte(0)
}
if c2 == filepath.Separator {
c2 = byte(0)
}
if c1 < c2 {
return -1
}
if c1 > c2 {
return +1
}
}
if len(a) < len(b) {
return -1
}
if len(a) > len(b) {
return +1
}
return 0
}
func sameFile(f1, f2 *currentPath) (bool, error) {
if os.SameFile(f1.f, f2.f) {
return true, nil
}
equalStat, err := compareSysStat(f1.f.Sys(), f2.f.Sys())
if err != nil || !equalStat {
return equalStat, err
}
if eq, err := compareCapabilities(f1.fullPath, f2.fullPath); err != nil || !eq {
return eq, err
}
// If not a directory also check size, modtime, and content
if !f1.f.IsDir() {
if f1.f.Size() != f2.f.Size() {
return false, nil
}
t1 := f1.f.ModTime()
t2 := f2.f.ModTime()
if t1.Unix() != t2.Unix() {
return false, nil
}
// If the timestamp may have been truncated in both of the
// files, check content of file to determine difference
if t1.Nanosecond() == 0 && t2.Nanosecond() == 0 {
var eq bool
if (f1.f.Mode() & os.ModeSymlink) == os.ModeSymlink {
eq, err = compareSymlinkTarget(f1.fullPath, f2.fullPath)
} else if f1.f.Size() > 0 {
eq, err = compareFileContent(f1.fullPath, f2.fullPath)
}
if err != nil || !eq {
return eq, err
}
} else if t1.Nanosecond() != t2.Nanosecond() {
return false, nil
}
}
return true, nil
}
func compareSymlinkTarget(p1, p2 string) (bool, error) {
t1, err := os.Readlink(p1)
if err != nil {
return false, err
}
t2, err := os.Readlink(p2)
if err != nil {
return false, err
}
return t1 == t2, nil
}
const compareChuckSize = 32 * 1024
// compareFileContent compares the content of 2 same sized files
// by comparing each byte.
func compareFileContent(p1, p2 string) (bool, error) {
f1, err := os.Open(p1)
if err != nil {
return false, err
}
defer f1.Close()
f2, err := os.Open(p2)
if err != nil {
return false, err
}
defer f2.Close()
b1 := make([]byte, compareChuckSize)
b2 := make([]byte, compareChuckSize)
for {
n1, err1 := f1.Read(b1)
if err1 != nil && err1 != io.EOF {
return false, err1
}
n2, err2 := f2.Read(b2)
if err2 != nil && err2 != io.EOF {
return false, err2
}
if n1 != n2 || !bytes.Equal(b1[:n1], b2[:n2]) {
return false, nil
}
if err1 == io.EOF && err2 == io.EOF {
return true, nil
}
}
}
func pathWalk(ctx context.Context, root string, pathC chan<- *currentPath) error {
return filepath.Walk(root, func(path string, f os.FileInfo, err error) error {
if err != nil {
return err
}
// Rebase path
path, err = filepath.Rel(root, path)
if err != nil {
return err
}
path = filepath.Join(string(os.PathSeparator), path)
// Skip root
if path == string(os.PathSeparator) {
return nil
}
p := &currentPath{
path: path,
f: f,
fullPath: filepath.Join(root, path),
}
select {
case <-ctx.Done():
return ctx.Err()
case pathC <- p:
return nil
}
})
}
func nextPath(ctx context.Context, pathC <-chan *currentPath) (*currentPath, error) {
select {
case <-ctx.Done():
return nil, ctx.Err()
case p := <-pathC:
return p, nil
}
}
// RootPath joins a path with a root, evaluating and bounding any
// symlink to the root directory.
func RootPath(root, path string) (string, error) {
if path == "" {
return root, nil
}
var linksWalked int // to protect against cycles
for {
i := linksWalked
newpath, err := walkLinks(root, path, &linksWalked)
if err != nil {
return "", err
}
path = newpath
if i == linksWalked {
newpath = filepath.Join("/", newpath)
if path == newpath {
return filepath.Join(root, newpath), nil
}
path = newpath
}
}
}
func walkLink(root, path string, linksWalked *int) (newpath string, islink bool, err error) {
if *linksWalked > 255 {
return "", false, errTooManyLinks
}
path = filepath.Join("/", path)
if path == "/" {
return path, false, nil
}
realPath := filepath.Join(root, path)
fi, err := os.Lstat(realPath)
if err != nil {
// If path does not yet exist, treat as non-symlink
if os.IsNotExist(err) {
return path, false, nil
}
return "", false, err
}
if fi.Mode()&os.ModeSymlink == 0 {
return path, false, nil
}
newpath, err = os.Readlink(realPath)
if err != nil {
return "", false, err
}
*linksWalked++
return newpath, true, nil
}
func walkLinks(root, path string, linksWalked *int) (string, error) {
switch dir, file := filepath.Split(path); {
case dir == "":
newpath, _, err := walkLink(root, file, linksWalked)
return newpath, err
case file == "":
if os.IsPathSeparator(dir[len(dir)-1]) {
if dir == "/" {
return dir, nil
}
return walkLinks(root, dir[:len(dir)-1], linksWalked)
}
newpath, _, err := walkLink(root, dir, linksWalked)
return newpath, err
default:
newdir, err := walkLinks(root, dir, linksWalked)
if err != nil {
return "", err
}
newpath, islink, err := walkLink(root, filepath.Join(newdir, file), linksWalked)
if err != nil {
return "", err
}
if !islink {
return newpath, nil
}
if filepath.IsAbs(newpath) {
return newpath, nil
}
return filepath.Join(newdir, newpath), nil
}
}