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further refactor num-bigint conversion
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@davidhewitt
davidhewitt committed Aug 18, 2023
1 parent d1f0561 commit a556bae
Showing 1 changed file with 163 additions and 169 deletions.
332 changes: 163 additions & 169 deletions src/conversions/num_bigint.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -51,54 +51,10 @@ use crate::{
ffi, types::*, FromPyObject, IntoPy, Py, PyAny, PyObject, PyResult, Python, ToPyObject,
};

use num_bigint::{BigInt, BigUint, Sign};
use std::os::raw::c_int;
use num_bigint::{BigInt, BigUint};

#[cfg(not(Py_LIMITED_API))]
use std::os::raw::c_uchar;

#[cfg(Py_LIMITED_API)]
use std::slice;

#[cfg(not(Py_LIMITED_API))]
#[inline]
unsafe fn extract(ob: &PyLong, length: usize, is_signed: c_int) -> PyResult<Vec<u32>> {
let mut buffer = Vec::<u32>::with_capacity(length);
crate::err::error_on_minusone(
ob.py(),
ffi::_PyLong_AsByteArray(
ob.as_ptr() as *mut ffi::PyLongObject,
buffer.as_mut_ptr() as *mut u8,
length * 4,
1,
is_signed,
),
)?;
buffer.set_len(length);

Ok(buffer)
}

#[cfg(Py_LIMITED_API)]
#[inline]
unsafe fn extract(ob: &PyLong, length: usize, is_signed: c_int) -> PyResult<Vec<u32>> {
use crate::intern;
let py = ob.py();
let kwargs = if is_signed != 0 {
let kwargs = PyDict::new(py);
kwargs.set_item(intern!(py, "signed"), true)?;
Some(kwargs)
} else {
None
};
let bytes_obj = ob
.getattr(intern!(py, "to_bytes"))?
.call((length * 4, intern!(py, "little")), kwargs)?;
let bytes: &PyBytes = bytes_obj.downcast_unchecked();
let bytes_u32 = slice::from_raw_parts(bytes.as_bytes().as_ptr().cast(), length);

Ok(bytes_u32.to_vec())
}
use num_bigint::Sign;

// for identical functionality between BigInt and BigUint
macro_rules! bigint_conversion {
Expand All @@ -110,7 +66,7 @@ macro_rules! bigint_conversion {
let bytes = $to_bytes(self);
unsafe {
let obj = ffi::_PyLong_FromByteArray(
bytes.as_ptr() as *const c_uchar,
bytes.as_ptr().cast(),
bytes.len(),
1,
$is_signed,
Expand Down Expand Up @@ -153,41 +109,46 @@ bigint_conversion!(BigInt, 1, BigInt::to_signed_bytes_le);
impl<'source> FromPyObject<'source> for BigInt {
fn extract(ob: &'source PyAny) -> PyResult<BigInt> {
let py = ob.py();
unsafe {
let num: Py<PyLong> = Py::from_owned_ptr_or_err(py, ffi::PyNumber_Index(ob.as_ptr()))?;
let n_bits = {
cfg_if::cfg_if! {
if #[cfg(not(Py_LIMITED_API))] {
// fast path
let n_bits = ffi::_PyLong_NumBits(num.as_ptr());
if n_bits == (-1isize as usize) {
return Err(crate::PyErr::fetch(py));
}
n_bits
} else {
// slow path
let n_bits_obj = num.getattr(py, crate::intern!(py, "bit_length"))?.call0(py)?;
let n_bits_int: &PyLong = n_bits_obj.downcast_unchecked(py);
n_bits_int.extract::<usize>()?
// fast path - checking for subclass of `int` just checks a bit in the type object
let num_owned: Py<PyLong>;
let num = if let Ok(long) = ob.downcast::<PyLong>() {
long
} else {
num_owned = unsafe { Py::from_owned_ptr_or_err(py, ffi::PyNumber_Index(ob.as_ptr()))? };
num_owned.as_ref(py)
};
let n_bits = int_n_bits(num)?;
if n_bits == 0 {
return Ok(BigInt::from(0isize));
}
#[cfg(not(Py_LIMITED_API))]
{
let mut buffer = int_to_u32_vec(num, (n_bits + 32) / 32, true)?;
let sign = if buffer.last().copied().map_or(false, |last| last >> 31 != 0) {
// BigInt::new takes an unsigned array, so need to convert from two's complement
// flip all bits, 'subtract' 1 (by adding one to the unsigned array)
let mut elements = buffer.iter_mut();
while let Some(element) = elements.next() {
*element = (!*element).wrapping_add(1);
if *element != 0 {
// if the element didn't wrap over, no need to keep adding further ...
break;
}
}
};

if n_bits == 0 {
return Ok(BigInt::from(0isize));
}
let n_digits = (n_bits + 32) / 32;
let mut buffer = extract(num.as_ref(py), n_digits, 1)?;
buffer
.iter_mut()
.for_each(|chunk| *chunk = u32::from_le(*chunk));

