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moby--moby/pkg/symlink/fs_windows.go

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