build.rs

const TRUSTED_SETUP_FILE: &str = include_str!("src/trusted_setup.txt");

include!("src/enums.rs");
include!("src/consts.rs");
include!("src/pairings.rs");

#[cfg(not(any(target_arch = "riscv32", doc)))]
fn main() {
    use std::{env, fs, io::Write, path::Path};
    #[derive(Debug, Clone, PartialEq, Eq)]
    pub struct KzgSettingsOwned {
        pub roots_of_unity: [Scalar; NUM_ROOTS_OF_UNITY],
        pub g1_points: [G1Affine; NUM_G1_POINTS],
        pub g2_points: [G2Affine; NUM_G2_POINTS],
    }

    fn hex_to_bytes(hex_str: &str) -> Result<Vec<u8>, KzgError> {
        let trimmed_str = hex_str.strip_prefix("0x").unwrap_or(hex_str);
        hex::decode(trimmed_str)
            .map_err(|e| KzgError::InvalidHexFormat(format!("Failed to decode hex: {}", e)))
    }

    pub fn load_trusted_setup_file_brute() -> Result<KzgSettingsOwned, KzgError> {
        let trusted_setup_file: Vec<String> = TRUSTED_SETUP_FILE
            .split('\n')
            .map(|x| x.to_string())
            .collect();

        let num_g1_points = trusted_setup_file[0].parse::<usize>().unwrap();
        let num_g2_points = trusted_setup_file[1].parse::<usize>().unwrap();
        let g1_points_idx = num_g1_points + 2;
        let g2_points_idx = g1_points_idx + num_g2_points;

        let _g1_points: Vec<[u8; BYTES_PER_G1_POINT]> =
            hex_to_bytes(&trusted_setup_file[2..g1_points_idx].join(""))
                .unwrap()
                .chunks_exact(BYTES_PER_G1_POINT)
                .map(|chunk| {
                    let mut array = [0u8; BYTES_PER_G1_POINT];
                    array.copy_from_slice(chunk);
                    array
                })
                .collect();
        let _g2_points: Vec<[u8; BYTES_PER_G2_POINT]> =
            hex_to_bytes(&trusted_setup_file[g1_points_idx..g2_points_idx].join(""))
                .unwrap()
                .chunks_exact(BYTES_PER_G2_POINT)
                .map(|chunk| {
                    let mut array = [0u8; BYTES_PER_G2_POINT];
                    array.copy_from_slice(chunk);
                    array
                })
                .collect();

        assert_eq!(_g1_points.len(), num_g1_points);
        assert_eq!(_g2_points.len(), num_g2_points);

        let mut max_scale = 0;
        while (1 << max_scale) < _g1_points.len() {
            max_scale += 1;
        }

        let roots_of_unity = compute_roots_of_unity(max_scale)?;
        let mut g1_points: [G1Affine; NUM_G1_POINTS] = [G1Affine::identity(); NUM_G1_POINTS];
        let mut g2_points: [G2Affine; NUM_G2_POINTS] = [G2Affine::identity(); NUM_G2_POINTS];

        _g1_points.iter().enumerate().for_each(|(i, bytes)| {
            g1_points[i] = G1Affine::from_compressed_unchecked(bytes)
                .expect("load_trusted_setup Invalid g1 bytes");
        });

        _g2_points.iter().enumerate().for_each(|(i, bytes)| {
            g2_points[i] = G2Affine::from_compressed_unchecked(bytes)
                .expect("load_trusted_setup Invalid g2 bytes");
        });

        let _ = is_trusted_setup_in_lagrange_form(&g1_points, &g2_points);

        let bit_reversed_permutation = bit_reversal_permutation(&g1_points)?;
        let g1_points = bit_reversed_permutation;

        Ok(KzgSettingsOwned {
            roots_of_unity,
            g1_points,
            g2_points,
        })
    }

    fn bit_reversal_permutation<T, const N: usize>(array: &[T]) -> Result<[T; N], KzgError>
    where
        T: Default + Copy,
    {
        let n = array.len();
        assert!(n.is_power_of_two(), "n must be a power of 2");

        let mut bit_reversed_permutation = [T::default(); N];
        let unused_bit_len = array.len().leading_zeros();

        for (i, item) in array.iter().enumerate().take(n) {
            let r = i.reverse_bits() >> (unused_bit_len + 1);
            bit_reversed_permutation[r] = *item;
        }