Ok(if buffer.last().unwrap() >> 31 != 0 {
buffer.iter_mut().for_each(|element| *element = !*element);
BigInt::new(Sign::Minus, buffer) - 1
// ... so just two's complement the rest
for element in elements {
*element = !*element;
}
Sign::Minus
} else {
BigInt::new(Sign::Plus, buffer)
})
Sign::Plus
};
Ok(BigInt::new(sign, buffer))
}
#[cfg(Py_LIMITED_API)]
{
let bytes = int_to_py_bytes(num, (n_bits + 8) / 8, true)?;
Ok(BigInt::from_signed_bytes_le(bytes.as_bytes()))
}
}
}
Expand All @@ -196,37 +157,92 @@ impl<'source> FromPyObject<'source> for BigInt {
impl<'source> FromPyObject<'source> for BigUint {
fn extract(ob: &'source PyAny) -> PyResult<BigUint> {
let py = ob.py();
unsafe {
let num: Py<PyLong> = Py::from_owned_ptr_or_err(py, ffi::PyNumber_Index(ob.as_ptr()))?;
let n_bits = {
cfg_if::cfg_if! {
if #[cfg(not(Py_LIMITED_API))] {
// fast path
let n_bits = ffi::_PyLong_NumBits(num.as_ptr());
if n_bits == (-1isize as usize) {
return Err(crate::PyErr::fetch(py));
}
n_bits
} else {
// slow path
let n_bits_obj = num.getattr(py, crate::intern!(py, "bit_length"))?.call0(py)?;
let n_bits_int: &PyLong = n_bits_obj.downcast_unchecked(py);
n_bits_int.extract::<usize>()?
}
}
};
// fast path - checking for subclass of `int` just checks a bit in the type object
let num_owned: Py<PyLong>;
let num = if let Ok(long) = ob.downcast::<PyLong>() {
long
} else {
num_owned = unsafe { Py::from_owned_ptr_or_err(py, ffi::PyNumber_Index(ob.as_ptr()))? };
num_owned.as_ref(py)
};
let n_bits = int_n_bits(num)?;
if n_bits == 0 {
return Ok(BigUint::from(0usize));
}
#[cfg(not(Py_LIMITED_API))]
{
let buffer = int_to_u32_vec(num, (n_bits + 31) / 32, false)?;
Ok(BigUint::new(buffer))
}
#[cfg(Py_LIMITED_API)]
{
let bytes = int_to_py_bytes(num, (n_bits + 7) / 8, false)?;
Ok(BigUint::from_bytes_le(bytes.as_bytes()))
}
}
}

if n_bits == 0 {
return Ok(BigUint::from(0usize));
}
let n_digits = (n_bits + 31) / 32;
let mut buffer = extract(num.as_ref(py), n_digits, 0)?;
buffer
.iter_mut()
.for_each(|chunk| *chunk = u32::from_le(*chunk));
#[cfg(not(Py_LIMITED_API))]
#[inline]
fn int_to_u32_vec(long: &PyLong, n_digits: usize, is_signed: bool) -> PyResult<Vec<u32>> {
let mut buffer = Vec::with_capacity(n_digits);
unsafe {
crate::err::error_on_minusone(
long.py(),
ffi::_PyLong_AsByteArray(
long.as_ptr().cast(),
buffer.as_mut_ptr() as *mut u8,
n_digits * 4,
1,
is_signed.into(),
),
)?;
buffer.set_len(n_digits)
};
buffer
.iter_mut()
.for_each(|chunk| *chunk = u32::from_le(*chunk));

Ok(BigUint::new(buffer))
Ok(buffer)
}

#[cfg(Py_LIMITED_API)]
fn int_to_py_bytes(long: &PyLong, n_bytes: usize, is_signed: bool) -> PyResult<&PyBytes> {
use crate::intern;
let py = long.py();
let kwargs = if is_signed {
let kwargs = PyDict::new(py);
kwargs.set_item(intern!(py, "signed"), true)?;
Some(kwargs)
} else {
None
};
let bytes = long.call_method(
intern!(py, "to_bytes"),
(n_bytes, intern!(py, "little")),
kwargs,
)?;
Ok(bytes.downcast()?)
}

#[inline]
fn int_n_bits(long: &PyLong) -> PyResult<usize> {
let py = long.py();
#[cfg(not(Py_LIMITED_API))]
{
// fast path
let n_bits = unsafe { ffi::_PyLong_NumBits(long.as_ptr()) };
if n_bits == (-1isize as usize) {
return Err(crate::PyErr::fetch(py));
}
return Ok(n_bits);
}

#[cfg(Py_LIMITED_API)]
{
// slow path
long.call_method0(crate::intern!(py, "bit_length"))
.and_then(PyAny::extract)
}
}

