halo2_ecc/bigint/
select.rs

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1use super::{CRTInteger, OverflowInteger};
2use halo2_base::{gates::GateInstructions, utils::ScalarField, AssignedValue, Context};
3use itertools::Itertools;
4use std::cmp::max;
5
6/// # Assumptions
7/// * `a, b` have same number of limbs
8/// * Number of limbs is nonzero
9pub fn assign<F: ScalarField>(
10    gate: &impl GateInstructions<F>,
11    ctx: &mut Context<F>,
12    a: OverflowInteger<F>,
13    b: OverflowInteger<F>,
14    sel: AssignedValue<F>,
15) -> OverflowInteger<F> {
16    let out_limbs = a
17        .limbs
18        .into_iter()
19        .zip_eq(b.limbs)
20        .map(|(a_limb, b_limb)| gate.select(ctx, a_limb, b_limb, sel))
21        .collect();
22
23    OverflowInteger::new(out_limbs, max(a.max_limb_bits, b.max_limb_bits))
24}
25
26pub fn crt<F: ScalarField>(
27    gate: &impl GateInstructions<F>,
28    ctx: &mut Context<F>,
29    a: CRTInteger<F>,
30    b: CRTInteger<F>,
31    sel: AssignedValue<F>,
32) -> CRTInteger<F> {
33    debug_assert_eq!(a.truncation.limbs.len(), b.truncation.limbs.len());
34    let out_limbs = a
35        .truncation
36        .limbs
37        .into_iter()
38        .zip_eq(b.truncation.limbs)
39        .map(|(a_limb, b_limb)| gate.select(ctx, a_limb, b_limb, sel))
40        .collect();
41
42    let out_trunc = OverflowInteger::new(
43        out_limbs,
44        max(a.truncation.max_limb_bits, b.truncation.max_limb_bits),
45    );
46
47    let out_native = gate.select(ctx, a.native, b.native, sel);
48    let out_val = if sel.value().is_zero_vartime() { b.value } else { a.value };
49    CRTInteger::new(out_trunc, out_native, out_val)
50}
halo2_ecc/bigint/select.rs

halo2_ecc/bigint/
select.rs
