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Add radix51 impl of from_bytes

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Henry de Valence 2017-03-12 23:18:35 -07:00
parent 7f8b3fe594
commit 08ac5a9068
1 changed files with 16 additions and 15 deletions
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31
src/field.rs
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@ -75,21 +75,6 @@ pub fn mul64(a: &[u64;5], b: &[u64;5]) -> [u64;5] {
[c0,c1,c2,c3,c4]
}
fn from_bytes_64(bytes: &[u8;32]) -> [u64; 5] {
let low_51_bit_mask = (1u64 << 51) - 1;
// load bits [ 0, 64), no shift
[ load8(&bytes[ 0..]) & low_51_bit_mask
// load bits [ 48,112), shift to [ 51,112)
, (load8(&bytes[ 6..]) >> 3) & low_51_bit_mask
// load bits [ 96,160), shift to [102,160)
, (load8(&bytes[12..]) >> 6) & low_51_bit_mask
// load bits [152,216), shift to [153,216)
, (load8(&bytes[19..]) >> 1) & low_51_bit_mask
// load bits [192,256), shift to [204,112)
, (load8(&bytes[24..]) >> 12) & low_51_bit_mask
]
}
fn to_bytes_64(limbs: &[u64;5]) -> [u8;32] {
let mut s = [0u8;32];
s[ 0] = limbs[0] as u8;
@ -507,6 +492,22 @@ impl FieldElement {
FieldElement::reduce(&h)
}
#[cfg(feature="radix_51")]
pub fn from_bytes(bytes: &[u8;32]) -> FieldElement {
let low_51_bit_mask = (1u64 << 51) - 1;
FieldElement(
// load bits [ 0, 64), no shift
[ load8(&bytes[ 0..]) & low_51_bit_mask
// load bits [ 48,112), shift to [ 51,112)
, (load8(&bytes[ 6..]) >> 3) & low_51_bit_mask
// load bits [ 96,160), shift to [102,160)
, (load8(&bytes[12..]) >> 6) & low_51_bit_mask
// load bits [152,216), shift to [153,216)
, (load8(&bytes[19..]) >> 1) & low_51_bit_mask
// load bits [192,256), shift to [204,112)
, (load8(&bytes[24..]) >> 12) & low_51_bit_mask
])
}
/// Marshal this FieldElement into a 32-byte array.
///