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Copy pathrandom.rs
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155 lines (141 loc) · 4.65 KB
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//! Random module.
pub(crate) use _random::make_module;
#[pymodule]
mod _random {
use crate::common::lock::PyMutex;
use crate::vm::{
builtins::{PyInt, PyTypeRef},
function::OptionalOption,
types::Constructor,
PyObjectRef, PyPayload, PyResult, VirtualMachine,
};
use num_bigint::{BigInt, Sign};
use num_traits::{Signed, Zero};
use rand::{rngs::StdRng, RngCore, SeedableRng};
#[derive(Debug)]
enum PyRng {
Std(Box<StdRng>),
MT(Box<mt19937::MT19937>),
}
impl Default for PyRng {
fn default() -> Self {
PyRng::Std(Box::new(StdRng::from_entropy()))
}
}
impl RngCore for PyRng {
fn next_u32(&mut self) -> u32 {
match self {
Self::Std(s) => s.next_u32(),
Self::MT(m) => m.next_u32(),
}
}
fn next_u64(&mut self) -> u64 {
match self {
Self::Std(s) => s.next_u64(),
Self::MT(m) => m.next_u64(),
}
}
fn fill_bytes(&mut self, dest: &mut [u8]) {
match self {
Self::Std(s) => s.fill_bytes(dest),
Self::MT(m) => m.fill_bytes(dest),
}
}
fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), rand::Error> {
match self {
Self::Std(s) => s.try_fill_bytes(dest),
Self::MT(m) => m.try_fill_bytes(dest),
}
}
}
#[pyattr]
#[pyclass(name = "Random")]
#[derive(Debug, PyPayload)]
struct PyRandom {
rng: PyMutex<PyRng>,
}
impl Constructor for PyRandom {
type Args = OptionalOption<PyObjectRef>;
fn py_new(
cls: PyTypeRef,
// TODO: use x as the seed.
_x: Self::Args,
vm: &VirtualMachine,
) -> PyResult {
PyRandom {
rng: PyMutex::default(),
}
.into_ref_with_type(vm, cls)
.map(Into::into)
}
}
#[pyclass(flags(BASETYPE), with(Constructor))]
impl PyRandom {
#[pymethod]
fn random(&self) -> f64 {
let mut rng = self.rng.lock();
mt19937::gen_res53(&mut *rng)
}
#[pymethod]
fn seed(&self, n: OptionalOption<PyObjectRef>, vm: &VirtualMachine) -> PyResult<()> {
let new_rng = n
.flatten()
.map(|n| {
// Fallback to using hash if object isn't Int-like.
let (_, mut key) = match n.downcast::<PyInt>() {
Ok(n) => n.as_bigint().abs(),
Err(obj) => BigInt::from(obj.hash(vm)?).abs(),
}
.to_u32_digits();
if cfg!(target_endian = "big") {
key.reverse();
}
let key = if key.is_empty() { &[0] } else { key.as_slice() };
Ok(PyRng::MT(Box::new(mt19937::MT19937::new_with_slice_seed(
key,
))))
})
.transpose()?
.unwrap_or_default();
*self.rng.lock() = new_rng;
Ok(())
}
#[pymethod]
fn getrandbits(&self, k: isize, vm: &VirtualMachine) -> PyResult<BigInt> {
match k {
k if k < 0 => {
Err(vm.new_value_error("number of bits must be non-negative".to_owned()))
}
0 => Ok(BigInt::zero()),
_ => {
let mut rng = self.rng.lock();
let mut k = k;
let mut gen_u32 = |k| {
let r = rng.next_u32();
if k < 32 {
r >> (32 - k)
} else {
r
}
};
let words = (k - 1) / 32 + 1;
let wordarray = (0..words)
.map(|_| {
let word = gen_u32(k);
k = k.wrapping_sub(32);
word
})
.collect::<Vec<_>>();
let uint = num_bigint::BigUint::new(wordarray);
// very unlikely but might as well check
let sign = if uint.is_zero() {
Sign::NoSign
} else {
Sign::Plus
};
Ok(BigInt::from_biguint(sign, uint))
}
}
}
}
}