Add no-std support via a default-enabled std feature flag

Cargo.toml

@@ -24,27 +24,27 @@ rustdoc-args = ["--cfg", "docsrs", "--html-in-header", "katex-header.html"]
 
 [dependencies]
 aes = "0.8"
-bitvec = "1"
-blake2b_simd = "1"
-ff = "0.13"
-fpe = "0.6"
-group = { version = "0.13", features = ["wnaf-memuse"] }
-hex = "0.4"
+bitvec = { version = "1", default-features = false }
+blake2b_simd = { version = "1", default-features = false }
+ff = { version = "0.13", default-features = false }
+fpe = { version = "0.6", default-features = false, features = ["alloc"] }
+group = "0.13"
+hex = { version = "0.4", default-features = false, features = ["alloc"] }
 lazy_static = "1"
-memuse = { version = "0.2.1", features = ["nonempty"] }
+memuse = { version = "0.2.2", default-features = false }
 pasta_curves = "0.5"
 proptest = { version = "1.0.0", optional = true }
-rand = "0.8"
-reddsa = "0.5"
-nonempty = "0.7"
+rand = { version = "0.8", default-features = false }
+reddsa = { version = "0.5", default-features = false }
+nonempty = { version = "0.10", default-features = false }
 poseidon = { package = "halo2_poseidon", version = "0.1" }
-serde = { version = "1.0", features = ["derive"] }
+serde = { version = "1.0", default-features = false, features = ["derive"] }
 sinsemilla = "0.1"
-subtle = "2.3"
+subtle = { version = "2.3", default-features = false }
 zcash_note_encryption = "0.4"
-incrementalmerkletree = "0.7"
+incrementalmerkletree = { version = "0.7", default-features = false }
 zcash_spec = "0.1"
-zip32 = "0.1"
+zip32 = { version = "0.1", default-features = false }
 visibility = "0.1.1"
 
 # Circuit
@@ -55,7 +55,10 @@ halo2_proofs = { version = "0.3", optional = true, default-features = false, fea
 getset = "0.1"
 
 # Logging
-tracing = "0.1"
+tracing = { version = "0.1", default-features = false }
+
+# No-std support
+core2 = { version = "0.3", default-features = false, features = ["alloc"] }
 
 # Developer tooling dependencies
 image = { version = "0.24", optional = true }
@@ -78,8 +81,9 @@ pprof = { version = "0.11", features = ["criterion", "flamegraph"] }
 bench = false
 
 [features]
-default = ["circuit", "multicore"]
-circuit = ["dep:halo2_gadgets", "dep:halo2_proofs"]
+default = ["circuit", "multicore", "std"]
+std = ["core2/std", "group/wnaf-memuse", "reddsa/std"]
+circuit = ["dep:halo2_gadgets", "dep:halo2_proofs", "std"]
 unstable-frost = []
 multicore = ["halo2_proofs?/multicore"]
 dev-graph = ["halo2_proofs?/dev-graph", "image", "plotters"]
@@ -102,3 +106,6 @@ debug = true
 
 [profile.bench]
 debug = true
+
+[patch.crates-io]
+nonempty = { git = "https://github.com/nuttycom/nonempty.git", rev = "090815ca02ff969d23c6331f9f5b1e4c7720160a" }

src/builder.rs

@@ -1,9 +1,9 @@
 //! Logic for building Orchard components of transactions.
 
+use alloc::collections::BTreeMap;
+use alloc::vec::Vec;
 use core::fmt;
 use core::iter;
-use std::collections::BTreeMap;
-use std::fmt::Display;
 
 use ff::Field;
 use pasta_curves::pallas;
@@ -141,7 +141,7 @@ pub enum BuildError {
     BundleTypeNotSatisfiable,
 }
 
-impl Display for BuildError {
+impl fmt::Display for BuildError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use BuildError::*;
         match self {
@@ -163,6 +163,7 @@ impl Display for BuildError {
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for BuildError {}
 
 #[cfg(feature = "circuit")]
@@ -189,7 +190,7 @@ pub enum SpendError {
     FvkMismatch,
 }
 
-impl Display for SpendError {
+impl fmt::Display for SpendError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use SpendError::*;
         f.write_str(match self {
@@ -200,18 +201,20 @@ impl Display for SpendError {
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for SpendError {}
 
 /// The only error that can occur here is if outputs are disabled for this builder.
 #[derive(Debug, PartialEq, Eq)]
 pub struct OutputError;
 
-impl Display for OutputError {
+impl fmt::Display for OutputError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str("Outputs are not enabled for this builder")
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for OutputError {}
 
 /// Information about a specific note to be spent in an [`Action`].
@@ -1137,7 +1140,9 @@ impl OutputView for OutputInfo {
 #[cfg(any(test, feature = "test-dependencies"))]
 #[cfg_attr(docsrs, doc(cfg(feature = "test-dependencies")))]
 pub mod testing {
+    use alloc::vec::Vec;
     use core::fmt::Debug;
+
     use incrementalmerkletree::{frontier::Frontier, Hashable};
     use rand::{rngs::StdRng, CryptoRng, SeedableRng};
 

src/bundle.rs

@@ -1,5 +1,7 @@
 //! Structs related to bundles of Orchard actions.
 