Expand All @@ -236,82 +252,62 @@ mod tests {
use crate::types::{PyDict, PyModule};
use indoc::indoc;

fn python_fib(py: Python<'_>) -> &PyModule {
let fib_code = indoc!(
r#"
def fib(n):
f0, f1 = 0, 1
for _ in range(n):
f0, f1 = f1, f0 + f1
return f0
def fib_neg(n):
return -fib(n)
"#
);
PyModule::from_code(py, fib_code, "fib.py", "fib").unwrap()
}

fn rust_fib<T>(n: usize) -> T
fn rust_fib<T>() -> impl Iterator<Item = T>
where
T: From<u16>,
for<'a> &'a T: std::ops::Add<Output = T>,
{
let mut f0: T = T::from(0);
let mut f0: T = T::from(1);
let mut f1: T = T::from(1);
for _ in 0..n {
std::iter::from_fn(move || {
let f2 = &f0 + &f1;
f0 = std::mem::replace(&mut f1, f2);
}
f0
Some(std::mem::replace(&mut f0, std::mem::replace(&mut f1, f2)))
})
}

fn python_fib(py: Python<'_>) -> impl Iterator<Item = PyObject> + '_ {
let mut f0 = 1.to_object(py);
let mut f1 = 1.to_object(py);
std::iter::from_fn(move || {
let f2 = f0.call_method1(py, "__add__", (f1.as_ref(py),)).unwrap();
Some(std::mem::replace(&mut f0, std::mem::replace(&mut f1, f2)))
})
}

#[test]
fn convert_biguint() {
Python::with_gil(|py| {
let rs_result: BigUint = rust_fib(400);
let fib = python_fib(py);
let locals = PyDict::new(py);
locals.set_item("rs_result", &rs_result).unwrap();
locals.set_item("fib", fib).unwrap();
// Checks if Rust BigUint -> Python Long conversion is correct
py.run("assert fib.fib(400) == rs_result", None, Some(locals))
.unwrap();
// Checks if Python Long -> Rust BigUint conversion is correct if N is small
let py_result: BigUint =
FromPyObject::extract(fib.getattr("fib").unwrap().call1((400,)).unwrap()).unwrap();
assert_eq!(rs_result, py_result);
// Checks if Python Long -> Rust BigUint conversion is correct if N is large
let rs_result: BigUint = rust_fib(2000);
let py_result: BigUint =
FromPyObject::extract(fib.getattr("fib").unwrap().call1((2000,)).unwrap()).unwrap();
assert_eq!(rs_result, py_result);
// check the first 2000 numbers in the fibonacci sequence
for (py_result, rs_result) in python_fib(py).zip(rust_fib::<BigUint>()).take(2000) {
// Python -> Rust
assert_eq!(py_result.extract::<BigUint>(py).unwrap(), rs_result);
// Rust -> Python
assert!(py_result.as_ref(py).eq(rs_result).unwrap());
}
});
}

#[test]
fn convert_bigint() {
Python::with_gil(|py| {
let rs_result = rust_fib::<BigInt>(400) * -1;
let fib = python_fib(py);
let locals = PyDict::new(py);
locals.set_item("rs_result", &rs_result).unwrap();
locals.set_item("fib", fib).unwrap();
// Checks if Rust BigInt -> Python Long conversion is correct
py.run("assert fib.fib_neg(400) == rs_result", None, Some(locals))
.unwrap();
// Checks if Python Long -> Rust BigInt conversion is correct if N is small
let py_result: BigInt =
FromPyObject::extract(fib.getattr("fib_neg").unwrap().call1((400,)).unwrap())
.unwrap();
assert_eq!(rs_result, py_result);
// Checks if Python Long -> Rust BigInt conversion is correct if N is large
let rs_result = rust_fib::<BigInt>(2000) * -1;
let py_result: BigInt =
FromPyObject::extract(fib.getattr("fib_neg").unwrap().call1((2000,)).unwrap())
.unwrap();
assert_eq!(rs_result, py_result);
})
// check the first 2000 numbers in the fibonacci sequence
for (py_result, rs_result) in python_fib(py).zip(rust_fib::<BigInt>()).take(2000) {
// Python -> Rust
assert_eq!(py_result.extract::<BigInt>(py).unwrap(), rs_result);
// Rust -> Python
assert!(py_result.as_ref(py).eq(&rs_result).unwrap());

// negate

let rs_result = rs_result * -1;
let py_result = py_result.call_method0(py, "__neg__").unwrap();

// Python -> Rust
assert_eq!(py_result.extract::<BigInt>(py).unwrap(), rs_result);
// Rust -> Python
assert!(py_result.as_ref(py).eq(rs_result).unwrap());
}
});
}

fn python_index_class(py: Python<'_>) -> &PyModule {
Expand Down Expand Up @@ -341,9 +337,7 @@ mod tests {
#[test]
fn handle_zero() {
Python::with_gil(|py| {
let fib = python_fib(py);
let zero: BigInt =
FromPyObject::extract(fib.getattr("fib").unwrap().call1((0,)).unwrap()).unwrap();
let zero: BigInt = 0.to_object(py).extract(py).unwrap();
assert_eq!(zero, BigInt::from(0));
})
}
Expand Down

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