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Remove dependency on cfg(target_pointer_width) in src/scalar.rs #35

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Remove dependency on cfg(target_pointer_width) in src/scalar.rs #35

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6389874
Remove dependency on cfg(target_pointer_width) in src/scalar.rs
dot-asm Feb 2, 2022
e8c99ed
Resolve 'dead_code' warning in 32-bit build.
dot-asm Feb 2, 2022
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67 changes: 11 additions & 56 deletions src/scalar.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,6 @@ use core::{
};

use blst::*;
use byte_slice_cast::AsByteSlice;
use ff::{Field, FieldBits, PrimeField, PrimeFieldBits};
use rand_core::RngCore;
use subtle::{Choice, ConditionallySelectable, ConstantTimeEq, CtOption};
Expand Down Expand Up @@ -41,19 +40,6 @@ const MODULUS: [u64; 4] = [
0x73ed_a753_299d_7d48,
];

/// The modulus as u32 limbs.
#[cfg(not(target_pointer_width = "64"))]
const MODULUS_LIMBS_32: [u32; 8] = [
0x0000_0001,
0xffff_ffff,
0xfffe_5bfe,
0x53bd_a402,
0x09a1_d805,
0x3339_d808,
0x299d_7d48,
0x73ed_a753,
];

// Little-endian non-Montgomery form not reduced mod p.
const MODULUS_REPR: [u8; 32] = [
0x01, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xfe, 0x5b, 0xfe, 0xff, 0x02, 0xa4, 0xbd, 0x53,
Expand Down Expand Up @@ -478,62 +464,31 @@ impl PrimeField for Scalar {
}
}

#[cfg(not(target_pointer_width = "64"))]
type ReprBits = [u32; 8];

#[cfg(target_pointer_width = "64")]
type ReprBits = [u64; 4];

impl PrimeFieldBits for Scalar {
// Representation in non-Montgomery form.
type ReprBits = ReprBits;
type ReprBits = [u8; 32];
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this change doesn't quite work for us, as I am trying to mirror this: https://github.com/zkcrypto/bls12_381/blob/main/src/scalar.rs#L729


#[cfg(target_pointer_width = "64")]
fn to_le_bits(&self) -> FieldBits<Self::ReprBits> {
let mut limbs = [0u64; 4];
unsafe { blst_uint64_from_fr(limbs.as_mut_ptr(), &self.0) };
let mut out = blst_scalar::default();
unsafe { blst_scalar_from_fr(&mut out, &self.0) };

FieldBits::new(limbs)
}

#[cfg(not(target_pointer_width = "64"))]
fn to_le_bits(&self) -> FieldBits<Self::ReprBits> {
let bytes = self.to_bytes_le();
let limbs = [
u32::from_le_bytes(bytes[0..4].try_into().unwrap()),
u32::from_le_bytes(bytes[4..8].try_into().unwrap()),
u32::from_le_bytes(bytes[8..12].try_into().unwrap()),
u32::from_le_bytes(bytes[12..16].try_into().unwrap()),
u32::from_le_bytes(bytes[16..20].try_into().unwrap()),
u32::from_le_bytes(bytes[20..24].try_into().unwrap()),
u32::from_le_bytes(bytes[24..28].try_into().unwrap()),
u32::from_le_bytes(bytes[28..32].try_into().unwrap()),
];
FieldBits::new(limbs)
FieldBits::new(out.b)
}

fn char_le_bits() -> FieldBits<Self::ReprBits> {
#[cfg(not(target_pointer_width = "64"))]
{
FieldBits::new(MODULUS_LIMBS_32)
}

#[cfg(target_pointer_width = "64")]
FieldBits::new(MODULUS)
FieldBits::new(MODULUS_REPR)
}
}

impl Scalar {
/// Attempts to convert a little-endian byte representation of
/// a scalar into a `Scalar`, failing if the input is not canonical.
pub fn from_bytes_le(bytes: &[u8; 32]) -> CtOption<Scalar> {
let is_some =
Choice::from(unsafe { blst_scalar_fr_check(&blst_scalar { b: *bytes }) as u8 });

let s = bytes.as_ptr() as *const blst_scalar;
let is_some = Choice::from(unsafe { blst_scalar_fr_check(s) as u8 });
let mut out = blst_fr::default();
let bytes_u64 = u64s_from_bytes(bytes);

unsafe { blst_fr_from_uint64(&mut out, bytes_u64.as_ptr()) };
unsafe { blst_fr_from_scalar(&mut out, s) };

CtOption::new(Scalar(out), is_some)
}
Expand All @@ -550,9 +505,9 @@ impl Scalar {
/// little-endian byte order.
#[inline]
pub fn to_bytes_le(&self) -> [u8; 32] {
let mut out = [0u64; 4];
unsafe { blst_uint64_from_fr(out.as_mut_ptr(), &self.0) };
out.as_byte_slice().try_into().unwrap()
let mut out = blst_scalar::default();
unsafe { blst_scalar_from_fr(&mut out, &self.0) };
out.b
}

/// Converts an element of `Scalar` into a byte representation in
Expand Down