        Ok(bit_reversed_permutation)
    }

    fn is_trusted_setup_in_lagrange_form(
        g1_points: &[G1Affine],
        g2_points: &[G2Affine],
    ) -> Result<(), KzgError> {
        let n1 = g1_points.len();
        let n2 = g2_points.len();

        if n1 < 2 || n2 < 2 {
            return Err(KzgError::BadArgs("invalid args".to_string()));
        }

        let a1 = g1_points[1];
        let a2 = g2_points[0];
        let b1 = g1_points[0];
        let b2 = g2_points[1];

        let is_monomial_form = pairings_verify(a1, a2, b1, b2);
        if !is_monomial_form {
            return Err(KzgError::BadArgs("not in monomial form".to_string()));
        }

        Ok(())
    }

    fn compute_roots_of_unity<const N: usize>(max_scale: usize) -> Result<[Scalar; N], KzgError> {
        if max_scale >= SCALE2_ROOT_OF_UNITY.len() {
            return Err(KzgError::BadArgs(format!(
                "The max scale should be lower than {}",
                SCALE2_ROOT_OF_UNITY.len()
            )));
        }

        let root_of_unity = Scalar::from_raw(SCALE2_ROOT_OF_UNITY[max_scale]);
        let mut expanded_roots = expand_root_of_unity(root_of_unity, N)?;
        let _ = expanded_roots.pop();

        bit_reversal_permutation(&expanded_roots)
    }

    fn expand_root_of_unity(root: Scalar, width: usize) -> Result<Vec<Scalar>, KzgError> {
        if width < 2 {
            return Err(KzgError::BadArgs(
                "The width must be greater or equal to 2".to_string(),
            ));
        }

        let mut expanded = vec![Scalar::one(), root];

        for _ in 2..=width {
            let current = expanded.last().unwrap() * root;
            expanded.push(current);
            if current == Scalar::one() {
                break;
            }
        }

        if expanded.last().unwrap() != &Scalar::one() {
            return Err(KzgError::InvalidBytesLength(
                "The last element value should be equal to 1".to_string(),
            ));
        }

        Ok(expanded)
    }

    let out_dir = env::var("OUT_DIR").unwrap();
    let g1_path = Path::new(&out_dir).join("g1.bin");
    let g2_path = Path::new(&out_dir).join("g2.bin");
    let roots_of_unity_path = Path::new(&out_dir).join("roots_of_unity.bin");

    let g1_exists = g1_path.exists();
    let g2_exists = g2_path.exists();
    let roots_of_unity_exists = roots_of_unity_path.exists();

    if g1_exists && g2_exists && roots_of_unity_exists {
        println!("cargo:rerun-if-changed=src/trusted_setup.rs"); // Re-run this build script if the `g1.bin`,`g2.bin`, or `roots_of_unity.bin` files are changed
    }

    let KzgSettingsOwned {
        roots_of_unity,
        g1_points,
        g2_points,
    } = load_trusted_setup_file_brute().unwrap();

    let mut roots_of_unity_bytes: Vec<u8> = Vec::new();
    let mut g1_bytes: Vec<u8> = Vec::new();
    let mut g2_bytes: Vec<u8> = Vec::new();

    roots_of_unity.iter().for_each(|&v| {
        roots_of_unity_bytes
            .extend_from_slice(unsafe { &std::mem::transmute::<Scalar, [u8; 32]>(v) });
    });

    g1_points.iter().for_each(|&v| {
        g1_bytes.extend_from_slice(unsafe { &std::mem::transmute::<G1Affine, [u8; 104]>(v) });
    });

    g2_points.iter().for_each(|&v| {
        g2_bytes.extend_from_slice(unsafe { &std::mem::transmute::<G2Affine, [u8; 200]>(v) });
    });

    let mut roots_of_unity_file = fs::OpenOptions::new()
        .create(true)
        .truncate(true)
        .write(true)
        .open(&roots_of_unity_path)
        .unwrap();

    roots_of_unity_file
        .write_all(&roots_of_unity_bytes)
        .unwrap();

    let mut g1_file = fs::OpenOptions::new()
        .create(true)
        .truncate(true)
        .write(true)
        .open(&g1_path)
        .unwrap();

    g1_file.write_all(&g1_bytes).unwrap();

    let mut g2_file = fs::OpenOptions::new()
        .create(true)
        .truncate(true)
        .write(true)
        .open(&g2_path)
        .unwrap();

    g2_file.write_all(&g2_bytes).unwrap();
}

#[cfg(any(target_arch = "riscv32", doc))]
fn main() {
    // Binaries cannot be built in a RISC-V environment or when building docs
}