225 lines
6.3 KiB
Go
225 lines
6.3 KiB
Go
package loggerutils
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import (
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"os"
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"syscall"
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"unsafe"
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"github.com/pkg/errors"
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)
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func openFile(name string, flag int, perm os.FileMode) (*os.File, error) {
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if name == "" {
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return nil, &os.PathError{Op: "open", Path: name, Err: syscall.ENOENT}
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}
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h, err := syscallOpen(fixLongPath(name), flag|syscall.O_CLOEXEC, syscallMode(perm))
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if err != nil {
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return nil, errors.Wrap(err, "error opening file")
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}
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return os.NewFile(uintptr(h), name), nil
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}
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// syscallOpen is copied from syscall.Open but is modified to
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// always open a file with FILE_SHARE_DELETE
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func syscallOpen(path string, mode int, perm uint32) (fd syscall.Handle, err error) {
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if len(path) == 0 {
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return syscall.InvalidHandle, syscall.ERROR_FILE_NOT_FOUND
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}
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pathp, err := syscall.UTF16PtrFromString(path)
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if err != nil {
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return syscall.InvalidHandle, err
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}
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var access uint32
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switch mode & (syscall.O_RDONLY | syscall.O_WRONLY | syscall.O_RDWR) {
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case syscall.O_RDONLY:
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access = syscall.GENERIC_READ
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case syscall.O_WRONLY:
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access = syscall.GENERIC_WRITE
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case syscall.O_RDWR:
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access = syscall.GENERIC_READ | syscall.GENERIC_WRITE
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}
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if mode&syscall.O_CREAT != 0 {
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access |= syscall.GENERIC_WRITE
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}
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if mode&syscall.O_APPEND != 0 {
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access &^= syscall.GENERIC_WRITE
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access |= syscall.FILE_APPEND_DATA
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}
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sharemode := uint32(syscall.FILE_SHARE_READ | syscall.FILE_SHARE_WRITE | syscall.FILE_SHARE_DELETE)
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var sa *syscall.SecurityAttributes
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if mode&syscall.O_CLOEXEC == 0 {
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sa = makeInheritSa()
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}
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var createmode uint32
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switch {
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case mode&(syscall.O_CREAT|syscall.O_EXCL) == (syscall.O_CREAT | syscall.O_EXCL):
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createmode = syscall.CREATE_NEW
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case mode&(syscall.O_CREAT|syscall.O_TRUNC) == (syscall.O_CREAT | syscall.O_TRUNC):
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createmode = syscall.CREATE_ALWAYS
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case mode&syscall.O_CREAT == syscall.O_CREAT:
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createmode = syscall.OPEN_ALWAYS
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case mode&syscall.O_TRUNC == syscall.O_TRUNC:
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createmode = syscall.TRUNCATE_EXISTING
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default:
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createmode = syscall.OPEN_EXISTING
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}
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h, e := syscall.CreateFile(pathp, access, sharemode, sa, createmode, syscall.FILE_ATTRIBUTE_NORMAL, 0)
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return h, e
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}
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func makeInheritSa() *syscall.SecurityAttributes {
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var sa syscall.SecurityAttributes
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sa.Length = uint32(unsafe.Sizeof(sa))
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sa.InheritHandle = 1
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return &sa
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}
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// fixLongPath returns the extended-length (\\?\-prefixed) form of
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// path when needed, in order to avoid the default 260 character file
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// path limit imposed by Windows. If path is not easily converted to
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// the extended-length form (for example, if path is a relative path
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// or contains .. elements), or is short enough, fixLongPath returns
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// path unmodified.
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//
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// See https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx#maxpath
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//
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// Copied from os.OpenFile
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func fixLongPath(path string) string {
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// Do nothing (and don't allocate) if the path is "short".
