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Faster const decoding of UInt #113

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Aug 25, 2022
Merged

Faster const decoding of UInt #113

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6 changes: 4 additions & 2 deletions src/uint.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -307,12 +307,14 @@ macro_rules! impl_uint_aliases {

type Repr = [u8; $bits / 8];

#[inline]
fn from_be_bytes(bytes: Self::Repr) -> Self {
$crate::uint::encoding::uint_from_be_bytes(&bytes)
Self::from_be_slice(&bytes)
}

#[inline]
fn from_le_bytes(bytes: Self::Repr) -> Self {
$crate::uint::encoding::uint_from_le_bytes(&bytes)
Self::from_le_slice(&bytes)
}

#[inline]
Expand Down
145 changes: 45 additions & 100 deletions src/uint/encoding.rs
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Original file line number Diff line number Diff line change
@@ -1,16 +1,13 @@
//! Const-friendly decoding operations for [`UInt`]

mod decoder;

#[cfg(all(feature = "der", feature = "generic-array"))]
mod der;

#[cfg(feature = "rlp")]
mod rlp;

use super::UInt;
use crate::{Encoding, Limb};
use decoder::Decoder;
use crate::{Encoding, Limb, Word};

impl<const LIMBS: usize> UInt<LIMBS> {
/// Create a new [`UInt`] from the provided big endian bytes.
Expand All @@ -20,15 +17,21 @@ impl<const LIMBS: usize> UInt<LIMBS> {
"bytes are not the expected size"
);

let mut decoder = Decoder::new();
let mut res = [Limb::ZERO; LIMBS];
let mut buf = [0u8; Limb::BYTE_SIZE];
let mut i = 0;

while i < Limb::BYTE_SIZE * LIMBS {
while i < LIMBS {
let mut j = 0;
while j < Limb::BYTE_SIZE {
buf[j] = bytes[i * Limb::BYTE_SIZE + j];
j += 1;
}
res[LIMBS - i - 1] = Limb(Word::from_be_bytes(buf));
i += 1;
decoder = decoder.add_byte(bytes[bytes.len() - i]);
}

decoder.finish()
UInt::new(res)
}

/// Create a new [`UInt`] from the provided big endian hex string.
Expand All @@ -40,17 +43,22 @@ impl<const LIMBS: usize> UInt<LIMBS> {
"hex string is not the expected size"
);

let mut decoder = Decoder::new();
let mut res = [Limb::ZERO; LIMBS];
let mut buf = [0u8; Limb::BYTE_SIZE];
let mut i = 0;

while i < Limb::BYTE_SIZE * LIMBS * 2 {
i += 2;
let offset = bytes.len() - i;
let byte = decode_hex_byte([bytes[offset], bytes[offset + 1]]);
decoder = decoder.add_byte(byte);
while i < LIMBS {
let mut j = 0;
while j < Limb::BYTE_SIZE {
let offset = (i * Limb::BYTE_SIZE + j) * 2;
buf[j] = decode_hex_byte([bytes[offset], bytes[offset + 1]]);
j += 1;
}
res[LIMBS - i - 1] = Limb(Word::from_be_bytes(buf));
i += 1;
}

decoder.finish()
UInt::new(res)
}

/// Create a new [`UInt`] from the provided little endian bytes.
Expand All @@ -60,15 +68,21 @@ impl<const LIMBS: usize> UInt<LIMBS> {
"bytes are not the expected size"
);

let mut decoder = Decoder::new();
let mut res = [Limb::ZERO; LIMBS];
let mut buf = [0u8; Limb::BYTE_SIZE];
let mut i = 0;

while i < Limb::BYTE_SIZE * LIMBS {
decoder = decoder.add_byte(bytes[i]);
while i < LIMBS {
let mut j = 0;
while j < Limb::BYTE_SIZE {
buf[j] = bytes[i * Limb::BYTE_SIZE + j];
j += 1;
}
res[i] = Limb(Word::from_le_bytes(buf));
i += 1;
}

decoder.finish()
UInt::new(res)
}

/// Create a new [`UInt`] from the provided little endian hex string.
Expand All @@ -80,16 +94,22 @@ impl<const LIMBS: usize> UInt<LIMBS> {
"bytes are not the expected size"
);

