From d6284beca7430df850dbed9ee9c867d546de8b78 Mon Sep 17 00:00:00 2001
From: Tomek Czajka <tczajka@gmail.com>
Date: Thu, 7 Sep 2023 18:37:44 +0200
Subject: [PATCH] Use BITS from core.

---
 src/convert.rs     |  2 +-
 src/math.rs        |  8 ++++----
 src/modular/pow.rs |  6 +++---
 src/pow.rs         |  3 +--
 src/primitive.rs   | 14 +++++++-------
 5 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/src/convert.rs b/src/convert.rs
index 86d2c1c..41c986b 100644
--- a/src/convert.rs
+++ b/src/convert.rs
@@ -583,7 +583,7 @@ where
         Err(OutOfBoundsError)
     } else {
         assert!(
-            T::BIT_SIZE % WORD_BITS == 0,
+            T::BITS % WORD_BITS == 0,
             "A large primitive type not a multiple of word size."
         );
         let mut repr = T::default().to_le_bytes();
diff --git a/src/math.rs b/src/math.rs
index e9a03a8..65845e6 100644
--- a/src/math.rs
+++ b/src/math.rs
@@ -6,14 +6,14 @@ use crate::{arch::word::Word, primitive::PrimitiveUnsigned};
 /// 0 for 0.
 #[inline]
 pub(crate) fn bit_len<T: PrimitiveUnsigned>(x: T) -> u32 {
-    T::BIT_SIZE - x.leading_zeros()
+    T::BITS - x.leading_zeros()
 }
 
 /// The length of an integer in bits.
 /// 0 for 0.
 #[inline]
 pub(crate) const fn bit_len_word(x: Word) -> u32 {
-    Word::BIT_SIZE - x.leading_zeros()
+    Word::BITS - x.leading_zeros()
 }
 
 /// Ceiling of log_2(x).
@@ -73,7 +73,7 @@ where
     if n == 0 {
         T::from(0u8)
     } else {
-        T::MAX >> (T::BIT_SIZE - n)
+        T::MAX >> (T::BITS - n)
     }
 }
 
@@ -83,7 +83,7 @@ pub(crate) const fn ones_word(n: u32) -> Word {
     if n == 0 {
         0
     } else {
-        Word::MAX >> (Word::BIT_SIZE - n)
+        Word::MAX >> (Word::BITS - n)
     }
 }
 
diff --git a/src/modular/pow.rs b/src/modular/pow.rs
index c60ff76..29b55ac 100644
--- a/src/modular/pow.rs
+++ b/src/modular/pow.rs
@@ -7,7 +7,7 @@ use crate::{
         modulo::{Modulo, ModuloLarge, ModuloRepr, ModuloSmall, ModuloSmallRaw},
         modulo_ring::ModuloRingSmall,
     },
-    primitive::{double_word, split_double_word, PrimitiveUnsigned, WORD_BITS, WORD_BITS_USIZE},
+    primitive::{double_word, split_double_word, WORD_BITS, WORD_BITS_USIZE},
     sign::Sign::*,
     ubig::{Repr::*, UBig},
 };
@@ -226,14 +226,14 @@ impl<'a> ModuloLarge<'a> {
     }
 
     /// Choose the optimal window size for n-bit exponents.
-    /// 1 <= window_size < min(WORD_BITS, usize::BIT_SIZE) inclusive.
+    /// 1 <= window_size < min(WORD_BITS, usize::BITS) inclusive.
     fn choose_pow_window_len(n: usize) -> u32 {
         // This won't overflow because cost(3) is already approximately usize::MAX / 4
         // and it can only grow by a factor of 2.
         let cost = |window_size| (1usize << (window_size - 1)) - 1 + n / (window_size as usize + 1);
         let mut window_size = 1;
         let mut c = cost(window_size);
-        while window_size + 1 < WORD_BITS.min(usize::BIT_SIZE) {
+        while window_size + 1 < WORD_BITS.min(usize::BITS) {
             let c2 = cost(window_size + 1);
             if c <= c2 {
                 break;
diff --git a/src/pow.rs b/src/pow.rs
index 6f79b24..515378f 100644
--- a/src/pow.rs
+++ b/src/pow.rs
@@ -2,7 +2,6 @@
 
 use crate::{
     ibig::IBig,
-    primitive::PrimitiveUnsigned,
     sign::Sign::*,
     ubig::{Repr::*, UBig},
 };
@@ -34,7 +33,7 @@ impl UBig {
             }
             _ => {}
         }
-        let mut p = usize::BIT_SIZE - 2 - exp.leading_zeros();
+        let mut p = usize::BITS - 2 - exp.leading_zeros();
         let mut res = self * self;
         loop {
             if exp & (1 << p) != 0 {
diff --git a/src/primitive.rs b/src/primitive.rs
index d93b0f7..0f8df73 100644
--- a/src/primitive.rs
+++ b/src/primitive.rs
@@ -46,7 +46,7 @@ where
     Self: Shr<u32, Output = Self>,
 {
     const BYTE_SIZE: usize = mem::size_of::<Self>();
-    const BIT_SIZE: u32 = 8 * Self::BYTE_SIZE as u32;
+    const BITS: u32;
     const MAX: Self;
     type ByteRepr: AsRef<[u8]> + AsMut<[u8]>;
 
@@ -72,8 +72,8 @@ where
 macro_rules! impl_primitive_unsigned {
     ($t:ty) => {
         impl PrimitiveUnsigned for $t {
-            // LEGACY: In Rust 1.49 this could be [u8; Self::BYTE_SIZE].
-            type ByteRepr = [u8; mem::size_of::<Self>()];
+            type ByteRepr = [u8; Self::BYTE_SIZE];
+            const BITS: u32 = Self::BITS;
             const MAX: Self = Self::MAX;
 
             #[inline]
@@ -143,7 +143,7 @@ impl_primitive_signed!(i64, u64);
 impl_primitive_signed!(i128, u128);
 impl_primitive_signed!(isize, usize);
 
-pub(crate) const WORD_BITS: u32 = Word::BIT_SIZE;
+pub(crate) const WORD_BITS: u32 = Word::BITS;
 pub(crate) const WORD_BITS_USIZE: usize = WORD_BITS as usize;
 pub(crate) const WORD_BYTES: usize = Word::BYTE_SIZE;
 
@@ -167,8 +167,8 @@ mod tests {
 
     #[test]
     fn test_bits_bytes() {
-        assert_eq!(u8::BIT_SIZE, 8);
-        assert_eq!(u64::BIT_SIZE, 64);
+        assert_eq!(u8::BITS, 8);
+        assert_eq!(u64::BITS, 64);
         assert_eq!(u8::BYTE_SIZE, 1);
         assert_eq!(u64::BYTE_SIZE, 8);
     }
@@ -185,7 +185,7 @@ mod tests {
 
     #[test]
     fn test_double_word() {
-        assert_eq!(DoubleWord::BIT_SIZE, 2 * WORD_BITS);
+        assert_eq!(DoubleWord::BITS, 2 * WORD_BITS);
         assert_eq!(split_double_word(double_word(3, 4)), (3, 4));
     }