156 lines
3.6 KiB
Go
156 lines
3.6 KiB
Go
package symlink
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import (
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"bytes"
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"errors"
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"os"
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"path/filepath"
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"strings"
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"syscall"
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"github.com/docker/docker/pkg/longpath"
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)
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func toShort(path string) (string, error) {
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p, err := syscall.UTF16FromString(path)
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if err != nil {
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return "", err
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}
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b := p // GetShortPathName says we can reuse buffer
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n, err := syscall.GetShortPathName(&p[0], &b[0], uint32(len(b)))
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if err != nil {
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return "", err
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}
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if n > uint32(len(b)) {
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b = make([]uint16, n)
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n, err = syscall.GetShortPathName(&p[0], &b[0], uint32(len(b)))
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if err != nil {
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return "", err
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}
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}
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return syscall.UTF16ToString(b), nil
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}
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func toLong(path string) (string, error) {
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p, err := syscall.UTF16FromString(path)
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if err != nil {
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return "", err
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}
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b := p // GetLongPathName says we can reuse buffer
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n, err := syscall.GetLongPathName(&p[0], &b[0], uint32(len(b)))
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if err != nil {
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return "", err
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}
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if n > uint32(len(b)) {
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b = make([]uint16, n)
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n, err = syscall.GetLongPathName(&p[0], &b[0], uint32(len(b)))
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if err != nil {
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return "", err
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}
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}
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b = b[:n]
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return syscall.UTF16ToString(b), nil
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}
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func evalSymlinks(path string) (string, error) {
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path, err := walkSymlinks(path)
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if err != nil {
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return "", err
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}
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p, err := toShort(path)
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if err != nil {
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return "", err
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}
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p, err = toLong(p)
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if err != nil {
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return "", err
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}
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// syscall.GetLongPathName does not change the case of the drive letter,
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// but the result of EvalSymlinks must be unique, so we have
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// EvalSymlinks(`c:\a`) == EvalSymlinks(`C:\a`).
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// Make drive letter upper case.
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if len(p) >= 2 && p[1] == ':' && 'a' <= p[0] && p[0] <= 'z' {
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p = string(p[0]+'A'-'a') + p[1:]
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} else if len(p) >= 6 && p[5] == ':' && 'a' <= p[4] && p[4] <= 'z' {
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p = p[:3] + string(p[4]+'A'-'a') + p[5:]
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}
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return filepath.Clean(p), nil
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}
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const utf8RuneSelf = 0x80
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func walkSymlinks(path string) (string, error) {
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const maxIter = 255
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originalPath := path
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// consume path by taking each frontmost path element,
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// expanding it if it's a symlink, and appending it to b
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var b bytes.Buffer
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for n := 0; path != ""; n++ {
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if n > maxIter {
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return "", errors.New("EvalSymlinks: too many links in " + originalPath)
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}
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// A path beginnging with `\\?\` represents the root, so automatically
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// skip that part and begin processing the next segment.
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if strings.HasPrefix(path, longpath.Prefix) {
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b.WriteString(longpath.Prefix)
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path = path[4:]
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continue
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}
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// find next path component, p
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var i = -1
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for j, c := range path {
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if c < utf8RuneSelf && os.IsPathSeparator(uint8(c)) {
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i = j
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break
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}
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}
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var p string
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if i == -1 {
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p, path = path, ""
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} else {
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p, path = path[:i], path[i+1:]
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}
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if p == "" {
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if b.Len() == 0 {
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// must be absolute path
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b.WriteRune(filepath.Separator)
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}
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continue
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}
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// If this is the first segment after the long path prefix, accept the
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// current segment as a volume root or UNC share and move on to the next.
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if b.String() == longpath.Prefix {
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b.WriteString(p)
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b.WriteRune(filepath.Separator)
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continue
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}
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fi, err := os.Lstat(b.String() + p)
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if err != nil {
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return "", err
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}
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if fi.Mode()&os.ModeSymlink == 0 {
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b.WriteString(p)
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if path != "" || (b.Len() == 2 && len(p) == 2 && p[1] == ':') {
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b.WriteRune(filepath.Separator)
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}
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continue
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}
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// it's a symlink, put it at the front of path
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dest, err := os.Readlink(b.String() + p)
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if err != nil {
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return "", err
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}
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if filepath.IsAbs(dest) || os.IsPathSeparator(dest[0]) {
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b.Reset()
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}
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path = dest + string(filepath.Separator) + path
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}
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return filepath.Clean(b.String()), nil
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}
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