1 files changed, 123 insertions, 0 deletions
diff --git a/hash/murmur.cpp b/hash/murmur.cpp
new file mode 100644
index 00000000..4f99fc62
--- /dev/null
+++ b/hash/murmur.cpp
@@ -0,0 +1,123 @@
+#include "hash-impl.hpp"
+#include <bit>
+
+#ifdef __GNUG__
+#pragma GCC diagnostic ignored "-Wcast-align"
+#pragma GCC diagnostic ignored "-Wsign-conversion"
+#endif
+
+// ReSharper disable CppDefaultCaseNotHandledInSwitchStatement
+// NOLINTBEGIN(*-switch-missing-default-case)
+
+namespace floormat::MurmurHash {
+namespace {
+//-----------------------------------------------------------------------------
+// MurmurHash3 was written by Austin Appleby, and is placed in the public
+// domain. The author hereby disclaims copyright to this source code.
+
+// Note - The x86 and x64 versions do _not_ produce the same results, as the
+// algorithms are optimized for their respective platforms. You can still
+// compile and run any of them on any platform, but your performance with the
+// non-native version will be less than optimal.
+
+//-----------------------------------------------------------------------------
+// Block read - if your platform needs to do endian-swapping or can only
+// handle aligned reads, do the conversion here
+
+CORRADE_ALWAYS_INLINE uint32_t getblock32 ( const uint32_t * p, int i )
+{
+  return p[i];
+}
+
+//-----------------------------------------------------------------------------
+// Finalization mix - force all bits of a hash block to avalanche
+
+CORRADE_ALWAYS_INLINE uint32_t fmix32 ( uint32_t h )
+{
+  h ^= h >> 16;
+  h *= 0x85ebca6b;
+  h ^= h >> 13;
+  h *= 0xc2b2ae35;
+  h ^= h >> 16;
+
+  return h;
+}
+
+//-----------------------------------------------------------------------------
+
+void MurmurHash3_x86_32 ( const void * __restrict key, size_t len, void * __restrict out )
+{
+  constexpr auto seed = uint32_t{0xa6b8edcd};
+  const auto* data = (const uint8_t*)key;
+  const int nblocks = (int)(len / 4);
+
+  uint32_t h1 = seed;
+
+  constexpr uint32_t c1 = 0xcc9e2d51;
+  constexpr uint32_t c2 = 0x1b873593;
+
+  //----------
+  // body
+
+  const auto* blocks = (const uint32_t *)(data + (size_t)(nblocks*4));
+
+  for(int i = -nblocks; i; i++)
+  {
+    uint32_t k1 = getblock32(blocks,i);
+
+    k1 *= c1;
+    k1 = std::rotl(k1,15);
+    k1 *= c2;
+
+    h1 ^= k1;
+    h1 = std::rotl(h1,13);
+    h1 = h1*5+0xe6546b64;
+  }
+
+  //----------
+  // tail
+
+  const auto* tail = (const uint8_t*)(data + (size_t)(nblocks*4));
+
+  uint32_t k1 = 0;
+
+  switch(len & 3)
+  {
+  case 3: k1 ^= tail[2] << 16; [[fallthrough]];
+  case 2: k1 ^= tail[1] << 8;  [[fallthrough]];
+  case 1: k1 ^= tail[0];
+          k1 *= c1; k1 = std::rotl(k1,15); k1 *= c2; h1 ^= k1;
+  }
+
+  //----------
+  // finalization
+
+  h1 ^= len;
+
+  h1 = fmix32(h1);
+
+  *(uint32_t*)out = h1;
+}
+
+} // namespace
+
+size_t hash_buf(const void* __restrict buf, size_t size) noexcept
+{
+    uint32_t ret;
+    MurmurHash3_x86_32(buf, size, &ret);
+    return ret;
+}
+
+size_t hash_int(uint32_t x) noexcept
+{
+    return hash_buf(&x, sizeof x);
+}
+
+size_t hash_int(uint64_t x) noexcept
+{
+    return hash_buf(&x, sizeof x);
+}
+
+} // namespace floormat::MurmurHash
+
+// NOLINTEND(*-switch-missing-default-case)