/rust/registry/src/index.crates.io-1949cf8c6b5b557f/bitvec-1.0.1/src/field.rs

Source
#![doc = include_str!("../doc/field.md")]

use core::{
  mem,
  ptr,
};

use funty::Integral;
use tap::Pipe;
use wyz::comu::{
  Const,
  Mut,
};

use crate::{
  array::BitArray,
  devel as dvl,
  domain::{
    Domain,
    PartialElement,
  },
  mem::bits_of,
  order::{
    BitOrder,
    Lsb0,
    Msb0,
  },
  slice::BitSlice,
  store::BitStore,
  view::BitViewSized,
};
#[cfg(feature = "alloc")]
use crate::{
  boxed::BitBox,
  vec::BitVec,
};

mod io;
mod tests;

#[doc = include_str!("../doc/field/BitField.md")]
pub trait BitField {
  #[inline]
  #[cfg(not(tarpaulin_include))]
  #[doc = include_str!("../doc/field/BitField_load.md")]
  fn load<I>(&self) -> I
  where I: Integral {
    if cfg!(target_endian = "little") {
      self.load_le::<I>()
    }
    else if cfg!(target_endian = "big") {
      self.load_be::<I>()
    }
    else {
      match option_env!("CARGO_PKG_REPOSITORY") {
        Some(env) => unreachable!(
          "This architecture is not supported! Please consider \
           filing an issue at {}",
          env
        ),
        None => unreachable!(
          "This architecture is not supported! Please consider \
           filing an issue"
        ),
      }
    }
  }

  #[inline]
  #[cfg(not(tarpaulin_include))]
  #[doc = include_str!("../doc/field/BitField_store.md")]
  fn store<I>(&mut self, value: I)
  where I: Integral {
    if cfg!(target_endian = "little") {
      self.store_le::<I>(value);
    }
    else if cfg!(target_endian = "big") {
      self.store_be::<I>(value);
    }
    else {
      match option_env!("CARGO_PKG_REPOSITORY") {
        Some(env) => unreachable!(
          "This architecture is not supported! Please consider \
           filing an issue at {}",
          env
        ),
        None => unreachable!(
          "This architecture is not supported! Please consider \
           filing an issue"
        ),
      }
    }
  }

  #[doc = include_str!("../doc/field/BitField_load_le.md")]
  fn load_le<I>(&self) -> I
  where I: Integral;

  #[doc = include_str!("../doc/field/BitField_load_be.md")]
  fn load_be<I>(&self) -> I
  where I: Integral;

  #[doc = include_str!("../doc/field/BitField_store_le.md")]
  fn store_le<I>(&mut self, value: I)
  where I: Integral;

  #[doc = include_str!("../doc/field/BitField_store_be.md")]
  fn store_be<I>(&mut self, value: I)
  where I: Integral;
}

#[doc = include_str!("../doc/field/BitField_Lsb0.md")]
impl<T> BitField for BitSlice<T, Lsb0>
where T: BitStore
{
  #[inline]
  #[doc = include_str!("../doc/field/BitField_Lsb0_load_le.md")]
  fn load_le<I>(&self) -> I
  where I: Integral {
    let len = self.len();
    check::<I>("load", len);

    match self.domain() {
      //  In Lsb0, the head counts distance from LSedge to first live bit.
      Domain::Enclave(elem) => get(elem, elem.head().into_inner()),
      Domain::Region { head, body, tail } => {
        let mut accum = I::ZERO;

        if let Some(elem) = tail {
          accum = get(elem, 0);
        }

        for elem in body.iter().rev().map(BitStore::load_value) {
          maybe_shift_left(&mut accum, bits_of::<T>());
          accum |= resize::<T::Mem, I>(elem);
        }

        if let Some(elem) = head {
          let shamt = elem.head().into_inner();
          maybe_shift_left(
            &mut accum,
            bits_of::<T>() - shamt as usize,
          );
          accum |= get::<_, _, I>(elem, shamt);
        }

        accum
      },
    }
    .pipe(|elem| sign(elem, len))
  }

  #[inline]
  #[doc = include_str!("../doc/field/BitField_Lsb0_load_be.md")]
  fn load_be<I>(&self) -> I
  where I: Integral {
    let len = self.len();
    check::<I>("load", len);

    match self.domain() {
      Domain::Enclave(elem) => get(elem, elem.head().into_inner()),
      Domain::Region { head, body, tail } => {
        let mut accum = I::ZERO;

        if let Some(elem) = head {
          accum = get(elem, elem.head().into_inner());
        }

