Clean up the siphash mess

Previously we had removed `Default` impl on `siphash24::HashEngine` by
reimplementing the type manually. This was a really bad idea as it
inevitably led to API differences that broke the build which we didn't
notice because of unrelated bug. It should've just split the macro from
the start as was suggested but it was claimed to be difficult, I don't
think was the case as can be seen by this PR.

This commit does what the previous one should've done: it renames the
macro to have `_no_default` suffix, creates another one of the original
name that calls into `_no_default` one and moves anything related to
`Default`. This cleanly ensures all previous hashes stay the same while
siphash gets `Default` removed. This also removes all now-conflicting
impls from `siphash24` module which makes the module almost identical to
what it looked like before the change. The only differences are removed
`Default`/`new`, fixes in tests and recent rename of `as_u64` to
`to_u64`.

hashes/src/internal_macros.rs

@@ -102,8 +102,6 @@ macro_rules! hash_trait_impls {
         impl<$($gen: $gent),*> crate::GeneralHash for Hash<$($gen),*> {
             type Engine = HashEngine;
 
-            fn engine() -> HashEngine { Self::engine() }
-
             fn from_engine(e: HashEngine) -> Hash<$($gen),*> { Self::from_engine(e) }
         }
 
@@ -142,6 +140,37 @@ pub(crate) use hash_trait_impls;
 /// The `from_engine` free-standing function is still required with this macro. See the doc of
 /// [`hash_trait_impls`].
 macro_rules! hash_type {
+    ($bits:expr, $reverse:expr, $doc:literal) => {
+        $crate::internal_macros::hash_type_no_default!($bits, $reverse, $doc);
+
+        impl Hash {
+            /// Constructs a new engine.
+            pub fn engine() -> HashEngine { Default::default() }
+
+            /// Hashes some bytes.
+            #[allow(clippy::self_named_constructors)] // Hash is a noun and a verb.
+            pub fn hash(data: &[u8]) -> Self { <Self as crate::GeneralHash>::hash(data) }
+
+            /// Hashes all the byte slices retrieved from the iterator together.
+            pub fn hash_byte_chunks<B, I>(byte_slices: I) -> Self
+            where
+                B: AsRef<[u8]>,
+                I: IntoIterator<Item = B>,
+            {
+                <Self as crate::GeneralHash>::hash_byte_chunks(byte_slices)
+            }
+
+            /// Hashes the entire contents of the `reader`.
+            #[cfg(feature = "bitcoin-io")]
+            pub fn hash_reader<R: io::BufRead>(reader: &mut R) -> Result<Self, io::Error> {
+                <Self as crate::GeneralHash>::hash_reader(reader)
+            }
+        }
+    }
+}
+pub(crate) use hash_type;
+
+macro_rules! hash_type_no_default {
     ($bits:expr, $reverse:expr, $doc:literal) => {
         #[doc = $doc]
         #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -165,9 +194,6 @@ macro_rules! hash_type {
                 unsafe { &mut *(bytes as *mut _ as *mut Self) }
             }
 
-            /// Constructs a new engine.
-            pub fn engine() -> HashEngine { Default::default() }
-
             /// Produces a hash from the current state of a given engine.
             pub fn from_engine(e: HashEngine) -> Hash { from_engine(e) }
 
@@ -184,25 +210,6 @@ macro_rules! hash_type {
                 }
             }
 
-            /// Hashes some bytes.
-            #[allow(clippy::self_named_constructors)] // Hash is a noun and a verb.
-            pub fn hash(data: &[u8]) -> Self { <Self as crate::GeneralHash>::hash(data) }
-
-            /// Hashes all the byte slices retrieved from the iterator together.
-            pub fn hash_byte_chunks<B, I>(byte_slices: I) -> Self
-            where
-                B: AsRef<[u8]>,
-                I: IntoIterator<Item = B>,
-            {
-                <Self as crate::GeneralHash>::hash_byte_chunks(byte_slices)
-            }
-
-            /// Hashes the entire contents of the `reader`.
-            #[cfg(feature = "bitcoin-io")]
-            pub fn hash_reader<R: io::BufRead>(reader: &mut R) -> Result<Self, io::Error> {
-                <Self as crate::GeneralHash>::hash_reader(reader)
-            }
-
             /// Returns the underlying byte array.
             pub const fn to_byte_array(self) -> [u8; $bits / 8] { self.0 }
 
