Generate Bulletproofs(+) generators at compile time

Creates a new monero-generators crate so the monero crate can run the 
code in question at build time.

Saves several seconds from running the tests.

Closes https://github.com/serai-dex/serai/issues/101.

coins/monero/src/ringct/bulletproofs/core.rs

@@ -13,10 +13,9 @@ use dalek_ff_group::{Scalar, EdwardsPoint};
 
 use multiexp::multiexp as multiexp_const;
 
-use crate::{
-  H as DALEK_H, Commitment, hash, hash_to_scalar as dalek_hash,
-  ringct::hash_to_point::raw_hash_to_point, serialize::write_varint,
-};
+pub(crate) use monero_generators::Generators;
+
+use crate::{H as DALEK_H, Commitment, hash_to_scalar as dalek_hash};
 pub(crate) use crate::ringct::bulletproofs::scalar_vector::*;
 
 // Bring things into ff/group
@@ -33,29 +32,6 @@ pub(crate) fn hash_to_scalar(data: &[u8]) -> Scalar {
 pub(crate) const MAX_M: usize = 16;
 pub(crate) const LOG_N: usize = 6; // 2 << 6 == N
 pub(crate) const N: usize = 64;
-pub(crate) const MAX_MN: usize = MAX_M * N;
-
-pub(crate) struct Generators {
-  pub(crate) G: Vec<EdwardsPoint>,
-  pub(crate) H: Vec<EdwardsPoint>,
-}
-
-pub(crate) fn generators_core(prefix: &'static [u8]) -> Generators {
-  let mut res = Generators { G: Vec::with_capacity(MAX_MN), H: Vec::with_capacity(MAX_MN) };
-  for i in 0 .. MAX_MN {
-    let i = 2 * i;
-
-    let mut even = (*H).compress().to_bytes().to_vec();
-    even.extend(prefix);
-    let mut odd = even.clone();
-
-    write_varint(&i.try_into().unwrap(), &mut even).unwrap();
-    write_varint(&(i + 1).try_into().unwrap(), &mut odd).unwrap();
-    res.H.push(EdwardsPoint(raw_hash_to_point(hash(&even))));
-    res.G.push(EdwardsPoint(raw_hash_to_point(hash(&odd))));
-  }
-  res
-}
 
 pub(crate) fn prove_multiexp(pairs: &[(Scalar, EdwardsPoint)]) -> EdwardsPoint {
   multiexp_const(pairs) * *INV_EIGHT
@@ -153,12 +129,6 @@ lazy_static! {
   pub(crate) static ref TWO_N: ScalarVector = ScalarVector::powers(Scalar::from(2u8), N);
 }
 
-pub(crate) fn init() {
-  let _ = &*INV_EIGHT;
-  let _ = &*H;
-  let _ = &*TWO_N;
-}
-
 pub(crate) fn challenge_products(w: &[Scalar], winv: &[Scalar]) -> Vec<Scalar> {
   let mut products = vec![Scalar::zero(); 1 << w.len()];
   products[0] = winv[0];

coins/monero/src/ringct/bulletproofs/mod.rs

@@ -43,14 +43,6 @@ impl Bulletproofs {
     len + clawback
   }
 
-  pub fn init(plus: bool) {
-    if !plus {
-      OriginalStruct::init();
-    } else {
-      PlusStruct::init();
-    }
-  }
-
   pub fn prove<R: RngCore + CryptoRng>(
     rng: &mut R,
     outputs: &[Commitment],

coins/monero/src/ringct/bulletproofs/original.rs

@@ -12,8 +12,9 @@ use multiexp::BatchVerifier;
 
 use crate::{Commitment, ringct::bulletproofs::core::*};
 
+include!("../../../.generators/generators.rs");
+
 lazy_static! {
-  static ref GENERATORS: Generators = generators_core(b"bulletproof");
   static ref ONE_N: ScalarVector = ScalarVector(vec![Scalar::one(); N]);
   static ref IP12: Scalar = inner_product(&ONE_N, &TWO_N);
 }
@@ -34,13 +35,6 @@ pub struct OriginalStruct {
 }
 
 impl OriginalStruct {
-  pub(crate) fn init() {
-    init();
-    let _ = &*GENERATORS;
-    let _ = &*ONE_N;
-    let _ = &*IP12;
-  }
-
   pub(crate) fn prove<R: RngCore + CryptoRng>(
     rng: &mut R,
     commitments: &[Commitment],

coins/monero/src/ringct/bulletproofs/plus.rs

@@ -15,8 +15,9 @@ use crate::{
   ringct::{hash_to_point::raw_hash_to_point, bulletproofs::core::*},
 };
 
+include!("../../../.generators/generators_plus.rs");
+
 lazy_static! {
-  static ref GENERATORS: Generators = generators_core(b"bulletproof_plus");
   static ref TRANSCRIPT: [u8; 32] =
     EdwardsPoint(raw_hash_to_point(hash(b"bulletproof_plus_transcript"))).compress().to_bytes();
 }
@@ -52,12 +53,6 @@ pub struct PlusStruct {
 }
 
 impl PlusStruct {
-  pub(crate) fn init() {
-    init();
-    let _ = &*GENERATORS;
-    let _ = &*TRANSCRIPT;
-  }
-
   pub(crate) fn prove<R: RngCore + CryptoRng>(
     rng: &mut R,
     commitments: &[Commitment],