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perf: improve pack/unpack endian conversions #55

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perf: improve pack/unpack endian conversions
DaniPopes Feb 11, 2026
cebe082
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DaniPopes Feb 11, 2026
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48 changes: 3 additions & 45 deletions src/nibbles.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -424,37 +424,7 @@ impl Nibbles {
pub unsafe fn unpack_unchecked(data: &[u8]) -> Self {
let len = data.len() * 2;
debug_assert!(len <= NIBBLES);

cfg_if! {
if #[cfg(target_endian = "little")] {
let mut nibbles = U256::ZERO;
let nibbles_slice = unsafe { nibbles.as_le_slice_mut() };
} else {
let mut nibbles_slice = [0u8; 32];
}
}

// Source pointer is at the beginning
let mut src = data.as_ptr().cast::<u8>();
// Move destination pointer to the end of the little endian slice
let mut dst = unsafe { nibbles_slice.as_mut_ptr().add(U256::BYTES) };
// On each iteration, decrement the destination pointer by one, set the destination
// byte, and increment the source pointer by one
for _ in 0..data.len() {
unsafe {
dst = dst.sub(1);
*dst = *src;
src = src.add(1);
}
}

cfg_if! {
if #[cfg(target_endian = "big")] {
let nibbles = U256::from_le_bytes(nibbles_slice);
}
}

Self { len, nibbles }
Self { len, nibbles: U256::from_be_slice(data) }
}

/// Converts a fixed 32 byte array into a [`Nibbles`] instance. Similar to [`Nibbles::unpack`],
Expand Down Expand Up @@ -1135,20 +1105,8 @@ impl<'a> ExactSizeIterator for NibblesIter<'a> {
unsafe fn pack_to_unchecked(nibbles: &Nibbles, out: &mut [MaybeUninit<u8>]) {
let byte_len = nibbles.byte_len();
debug_assert!(out.len() >= byte_len);
// Move source pointer to the end of the little endian slice
let sl = as_le_slice(&nibbles.nibbles);
let mut src = unsafe { sl.as_ptr().add(U256::BYTES) };
// Destination pointer is at the beginning of the output slice
let mut dst = out.as_mut_ptr().cast::<u8>();
// On each iteration, decrement the source pointer by one, set the destination byte, and
// increment the destination pointer by one
for _ in 0..byte_len {
unsafe {
src = src.sub(1);
*dst = *src;
dst = dst.add(1);
}
}
let be = nibbles.nibbles.to_be_bytes::<{ U256::BYTES }>();
unsafe { out.as_mut_ptr().cast::<u8>().copy_from_nonoverlapping(be.as_ptr(), byte_len) };
}

/// Initializes a smallvec with the given length and a closure that initializes the buffer.
Expand Down
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