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Refactor Windows parse_prefix #74220

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merged 8 commits into from
Jul 14, 2020
+103 −69
Merged

Refactor Windows parse_prefix #74220

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9a8b516
Sorting feature attributes in std
tesuji Jul 10, 2020
1e05e09
Remove the useless indentation
tesuji Jul 10, 2020
0ff820c
Move constants to top file
tesuji Jul 12, 2020
90a7d24
Make is_valid_drive_letter function
tesuji Jul 10, 2020
27a966a
Make use of slice::strip_prefix and slice pattern
tesuji Jul 10, 2020
b1d6798
Rewrite parse_two_comps
tesuji Jul 10, 2020
0281a05
Prefer empty OsStr over unsafe cast from [u8]
tesuji Jul 10, 2020
e31898b
Reduce unsafe scope
tesuji Jul 12, 2020
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Reduce unsafe scope
@tesuji
tesuji committed Jul 12, 2020

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Learn about vigilant mode
commit e31898b02409b8ce5db32761d45c78f9f74dbdc6
97 changes: 48 additions & 49 deletions src/libstd/sys/windows/path.rs
View file
Original file line number Diff line number Diff line change
@@ -8,6 +8,10 @@ mod tests;
pub const MAIN_SEP_STR: &str = "\\";
pub const MAIN_SEP: char = '\\';

// The unsafety here stems from converting between `&OsStr` and `&[u8]`
// and back. This is safe to do because (1) we only look at ASCII
// contents of the encoding and (2) new &OsStr values are produced
// only from ASCII-bounded slices of existing &OsStr values.
fn os_str_as_u8_slice(s: &OsStr) -> &[u8] {
unsafe { mem::transmute(s) }
}
@@ -33,62 +37,57 @@ pub fn is_valid_drive_letter(disk: u8) -> bool {

pub fn parse_prefix(path: &OsStr) -> Option<Prefix<'_>> {
use Prefix::{DeviceNS, Disk, Verbatim, VerbatimDisk, VerbatimUNC, UNC};
unsafe {
// The unsafety here stems from converting between &OsStr and &[u8]
// and back. This is safe to do because (1) we only look at ASCII
// contents of the encoding and (2) new &OsStr values are produced
// only from ASCII-bounded slices of existing &OsStr values.
let path = os_str_as_u8_slice(path);

// \\
if let Some(path) = path.strip_prefix(br"\\") {
// \\?\
if let Some(path) = path.strip_prefix(br"?\") {
// \\?\UNC\server\share
if let Some(path) = path.strip_prefix(br"UNC\") {
let (server, share) = match get_first_two_components(path, is_verbatim_sep) {
Some((server, share)) => {
(u8_slice_as_os_str(server), u8_slice_as_os_str(share))
}
None => (u8_slice_as_os_str(path), OsStr::new("")),
};
return Some(VerbatimUNC(server, share));
} else {
// \\?\path
match path {
// \\?\C:\path
[c, b':', b'\\', ..] if is_valid_drive_letter(*c) => {
return Some(VerbatimDisk(c.to_ascii_uppercase()));
}
// \\?\cat_pics
_ => {
let idx = path.iter().position(|&b| b == b'\\').unwrap_or(path.len());
let slice = &path[..idx];
return Some(Verbatim(u8_slice_as_os_str(slice)));
}
let path = os_str_as_u8_slice(path);

// \\
if let Some(path) = path.strip_prefix(br"\\") {
// \\?\
if let Some(path) = path.strip_prefix(br"?\") {
// \\?\UNC\server\share
if let Some(path) = path.strip_prefix(br"UNC\") {
let (server, share) = match get_first_two_components(path, is_verbatim_sep) {
Some((server, share)) => unsafe {
(u8_slice_as_os_str(server), u8_slice_as_os_str(share))
},
None => (unsafe { u8_slice_as_os_str(path) }, OsStr::new("")),
};
return Some(VerbatimUNC(server, share));
} else {
// \\?\path
match path {
// \\?\C:\path
[c, b':', b'\\', ..] if is_valid_drive_letter(*c) => {
return Some(VerbatimDisk(c.to_ascii_uppercase()));
}
// \\?\cat_pics
_ => {
let idx = path.iter().position(|&b| b == b'\\').unwrap_or(path.len());
let slice = &path[..idx];
return Some(Verbatim(unsafe { u8_slice_as_os_str(slice) }));
}
}
} else if let Some(path) = path.strip_prefix(b".\\") {
// \\.\COM42
let idx = path.iter().position(|&b| b == b'\\').unwrap_or(path.len());
let slice = &path[..idx];
return Some(DeviceNS(u8_slice_as_os_str(slice)));
}
match get_first_two_components(path, is_sep_byte) {
Some((server, share)) if !server.is_empty() && !share.is_empty() => {
// \\server\share
return Some(UNC(u8_slice_as_os_str(server), u8_slice_as_os_str(share)));
}
_ => {}
}
} else if let [c, b':', ..] = path {
// C:
if is_valid_drive_letter(*c) {
return Some(Disk(c.to_ascii_uppercase()));
} else if let Some(path) = path.strip_prefix(b".\\") {
// \\.\COM42
let idx = path.iter().position(|&b| b == b'\\').unwrap_or(path.len());
let slice = &path[..idx];
return Some(DeviceNS(unsafe { u8_slice_as_os_str(slice) }));
}
match get_first_two_components(path, is_sep_byte) {
Some((server, share)) if !server.is_empty() && !share.is_empty() => {
// \\server\share
return Some(unsafe { UNC(u8_slice_as_os_str(server), u8_slice_as_os_str(share)) });
}
_ => {}
}
} else if let [c, b':', ..] = path {
// C:
if is_valid_drive_letter(*c) {
return Some(Disk(c.to_ascii_uppercase()));
}
return None;
}
None
}

/// Returns the first two path components with predicate `f`.