1 files changed, 104 insertions, 0 deletions
diff --git a/hash/fnv.cpp b/hash/fnv.cpp
new file mode 100644
index 00000000..80ed9d52
--- /dev/null
+++ b/hash/fnv.cpp
@@ -0,0 +1,104 @@
+#include "hash-impl.hpp"
+#include "compat/defs.hpp"
+#include <utility>
+
+// ReSharper disable CppDefaultCaseNotHandledInSwitchStatement
+// NOLINTBEGIN(*-multiway-paths-covered, *-switch-missing-default-case)
+
+namespace floormat::FNVHash {
+
+namespace {
+template<size_t N = sizeof nullptr * 8> struct fnvhash_params;
+template<> struct fnvhash_params<32> { [[maybe_unused]] static constexpr uint32_t a = 0x811c9dc5u, b = 0x01000193u; };
+template<> struct fnvhash_params<64> { [[maybe_unused]] static constexpr uint64_t a = 0xcbf29ce484222325u, b = 0x100000001b3u; };
+
+CORRADE_ALWAYS_INLINE size_t fnvhash_uint(uint64_t x)
+{
+    constexpr auto params = fnvhash_params{};
+    constexpr auto a = params.a, b = params.b;
+    auto hash = a;
+    const auto* str = (const uint8_t*)&x;
+
+    hash *= b; hash ^= *str++; // 0
+    hash *= b; hash ^= *str++; // 1
+    hash *= b; hash ^= *str++; // 2
+    hash *= b; hash ^= *str++; // 3
+    hash *= b; hash ^= *str++; // 4
+    hash *= b; hash ^= *str++; // 5
+    hash *= b; hash ^= *str++; // 6
+    hash *= b; hash ^= *str++; // 7
+
+    return hash;
+}
+
+CORRADE_ALWAYS_INLINE size_t fnvhash_uint(uint32_t x)
+{
+    constexpr auto params = fnvhash_params{};
+    constexpr auto a = params.a, b = params.b;
+
+    auto hash = a;
+    const auto* str = (const uint8_t*)&x;
+
+    hash *= b; hash ^= *str++; // 0
+    hash *= b; hash ^= *str++; // 1
+    hash *= b; hash ^= *str++; // 2
+    hash *= b; hash ^= *str++; // 3
+
+    return hash;
+}
+
+CORRADE_ALWAYS_INLINE size_t fnvhash_buf(const void* __restrict buf, size_t size) noexcept
+{
+    constexpr auto params = fnvhash_params{};
+    constexpr auto a = params.a, b = params.b;
+    size_t full_rounds = size / 8, rest = size % 8;
+    size_t hash = a;
+    const auto* str = (const uint8_t*)buf;
+
+    while (full_rounds--)
+    {
+        hash *= b; hash ^= *str++; // 0
+        hash *= b; hash ^= *str++; // 1
+        hash *= b; hash ^= *str++; // 2
+        hash *= b; hash ^= *str++; // 3
+        hash *= b; hash ^= *str++; // 4
+        hash *= b; hash ^= *str++; // 5
+        hash *= b; hash ^= *str++; // 6
+        hash *= b; hash ^= *str++; // 7
+    }
+
+    switch (rest)
+    {
+    case 7: hash *= b; hash ^= *str++; [[fallthrough]];
+    case 6: hash *= b; hash ^= *str++; [[fallthrough]];
+    case 5: hash *= b; hash ^= *str++; [[fallthrough]];
+    case 4: hash *= b; hash ^= *str++; [[fallthrough]];
+    case 3: hash *= b; hash ^= *str++; [[fallthrough]];
+    case 2: hash *= b; hash ^= *str++; [[fallthrough]];
+    case 1: hash *= b; hash ^= *str++; [[fallthrough]];
+    case 0: break;
+    }
+
+    return hash;
+}
+
+} // namespace
+
+size_t hash_buf(const void* __restrict buf, size_t size) noexcept
+{
+    return fnvhash_buf(buf, size);
+}
+
+size_t hash_int(uint32_t x) noexcept
+{
+    return fnvhash_uint(x);
+}
+
+size_t hash_int(uint64_t x) noexcept
+{
+    return fnvhash_uint(x);
+}
+
+} // namespace floormat::FNVHash
+
+// NOLINTEND(*-multiway-paths-covered, *-switch-missing-default-case)