feat: add no-std feature to o1-utils crate

- Add `no-std` and `std` features to Cargo.toml (std is default) - Add conditional `#![no_std]` attribute to lib.rs - Replace `std::` imports with `core::` equivalents where possible - Add conditional `alloc` crate imports for Vec and other types - Feature-gate std-only modules (serialization, lazy_cache, chunked_evaluations) - Enable o1-utils in no-std CI workflow Closes: o1-labs/mina-rust#1988

Author: dannywillems

.github/workflows/no-std.yml

@@ -25,11 +25,11 @@ jobs:
  - { name: "mina-poseidon", path: "poseidon" } # https://github.com/o1-labs/mina-rust/issues/1996
  - { name: "mina-signer", path: "signer" } # https://github.com/o1-labs/mina-rust/issues/1995
  - { name: "groupmap", path: "groupmap" } # https://github.com/o1-labs/mina-rust/issues/1985
+ - { name: "o1-utils", path: "utils" } # https://github.com/o1-labs/mina-rust/issues/1988
  # TODO: Add no-std feature to these crates
  # - { name: "wasm-types", path: "crates/wasm-types" }
  # - { name: "turshi", path: "turshi" } # https://github.com/o1-labs/mina-rust/issues/1986
  # - { name: "mina-curves", path: "curves" } # https://github.com/o1-labs/mina-rust/issues/1987
- # - { name: "o1-utils", path: "utils" } # https://github.com/o1-labs/mina-rust/issues/1988
  # - { name: "internal-tracing", path: "internal-tracing" } # https://github.com/o1-labs/mina-rust/issues/1989
  # - { name: "poly-commitment", path: "poly-commitment" } # https://github.com/o1-labs/mina-rust/issues/1990
  # - { name: "kimchi", path: "kimchi" } # https://github.com/o1-labs/mina-rust/issues/1991

utils/Cargo.toml

@@ -39,4 +39,7 @@ mina-curves.workspace = true
 secp256k1.workspace = true
 
 [features]
+default = ["std"]
+std = []
+no-std = []
 diagnostics = ["tikv-jemalloc-ctl", "tikv-jemallocator"]

utils/src/array.rs

@@ -6,6 +6,9 @@
 //! better performance, either optimise this code, or use
 //! (non-fixed-sized) vectors.
 
+#[cfg(feature = "no-std")]
+use alloc::{boxed::Box, vec, vec::Vec};
+
 // Use a generic function so that the pointer cast remains type-safe
 /// Converts a vector of elements to a boxed one. Semantically
 /// equivalent to `vector.into_boxed_slice().try_into().unwrap()`.
@@ -26,7 +29,7 @@ pub fn vec_to_boxed_array2<T: Clone, const N: usize, const M: usize>(
  let z: Box<[T; N]> = y
  .try_into()
  .unwrap_or_else(|_| panic!("vec_to_boxed_array2: length mismatch inner array"));
- let zz: &[[T; N]] = std::slice::from_ref(z.as_ref());
+ let zz: &[[T; N]] = core::slice::from_ref(z.as_ref());
  vec_of_slices2.extend_from_slice(zz);
  });
 
@@ -43,7 +46,7 @@ pub fn vec_to_boxed_array3<T: Clone, const N: usize, const M: usize, const K: us
  let mut vec_of_slices2: Vec<[[T; N]; M]> = vec![];
  vec.into_iter().for_each(|x| {
  let r: Box<[[T; N]; M]> = vec_to_boxed_array2(x);
- let zz: &[[[T; N]; M]] = std::slice::from_ref(r.as_ref());
+ let zz: &[[[T; N]; M]] = core::slice::from_ref(r.as_ref());
  vec_of_slices2.extend_from_slice(zz);
  });
 
