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|
use bstr::ByteSlice;
use std::fmt::{self, Debug, Display};
/// A wrapper type for symlink targets.
/// Internally uses a [bytes::Bytes], but disallows empty targets and those
/// containing null bytes.
#[repr(transparent)]
#[derive(Clone, PartialEq, Eq)]
pub struct SymlinkTarget {
inner: bytes::Bytes,
}
/// The maximum length a symlink target can have.
/// Linux allows 4095 bytes here.
pub const MAX_TARGET_LEN: usize = 4095;
impl AsRef<[u8]> for SymlinkTarget {
fn as_ref(&self) -> &[u8] {
self.inner.as_ref()
}
}
impl From<SymlinkTarget> for bytes::Bytes {
fn from(value: SymlinkTarget) -> Self {
value.inner
}
}
fn validate_symlink_target<B: AsRef<[u8]>>(symlink_target: B) -> Result<B, SymlinkTargetError> {
let v = symlink_target.as_ref();
if v.is_empty() {
return Err(SymlinkTargetError::Empty);
}
if v.len() > MAX_TARGET_LEN {
return Err(SymlinkTargetError::TooLong);
}
if v.contains(&0x00) {
return Err(SymlinkTargetError::Null);
}
Ok(symlink_target)
}
impl TryFrom<bytes::Bytes> for SymlinkTarget {
type Error = SymlinkTargetError;
fn try_from(value: bytes::Bytes) -> Result<Self, Self::Error> {
if let Err(e) = validate_symlink_target(&value) {
return Err(SymlinkTargetError::Convert(value, Box::new(e)));
}
Ok(Self { inner: value })
}
}
impl TryFrom<&'static [u8]> for SymlinkTarget {
type Error = SymlinkTargetError;
fn try_from(value: &'static [u8]) -> Result<Self, Self::Error> {
if let Err(e) = validate_symlink_target(&value) {
return Err(SymlinkTargetError::Convert(value.into(), Box::new(e)));
}
Ok(Self {
inner: bytes::Bytes::from_static(value),
})
}
}
impl TryFrom<&str> for SymlinkTarget {
type Error = SymlinkTargetError;
fn try_from(value: &str) -> Result<Self, Self::Error> {
if let Err(e) = validate_symlink_target(value) {
return Err(SymlinkTargetError::Convert(
value.to_owned().into(),
Box::new(e),
));
}
Ok(Self {
inner: bytes::Bytes::copy_from_slice(value.as_bytes()),
})
}
}
impl Debug for SymlinkTarget {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
Debug::fmt(self.inner.as_bstr(), f)
}
}
impl Display for SymlinkTarget {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
Display::fmt(self.inner.as_bstr(), f)
}
}
/// Errors created when constructing / converting to [SymlinkTarget].
#[derive(Debug, PartialEq, Eq, thiserror::Error)]
#[cfg_attr(test, derive(Clone))]
pub enum SymlinkTargetError {
#[error("cannot be empty")]
Empty,
#[error("cannot contain null bytes")]
Null,
#[error("cannot be over {} bytes long", MAX_TARGET_LEN)]
TooLong,
#[error("unable to convert '{:?}", .0.as_bstr())]
Convert(bytes::Bytes, Box<Self>),
}
#[cfg(test)]
mod tests {
use bytes::Bytes;
use rstest::rstest;
use super::validate_symlink_target;
use super::{SymlinkTarget, SymlinkTargetError};
#[rstest]
#[case::empty(b"", SymlinkTargetError::Empty)]
#[case::null(b"foo\0", SymlinkTargetError::Null)]
fn errors(#[case] v: &'static [u8], #[case] err: SymlinkTargetError) {
{
assert_eq!(
Err(err.clone()),
validate_symlink_target(v),
"validate_symlink_target must fail as expected"
);
}
let exp_err_v = Bytes::from_static(v);
// Bytes
{
let v = Bytes::from_static(v);
assert_eq!(
Err(SymlinkTargetError::Convert(
exp_err_v.clone(),
Box::new(err.clone())
)),
SymlinkTarget::try_from(v),
"conversion must fail as expected"
);
}
// &[u8]
{
assert_eq!(
Err(SymlinkTargetError::Convert(
exp_err_v.clone(),
Box::new(err.clone())
)),
SymlinkTarget::try_from(v),
"conversion must fail as expected"
);
}
// &str, if this is valid UTF-8
{
if let Ok(v) = std::str::from_utf8(v) {
assert_eq!(
Err(SymlinkTargetError::Convert(
exp_err_v.clone(),
Box::new(err.clone())
)),
SymlinkTarget::try_from(v),
"conversion must fail as expected"
);
}
}
}
#[test]
fn error_toolong() {
assert_eq!(
Err(SymlinkTargetError::TooLong),
validate_symlink_target("X".repeat(5000).into_bytes().as_slice())
)
}
#[rstest]
#[case::boring(b"aa")]
#[case::dot(b".")]
#[case::dotsandslashes(b"./..")]
#[case::dotdot(b"..")]
#[case::slashes(b"a/b")]
#[case::slashes_and_absolute(b"/a/b")]
#[case::invalid_utf8(b"\xc5\xc4\xd6")]
fn success(#[case] v: &'static [u8]) {
let exp = SymlinkTarget { inner: v.into() };
// Bytes
{
let v: Bytes = v.into();
assert_eq!(
Ok(exp.clone()),
SymlinkTarget::try_from(v),
"conversion must succeed"
)
}
// &[u8]
{
assert_eq!(
Ok(exp.clone()),
SymlinkTarget::try_from(v),
"conversion must succeed"
)
}
// &str, if this is valid UTF-8
{
if let Ok(v) = std::str::from_utf8(v) {
assert_eq!(
Ok(exp.clone()),
SymlinkTarget::try_from(v),
"conversion must succeed"
)
}
}
}
}
|