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// Empirically (at least on the Windows Server 2013 builder),
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// the kernel is arbitrarily okay with < 248 bytes. That
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// matches what the docs above say:
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// "When using an API to create a directory, the specified
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// path cannot be so long that you cannot append an 8.3 file
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// name (that is, the directory name cannot exceed MAX_PATH
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// minus 12)." Since MAX_PATH is 260, 260 - 12 = 248.
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//
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// The MSDN docs appear to say that a normal path that is 248 bytes long
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// will work; empirically the path must be less then 248 bytes long.
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if len(path) < 248 {
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// Don't fix. (This is how Go 1.7 and earlier worked,
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// not automatically generating the \\?\ form)
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return path
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}
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// The extended form begins with \\?\, as in
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// \\?\c:\windows\foo.txt or \\?\UNC\server\share\foo.txt.
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// The extended form disables evaluation of . and .. path
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// elements and disables the interpretation of / as equivalent
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// to \. The conversion here rewrites / to \ and elides
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// . elements as well as trailing or duplicate separators. For
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// simplicity it avoids the conversion entirely for relative
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// paths or paths containing .. elements. For now,
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// \\server\share paths are not converted to
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// \\?\UNC\server\share paths because the rules for doing so
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// are less well-specified.
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if len(path) >= 2 && path[:2] == `\\` {
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// Don't canonicalize UNC paths.
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return path
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}
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if !isAbs(path) {
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// Relative path
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return path
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}
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const prefix = `\\?`
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pathbuf := make([]byte, len(prefix)+len(path)+len(`\`))
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copy(pathbuf, prefix)
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n := len(path)
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r, w := 0, len(prefix)
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for r < n {
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switch {
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case os.IsPathSeparator(path[r]):
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// empty block
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r++
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case path[r] == '.' && (r+1 == n || os.IsPathSeparator(path[r+1])):
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// /./
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r++
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case r+1 < n && path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
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// /../ is currently unhandled
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return path
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default:
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pathbuf[w] = '\\'
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w++
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for ; r < n && !os.IsPathSeparator(path[r]); r++ {
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pathbuf[w] = path[r]
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w++
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}
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}
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}
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// A drive's root directory needs a trailing \
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if w == len(`\\?\c:`) {
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pathbuf[w] = '\\'
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w++
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}
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return string(pathbuf[:w])
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}
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// copied from os package for os.OpenFile
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func syscallMode(i os.FileMode) (o uint32) {
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o |= uint32(i.Perm())
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if i&os.ModeSetuid != 0 {
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o |= syscall.S_ISUID
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}
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if i&os.ModeSetgid != 0 {
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o |= syscall.S_ISGID
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}
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if i&os.ModeSticky != 0 {
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o |= syscall.S_ISVTX
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}
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// No mapping for Go's ModeTemporary (plan9 only).
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return
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}
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func isAbs(path string) (b bool) {
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v := volumeName(path)
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if v == "" {
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return false
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}
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path = path[len(v):]
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if path == "" {
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return false
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}
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return os.IsPathSeparator(path[0])
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}
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func volumeName(path string) (v string) {
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if len(path) < 2 {
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return ""
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}
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// with drive letter
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c := path[0]
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if path[1] == ':' &&
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('0' <= c && c <= '9' || 'a' <= c && c <= 'z' ||
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'A' <= c && c <= 'Z') {
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return path[:2]
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}
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// is it UNC
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if l := len(path); l >= 5 && os.IsPathSeparator(path[0]) && os.IsPathSeparator(path[1]) &&
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!os.IsPathSeparator(path[2]) && path[2] != '.' {
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// first, leading `\\` and next shouldn't be `\`. its server name.
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for n := 3; n < l-1; n++ {
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// second, next '\' shouldn't be repeated.
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if os.IsPathSeparator(path[n]) {
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n++
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// third, following something characters. its share name.
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if !os.IsPathSeparator(path[n]) {
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if path[n] == '.' {
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break
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}
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for ; n < l; n++ {
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if os.IsPathSeparator(path[n]) {
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break
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}
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}
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return path[:n]
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}
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break
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}
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}
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}
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return ""
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}
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