@@ -96,7 +99,7 @@ macro_rules! box_array2 {
  let z: Box<[T; N]> = y
  .try_into()
  .unwrap_or_else(|_| panic!("vec_to_boxed_array2: length mismatch inner array"));
- let zz: &[[T; N]] = std::slice::from_ref(z.as_ref());
+ let zz: &[[T; N]] = core::slice::from_ref(z.as_ref());
  vec_of_slices2.extend_from_slice(zz);
  });
 

utils/src/bitwise_operations.rs

@@ -1,7 +1,12 @@
 //! This module provides a set of functions to perform bit operations on big integers.
 //! In particular, it gives XOR and NOT for BigUint.
+#[cfg(feature = "no-std")]
+use alloc::vec;
+#[cfg(feature = "no-std")]
+use alloc::vec::Vec;
+
+use core::cmp::{max, Ordering};
 use num_bigint::BigUint;
-use std::cmp::{max, Ordering};
 
 use crate::BigUintHelpers;
 

utils/src/chunked_evaluations.rs

@@ -1,3 +1,4 @@
+#![cfg(not(feature = "no-std"))]
 //! This module contains a type [ChunkedEvaluations],
 
 use ark_ff::PrimeField;

utils/src/chunked_polynomial.rs

@@ -2,6 +2,9 @@
 //! and a number of helper methods to deal with chunked polynomials.
 //! Polynomials that cut in several polynomials of the same length.
 
+#[cfg(feature = "no-std")]
+use alloc::{vec, vec::Vec};
+
 use ark_ff::Field;
 use ark_poly::polynomial::{univariate::DensePolynomial, Polynomial};
 

utils/src/dense_polynomial.rs

@@ -1,5 +1,8 @@
 //! This adds a few utility functions for the [DensePolynomial] arkworks type.
 
+#[cfg(feature = "no-std")]
+use alloc::{vec, vec::Vec};
+
 use ark_ff::Field;
 use ark_poly::{univariate::DensePolynomial, DenseUVPolynomial, Polynomial};
 use rayon::prelude::*;

utils/src/evaluations.rs

@@ -1,5 +1,8 @@
 //! This adds a few utility functions for the [Evaluations] arkworks type.
 
+#[cfg(feature = "no-std")]
+use alloc::vec::Vec;
+
 use ark_ff::FftField;
 use ark_poly::{Evaluations, Radix2EvaluationDomain};
 use rayon::prelude::*;

utils/src/field_helpers.rs

@@ -1,9 +1,12 @@
 //! Useful helper methods to extend [ark_ff::Field].
 
+#[cfg(feature = "no-std")]
+use alloc::{string::String, vec, vec::Vec};
+use core::ops::Neg;
+
 use ark_ff::{BigInteger, Field, PrimeField};
 use num_bigint::{BigInt, BigUint, RandBigInt, Sign};
 use rand::rngs::StdRng;
-use std::ops::Neg;
 use thiserror::Error;
 
 /// Field helpers error
@@ -21,7 +24,7 @@ pub enum FieldHelpersError {
 }
 
 /// Result alias using [FieldHelpersError]
-pub type Result<T> = std::result::Result<T, FieldHelpersError>;
+pub type Result<T> = core::result::Result<T, FieldHelpersError>;
 
 /// Helper to generate random field elements
 pub trait RandomField<F> {

utils/src/foreign_field.rs

@@ -3,16 +3,21 @@
 //! - `B` is a bit length of one limb
 //! - `N` is a number of limbs that is used to represent one foreign field element
 
+#[cfg(feature = "no-std")]
+use alloc::vec;
+#[cfg(feature = "no-std")]
+use alloc::vec::Vec;
+use core::{
+ fmt::{Debug, Formatter},
+ ops::{Index, IndexMut},
+};
+
 use crate::{
  field_helpers::FieldHelpers,
  math::{div_ceil, is_multiple_of},
 };
 use ark_ff::{Field, PrimeField};
 use num_bigint::BigUint;
-use std::{
- fmt::{Debug, Formatter},
- ops::{Index, IndexMut},
-};
 
 /// Represents a foreign field element
 #[derive(Clone, PartialEq, Eq)]
@@ -154,7 +159,7 @@ impl<F: Field, const B: usize, const N: usize> IndexMut<usize> for ForeignElemen
 }
 
 impl<F: Field, const B: usize, const N: usize> Debug for ForeignElement<F, B, N> {
- fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+ fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
  write!(f, "ForeignElement(")?;
  for i in 0..self.len {
  write!(f, "{:?}", self.limbs[i].to_hex())?;