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/// A trait for adding some helper routines to pointers.
pub(crate) trait Pointer {
/// Returns the distance, in units of `T`, between `self` and `origin`.
///
/// # Safety
///
/// Same as `ptr::offset_from` in addition to `self >= origin`.
unsafe fn distance(self, origin: Self) -> usize;
/// Casts this pointer to `usize`.
///
/// Callers should not convert the `usize` back to a pointer if at all
/// possible. (And if you believe it's necessary, open an issue to discuss
/// why. Otherwise, it has the potential to violate pointer provenance.)
/// The purpose of this function is just to be able to do arithmetic, i.e.,
/// computing offsets or alignments.
fn as_usize(self) -> usize;
}
impl<T> Pointer for *const T {
unsafe fn distance(self, origin: *const T) -> usize {
// TODO: Replace with `ptr::sub_ptr` once stabilized.
usize::try_from(self.offset_from(origin)).unwrap_unchecked()
}
fn as_usize(self) -> usize {
self as usize
}
}
impl<T> Pointer for *mut T {
unsafe fn distance(self, origin: *mut T) -> usize {
(self as *const T).distance(origin as *const T)
}
fn as_usize(self) -> usize {
(self as *const T).as_usize()
}
}
/// A trait for adding some helper routines to raw bytes.
#[cfg(test)]
pub(crate) trait Byte {
/// Converts this byte to a `char` if it's ASCII. Otherwise panics.
fn to_char(self) -> char;
}
#[cfg(test)]
impl Byte for u8 {
fn to_char(self) -> char {
assert!(self.is_ascii());
char::from(self)
}
}