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use {Bits, BitsMut};
use range_compat::*;

/// Types that support slicing by ranges.
///
/// Note that the [`bit_slice`] method takes `self` by value, which allows
/// the `Slice` associated type to refer to the lifetime of `Self` in impls
/// for borrowed types. For example, the impl for `&'a BitVec<u32>` has a
/// `Slice` type of `BitSlice<'a, u32>`.
///
/// [`bit_slice`]: #tymethod.bit_slice
pub trait BitSliceable<Range>: Bits {
    /// The type of the slice produced.
    type Slice: Bits<Block = Self::Block>;

    /// Slices or re-slices the given object.
    ///
    /// # Examples
    ///
    /// ```
    /// use bv::{BitSlice, BitSliceable};
    ///
    /// let array = [0b01010011u16];
    /// let slice = BitSlice::from_slice(&array);
    ///
    /// assert_eq!( slice.bit_slice(1..3), slice.bit_slice(4..6) );
    /// assert_eq!( slice.bit_slice(1..3), slice.bit_slice(6..8) );
    ///
    /// assert_ne!( slice.bit_slice(2..4), slice.bit_slice(6..8) );
    /// assert_eq!( slice.bit_slice(2..4), slice.bit_slice(7..9) );
    /// ```
    fn bit_slice(self, range: Range) -> Self::Slice;
}

/// Types that produce mutable slices.
///
/// Do not implement this trait; there is a blanket impl for all
/// [`BitSliceable`] types whose associated `Slice` types implement `BitsMut`.
///
/// [`BitSliceable`]: trait.BitSliceable.html
pub trait BitSliceableMut<Range>: BitSliceable<Range> {
    /// An alias for
    /// [`BitSliceable::bit_slice`](trait.BitSliceable.html#tymethod.bit_slice).
    ///
    /// This method provides no additional functionality over `bit_slice`.
    /// However, it can be used to force auto-ref to choose a `Self` type
    /// that implements `BitSliceableMut`.
    fn bit_slice_mut(self, range: Range) -> Self::Slice where Self: Sized {
        self.bit_slice(range)
    }
}

impl<Range, T> BitSliceableMut<Range> for T
    where T: BitSliceable<Range>,
          T::Slice: BitsMut { }


impl<'a> BitSliceable<RangeFull> for &'a [bool] {
    type Slice = &'a [bool];

    fn bit_slice(self, _: RangeFull) -> &'a [bool] {
        self
    }
}

impl<'a> BitSliceable<RangeFull> for &'a mut [bool] {
    type Slice = &'a mut [bool];

    fn bit_slice(self, _: RangeFull) -> &'a mut [bool] {
        self
    }
}

impl<'a> BitSliceable<Range<u64>> for &'a [bool] {
    type Slice = &'a [bool];

    fn bit_slice(self, range: Range<u64>) -> &'a [bool] {
        &self[range.start as usize .. range.end as usize]
    }
}

impl<'a> BitSliceable<Range<u64>> for &'a mut [bool] {
    type Slice = &'a mut [bool];

    fn bit_slice(self, range: Range<u64>) -> &'a mut [bool] {
        &mut self[range.start as usize .. range.end as usize]
    }
}

#[cfg(inclusive_range)]
impl<'a> BitSliceable<RangeInclusive<u64>> for &'a [bool] {
    type Slice = &'a [bool];

    fn bit_slice(self, range: RangeInclusive<u64>) -> &'a [bool] {
        let (start, end) = get_inclusive_bounds(range)
            .expect("<&[bool]>::bit_slice: bad inclusive range");
        // Adding 1 means we could overflow a 32-bit `usize` here, but
        // we can't construct a RangeInclusive on stable without using
        // the `..=` token, which breaks older rustcs.
        &self[start as usize .. end as usize + 1]
    }
}

#[cfg(inclusive_range)]
impl<'a> BitSliceable<RangeInclusive<u64>> for &'a mut [bool] {
    type Slice = &'a mut [bool];

    fn bit_slice(self, range: RangeInclusive<u64>) -> &'a mut [bool] {
        let (start, end) = get_inclusive_bounds(range)
            .expect("<&mut [bool]>::bit_slice: bad inclusive range");
        &mut self[start as usize .. end as usize + 1]
    }
}

impl<'a> BitSliceable<RangeFrom<u64>> for &'a [bool] {
    type Slice = &'a [bool];

    fn bit_slice(self, range: RangeFrom<u64>) -> &'a [bool] {
        &self[range.start as usize ..]
    }
}

impl<'a> BitSliceable<RangeFrom<u64>> for &'a mut [bool] {
    type Slice = &'a mut [bool];

    fn bit_slice(self, range: RangeFrom<u64>) -> &'a mut [bool] {
        &mut self[range.start as usize ..]
    }
}

impl<'a> BitSliceable<RangeTo<u64>> for &'a [bool] {
    type Slice = &'a [bool];

    fn bit_slice(self, range: RangeTo<u64>) -> &'a [bool] {
        &self[.. range.end as usize]
    }
}

impl<'a> BitSliceable<RangeTo<u64>> for &'a mut [bool] {
    type Slice = &'a mut [bool];

    fn bit_slice(self, range: RangeTo<u64>) -> &'a mut [bool] {
        &mut self[.. range.end as usize]
    }
}

#[cfg(inclusive_range)]
impl<'a> BitSliceable<RangeToInclusive<u64>> for &'a [bool] {
    type Slice = &'a [bool];

    fn bit_slice(self, range: RangeToInclusive<u64>) -> &'a [bool] {
        &self[RangeToInclusive { end: range.end as usize }]
    }
}

#[cfg(inclusive_range)]
impl<'a> BitSliceable<RangeToInclusive<u64>> for &'a mut [bool] {
    type Slice = &'a mut [bool];

    fn bit_slice(self, range: RangeToInclusive<u64>) -> &'a mut [bool] {
        &mut self[RangeToInclusive { end: range.end as usize }]
    }
}