1use itertools::izip;
  2use rand_distr::num_traits::Zero;
  3
  4pub trait ZnxInfos {
  5    /// Returns the ring degree of the polynomials.
  6    fn n(&self) -> usize;
  7
  8    /// Returns the base two logarithm of the ring dimension of the polynomials.
  9    fn log_n(&self) -> usize {
 10        (usize::BITS - (self.n() - 1).leading_zeros()) as _
 11    }
 12
 13    /// Returns the number of rows.
 14    fn rows(&self) -> usize;
 15
 16    /// Returns the number of polynomials in each row.
 17    fn cols(&self) -> usize;
 18
 19    /// Returns the number of size per polynomial.
 20    fn size(&self) -> usize;
 21
 22    /// Returns the total number of small polynomials.
 23    fn poly_count(&self) -> usize {
 24        self.rows() * self.cols() * self.size()
 25    }
 26}
 27
 28pub trait ZnxSliceSize {
 29    /// Returns the slice size, which is the offset between
 30    /// two size of the same column.
 31    fn sl(&self) -> usize;
 32}
 33
 34pub trait DataView {
 35    type D;
 36    fn data(&self) -> &Self::D;
 37}
 38
 39pub trait DataViewMut: DataView {
 40    fn data_mut(&mut self) -> &mut Self::D;
 41}
 42
 43pub trait ZnxView: ZnxInfos + DataView<D: AsRef<[u8]>> {
 44    type Scalar: Copy;
 45
 46    /// Returns a non-mutable pointer to the underlying coefficients array.
 47    fn as_ptr(&self) -> *const Self::Scalar {
 48        self.data().as_ref().as_ptr() as *const Self::Scalar
 49    }
 50
 51    /// Returns a non-mutable reference to the entire underlying coefficient array.
 52    fn raw(&self) -> &[Self::Scalar] {
 53        unsafe { std::slice::from_raw_parts(self.as_ptr(), self.n() * self.poly_count()) }
 54    }
 55
 56    /// Returns a non-mutable pointer starting at the j-th small polynomial of the i-th column.
 57    fn at_ptr(&self, i: usize, j: usize) -> *const Self::Scalar {
 58        #[cfg(debug_assertions)]
 59        {
 60            assert!(i < self.cols());
 61            assert!(j < self.size());
 62        }
 63        let offset: usize = self.n() * (j * self.cols() + i);
 64        unsafe { self.as_ptr().add(offset) }
 65    }
 66
 67    /// Returns non-mutable reference to the (i, j)-th small polynomial.
 68    fn at(&self, i: usize, j: usize) -> &[Self::Scalar] {
 69        unsafe { std::slice::from_raw_parts(self.at_ptr(i, j), self.n()) }
 70    }
 71}
 72
 73pub trait ZnxViewMut: ZnxView + DataViewMut<D: AsMut<[u8]>> {
 74    /// Returns a mutable pointer to the underlying coefficients array.
 75    fn as_mut_ptr(&mut self) -> *mut Self::Scalar {
 76        self.data_mut().as_mut().as_mut_ptr() as *mut Self::Scalar
 77    }
 78
 79    /// Returns a mutable reference to the entire underlying coefficient array.
 80    fn raw_mut(&mut self) -> &mut [Self::Scalar] {
 81        unsafe { std::slice::from_raw_parts_mut(self.as_mut_ptr(), self.n() * self.poly_count()) }
 82    }
 83
 84    /// Returns a mutable pointer starting at the j-th small polynomial of the i-th column.
 85    fn at_mut_ptr(&mut self, i: usize, j: usize) -> *mut Self::Scalar {
 86        #[cfg(debug_assertions)]
 87        {
 88            assert!(i < self.cols());
 89            assert!(j < self.size());
 90        }
 91        let offset: usize = self.n() * (j * self.cols() + i);
 92        unsafe { self.as_mut_ptr().add(offset) }
 93    }
 94
 95    /// Returns mutable reference to the (i, j)-th small polynomial.
 96    fn at_mut(&mut self, i: usize, j: usize) -> &mut [Self::Scalar] {
 97        unsafe { std::slice::from_raw_parts_mut(self.at_mut_ptr(i, j), self.n()) }
 98    }
 99}
100
101//(Jay)Note: Can't provide blanket impl. of ZnxView because Scalar is not known
102impl<T> ZnxViewMut for T where T: ZnxView + DataViewMut<D: AsMut<[u8]>> {}
103
104pub trait ZnxZero: ZnxViewMut
105where
106    Self: Sized,
107{
108    fn zero(&mut self) {
109        unsafe {
110            std::ptr::write_bytes(self.as_mut_ptr(), 0, self.n() * self.poly_count());
111        }
112    }
113
114    fn zero_at(&mut self, i: usize, j: usize) {
115        unsafe {
116            std::ptr::write_bytes(self.at_mut_ptr(i, j), 0, self.n());
117        }
118    }
119}
120
121// Blanket implementations
122impl<T> ZnxZero for T where T: ZnxViewMut {}
123
124use std::ops::{Add, AddAssign, Div, Mul, Neg, Shl, Shr, Sub};
125
126use crate::Scratch;
127pub trait Integer:
128    Copy
129    + Default
130    + PartialEq
131    + PartialOrd
132    + Add<Output = Self>
133    + Sub<Output = Self>
134    + Mul<Output = Self>
135    + Div<Output = Self>
136    + Neg<Output = Self>
137    + Shl<Output = Self>
138    + Shr<Output = Self>
139    + AddAssign
140{
141    const BITS: u32;
142}
143
144impl Integer for i64 {
145    const BITS: u32 = 64;
146}
147
148impl Integer for i128 {
149    const BITS: u32 = 128;
150}
151
152//(Jay)Note: `rsh` impl. ignores the column
153pub fn rsh<V: ZnxZero>(k: usize, log_base2k: usize, a: &mut V, _a_col: usize, scratch: &mut Scratch)
154where
155    V::Scalar: From<usize> + Integer + Zero,
156{
157    let n: usize = a.n();
158    let _size: usize = a.size();
159    let cols: usize = a.cols();
160
161    let size: usize = a.size();
162    let steps: usize = k / log_base2k;
163
164    a.raw_mut().rotate_right(n * steps * cols);
165    (0..cols).for_each(|i| {
166        (0..steps).for_each(|j| {
167            a.zero_at(i, j);
168        })
169    });
170
171    let k_rem: usize = k % log_base2k;
172
173    if k_rem != 0 {
174        let (carry, _) = scratch.tmp_slice::<V::Scalar>(rsh_tmp_bytes::<V::Scalar>(n));
175
176        unsafe {
177            std::ptr::write_bytes(carry.as_mut_ptr(), 0, n * size_of::<V::Scalar>());
178        }
179
180        let log_base2k_t = V::Scalar::from(log_base2k);
181        let shift = V::Scalar::from(V::Scalar::BITS as usize - k_rem);
182        let k_rem_t = V::Scalar::from(k_rem);
183
184        (0..cols).for_each(|i| {
185            (steps..size).for_each(|j| {
186                izip!(carry.iter_mut(), a.at_mut(i, j).iter_mut()).for_each(|(ci, xi)| {
187                    *xi += *ci << log_base2k_t;
188                    *ci = (*xi << shift) >> shift;
189                    *xi = (*xi - *ci) >> k_rem_t;
190                });
191            });
192            carry.iter_mut().for_each(|r| *r = V::Scalar::zero());
193        })
194    }
195}
196
197pub fn rsh_tmp_bytes<T>(n: usize) -> usize {
198    n * std::mem::size_of::<T>()
199}