Optimize unique_hash and make portable.

evoskuil · Sep 6, 2024 · ce8cb51 · ce8cb51
1 parent 2e2929d
commit ce8cb51
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Showing 2 changed files with 6 additions and 8 deletions.
diff --git a/include/bitcoin/system/impl/hash/functions.ipp b/include/bitcoin/system/impl/hash/functions.ipp
@@ -22,6 +22,7 @@
 #include <utility>
 #include <bitcoin/system/data/data.hpp>
 #include <bitcoin/system/define.hpp>
+#include <bitcoin/system/endian/endian.hpp>
 #include <bitcoin/system/hash/accumulator.hpp>
 #include <bitcoin/system/hash/algorithms.hpp>
 #include <bitcoin/system/hash/scrypt.hpp>
@@ -212,13 +213,10 @@ struct unique_hash_t
 template <size_t Size>
 INLINE constexpr size_t unique_hash(const data_array<Size>& key) NOEXCEPT
 {
-    constexpr auto size = std::min(Size, sizeof(size_t));
+    constexpr auto size = sizeof(size_t);
 
-    // This optimization breaks data portability (by endianness).
-    // Could be modified to use an endian conversion vs. simple copy.
-    size_t value{};
-    std::copy_n(key.begin(), size, system::byte_cast(value).begin());
-    return value;
+    // Conversion is nop on LE architecture, preserves data portability for BE.
+    return native_to_little_end(byte_cast(array_cast<uint8_t, size>(key)));
 }
 
 // Value will vary with sizeof(size_t).

diff --git a/test/hash/functions.cpp b/test/hash/functions.cpp
@@ -392,11 +392,11 @@ BOOST_AUTO_TEST_CASE(functions__unique_hash__some_hash__expected)
 
     if constexpr (sizeof(size_t) == sizeof(uint32_t))
     {
-        BOOST_REQUIRE_EQUAL(hash, 0x60989953_u32);
+        BOOST_REQUIRE_EQUAL(hash, native_to_little_end(0x60989953_u32));
     }
     else
     {
-        BOOST_REQUIRE_EQUAL(hash, 0x6636626660989953_u64);
+        BOOST_REQUIRE_EQUAL(hash, native_to_little_end(0x6636626660989953_u64));
     }
 }