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Add u64/u128 atom exports #127

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merged 9 commits into from
Nov 17, 2023
Merged

Add u64/u128 atom exports #127

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804ac35
Add u64/u128 atom exports
sigilante Nov 15, 2023
1f0fec0
Satisfy linter
sigilante Nov 15, 2023
7debba4
Satisfy linter
sigilante Nov 15, 2023
1ae6303
Move u64/u128 to IndirectAtom as well
sigilante Nov 15, 2023
44ba80c
Fix minor unsafe blocks
sigilante Nov 15, 2023
a2749a7
Rename u128_pair to u64_pair and clarify SoftFloat intent
sigilante Nov 15, 2023
0cb6cb3
Switch to doc comment format.
sigilante Nov 15, 2023
379bd22
Mark manually-checked pair as safe.
sigilante Nov 17, 2023
15a8745
Swap high.low bytes in pair
sigilante Nov 17, 2023
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37 changes: 37 additions & 0 deletions rust/ares/src/noun.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -464,6 +464,24 @@ impl IndirectAtom {
UBig::from_le_bytes_stack(stack, self.as_bytes())
}

pub unsafe fn as_u64(self) -> Result<u64> {
if self.size() == 1 {
Ok(*(self.data_pointer()))
} else {
Err(Error::NotRepresentable)
}
}

pub unsafe fn as_u128_pair(self) -> Result<[u64; 2]> {
if self.size() <= 2 {
let u128_array = &mut [0u64; 2];
u128_array.copy_from_slice(&(self.as_slice()[0..2]));
Ok(*u128_array)
} else {
Err(Error::NotRepresentable)
}
}
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Rust has a native u128 type: https://doc.rust-lang.org/std/primitive.u128.html

You could make a 16-element byte array, copy into it from atom.as_bytes(), and then call u128::from_le_bytes() on the array to get the atom.

Suggested change
pub unsafe fn as_u128_pair(self) -> Result<[u64; 2]> {
if self.size() <= 2 {
let u128_array = &mut [0u64; 2];
u128_array.copy_from_slice(&(self.as_slice()[0..2]));
Ok(*u128_array)
} else {
Err(Error::NotRepresentable)
}
}
pub unsafe fn as_u128(self) -> Result<u128> {
if self.size() <= 2 {
let mut u128_array = [0u8; 16];
let self_bytes = self.as_bytes();
u128_array[0..self.as_bytes()].copy_from_slice(self_bytes);
Ok(u128::from_le_bytes(u128_array)
} else {
Err(Error::NotRepresentable)
}
}

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It's a pair of u64 to match the SoftFloat interface.

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It's not a generic u128, it's to solve a particular use case from urcrypt.

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urcrypt urfloat, whatever we end up calling it


/** Ensure that the size does not contain any trailing 0 words */
pub unsafe fn normalize(&mut self) -> &Self {
let mut index = self.size() - 1;
Expand Down Expand Up @@ -738,6 +756,25 @@ impl Atom {
}
}

pub fn as_u64(self) -> Result<u64> {
if self.is_direct() {
Ok(unsafe { self.direct.data() })
} else {
unsafe { self.indirect.as_u64() }
}
}

pub unsafe fn as_u128_pair(self) -> Result<[u64; 2]> {
if self.is_direct() {
let u128_array = &mut [0u64; 2];
u128_array[0] = 0x0_u64;
u128_array[1] = self.as_direct()?.data();
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Ok(*u128_array)
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} else {
unsafe { self.indirect.as_u128_pair() }
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}
}

pub fn as_bitslice(&self) -> &BitSlice<u64, Lsb0> {
if self.is_indirect() {
unsafe { self.indirect.as_bitslice() }
Expand Down