        for elem in body.iter().map(BitStore::load_value) {
          maybe_shift_left(&mut accum, bits_of::<T>());
          accum |= resize::<T::Mem, I>(elem);
        }

        if let Some(elem) = tail {
          let shamt = elem.tail().into_inner() as usize;
          maybe_shift_left(&mut accum, shamt);
          accum |= get::<_, _, I>(elem, 0);
        }

        accum
      },
    }
    .pipe(|elem| sign(elem, len))
  }

  #[inline]
  #[doc = include_str!("../doc/field/BitField_Lsb0_store_le.md")]
  fn store_le<I>(&mut self, mut value: I)
  where I: Integral {
    check::<I>("store", self.len());

    match self.domain_mut() {
      Domain::Enclave(elem) => {
        let shamt = elem.head().into_inner();
        set(elem, value, shamt);
      },
      Domain::Region { head, body, tail } => {
        if let Some(elem) = head {
          let shamt = elem.head().into_inner();
          set(elem, value, shamt);
          let rshamt = bits_of::<T>() - shamt as usize;
          maybe_shift_right(&mut value, rshamt);
        }

        for elem in body.iter_mut() {
          elem.store_value(resize(value));
          maybe_shift_right(&mut value, bits_of::<T>());
        }

        if let Some(elem) = tail {
          set(elem, value, 0);
        }
      },
    }
  }

  #[inline]
  #[doc = include_str!("../doc/field/BitField_Lsb0_store_be.md")]
  fn store_be<I>(&mut self, mut value: I)
  where I: Integral {
    check::<I>("store", self.len());

    match self.domain_mut() {
      Domain::Enclave(elem) => {
        let shamt = elem.head().into_inner();
        set(elem, value, shamt);
      },
      Domain::Region { head, body, tail } => {
        if let Some(elem) = tail {
          let shamt = elem.tail().into_inner() as usize;
          set(elem, value, 0);
          maybe_shift_right(&mut value, shamt);
        }

        for elem in body.iter_mut().rev() {
          elem.store_value(resize(value));
          maybe_shift_right(&mut value, bits_of::<T>());
        }

        if let Some(elem) = head {
          let shamt = elem.head().into_inner();
          set(elem, value, shamt);
        }
      },
    }
  }
}

#[doc = include_str!("../doc/field/BitField_Msb0.md")]
impl<T> BitField for BitSlice<T, Msb0>
where T: BitStore
{
  #[inline]
  #[doc = include_str!("../doc/field/BitField_Msb0_load_le.md")]
  fn load_le<I>(&self) -> I
  where I: Integral {
    let len = self.len();
    check::<I>("load", len);

    match self.domain() {
      Domain::Enclave(elem) => {
        let shamt = bits_of::<T>() as u8 - elem.tail().into_inner();
        get(elem, shamt)
      },
      Domain::Region { head, body, tail } => {
        let mut accum = I::ZERO;

        if let Some(elem) = tail {
          let shamt = bits_of::<T>() as u8 - elem.tail().into_inner();
          accum = get(elem, shamt);
        }

        for elem in body.iter().rev().map(BitStore::load_value) {
          maybe_shift_left(&mut accum, bits_of::<T>());
          accum |= resize::<T::Mem, I>(elem);
        }

        if let Some(elem) = head {
          let shamt =
            bits_of::<T>() - elem.head().into_inner() as usize;
          maybe_shift_left(&mut accum, shamt);
          accum |= get::<_, _, I>(elem, 0);
        }

        accum
      },
    }
    .pipe(|elem| sign(elem, len))
  }

  #[inline]
  #[doc = include_str!("../doc/field/BitField_Msb0_load_be.md")]
  fn load_be<I>(&self) -> I
  where I: Integral {
    let len = self.len();
    check::<I>("load", len);

    match self.domain() {
      Domain::Enclave(elem) => {
        let shamt = bits_of::<T>() as u8 - elem.tail().into_inner();
        get(elem, shamt)
      },
      Domain::Region { head, body, tail } => {
        let mut accum = I::ZERO;

        if let Some(elem) = head {
          accum = get(elem, 0);
        }

        for elem in body.iter().map(BitStore::load_value) {
          maybe_shift_left(&mut accum, bits_of::<T>());
          accum |= resize::<T::Mem, I>(elem);
        }

        if let Some(elem) = tail {
          let shamt = elem.tail().into_inner();
          maybe_shift_left(&mut accum, shamt as usize);
          accum |= get::<_, _, I>(elem, bits_of::<T>() as u8 - shamt);
        }

