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use super::*; // Note(Lokathor): We would call this module `voladdress` but then it would // conflict with the crate name itself. /// A volatile address. /// /// This type stores a memory address and provides ergonomic volatile access to /// said memory address. /// /// Note that this type has several methods for accessing the data at the /// address specified, and a particular instance of this type can use them /// unsafely, use them safely, or not use them at all based on the generic /// values of `R` and `W` (explained below). /// * `read` /// * `write` /// * `apply` (reads, runs a function, then writes) /// /// ## Generic Parameters /// /// * `T`: The type of the value stored at the address. /// * The target type type must impl `Copy` for reading and writing to be /// allowed. /// * `R`: If the address is readable. /// * If `R=Safe` then you can safely read from the address. /// * If `R=Unsafe` then you can unsafely read from the address. /// * Otherwise you cannot read from the address. /// * `W`: If the address is writable. /// * If `W=Safe` then you can safely write to the address. /// * If `W=Unsafe` then you can unsafely write to the address. /// * Otherwise you cannot write to the address. /// /// The `VolAddress` type is intended to represent a single value of a `T` type /// that is the size of a single machine register (or less). /// * If there's an array of contiguous `T` values you want to model, consider /// using [`VolBlock`] instead. /// * If there's a series of strided `T` values you want to model, consider /// using [`VolSeries`] instead. /// * If the `T` type is larger than a single machine register it's probably /// **not** a good fit for the `VolAddress` abstraction. /// /// ## Safety /// This type's safety follows the "unsafe creation, then safe use" strategy. /// /// * **Validity Invariant**: The address of a `VolAddress` must always be /// non-zero, or you will instantly trigger UB. /// * **Safety Invariant**: The address of a `VolAddress` must be an aligned and /// legal address for a `T` type value (with correct `R` and `W` permissions) /// within the device's memory space, otherwise the `read` and `write` methods /// will trigger UB when called. /// * **Synchronization Invariant**: Volatile access has **no** cross-thread /// synchronization behavior within the LLVM memory model. The results of /// *all* volatile access is target-dependent, including cross-thread access. /// Volatile access has no automatic synchronization of its own, and so if /// your target requires some sort of synchronization for volatile accesses of /// the address in question you must provide the appropriate synchronization /// in some way external to this type. #[repr(transparent)] #[derive(PartialEq, Eq, PartialOrd, Ord, Hash)] pub struct VolAddress<T, R, W> { pub(crate) address: NonZeroUsize, target: PhantomData<T>, read_status: PhantomData<R>, write_status: PhantomData<W>, } impl<T, R, W> VolAddress<T, R, W> { /// Constructs the value. /// /// ## Safety /// * As per the type docs. #[inline] #[must_use] pub const unsafe fn new(address: usize) -> Self { Self { address: NonZeroUsize::new_unchecked(address), target: PhantomData, read_status: PhantomData, write_status: PhantomData, } } /// Changes the target type from `T` to `Z`. /// /// ## Safety /// * As per the type docs #[inline] #[must_use] pub const unsafe fn cast<Z>(self) -> VolAddress<Z, R, W> { VolAddress { address: self.address, target: PhantomData, read_status: PhantomData, write_status: PhantomData, } } /// Converts the `VolAddress` back into a normal `usize` value. #[inline] #[must_use] pub const fn as_usize(self) -> usize { self.address.get() } /// Advances the pointer by the given number of positions (`usize`). /// /// Shorthand for `addr.offset(count as isize)` /// /// This is intended to basically work like [`<*mut /// T>::wrapping_add`](https://doc.rust-lang.org/std/primitive.pointer.html#method.wrapping_add-1). /// /// ## Safety /// * As per the type docs #[inline] #[must_use] pub const unsafe fn add(self, count: usize) -> Self { self.offset(count as isize) } /// Reverses the pointer by the given number of positions (`usize`). /// /// Shorthand for `addr.offset((count as isize).wrapping_neg())` /// /// This is intended to basically work like [`<*mut /// T>::wrapping_sub`](https://doc.rust-lang.org/std/primitive.pointer.html#method.wrapping_sub-1). /// /// ## Safety /// * As per the type docs #[inline] #[must_use] pub const unsafe fn sub(self, count: usize) -> Self { self.offset((count as isize).wrapping_neg()) } /// Offsets the address by the given number of positions (`isize`). /// /// This is intended to basically work like [`<*mut /// T>::wrapping_offset`](https://doc.rust-lang.org/std/primitive.pointer.html#method.wrapping_offset-1). /// /// ## Safety /// * As per the type docs #[inline] #[must_use] pub const unsafe fn offset(self, count: isize) -> Self { let total_delta = core::mem::size_of::<T>().wrapping_mul(count as usize); VolAddress { address: NonZeroUsize::new_unchecked( self.address.get().wrapping_add(total_delta), ), target: PhantomData, read_status: PhantomData, write_status: PhantomData, } } } impl<T, W> VolAddress<T, Safe, W> where T: Copy, { /// Volatile reads the current value of `A`. #[inline] #[must_use] pub fn read(self) -> T { // Safety: The declarer of the value gave this a `Safe` read typing, thus // they've asserted that this is a safe to read address. unsafe { read_volatile(self.address.get() as *const T) } } } impl<T, W> VolAddress<T, Unsafe, W> where T: Copy, { /// Volatile reads the current value of `A`. /// /// ## Safety /// * The safety rules of reading this address depend on the device. Consult /// your hardware manual. #[inline] #[must_use] pub unsafe fn read(self) -> T { read_volatile(self.address.get() as *const T) } } impl<T, R> VolAddress<T, R, Safe> where T: Copy, { /// Volatile writes a new value to `A`. #[inline] pub fn write(self, t: T) { // Safety: The declarer of the value gave this a `Safe` write typing, thus // they've asserted that this is a safe to write address. unsafe { write_volatile(self.address.get() as *mut T, t) } } } impl<T, R> VolAddress<T, R, Unsafe> where T: Copy, { /// Volatile writes a new value to `A`. /// /// ## Safety /// * The safety rules of writing this address depend on the device. Consult /// your hardware manual. #[inline] pub unsafe fn write(self, t: T) { write_volatile(self.address.get() as *mut T, t) } } impl<T> VolAddress<T, Safe, Safe> where T: Copy, { /// Reads the address, applies the operation, and writes back the new value. #[inline] pub fn apply<F: FnOnce(&mut T)>(self, op: F) { let mut temp = self.read(); op(&mut temp); self.write(temp); } } impl<T> VolAddress<T, Unsafe, Safe> where T: Copy, { /// Reads the address, applies the operation, and writes back the new value. /// /// ## Safety /// * The safety rules of reading/writing this address depend on the device. /// Consult your hardware manual. #[inline] pub unsafe fn apply<F: FnOnce(&mut T)>(self, op: F) { let mut temp = self.read(); op(&mut temp); self.write(temp); } } impl<T> VolAddress<T, Safe, Unsafe> where T: Copy, { /// Reads the address, applies the operation, and writes back the new value. /// /// ## Safety /// * The safety rules of reading/writing this address depend on the device. /// Consult your hardware manual. #[inline] pub unsafe fn apply<F: FnOnce(&mut T)>(self, op: F) { let mut temp = self.read(); op(&mut temp); self.write(temp); } } impl<T> VolAddress<T, Unsafe, Unsafe> where T: Copy, { /// Reads the address, applies the operation, and writes back the new value. /// /// ## Safety /// * The safety rules of reading/writing this address depend on the device. /// Consult your hardware manual. #[inline] pub unsafe fn apply<F: FnOnce(&mut T)>(self, op: F) { let mut temp = self.read(); op(&mut temp); self.write(temp); } } impl<T, R, W> Clone for VolAddress<T, R, W> { #[inline] #[must_use] fn clone(&self) -> Self { *self } } impl<T, R, W> Copy for VolAddress<T, R, W> {} impl<T, R, W> core::fmt::Debug for VolAddress<T, R, W> { #[cold] fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result { write!( f, "VolAddress<{elem_ty}, r{readability}, w{writeability}>({address:#X})", elem_ty = core::any::type_name::<T>(), readability = core::any::type_name::<R>(), writeability = core::any::type_name::<W>(), address = self.address.get() ) } }