bjoernager/rust
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Reduce unsafe scope

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This commit is contained in:
Lzu Tao 2020-07-12 14:46:00 +00:00
parent 0281a05f66
commit e31898b024
1 changed files with 49 additions and 50 deletions
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99
src/libstd/sys/windows/path.rs
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@ -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`.