Merge rust-bitcoin/rust-bitcoin#2988: Add additional `HashEngine` types

51010777bf hashes: Strongly type the hash160::HashEngine (Tobin C. Harding)
d5dd54a489 hashes: Strongly type the sha256d::HashEngine (Tobin C. Harding)
a7422a779c hashes: Add const hash engine constructors (Tobin C. Harding)

Pull request description:

  Currently we are using a type alias for a few of the hash engines.

  Type alias' allow for potential mixing of types, a struct can better serve our users with not much additional complexity or maintenance burden.

  - As preparation add const constructors where possible to hash engines (excl. `HmacEngine`).
  - Add a `sha256d::HashEngine` struct
  - Add a `hash160::HashEngine` struct

  If this goes in we can improve the `sha256t::HashEngine` in a similar manner.

ACKs for top commit:
  Kixunil:
    ACK 51010777bf
  apoelstra:
    ACK 51010777bf but will hold off on merging until tcharding indicates whether he wants to address the midstate thing

Tree-SHA512: 810db3a8cd66e4d135b04a65d5b4c926cf2e5e8ac531619bbd884db69df17b29b64daeb6fb31b8b1fb32bffbf81cf84e55cd46945c743451c73f1b7f63489f63

bitcoin/src/address/mod.rs

@@ -34,7 +34,7 @@ use core::str::FromStr;
 
 use bech32::primitives::gf32::Fe32;
 use bech32::primitives::hrp::Hrp;
-use hashes::{sha256, HashEngine};
+use hashes::{hash160, HashEngine};
 use secp256k1::{Secp256k1, Verification, XOnlyPublicKey};
 
 use crate::consensus::Params;
@@ -878,11 +878,11 @@ impl FromStr for Address<NetworkUnchecked> {
 }
 
 /// Convert a byte array of a pubkey hash into a segwit redeem hash
-fn segwit_redeem_hash(pubkey_hash: PubkeyHash) -> crate::hashes::hash160::Hash {
-    let mut sha_engine = sha256::Hash::engine();
+fn segwit_redeem_hash(pubkey_hash: PubkeyHash) -> hash160::Hash {
+    let mut sha_engine = hash160::Hash::engine();
     sha_engine.input(&[0, 20]);
     sha_engine.input(pubkey_hash.as_ref());
-    crate::hashes::hash160::Hash::from_engine(sha_engine)
+    hash160::Hash::from_engine(sha_engine)
 }
 
 #[cfg(test)]

bitcoin/src/crypto/sighash.rs

@@ -59,12 +59,12 @@ impl_message_from_hash!(SegwitV0Sighash);
 // but outside of it, it should not be possible to construct these hash
 // types from arbitrary data (except by casting via to/from_byte_array).
 impl LegacySighash {
-    fn engine() -> sha256::HashEngine { sha256d::Hash::engine() }
-    fn from_engine(e: sha256::HashEngine) -> Self { Self(sha256d::Hash::from_engine(e)) }
+    fn engine() -> sha256d::HashEngine { sha256d::Hash::engine() }
+    fn from_engine(e: sha256d::HashEngine) -> Self { Self(sha256d::Hash::from_engine(e)) }
 }
 impl SegwitV0Sighash {
-    fn engine() -> sha256::HashEngine { sha256d::Hash::engine() }
-    fn from_engine(e: sha256::HashEngine) -> Self { Self(sha256d::Hash::from_engine(e)) }
+    fn engine() -> sha256d::HashEngine { sha256d::Hash::engine() }
+    fn from_engine(e: sha256d::HashEngine) -> Self { Self(sha256d::Hash::from_engine(e)) }
 }
 
 sha256t_hash_newtype! {

hashes/src/hash160.rs

@@ -18,10 +18,30 @@ crate::internal_macros::hash_type! {
     "Output of the Bitcoin HASH160 hash function. (RIPEMD160(SHA256))"
 }
 
