Introduce Uint::new_overflowing_shr

RustCrypto · Jan 24, 2025 · b04e142 · b04e142
1 parent 1c98833
commit b04e142
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Showing 2 changed files with 20 additions and 9 deletions.
diff --git a/benches/uint.rs b/benches/uint.rs
@@ -1,8 +1,6 @@
+use std::ops::Mul;
 use criterion::{black_box, criterion_group, criterion_main, BatchSize, Criterion};
-use crypto_bigint::{
-    Limb, NonZero, Odd, Random, RandomBits, RandomMod, Reciprocal, Uint, U1024, U128, U2048, U256,
-    U4096, U512,
-};
+use crypto_bigint::{Limb, NonZero, Odd, Random, RandomBits, RandomMod, Reciprocal, Uint, U1024, U128, U2048, U256, U4096, U512, U64};
 use rand_chacha::ChaCha8Rng;
 use rand_core::{OsRng, RngCore, SeedableRng};
 
@@ -405,6 +403,14 @@ fn bench_shr(c: &mut Criterion) {
         )
     });
 
+    group.bench_function("new shr, U2048", |b| {
+        b.iter_batched(
+            || U2048::ONE,
+            |x| x.new_overflowing_shr(1024 + 10),
+            BatchSize::SmallInput,
+        )
+    });
+
     group.finish();
 }
 
@@ -487,11 +493,11 @@ fn bench_sqrt(c: &mut Criterion) {
 
 criterion_group!(
     benches,
-    bench_random,
-    bench_mul,
-    bench_division,
-    bench_gcd,
-    bench_shl,
+    // bench_random,
+    // bench_mul,
+    // bench_division,
+    // bench_gcd,
+    // bench_shl,
     bench_shr,
     bench_inv_mod,
     bench_sqrt

diff --git a/src/uint/shr.rs b/src/uint/shr.rs
@@ -47,6 +47,11 @@ impl<const LIMBS: usize> Uint<LIMBS> {
         ConstCtOption::new(Uint::select(&result, &Self::ZERO, overflow), overflow.not())
     }
 
+    pub const fn new_overflowing_shr(&self, shift: u32) -> ConstCtOption<Self> {
+        let (intra_limb_shift, limb_shift) = (shift % Limb::BITS, shift / Limb::BITS);
+        self.intra_limb_carrying_shr_internal(intra_limb_shift).full_limb_shr(limb_shift)
+    }
+
     /// Computes `self >> shift`, for `shift < Limb::BITS`.
     ///
     /// Returns `None` if `shift >= Limb::BITS`.