+use alloc::vec::Vec;
+
 pub mod commitments;
 
 #[cfg(feature = "circuit")]
@@ -10,10 +12,12 @@ pub use batch::BatchValidator;
 use core::fmt;
 
 use blake2b_simd::Hash as Blake2bHash;
-use memuse::DynamicUsage;
 use nonempty::NonEmpty;
 use zcash_note_encryption::{try_note_decryption, try_output_recovery_with_ovk};
 
+#[cfg(feature = "std")]
+use memuse::DynamicUsage;
+
 use crate::{
     action::Action,
     address::Address,
@@ -472,16 +476,17 @@ impl<V> Bundle<Authorized, V> {
     }
 }
 
+#[cfg(feature = "std")]
 impl<V: DynamicUsage> DynamicUsage for Bundle<Authorized, V> {
     fn dynamic_usage(&self) -> usize {
-        self.actions.dynamic_usage()
+        self.actions.tail.dynamic_usage()
             + self.value_balance.dynamic_usage()
             + self.authorization.proof.dynamic_usage()
     }
 
     fn dynamic_usage_bounds(&self) -> (usize, Option<usize>) {
         let bounds = (
-            self.actions.dynamic_usage_bounds(),
+            self.actions.tail.dynamic_usage_bounds(),
             self.value_balance.dynamic_usage_bounds(),
             self.authorization.proof.dynamic_usage_bounds(),
         );
@@ -519,6 +524,8 @@ pub struct BundleAuthorizingCommitment(pub Blake2bHash);
 #[cfg(any(test, feature = "test-dependencies"))]
 #[cfg_attr(docsrs, doc(cfg(feature = "test-dependencies")))]
 pub mod testing {
+    use alloc::vec::Vec;
+
     use group::ff::FromUniformBytes;
     use nonempty::NonEmpty;
     use pasta_curves::pallas;

src/bundle/batch.rs

@@ -1,3 +1,5 @@
+use alloc::vec::Vec;
+
 use halo2_proofs::plonk;
 use pasta_curves::vesta;
 use rand::{CryptoRng, RngCore};

src/circuit.rs

@@ -1,5 +1,7 @@
 //! The Orchard Action circuit implementation.
 
+use alloc::vec::Vec;
+
 use group::{Curve, GroupEncoding};
 use halo2_proofs::{
     circuit::{floor_planner, Layouter, Value},
@@ -919,6 +921,7 @@ impl Proof {
 
 #[cfg(test)]
 mod tests {
+    use alloc::vec::Vec;
     use core::iter;
 
     use ff::Field;

src/constants/fixed_bases.rs

@@ -1,4 +1,8 @@
 //! Orchard fixed bases.
+
+#[cfg(feature = "circuit")]
+use alloc::vec::Vec;
+
 use super::{L_ORCHARD_SCALAR, L_VALUE};
 
 #[cfg(feature = "circuit")]

src/keys.rs

@@ -1,6 +1,7 @@
 //! Key structures for Orchard.
 
-use std::io::{self, Read, Write};
+use alloc::vec::Vec;
+use core2::io::{self, Read, Write};
 
 use ::zip32::{AccountId, ChildIndex};
 use aes::Aes256;
@@ -405,7 +406,7 @@ impl FullViewingKey {
         Self::from_bytes(&data).ok_or_else(|| {
             io::Error::new(
                 io::ErrorKind::InvalidInput,
-                "Unable to deserialize a valid Orchard FullViewingKey from bytes".to_owned(),
+                "Unable to deserialize a valid Orchard FullViewingKey from bytes",
             )
         })
     }
@@ -681,6 +682,7 @@ impl IncomingViewingKey {
 #[derive(Clone, Debug)]
 pub struct PreparedIncomingViewingKey(PreparedNonZeroScalar);
 
+#[cfg(feature = "std")]
 impl memuse::DynamicUsage for PreparedIncomingViewingKey {
     fn dynamic_usage(&self) -> usize {
         self.0.dynamic_usage()

src/lib.rs

@@ -7,6 +7,7 @@
 //! implicitly mean it is an Orchard payment address (as opposed to e.g. a Sapling payment
 //! address, which is also shielded).
 
+#![no_std]
 #![cfg_attr(docsrs, feature(doc_cfg))]
 // Temporary until we have more of the crate implemented.
 #![allow(dead_code)]
@@ -16,6 +17,14 @@
 #![deny(missing_docs)]
 #![deny(unsafe_code)]
 
+#[macro_use]
+extern crate alloc;
+
+#[cfg(feature = "std")]
+extern crate std;
+
+use alloc::vec::Vec;
+
 mod action;
 mod address;
 pub mod builder;

src/note_encryption.rs

@@ -1,5 +1,6 @@
 //! In-band secret distribution for Orchard bundles.
 
+use alloc::vec::Vec;
 use core::fmt;
 
 use blake2b_simd::{Hash, Params};

src/pczt.rs

@@ -1,7 +1,9 @@
 //! PCZT support for Orchard.
 
-use std::collections::BTreeMap;
-use std::fmt;
+use alloc::collections::BTreeMap;
+use alloc::string::String;
+use alloc::vec::Vec;
+use core::fmt;
 
 use getset::Getters;
 use pasta_curves::pallas;

src/pczt/io_finalizer.rs

@@ -1,3 +1,5 @@
+use alloc::vec::Vec;
+
 use rand::{CryptoRng, RngCore};
 
 use crate::{

src/pczt/parse.rs

@@ -1,4 +1,6 @@
-use std::collections::BTreeMap;
+use alloc::collections::BTreeMap;
+use alloc::string::String;
+use alloc::vec::Vec;
 
 use ff::PrimeField;
 use incrementalmerkletree::Hashable;

src/pczt/prover.rs

@@ -1,3 +1,5 @@
+use alloc::vec::Vec;
+
 use halo2_proofs::plonk;
 use rand::{CryptoRng, RngCore};
 

src/pczt/updater.rs

@@ -1,3 +1,6 @@
+use alloc::string::String;
+use alloc::vec::Vec;
+
 use super::{Action, Bundle, Zip32Derivation};
 
 impl Bundle {