1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
//! Windows extended-length (`\\?\` verbatim) path semantics, owned in one
//! place so the `\\?\` / `\\?\UNC\` prefix rules live at a single source of
//! truth.
//!
//! Two paired directions:
//! - [`strip_windows_verbatim_prefix`] removes the prefix so a canonicalized
//! path parses under normal Windows rules (and can re-enter `/`-joining
//! code, or prefix-match a plain `C:\` mount point). It is pure string logic
//! and cross-platform: a well-formed absolute path off Windows never carries
//! the prefix, so callers on any platform may normalize a Windows-shaped
//! string through it.
//! - [`wide_maybe_verbatim`] adds the prefix to a `MoveFileExW` operand so a
//! durable write survives a path longer than the legacy 260-char `MAX_PATH`.
//! It mirrors the standard library's conservative `maybe_verbatim` rules and
//! is Windows-only.
use std::borrow::Cow;
/// Strip a Windows verbatim (`\\?\`) prefix from a path string:
/// `\\?\UNC\server\share` -> `\\server\share`, `\\?\C:\dir` -> `C:\dir`. Inputs
/// without the prefix — every well-formed Unix path, plain Windows paths, and
/// `\\.\` device paths — are returned unchanged.
pub fn strip_windows_verbatim_prefix(text: &str) -> Cow<'_, str> {
if let Some(rest) = text.strip_prefix(r"\\?\UNC\") {
Cow::Owned(format!(r"\\{rest}"))
} else if let Some(rest) = text.strip_prefix(r"\\?\") {
Cow::Borrowed(rest)
} else {
Cow::Borrowed(text)
}
}
/// Build a NUL-terminated UTF-16 buffer for `path`, prepending the `\\?\`
/// extended-length prefix so `MoveFileExW` accepts paths longer than the legacy
/// 260-char `MAX_PATH`.
///
/// std applies this automatically for its own file APIs (`File::open`,
/// `create_dir_all`), but a hand-rolled `MoveFileExW` call does not, so any
/// operand over the limit fails with `ERROR_PATH_NOT_FOUND`. Mirroring std's
/// conservative rules, only drive/UNC-absolute paths already in backslash
/// normal form are rewritten; a verbatim/device path, a relative path, or one
/// containing `/`, `.`, or `..` (which a verbatim prefix would treat literally)
/// is passed through unchanged.
#[cfg(windows)]
pub(crate) fn wide_maybe_verbatim(path: &std::path::Path) -> Vec<u16> {
use std::os::windows::ffi::OsStrExt;
use std::path::{Component, Prefix};
fn nul_terminated(mut wide: Vec<u16>) -> Vec<u16> {
wide.push(0);
wide
}
let raw: Vec<u16> = path.as_os_str().encode_wide().collect();
const BACKSLASH: u16 = b'\\' as u16;
const SLASH: u16 = b'/' as u16;
const QUESTION: u16 = b'?' as u16;
const DOT: u16 = b'.' as u16;
// Already verbatim (`\\?\`) or a device path (`\\.\`): leave untouched.
if raw.starts_with(&[BACKSLASH, BACKSLASH, QUESTION, BACKSLASH])
|| raw.starts_with(&[BACKSLASH, BACKSLASH, DOT, BACKSLASH])
{
return nul_terminated(raw);
}
// A forward slash is a literal filename character under a verbatim prefix,
// so such paths are ineligible.
if raw.contains(&SLASH) {
return nul_terminated(raw);
}
let mut components = path.components();
let is_supported_prefix = matches!(
components.next(),
Some(Component::Prefix(prefix))
if matches!(prefix.kind(), Prefix::Disk(_) | Prefix::UNC(_, _))
);
if !is_supported_prefix || !matches!(components.next(), Some(Component::RootDir)) {
return nul_terminated(raw);
}
// `.`/`..` components would resolve literally under a verbatim prefix.
if components.any(|component| !matches!(component, Component::Normal(_))) {
return nul_terminated(raw);
}
// Re-read the prefix kind to choose the correct verbatim form.
let prefix_kind = path
.components()
.next()
.and_then(|component| match component {
Component::Prefix(prefix) => Some(prefix.kind()),
_ => None,
});
let prefixed = match prefix_kind {
// `C:\...` -> `\\?\C:\...`
Some(Prefix::Disk(_)) => {
let mut out: Vec<u16> = r"\\?\".encode_utf16().collect();
out.extend_from_slice(&raw);
out
}
// `\\server\share\...` -> `\\?\UNC\server\share\...` (drop one leading `\`)
Some(Prefix::UNC(_, _)) => {
let mut out: Vec<u16> = r"\\?\UNC".encode_utf16().collect();
out.extend_from_slice(&raw[1..]);
out
}
_ => raw,
};
nul_terminated(prefixed)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn strips_drive_and_unc_verbatim_prefixes() {
assert_eq!(
strip_windows_verbatim_prefix(r"\\?\C:\Users\runner\Temp\harn-abc"),
r"C:\Users\runner\Temp\harn-abc"
);
assert_eq!(
strip_windows_verbatim_prefix(r"\\?\UNC\server\share\dir"),
r"\\server\share\dir"
);
}
#[test]
fn passes_through_non_verbatim_paths_unchanged() {
// Plain Windows, every Unix path, `\\.\` device paths, relative paths,
// slash-bearing and dot paths all lack the `\\?\` prefix.
assert_eq!(
strip_windows_verbatim_prefix(r"C:\Temp\harn-abc"),
r"C:\Temp\harn-abc"
);
assert_eq!(
strip_windows_verbatim_prefix("/tmp/harn-abc/child"),
"/tmp/harn-abc/child"
);
assert_eq!(
strip_windows_verbatim_prefix(r"\\.\PhysicalDrive0"),
r"\\.\PhysicalDrive0"
);
assert_eq!(
strip_windows_verbatim_prefix(r"relative\dir"),
r"relative\dir"
);
assert_eq!(strip_windows_verbatim_prefix(r"C:\a\..\b"), r"C:\a\..\b");
assert_eq!(
strip_windows_verbatim_prefix("C:/forward/slash"),
"C:/forward/slash"
);
}
#[test]
fn strips_prefix_from_paths_longer_than_max_path() {
let deep = format!(r"\\?\C:\{}", "segment\\".repeat(40));
let stripped = strip_windows_verbatim_prefix(&deep);
assert!(stripped.len() > 260, "test path must exceed MAX_PATH");
assert_eq!(stripped, &deep[r"\\?\".len()..]);
assert!(!stripped.starts_with(r"\\?\"));
}
}