no_std support

Based on the original work by Justin Moon.

*MSRV unchanged from 1.29.0.*

When `std` is off, `no-std` must be on, and we use the [`alloc`](https://doc.rust-lang.org/alloc/) and core2 crates. The `alloc` crate requires the user define a global allocator.

* Import from `core` and `alloc` instead of `std`
* `alloc` only used if `no-std` is on
* Create `std` feature
* Create `no-std` feature which adds a core2 dependency to polyfill `std::io` features. This is an experimental feature and should be
used with caution.
* CI runs tests `no-std`
* MSRV for `no-std` is 1.51 or so

Author: devrandom

.github/workflows/rust.yml

@@ -13,14 +13,17 @@ jobs:
             env:
               DO_COV: true
               AS_DEPENDENCY: true
+              DO_NO_STD: true
           - rust: beta
             env:
               AS_DEPENDENCY: true
+              DO_NO_STD: true
           - rust: nightly
             env:
               DO_FUZZ: true
               DO_BENCH: true
               AS_DEPENDENCY: true
+              DO_NO_STD: true
           - rust: 1.29.0
             env:
               AS_DEPENDENCY: true

Cargo.toml

@@ -12,7 +12,7 @@ readme = "README.md"
 
 
 [features]
-default = [ "secp-recovery" ]
+default = [ "std", "secp-recovery" ]
 base64 = [ "base64-compat" ]
 fuzztarget = []
 unstable = []
@@ -21,14 +21,24 @@ use-serde = ["serde", "bitcoin_hashes/serde", "secp256k1/serde"]
 secp-lowmemory = ["secp256k1/lowmemory"]
 secp-recovery = ["secp256k1/recovery"]
 
+# At least one of std, no-std must be enabled.
+#
+# The no-std feature doesn't disable std - you need to turn off the std feature for that by disabling default.
+# Instead no-std enables additional features required for this crate to be usable without std.
+# As a result, both can be enabled without conflict.
+std = ["secp256k1/std", "bitcoin_hashes/std", "bech32/std"]
+no-std = ["hashbrown", "core2/alloc", "bitcoin_hashes/alloc"]
+
 [dependencies]
-bech32 = "0.8.0"
-bitcoin_hashes = "0.9.6"
-secp256k1 = "0.20.2"
+bech32 = { version = "0.8.1", default-features = false }
+bitcoin_hashes = { version = "0.10.0", default-features = false }
+secp256k1 = { version = "0.20.2", default-features = false }
+core2 = { version = "0.3.0", optional = true, default-features = false }
 
 base64-compat = { version = "1.0.0", optional = true }
 bitcoinconsensus = { version = "0.19.0-3", optional = true }
 serde = { version = "1", features = [ "derive" ], optional = true }
+hashbrown = { version = "0.8", optional = true }
 
 [dev-dependencies]
 serde_json = "<1.0.45"
@@ -37,3 +47,10 @@ secp256k1 = { version = "0.20.0", features = [ "recovery", "rand-std" ] }
 bincode = "1.3.1"
 # We need to pin ryu (transitive dep from serde_json) to stay compatible with Rust 1.22.0
 ryu = "<1.0.5"
+
+[[example]]
+name = "bip32"
+
+[[example]]
+name = "handshake"
+required-features = ["std"]

contrib/test.sh

@@ -1,6 +1,12 @@
 #!/bin/sh -ex
 
-FEATURES="base64 bitcoinconsensus use-serde rand"
+FEATURES="base64 bitcoinconsensus use-serde rand secp-recovery"
+
+# Use toolchain if explicitly specified
+if [ -n "$TOOLCHAIN" ]
+then
+    alias cargo="cargo +$TOOLCHAIN"
+fi
 
 pin_common_verions() {
     cargo generate-lockfile --verbose
@@ -10,7 +16,7 @@ pin_common_verions() {
 }
 
 # Pin `cc` for Rust 1.29
-if [ -n "$PIN_VERSIONS" ]; then
+if [ "$PIN_VERSIONS" = true ]; then
     pin_common_verions
     cargo update -p byteorder --precise "1.3.4"
 fi
@@ -21,20 +27,43 @@ then
 fi
 