        accum
      },
    }
    .pipe(|elem| sign(elem, len))
  }

  #[inline]
  #[doc = include_str!("../doc/field/BitField_Msb0_store_le.md")]
  fn store_le<I>(&mut self, mut value: I)
  where I: Integral {
    check::<I>("store", self.len());

    match self.domain_mut() {
      Domain::Enclave(elem) => {
        let shamt = bits_of::<T>() as u8 - elem.tail().into_inner();
        set(elem, value, shamt);
      },
      Domain::Region { head, body, tail } => {
        if let Some(elem) = head {
          let shamt =
            bits_of::<T>() - elem.head().into_inner() as usize;
          set(elem, value, 0);
          maybe_shift_right(&mut value, shamt);
        }

        for elem in body.iter_mut() {
          elem.store_value(resize(value));
          maybe_shift_right(&mut value, bits_of::<T>());
        }

        if let Some(elem) = tail {
          let shamt = bits_of::<T>() as u8 - elem.tail().into_inner();
          set(elem, value, shamt);
        }
      },
    }
  }

  #[inline]
  #[doc = include_str!("../doc/field/BitField_Msb0_store_be.md")]
  fn store_be<I>(&mut self, mut value: I)
  where I: Integral {
    check::<I>("store", self.len());

    match self.domain_mut() {
      Domain::Enclave(elem) => {
        let shamt = bits_of::<T>() as u8 - elem.tail().into_inner();
        set(elem, value, shamt);
      },
      Domain::Region { head, body, tail } => {
        if let Some(elem) = tail {
          let tail = elem.tail().into_inner() as usize;
          let shamt = bits_of::<T>() - tail;
          set(elem, value, shamt as u8);
          maybe_shift_right(&mut value, tail);
        }

        for elem in body.iter_mut().rev() {
          elem.store_value(resize(value));
          maybe_shift_right(&mut value, bits_of::<T>());
        }

        if let Some(elem) = head {
          set(elem, value, 0);
        }
      },
    }
  }
}

#[doc = include_str!("../doc/field/impl_BitArray.md")]
impl<A, O> BitField for BitArray<A, O>
where
  O: BitOrder,
  A: BitViewSized,
  BitSlice<A::Store, O>: BitField,
{
  #[inline(always)]
  fn load_le<I>(&self) -> I
  where I: Integral {
    let mut accum = I::ZERO;

    for elem in self.as_raw_slice().iter().map(BitStore::load_value).rev() {
      maybe_shift_left(&mut accum, bits_of::<A::Store>());
      accum |= resize::<_, I>(elem);
    }

    sign(accum, self.len())
  }

  #[inline(always)]
  fn load_be<I>(&self) -> I
  where I: Integral {
    let mut accum = I::ZERO;

    for elem in self.as_raw_slice().iter().map(BitStore::load_value) {
      maybe_shift_left(&mut accum, bits_of::<A::Store>());
      accum |= resize::<_, I>(elem);
    }

    sign(accum, self.len())
  }

  #[inline(always)]
  fn store_le<I>(&mut self, mut value: I)
  where I: Integral {
    for slot in self.as_raw_mut_slice() {
      slot.store_value(resize(value));
      maybe_shift_right(&mut value, bits_of::<A::Store>());
    }
  }

  #[inline(always)]
  fn store_be<I>(&mut self, mut value: I)
  where I: Integral {
    for slot in self.as_raw_mut_slice().iter_mut().rev() {
      slot.store_value(resize(value));
      maybe_shift_right(&mut value, bits_of::<A::Store>());
    }
  }
}

#[cfg(feature = "alloc")]
#[cfg(not(tarpaulin_include))]
impl<T, O> BitField for BitBox<T, O>
where
  T: BitStore,
  O: BitOrder,
  BitSlice<T, O>: BitField,
{
  #[inline(always)]
  fn load_le<I>(&self) -> I
  where I: Integral {
    self.as_bitslice().load_le()
  }

  #[inline(always)]
  fn load_be<I>(&self) -> I
  where I: Integral {
    self.as_bitslice().load_be()
  }

  #[inline(always)]
  fn store_le<I>(&mut self, value: I)
  where I: Integral {
    self.as_mut_bitslice().store_le(value)
  }

  #[inline(always)]
  fn store_be<I>(&mut self, value: I)
  where I: Integral {
    self.as_mut_bitslice().store_be(value)
  }
}

#[cfg(feature = "alloc")]
#[cfg(not(tarpaulin_include))]
impl<T, O> BitField for BitVec<T, O>
where
  T: BitStore,
  O: BitOrder,
  BitSlice<T, O>: BitField,
{
  #[inline(always)]
  fn load_le<I>(&self) -> I
  where I: Integral {
    self.as_bitslice().load_le()
  }

  #[inline(always)]
  fn load_be<I>(&self) -> I
  where I: Integral {
    self.as_bitslice().load_be()
  }

  #[inline(always)]
  fn store_le<I>(&mut self, value: I)
  where I: Integral {
    self.as_mut_bitslice().store_le(value)
  }

  #[inline(always)]
  fn store_be<I>(&mut self, value: I)
  where I: Integral {
    self.as_mut_bitslice().store_be(value)
  }
}

/** Asserts that a bit-slice is not longer than a memory element.

