1 files changed, 126 insertions, 0 deletions
diff --git a/intern/cycles/util/murmurhash.cpp b/intern/cycles/util/murmurhash.cpp
new file mode 100644
index 00000000000..9ba0a282cc2
--- /dev/null
+++ b/intern/cycles/util/murmurhash.cpp
@@ -0,0 +1,126 @@
+/*
+ * Copyright 2018 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* This is taken from alShaders/Cryptomatte/MurmurHash3.h:
+ *
+ * MurmurHash3 was written by Austin Appleby, and is placed in the public
+ * domain. The author hereby disclaims copyright to this source code.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "util/algorithm.h"
+#include "util/murmurhash.h"
+
+#if defined(_MSC_VER)
+#  define ROTL32(x, y) _rotl(x, y)
+#  define ROTL64(x, y) _rotl64(x, y)
+#  define BIG_CONSTANT(x) (x)
+#else
+ccl_device_inline uint32_t rotl32(uint32_t x, int8_t r)
+{
+  return (x << r) | (x >> (32 - r));
+}
+#  define ROTL32(x, y) rotl32(x, y)
+#  define BIG_CONSTANT(x) (x##LLU)
+#endif
+
+CCL_NAMESPACE_BEGIN
+
+/* Block read - if your platform needs to do endian-swapping or can only
+ * handle aligned reads, do the conversion here. */
+ccl_device_inline uint32_t mm_hash_getblock32(const uint32_t *p, int i)
+{
+  return p[i];
+}
+
+/* Finalization mix - force all bits of a hash block to avalanche */
+ccl_device_inline uint32_t mm_hash_fmix32(uint32_t h)
+{
+  h ^= h >> 16;
+  h *= 0x85ebca6b;
+  h ^= h >> 13;
+  h *= 0xc2b2ae35;
+  h ^= h >> 16;
+  return h;
+}
+
+uint32_t util_murmur_hash3(const void *key, int len, uint32_t seed)
+{
+  const uint8_t *data = (const uint8_t *)key;
+  const int nblocks = len / 4;
+
+  uint32_t h1 = seed;
+
+  const uint32_t c1 = 0xcc9e2d51;
+  const uint32_t c2 = 0x1b873593;
+
+  const uint32_t *blocks = (const uint32_t *)(data + nblocks * 4);
+
+  for (int i = -nblocks; i; i++) {
+    uint32_t k1 = mm_hash_getblock32(blocks, i);
+
+    k1 *= c1;
+    k1 = ROTL32(k1, 15);
+    k1 *= c2;
+
+    h1 ^= k1;
+    h1 = ROTL32(h1, 13);
+    h1 = h1 * 5 + 0xe6546b64;
+  }
+
+  const uint8_t *tail = (const uint8_t *)(data + nblocks * 4);
+
+  uint32_t k1 = 0;
+
+  switch (len & 3) {
+    case 3:
+      k1 ^= tail[2] << 16;
+      ATTR_FALLTHROUGH;
+    case 2:
+      k1 ^= tail[1] << 8;
+      ATTR_FALLTHROUGH;
+    case 1:
+      k1 ^= tail[0];
+      k1 *= c1;
+      k1 = ROTL32(k1, 15);
+      k1 *= c2;
+      h1 ^= k1;
+  }
+
+  h1 ^= len;
+  h1 = mm_hash_fmix32(h1);
+  return h1;
+}
+
+/* This is taken from the cryptomatte specification 1.0 */
+float util_hash_to_float(uint32_t hash)
+{
+  uint32_t mantissa = hash & ((1 << 23) - 1);
+  uint32_t exponent = (hash >> 23) & ((1 << 8) - 1);
+  exponent = max(exponent, (uint32_t)1);
+  exponent = min(exponent, (uint32_t)254);
+  exponent = exponent << 23;
+  uint32_t sign = (hash >> 31);
+  sign = sign << 31;
+  uint32_t float_bits = sign | exponent | mantissa;
+  float f;
+  memcpy(&f, &float_bits, sizeof(uint32_t));
+  return f;
+}
+
+CCL_NAMESPACE_END