ceremonyclient/crates/vdf/build.rs
Cassie Heart ebb31fd792 v1.4.19
2024-06-08 11:32:45 +00:00

116 lines
3.9 KiB
Rust

// Copyright 2018 Chia Network Inc and POA Networks Ltd.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
use std::{env, fs::File, io::Write, path::PathBuf, u16};
/// The number of odd primes less than 65536.
const PRIMES_LEN: usize = 6541;
/// The number of integers that are:
///
/// * equal to 7 mod 8
/// * not divisible by any prime number less than or equal to 13.
/// * less than 8 * 3 * 5 * 7 * 11 * 13
const RESIDUES_LEN: usize = 5760;
/// The number of odd prime numbers between 13 and 65536 exclusive.
const SIEVE_INFO_LEN: usize = PRIMES_LEN - 5;
fn odd_primes_below_65536() -> Vec<usize> {
const N: usize = 1 << 16;
let mut sieve = vec![true; N >> 1];
let mut q = (N as f64).powf(0.5) as usize;
assert!(q * q <= N);
q += 1;
assert!(q * q > N);
for i in (3..q).step_by(2) {
if sieve[i >> 1] {
for i in ((i * i >> 1)..sieve.len()).step_by(i) {
sieve[i] = false;
}
}
}
// mega cheat ― we know the exact size of this vector
let res: Vec<_> = (1..N / 2)
.filter(|&i| sieve[i])
.map(|i| 2 * i + 1)
.collect();
assert_eq!(res.len(), PRIMES_LEN);
res
}
fn mod_exponentiation(base: usize, exponent: usize, modulus: usize) -> usize {
assert!(base < u16::MAX.into());
assert!(exponent < u16::MAX.into());
assert!(modulus < u16::MAX.into());
let (mut base, mut exponent, modulus) = (base as u32, exponent as u32, modulus as u32);
let mut state = 1;
loop {
if exponent & 1 != 0 {
state *= base;
state %= modulus;
}
exponent >>= 1;
if exponent == 0 {
return state as _;
}
base *= base;
base %= modulus;
}
}
macro_rules! const_fmt {
() => {
"#[allow(warnings)]\nconst {}: [{}; {}] = {:#?};\n\n";
};
}
/// A product of many small prime numbers. We precompute the numbers between
/// `1` and `M` that are coprime to `M`. Any number whose residue modulo `M` is
/// one of these is not divisible by any of the prime factors of `M`. This
/// speeds up the generation of random prime numbers.
const M: usize = 8 * 3 * 5 * 7 * 11 * 13;
fn emit<T: std::fmt::Debug>(f: &mut dyn Write, name: &str, t: &str, obj: &[T]) {
write!(f, const_fmt!(), name, t, obj.len(), obj).expect("i/o error in build script");
}
/// Write the generated code to `f`.
fn generate(f: &mut dyn Write) {
write!(f, "const M: u32 = 8 * 3 * 5 * 7 * 11 * 13;\n\n").expect("i/o error");
let residues: Vec<usize> = {
let primes = [3, 5, 7, 11, 13];
let not_divisible = |&x: &usize| primes.iter().all(|p| x % p != 0);
(7..M).step_by(8).filter(not_divisible).collect()
};
assert_eq!(residues.len(), RESIDUES_LEN);
emit(f, "RESIDUES", "u32", &residues[..]);
let sieve_info: Vec<(usize, usize)> = odd_primes_below_65536()[5..]
.iter()
.map(|&i| (i, mod_exponentiation(M % i, i - 2, i)))
.collect();
assert_eq!(sieve_info.len(), SIEVE_INFO_LEN);
emit(f, "SIEVE_INFO", "(u16, u16)", &sieve_info[..]);
}
fn main() {
println!("cargo:rerun-if-changed=build.rs");
uniffi::generate_scaffolding("src/lib.udl").expect("uniffi generation failed");
let manifest_path = env::var("OUT_DIR").expect("cargo should have set this");
let mut path = PathBuf::from(&manifest_path);
path.push("constants.rs");
let mut f = File::create(path).expect("cannot create constants.rs");
generate(&mut f);
}