 
-# Use toolchain if explicitly specified
-if [ -n "$TOOLCHAIN" ]
-then
-    alias cargo="cargo +$TOOLCHAIN"
-fi
+echo "********* Testing std *************"
+# Test without any features other than std first
+cargo test --verbose --no-default-features --features="std"
 
-# Test without any features first
-cargo test --verbose --no-default-features
+echo "********* Testing default *************"
 # Then test with the default features
 cargo test --verbose
 
+if [ "$DO_NO_STD" = true ]
+then
+echo "********* Testing no-std build *************"
+  # Build no_std, to make sure that cfg(test) doesn't hide any issues
+  cargo build --verbose --features="no-std" --no-default-features
+
+  # Build std + no_std, to make sure they are not incompatible
+  cargo build --verbose --features="no-std"
+
+  # Test no_std
+  cargo test --verbose --features="no-std" --no-default-features
+
+  # Build all features
+  cargo build --verbose --features="no-std $FEATURES" --no-default-features
+
+  # Build specific features
+  for feature in ${FEATURES}
+  do
+      cargo build --verbose --features="no-std $feature"
+  done
+
+  cargo run --example bip32 L1HKVVLHXiUhecWnwFYF6L3shkf1E12HUmuZTESvBXUdx3yqVP1D
+  cargo run --no-default-features --features no-std --example bip32 L1HKVVLHXiUhecWnwFYF6L3shkf1E12HUmuZTESvBXUdx3yqVP1D
+fi
+
 # Test each feature
 for feature in ${FEATURES}
 do
+    echo "********* Testing "$feature" *************"
     cargo test --verbose --features="$feature"
 done
 
@@ -55,7 +84,7 @@ then
 fi
 
 # Use as dependency if told to
-if [ -n "$AS_DEPENDENCY" ]
+if [ "$AS_DEPENDENCY" = true ]
 then
     cargo new dep_test
     cd dep_test

examples/bip32.rs

@@ -10,6 +10,7 @@ use bitcoin::util::bip32::ExtendedPubKey;
 use bitcoin::util::bip32::DerivationPath;
 use bitcoin::util::bip32::ChildNumber;
 use bitcoin::util::address::Address;
+use bitcoin::secp256k1::ffi::types::AlignedType;
 
 fn main() {
     // This example derives root xprv
@@ -36,7 +37,9 @@ fn main() {
     let seed = wif.to_bytes();
 
     // we need secp256k1 context for key derivation
-    let secp = Secp256k1::new();
+    let mut buf: Vec<AlignedType> = Vec::new();
+    buf.resize(Secp256k1::preallocate_size(), AlignedType::zeroed());
+    let secp = Secp256k1::preallocated_new(buf.as_mut_slice()).unwrap();
 
     // calculate root key from seed
     let root = ExtendedPrivKey::new_master(network, &seed).unwrap();

src/blockdata/block.rs

@@ -20,6 +20,8 @@
 //! these blocks and the blockchain.
 //!
 
+use prelude::*;
+
 use core::fmt;
 
 use util;
@@ -308,6 +310,7 @@ impl fmt::Display for Bip34Error {
     }
 }
 
+#[cfg(feature = "std")]
 impl ::std::error::Error for Bip34Error {}
 
 #[cfg(test)]

src/blockdata/constants.rs

@@ -19,9 +19,11 @@
 //! single transaction
 //!
 
+use prelude::*;
+
 use core::default::Default;
 
-use hashes::hex::FromHex;
+use hashes::hex::{HexIterator, Error as HexError};
 use hashes::sha256d;
 use blockdata::opcodes;
 use blockdata::script;
@@ -84,8 +86,11 @@ fn bitcoin_genesis_tx() -> Transaction {
     });
 
     // Outputs
+    let script_bytes: Result<Vec<u8>, HexError> =
+        HexIterator::new("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f").unwrap()
+            .collect();
     let out_script = script::Builder::new()
-        .push_slice(&Vec::from_hex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f").unwrap())
+        .push_slice(script_bytes.unwrap().as_slice())
         .push_opcode(opcodes::all::OP_CHECKSIG)
         .into_script();
     ret.output.push(TxOut {

src/blockdata/opcodes.rs

@@ -22,6 +22,8 @@
 
 #[cfg(feature = "serde")] use serde;
 
+#[cfg(feature = "serde")] use prelude::*;
+
 use core::{fmt, convert::From};
 
 // Note: I am deliberately not implementing PartialOrd or Ord on the

src/blockdata/script.rs

@@ -24,8 +24,9 @@
 //! This module provides the structures and functions needed to support scripts.
 //!
 