let mut decoder = Decoder::new();
let mut res = [Limb::ZERO; LIMBS];
let mut buf = [0u8; Limb::BYTE_SIZE];
let mut i = 0;

while i < Limb::BYTE_SIZE * LIMBS * 2 {
let byte = decode_hex_byte([bytes[i], bytes[i + 1]]);
decoder = decoder.add_byte(byte);
i += 2;
while i < LIMBS {
let mut j = 0;
while j < Limb::BYTE_SIZE {
let offset = (i * Limb::BYTE_SIZE + j) * 2;
buf[j] = decode_hex_byte([bytes[offset], bytes[offset + 1]]);
j += 1;
}
res[i] = Limb(Word::from_le_bytes(buf));
i += 1;
}

decoder.finish()
UInt::new(res)
}

/// Serialize this [`UInt`] as big-endian, writing it into the provided
Expand Down Expand Up @@ -154,45 +174,8 @@ const fn decode_hex_byte(bytes: [u8; 2]) -> u8 {
result
}

/// Create a new [`UInt`] from the provided big endian byte array.
pub(crate) fn uint_from_be_bytes<const N: usize, const LIMBS: usize>(
bytes: &[u8; N],
) -> UInt<LIMBS> {
assert!(
N == Limb::BYTE_SIZE * LIMBS,
"bytes are not the expected size",
);
let mut limbs = [Limb::ZERO; LIMBS];
for (chunk, limb) in bytes.rchunks_exact(Limb::BYTE_SIZE).zip(limbs.iter_mut()) {
*limb = Limb::from_be_bytes(match chunk.try_into() {
Ok(c) => c,
Err(_) => unreachable!(),
});
}
UInt { limbs }
}

/// Create a new [`UInt`] from the provided big endian byte array.
pub(crate) fn uint_from_le_bytes<const N: usize, const LIMBS: usize>(
bytes: &[u8; N],
) -> UInt<LIMBS> {
assert!(
N == Limb::BYTE_SIZE * LIMBS,
"bytes are not the expected size",
);
let mut limbs = [Limb::ZERO; LIMBS];
for (chunk, limb) in bytes.chunks_exact(Limb::BYTE_SIZE).zip(limbs.iter_mut()) {
*limb = Limb::from_le_bytes(match chunk.try_into() {
Ok(c) => c,
Err(_) => unreachable!(),
});
}
UInt { limbs }
}

#[cfg(test)]
mod tests {
use super::{uint_from_be_bytes, uint_from_le_bytes};
use crate::Limb;
use hex_literal::hex;

Expand Down Expand Up @@ -243,44 +226,6 @@ mod tests {
);
}

#[test]
#[cfg(target_pointer_width = "32")]
fn from_be_bytes() {
let bytes = hex!("0011223344556677");
let n: UIntEx = uint_from_be_bytes(&bytes);
assert_eq!(n.limbs(), &[Limb(0x44556677), Limb(0x00112233)]);
}

#[test]
#[cfg(target_pointer_width = "64")]
fn from_be_bytes() {
let bytes = hex!("00112233445566778899aabbccddeeff");
let n: UIntEx = uint_from_be_bytes(&bytes);
assert_eq!(
n.limbs(),
&[Limb(0x8899aabbccddeeff), Limb(0x0011223344556677)]
);
}

#[test]
#[cfg(target_pointer_width = "32")]
fn from_le_bytes() {
let bytes = hex!("7766554433221100");
let n: UIntEx = uint_from_le_bytes(&bytes);
assert_eq!(n.limbs(), &[Limb(0x44556677), Limb(0x00112233)]);
}

#[test]
#[cfg(target_pointer_width = "64")]
fn from_le_bytes() {
let bytes = hex!("ffeeddccbbaa99887766554433221100");
let n: UIntEx = uint_from_le_bytes(&bytes);
assert_eq!(
n.limbs(),
&[Limb(0x8899aabbccddeeff), Limb(0x0011223344556677)]
);
}

#[test]
#[cfg(target_pointer_width = "32")]
fn from_be_hex() {
Expand Down
57 changes: 0 additions & 57 deletions src/uint/encoding/decoder.rs
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