hash: add library with multiple hash implementations

1 files changed, 39 insertions, 0 deletions

diff --git a/hash/xxhash.cpp b/hash/xxhash.cpp
new file mode 100644
index 00000000..c720465e
--- /dev/null
+++ b/hash/xxhash.cpp
@@ -0,0 +1,39 @@
+#include "hash-impl.hpp"
+#include "compat/map.hpp"
+#include "compat/iota.hpp"
+#include <bit>
+
+#ifdef __GNUG__
+//#pragma GCC diagnostic ignored "-Wdisabled-macro-expansion"
+//#pragma GCC diagnostic ignored "-Wused-but-marked-unused"
+#include "xxhash.inl"
+#endif
+
+namespace floormat::xxHash {
+
+namespace {
+
+constexpr inline auto seed = std::bit_cast<uint64_t>(iota_array<uint8_t, 8>);
+
+CORRADE_ALWAYS_INLINE size_t do_xxhash(const void* __restrict buf, size_t size) noexcept
+{
+#ifdef __AVX2__
+    return XXH3_64bits(buf, size);
+#error "foo avx"
+#elif __SSE2__
+    return (size_t)XXH3_64bits(buf, size);
+#else
+    if constexpr(sizeof nullptr > 4)
+        return XXH364(buf, size);
+    else
+        return XXH32(buf, size);
+#endif
+}
+
+} // namespace
+
+size_t hash_buf(const void* __restrict buf, size_t size) noexcept { return do_xxhash(buf, size); }
+size_t hash_int(uint32_t x) noexcept { return do_xxhash(&x, sizeof x); }
+size_t hash_int(uint64_t x) noexcept { return do_xxhash(&x, sizeof x); }
+
+} // namespace floormat::xxHash