-use io;
+use prelude::*;
 
+use io;
 use core::{fmt, default::Default};
 
 #[cfg(feature = "serde")] use serde;
@@ -36,7 +37,7 @@ use consensus::{encode, Decodable, Encodable};
 use hashes::{Hash, hex};
 use policy::DUST_RELAY_TX_FEE;
 #[cfg(feature="bitcoinconsensus")] use bitcoinconsensus;
-#[cfg(feature="bitcoinconsensus")] use std::convert;
+#[cfg(feature="bitcoinconsensus")] use core::convert::From;
 #[cfg(feature="bitcoinconsensus")] use OutPoint;
 
 use util::ecdsa::PublicKey;
@@ -145,11 +146,12 @@ impl fmt::Display for Error {
     }
 }
 
+#[cfg(feature = "std")]
 impl ::std::error::Error for Error {}
 
 #[cfg(feature="bitcoinconsensus")]
 #[doc(hidden)]
-impl convert::From<bitcoinconsensus::Error> for Error {
+impl From<bitcoinconsensus::Error> for Error {
     fn from(err: bitcoinconsensus::Error) -> Error {
         match err {
             _ => Error::BitcoinConsensus(err)
@@ -421,11 +423,11 @@ impl Script {
         } else if self.is_witness_program() {
             32 + 4 + 1 + (107 / 4) + 4 + // The spend cost copied from Core
             8 + // The serialized size of the TxOut's amount field
-            self.consensus_encode(&mut ::std::io::sink()).unwrap() as u64 // The serialized size of this script_pubkey
+            self.consensus_encode(&mut sink()).unwrap() as u64 // The serialized size of this script_pubkey
         } else {
             32 + 4 + 1 + 107 + 4 + // The spend cost copied from Core
             8 + // The serialized size of the TxOut's amount field
-            self.consensus_encode(&mut ::std::io::sink()).unwrap() as u64 // The serialized size of this script_pubkey
+            self.consensus_encode(&mut sink()).unwrap() as u64 // The serialized size of this script_pubkey
         };
 
         ::Amount::from_sat(sats)

src/blockdata/transaction.rs

@@ -23,9 +23,11 @@
 //! This module provides the structures and functions needed to support transactions.
 //!
 
+use prelude::*;
+
 use io;
 use core::{fmt, str, default::Default};
-use std::error;
+#[cfg(feature = "std")] use std::error;
 
 use hashes::{self, Hash, sha256d};
 use hashes::hex::FromHex;
@@ -130,8 +132,9 @@ impl fmt::Display for ParseOutPointError {
     }
 }
 
-impl error::Error for ParseOutPointError {
-    fn cause(&self) -> Option<&dyn error::Error> {
+#[cfg(feature = "std")]
+impl  error::Error for ParseOutPointError {
+    fn cause(&self) -> Option<&dyn  error::Error> {
         match *self {
             ParseOutPointError::Txid(ref e) => Some(e),
             ParseOutPointError::Vout(ref e) => Some(e),
@@ -630,6 +633,7 @@ impl fmt::Display for NonStandardSigHashType {
     }
 }
 
+#[cfg(feature = "std")]
 impl error::Error for NonStandardSigHashType {}
 
 /// Hashtype of an input's signature, encoded in the last byte of the signature
@@ -1360,6 +1364,7 @@ mod tests {
         use hashes::hex::FromHex;
         use std::collections::HashMap;
         use blockdata::script;
+
         // a random recent segwit transaction from blockchain using both old and segwit inputs
         let mut spending: Transaction = deserialize(Vec::from_hex("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")
             .unwrap().as_slice()).unwrap();