-type HashEngine = sha256::HashEngine;
+/// Engine to compute HASH160 hash function.
+#[derive(Clone)]
+pub struct HashEngine(sha256::HashEngine);
+
+impl HashEngine {
+    /// Creates a new HASH160 hash engine.
+    pub const fn new() -> Self { Self(sha256::HashEngine::new()) }
+}
+
+impl Default for HashEngine {
+    fn default() -> Self { Self::new() }
+}
+
+impl crate::HashEngine for HashEngine {
+    type MidState = sha256::Midstate;
+    fn midstate(&self) -> Self::MidState { self.0.midstate() }
+
+    const BLOCK_SIZE: usize = 64; // Same as sha256::HashEngine::BLOCK_SIZE;
+    fn input(&mut self, data: &[u8]) { self.0.input(data) }
+    fn n_bytes_hashed(&self) -> usize { self.0.n_bytes_hashed() }
+}
 
 fn from_engine(e: HashEngine) -> Hash {
-    let sha2 = sha256::Hash::from_engine(e);
+    let sha2 = sha256::Hash::from_engine(e.0);
     let rmd = ripemd160::Hash::hash(&sha2[..]);
 
     let mut ret = [0; 20];

hashes/src/impls.rs

@@ -6,7 +6,16 @@
 
 use bitcoin_io::impl_write;
 
-use crate::{hmac, ripemd160, sha1, sha256, sha512, siphash24, HashEngine};
+use crate::{hash160, hmac, ripemd160, sha1, sha256, sha256d, sha512, siphash24, HashEngine};
+
+impl_write!(
+    hash160::HashEngine,
+    |us: &mut hash160::HashEngine, buf| {
+        us.input(buf);
+        Ok(buf.len())
+    },
+    |_us| { Ok(()) }
+);
 
 impl_write!(
     sha1::HashEngine,
@@ -26,6 +35,15 @@ impl_write!(
     |_us| { Ok(()) }
 );
 
+impl_write!(
+    sha256d::HashEngine,
+    |us: &mut sha256d::HashEngine, buf| {
+        us.input(buf);
+        Ok(buf.len())
+    },
+    |_us| { Ok(()) }
+);
+
 impl_write!(
     sha512::HashEngine,
     |us: &mut sha512::HashEngine, buf| {

hashes/src/ripemd160.rs

@@ -51,9 +51,10 @@ pub struct HashEngine {
     length: usize,
 }
 
-impl Default for HashEngine {
-    fn default() -> Self {
-        HashEngine {
+impl HashEngine {
+    /// Creates a new SHA256 hash engine.
+    pub const fn new() -> Self {
+        Self {
             h: [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0],
             length: 0,
             buffer: [0; BLOCK_SIZE],
@@ -61,6 +62,10 @@ impl Default for HashEngine {
     }
 }
 
+impl Default for HashEngine {
+    fn default() -> Self { Self::new() }
+}
+
 impl crate::HashEngine for HashEngine {
     type MidState = [u8; 20];
 

hashes/src/sha1.rs

@@ -43,9 +43,10 @@ pub struct HashEngine {
     length: usize,
 }
 
-impl Default for HashEngine {
-    fn default() -> Self {
-        HashEngine {
+impl HashEngine {
+    /// Creates a new SHA1 hash engine.
+    pub const fn new() -> Self {
+        Self {
             h: [0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476, 0xc3d2e1f0],
             length: 0,
             buffer: [0; BLOCK_SIZE],
@@ -53,6 +54,10 @@ impl Default for HashEngine {
     }
 }
 
+impl Default for HashEngine {
+    fn default() -> Self { Self::new() }
+}
+
 impl crate::HashEngine for HashEngine {
     type MidState = [u8; 20];
 

hashes/src/sha256.rs

@@ -59,9 +59,10 @@ pub struct HashEngine {
     length: usize,
 }
 
-impl Default for HashEngine {
-    fn default() -> Self {
-        HashEngine {
+impl HashEngine {
+    /// Creates a new SHA256 hash engine.
+    pub const fn new() -> Self {
+        Self {
             h: [
                 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab,
                 0x5be0cd19,
@@ -72,6 +73,10 @@ impl Default for HashEngine {
     }
 }
 
+impl Default for HashEngine {
+    fn default() -> Self { Self::new() }
+}
+
 impl crate::HashEngine for HashEngine {
     type MidState = Midstate;
 

hashes/src/sha256d.rs

@@ -13,10 +13,30 @@ crate::internal_macros::hash_type! {
     "Output of the SHA256d hash function."
 }
 
-type HashEngine = sha256::HashEngine;
+/// Engine to compute SHA256d hash function.
+#[derive(Clone)]
+pub struct HashEngine(sha256::HashEngine);
 