## Type Parameters

- `I`: The integer type being stored into or loaded out of a bit-slice.

## Parameters

- `action`: the verb being performed. One of `"load"` or `"store"`.
- `len`: the length of the bit-slice under test.

## Panics

This panics if `len` is not in `1 ..= U::BITS`.
**/
fn check<I>(action: &'static str, len: usize)
where I: Integral {
  assert!(
    (1 ..= bits_of::<I>()).contains(&len),
    "cannot {} {} bits from a {}-bit region",
    action,
    bits_of::<I>(),
    len,
  );
}

/// Shifts a value to the left, if it can support the shift amount.
fn maybe_shift_left<T: Integral>(elem: &mut T, shamt: usize) {
  if bits_of::<T>() > shamt {
    *elem <<= shamt;
  }
}

/// Shifts a value to the right, if it can support the shift amount.
fn maybe_shift_right<T: Integral>(elem: &mut T, shamt: usize) {
  if bits_of::<T>() > shamt {
    *elem >>= shamt;
  }
}

#[doc = include_str!("../doc/field/get.md")]
fn get<T, O, I>(elem: PartialElement<Const, T, O>, shamt: u8) -> I
where
  T: BitStore,
  O: BitOrder,
  I: Integral,
{
  resize::<T::Mem, I>(elem.load_value() >> shamt)
}

#[doc = include_str!("../doc/field/set.md")]
fn set<T, O, I>(mut elem: PartialElement<Mut, T, O>, value: I, shamt: u8)
where
  T: BitStore,
  O: BitOrder,
  I: Integral,
{
  elem.store_value(resize::<I, T::Mem>(value) << shamt);
}

#[doc = include_str!("../doc/field/sign.md")]
fn sign<I>(elem: I, width: usize) -> I
where I: Integral {
  if dvl::is_unsigned::<I>() {
    return elem;
  }
  //  Find the number of high bits that are not loaded.
  let shamt = bits_of::<I>() - width;
  //  Shift left, so that the highest loaded bit is now in the sign position.
  let shl: I = elem << shamt;
  //  Shift right with sign extension back to the original place.
  shl >> shamt
}

#[doc = include_str!("../doc/field/resize.md")]
fn resize<T, U>(value: T) -> U
where
  T: Integral,
  U: Integral,
{
  let mut out = U::ZERO;
  let size_t = mem::size_of::<T>();
  let size_u = mem::size_of::<U>();

  unsafe {
    resize_inner::<T, U>(&value, &mut out, size_t, size_u);
  }

  out
}

/// Performs little-endian byte-order register resizing.
#[cfg(target_endian = "little")]
unsafe fn resize_inner<T, U>(
  src: &T,
  dst: &mut U,
  size_t: usize,
  size_u: usize,
) {
  //  In LE, the least-significant byte is the base address, so resizing is
  //  just a `memmove` into a zeroed slot, taking only the lesser width.
  ptr::copy_nonoverlapping(
    src as *const T as *const u8,
    dst as *mut U as *mut u8,
    size_t.min(size_u),
  );
}

/// Performs big-endian byte-order register resizing.
#[cfg(target_endian = "big")]
unsafe fn resize_inner<T, U>(
  src: &T,
  dst: &mut U,
  size_t: usize,
  size_u: usize,
) {
  let src = src as *const T as *const u8;
  let dst = dst as *mut U as *mut u8;

  //  In BE, shrinking a value requires moving the source base-pointer up in
  //  memory (to a higher address, lower significance),
  if size_t > size_u {
    ptr::copy_nonoverlapping(src.add(size_t - size_u), dst, size_u);
  }
  //  While expanding a value requires moving the *destination* base-pointer
  //  up (and leaving the lower address, higher significance bytes zeroed).
  else {
    ptr::copy_nonoverlapping(src, dst.add(size_u - size_t), size_t);
  }
}

Coverage Report

Created: 2026-05-30 06:08