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//go:build windows
package fastwalk
import (
"io/fs"
"os"
"path/filepath"
"sync"
"syscall"
)
type fileKey struct {
VolumeSerialNumber uint32
FileIndexHigh uint32
FileIndexLow uint32
}
type EntryFilter struct {
mu sync.Mutex
seen map[fileKey]struct{}
}
func NewEntryFilter() *EntryFilter {
return &EntryFilter{seen: make(map[fileKey]struct{}, 128)}
}
func (e *EntryFilter) Entry(path string, _ fs.DirEntry) bool {
namep, err := syscall.UTF16PtrFromString(fixLongPath(path))
if err != nil {
return false
}
h, err := syscall.CreateFile(namep, 0, 0, nil, syscall.OPEN_EXISTING,
syscall.FILE_FLAG_BACKUP_SEMANTICS, 0)
if err != nil {
return false
}
var d syscall.ByHandleFileInformation
err = syscall.GetFileInformationByHandle(h, &d)
syscall.CloseHandle(h)
if err != nil {
return false
}
key := fileKey{
VolumeSerialNumber: d.VolumeSerialNumber,
FileIndexHigh: d.FileIndexHigh,
FileIndexLow: d.FileIndexLow,
}
e.mu.Lock()
if e.seen == nil {
e.seen = make(map[fileKey]struct{})
}
_, ok := e.seen[key]
if !ok {
e.seen[key] = struct{}{}
}
e.mu.Unlock()
return ok
}
func isAbs(path string) (b bool) {
v := filepath.VolumeName(path)
if v == "" {
return false
}
path = path[len(v):]
if path == "" {
return false
}
return os.IsPathSeparator(path[0])
}
// fixLongPath returns the extended-length (\\?\-prefixed) form of
// path when needed, in order to avoid the default 260 character file
// path limit imposed by Windows. If path is not easily converted to
// the extended-length form (for example, if path is a relative path
// or contains .. elements), or is short enough, fixLongPath returns
// path unmodified.
//
// See https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx#maxpath
func fixLongPath(path string) string {
// Do nothing (and don't allocate) if the path is "short".
// Empirically (at least on the Windows Server 2013 builder),
// the kernel is arbitrarily okay with < 248 bytes. That
// matches what the docs above say:
// "When using an API to create a directory, the specified
// path cannot be so long that you cannot append an 8.3 file
// name (that is, the directory name cannot exceed MAX_PATH
// minus 12)." Since MAX_PATH is 260, 260 - 12 = 248.
//
// The MSDN docs appear to say that a normal path that is 248 bytes long
// will work; empirically the path must be less then 248 bytes long.
if len(path) < 248 {
// Don't fix. (This is how Go 1.7 and earlier worked,
// not automatically generating the \\?\ form)
return path
}
// The extended form begins with \\?\, as in
// \\?\c:\windows\foo.txt or \\?\UNC\server\share\foo.txt.
// The extended form disables evaluation of . and .. path
// elements and disables the interpretation of / as equivalent
// to \. The conversion here rewrites / to \ and elides
// . elements as well as trailing or duplicate separators. For
// simplicity it avoids the conversion entirely for relative
// paths or paths containing .. elements. For now,
// \\server\share paths are not converted to
// \\?\UNC\server\share paths because the rules for doing so
// are less well-specified.
if len(path) >= 2 && path[:2] == `\\` {
// Don't canonicalize UNC paths.
return path
}
if !isAbs(path) {
// Relative path
return path
}
const prefix = `\\?`
pathbuf := make([]byte, len(prefix)+len(path)+len(`\`))
copy(pathbuf, prefix)
n := len(path)
r, w := 0, len(prefix)
for r < n {
switch {
case os.IsPathSeparator(path[r]):
// empty block
r++
case path[r] == '.' && (r+1 == n || os.IsPathSeparator(path[r+1])):
// /./
r++
case r+1 < n && path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
// /../ is currently unhandled
return path
default:
pathbuf[w] = '\\'
w++
for ; r < n && !os.IsPathSeparator(path[r]); r++ {
pathbuf[w] = path[r]
w++
}
}
}
// A drive's root directory needs a trailing \
if w == len(`\\?\c:`) {
pathbuf[w] = '\\'
w++
}
return string(pathbuf[:w])
}
|