@@ -234,4 +241,4 @@ macro_rules! hash_type {
         crate::internal_macros::hash_trait_impls!($bits, $reverse);
     };
 }
-pub(crate) use hash_type;
+pub(crate) use hash_type_no_default;

hashes/src/siphash24.rs

@@ -4,32 +4,14 @@
 
 use core::ops::Index;
 use core::slice::SliceIndex;
-use core::str::FromStr;
 use core::{cmp, mem, ptr};
 
-use hex::FromHex;
-
-use crate::internal_macros::arr_newtype_fmt_impl;
 use crate::HashEngine as _;
 
-#[doc = "Output of the SipHash24 hash function."]
-#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
-#[repr(transparent)]
-pub struct Hash([u8; 8]);
-
-#[cfg(feature = "schemars")]
-impl schemars::JsonSchema for Hash {
-    fn schema_name() -> String { "Hash".to_owned() }
-
-    fn json_schema(gen: &mut schemars::gen::SchemaGenerator) -> schemars::schema::Schema {
-        let mut schema: schemars::schema::SchemaObject = <String>::json_schema(gen).into();
-        schema.string = Some(Box::new(schemars::schema::StringValidation {
-            max_length: Some(8 * 2),
-            min_length: Some(8 * 2),
-            pattern: Some("[0-9a-fA-F]+".to_owned()),
-        }));
-        schema.into()
-    }
+crate::internal_macros::hash_type_no_default! {
+    64,
+    false,
+    "Output of the SipHash24 hash function."
 }
 
 #[cfg(not(hashes_fuzz))]
@@ -196,9 +178,6 @@ impl Hash {
         Hash::from_engine(engine)
     }
 
-    /// Produces a hash from the current state of a given engine.
-    pub fn from_engine(e: HashEngine) -> Hash { from_engine(e) }
-
     /// Hashes the given data directly to u64 with an engine with the provided keys.
     pub fn hash_to_u64_with_keys(k0: u64, k1: u64, data: &[u8]) -> u64 {
         let mut engine = HashEngine::with_keys(k0, k1);
@@ -228,57 +207,8 @@ impl Hash {
 
     /// Creates a hash from its (little endian) 64-bit integer representation.
     pub fn from_u64(hash: u64) -> Hash { Hash(hash.to_le_bytes()) }
-
-    /// Returns the underlying byte array.
-    pub const fn to_byte_array(self) -> [u8; 8] { self.0 }
-
-    /// Returns a reference to the underlying byte array.
-    pub const fn as_byte_array(&self) -> &[u8; 8] { &self.0 }
-
-    /// Constructs a hash from the underlying byte array.
-    pub const fn from_byte_array(bytes: [u8; 8]) -> Self { Self(bytes) }
-
-    fn from_slice(sl: &[u8]) -> Result<Self, crate::FromSliceError> {
-        let mut ret = [0; 8];
-        ret.copy_from_slice(sl);
-        Ok(Hash(ret))
-    }
 }
 
-impl crate::Hash for Hash {
-    type Bytes = [u8; 8];
-
-    const LEN: usize = 8;
-    const DISPLAY_BACKWARD: bool = false;
-
-    fn from_slice(sl: &[u8]) -> Result<Self, crate::FromSliceError> { Self::from_slice(sl) }
-
-    fn to_byte_array(self) -> Self::Bytes { self.to_byte_array() }
-
-    fn as_byte_array(&self) -> &Self::Bytes { self.as_byte_array() }
-
-    fn from_byte_array(bytes: Self::Bytes) -> Self { Self::from_byte_array(bytes) }
-}
-
-impl<I: SliceIndex<[u8]>> Index<I> for Hash {
-    type Output = I::Output;
-
-    #[inline]
-    fn index(&self, index: I) -> &Self::Output { &self.0[index] }
-}
-
-impl FromStr for Hash {
-    type Err = hex::HexToArrayError;
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let bytes = <[u8; 8]>::from_hex(s)?;
-        Ok(Self::from_byte_array(bytes))
-    }
-}
-
-arr_newtype_fmt_impl!(Hash, 8);
-serde_impl!(Hash, 8);
-borrow_slice_impl!(Hash);
-
 /// Load an u64 using up to 7 bytes of a byte slice.
 ///
 /// Unsafe because: unchecked indexing at `start..start+len`.