-fn from_engine(e: sha256::HashEngine) -> Hash {
-    let sha2 = sha256::Hash::from_engine(e);
+impl HashEngine {
+    /// Creates a new SHA256d hash engine.
+    pub const fn new() -> Self { Self(sha256::HashEngine::new()) }
+}
+
+impl Default for HashEngine {
+    fn default() -> Self { Self::new() }
+}
+
+impl crate::HashEngine for HashEngine {
+    type MidState = sha256::Midstate;
+    fn midstate(&self) -> Self::MidState { self.0.midstate() }
+
+    const BLOCK_SIZE: usize = 64; // Same as sha256::HashEngine::BLOCK_SIZE;
+    fn input(&mut self, data: &[u8]) { self.0.input(data) }
+    fn n_bytes_hashed(&self) -> usize { self.0.n_bytes_hashed() }
+}
+
+fn from_engine(e: HashEngine) -> Hash {
+    let sha2 = sha256::Hash::from_engine(e.0);
     let sha2d = sha256::Hash::hash(&sha2[..]);
 
     let mut ret = [0; 32];

hashes/src/sha384.rs

@@ -23,11 +23,13 @@ fn from_engine(e: HashEngine) -> Hash {
 #[derive(Clone)]
 pub struct HashEngine(sha512::HashEngine);
 
+impl HashEngine {
+    /// Creates a new SHA384 hash engine.
+    pub const fn new() -> Self { Self(sha512::HashEngine::sha384()) }
+}
+
 impl Default for HashEngine {
-    #[rustfmt::skip]
-    fn default() -> Self {
-        HashEngine(sha512::HashEngine::sha384())
-    }
+    fn default() -> Self { Self::new() }
 }
 
 impl crate::HashEngine for HashEngine {

hashes/src/sha512.rs

@@ -52,10 +52,11 @@ pub struct HashEngine {
     buffer: [u8; BLOCK_SIZE],
 }
 
-impl Default for HashEngine {
+impl HashEngine {
+    /// Creates a new SHA512 hash engine.
     #[rustfmt::skip]
-    fn default() -> Self {
-        HashEngine {
+    pub const fn new() -> Self {
+        Self {
             h: [
                 0x6a09e667f3bcc908, 0xbb67ae8584caa73b, 0x3c6ef372fe94f82b, 0xa54ff53a5f1d36f1,
                 0x510e527fade682d1, 0x9b05688c2b3e6c1f, 0x1f83d9abfb41bd6b, 0x5be0cd19137e2179,
@@ -66,10 +67,14 @@ impl Default for HashEngine {
     }
 }
 
+impl Default for HashEngine {
+    fn default() -> Self { Self::new() }
+}
+
 impl HashEngine {
-    /// Constructs a hash engine suitable for use inside the default `sha512_256::HashEngine`.
+    /// Constructs a hash engine suitable for use constructing a `sha512_256::HashEngine`.
     #[rustfmt::skip]
-    pub(crate) fn sha512_256() -> Self {
+    pub(crate) const fn sha512_256() -> Self {
         HashEngine {
             h: [
                 0x22312194fc2bf72c, 0x9f555fa3c84c64c2, 0x2393b86b6f53b151, 0x963877195940eabd,
@@ -80,9 +85,9 @@ impl HashEngine {
         }
     }
 
-    /// Constructs a hash engine suitable for use inside the default `sha384::HashEngine`.
+    /// Constructs a hash engine suitable for constructing `sha384::HashEngine`.
     #[rustfmt::skip]
-    pub(crate) fn sha384() -> Self {
+    pub(crate) const fn sha384() -> Self {
         HashEngine {
             h: [
                 0xcbbb9d5dc1059ed8, 0x629a292a367cd507, 0x9159015a3070dd17, 0x152fecd8f70e5939,

hashes/src/sha512_256.rs

@@ -33,11 +33,13 @@ fn from_engine(e: HashEngine) -> Hash {
 #[derive(Clone)]
 pub struct HashEngine(sha512::HashEngine);
 
+impl HashEngine {
+    /// Creates a new SHA512/256 hash engine.
+    pub const fn new() -> Self { Self(sha512::HashEngine::sha512_256()) }
+}
+
 impl Default for HashEngine {
-    #[rustfmt::skip]
-    fn default() -> Self {
-        HashEngine(sha512::HashEngine::sha512_256())
-    }
+    fn default() -> Self { Self::new() }
 }
 
 impl crate::HashEngine for HashEngine {