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

277 lines
5.8 KiB
Go

package fs
import (
"bytes"
"context"
"io"
"os"
"path/filepath"
"strings"
"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
}
// TODO: compare by directory
switch i := strings.Compare(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 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
}
if filepath.IsAbs(newpath) && strings.HasPrefix(newpath, root) {
newpath = newpath[:len(root)]
if !strings.HasPrefix(newpath, "/") {
newpath = "/" + newpath
}
}
*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
}
}