poulpy_hal/layouts/
module.rs

1use std::{fmt::Display, marker::PhantomData, ptr::NonNull};
2
3use rand_distr::num_traits::Zero;
4
5use crate::GALOISGENERATOR;
6
7#[allow(clippy::missing_safety_doc)]
8pub trait Backend: Sized {
9    type ScalarBig: Copy + Zero + Display;
10    type ScalarPrep: Copy + Zero + Display;
11    type Handle: 'static;
12    fn layout_prep_word_count() -> usize;
13    fn layout_big_word_count() -> usize;
14    unsafe fn destroy(handle: NonNull<Self::Handle>);
15}
16
17pub struct Module<B: Backend> {
18    ptr: NonNull<B::Handle>,
19    n: u64,
20    _marker: PhantomData<B>,
21}
22
23impl<B: Backend> Module<B> {
24    /// Construct from a raw pointer managed elsewhere.
25    /// SAFETY: `ptr` must be non-null and remain valid for the lifetime of this Module.
26    #[inline]
27    #[allow(clippy::missing_safety_doc)]
28    pub unsafe fn from_raw_parts(ptr: *mut B::Handle, n: u64) -> Self {
29        Self {
30            ptr: NonNull::new(ptr).expect("null module ptr"),
31            n,
32            _marker: PhantomData,
33        }
34    }
35
36    #[allow(clippy::missing_safety_doc)]
37    #[inline]
38    pub unsafe fn ptr(&self) -> *mut <B as Backend>::Handle {
39        self.ptr.as_ptr()
40    }
41
42    #[inline]
43    pub fn n(&self) -> usize {
44        self.n as usize
45    }
46    #[inline]
47    pub fn as_mut_ptr(&self) -> *mut B::Handle {
48        self.ptr.as_ptr()
49    }
50
51    #[inline]
52    pub fn log_n(&self) -> usize {
53        (usize::BITS - (self.n() - 1).leading_zeros()) as _
54    }
55
56    #[inline]
57    pub fn cyclotomic_order(&self) -> u64 {
58        (self.n() << 1) as _
59    }
60
61    // Returns GALOISGENERATOR^|generator| * sign(generator)
62    #[inline]
63    pub fn galois_element(&self, generator: i64) -> i64 {
64        if generator == 0 {
65            return 1;
66        }
67        ((mod_exp_u64(GALOISGENERATOR, generator.unsigned_abs() as usize) & (self.cyclotomic_order() - 1)) as i64)
68            * generator.signum()
69    }
70
71    // Returns gen^-1
72    #[inline]
73    pub fn galois_element_inv(&self, gal_el: i64) -> i64 {
74        if gal_el == 0 {
75            panic!("cannot invert 0")
76        }
77        ((mod_exp_u64(
78            gal_el.unsigned_abs(),
79            (self.cyclotomic_order() - 1) as usize,
80        ) & (self.cyclotomic_order() - 1)) as i64)
81            * gal_el.signum()
82    }
83}
84
85impl<B: Backend> Drop for Module<B> {
86    fn drop(&mut self) {
87        unsafe { B::destroy(self.ptr) }
88    }
89}
90
91pub fn mod_exp_u64(x: u64, e: usize) -> u64 {
92    let mut y: u64 = 1;
93    let mut x_pow: u64 = x;
94    let mut exp = e;
95    while exp > 0 {
96        if exp & 1 == 1 {
97            y = y.wrapping_mul(x_pow);
98        }
99        x_pow = x_pow.wrapping_mul(x_pow);
100        exp >>= 1;
101    }
102    y
103}
poulpy_hal/layouts/module.rs

poulpy_hal/layouts/
module.rs
