From 3059353b38ed1fc432cce584afad5bef3b7f2227 Mon Sep 17 00:00:00 2001
From: Jacques Lucke <jacques@blender.org>
Date: Tue, 21 Apr 2020 17:31:56 +0200
Subject: BLI: Use .hh extension for C++ headers in blenlib

---
 source/blender/blenlib/BLI_hash.hh | 112 +++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 source/blender/blenlib/BLI_hash.hh

(limited to 'source/blender/blenlib/BLI_hash.hh')

diff --git a/source/blender/blenlib/BLI_hash.hh b/source/blender/blenlib/BLI_hash.hh
new file mode 100644
index 00000000000..b5041012189
--- /dev/null
+++ b/source/blender/blenlib/BLI_hash.hh
@@ -0,0 +1,112 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __BLI_HASH_HH__
+#define __BLI_HASH_HH__
+
+/** \file
+ * \ingroup bli
+ *
+ * This file provides default hash functions for some primitive types. The hash functions can be
+ * used by containers such as Map and Set.
+ */
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "BLI_math_base.h"
+#include "BLI_utildefines.h"
+
+namespace BLI {
+
+template<typename T> struct DefaultHash {
+};
+
+#define TRIVIAL_DEFAULT_INT_HASH(TYPE) \
+  template<> struct DefaultHash<TYPE> { \
+    uint32_t operator()(TYPE value) const \
+    { \
+      return (uint32_t)value; \
+    } \
+  }
+
+/**
+ * Cannot make any assumptions about the distribution of keys, so use a trivial hash function by
+ * default. The hash table implementations are designed to take all bits of the hash into account
+ * to avoid really bad behavior when the lower bits are all zero. Special hash functions can be
+ * implemented when more knowledge about a specific key distribution is available.
+ */
+TRIVIAL_DEFAULT_INT_HASH(int8_t);
+TRIVIAL_DEFAULT_INT_HASH(uint8_t);
+TRIVIAL_DEFAULT_INT_HASH(int16_t);
+TRIVIAL_DEFAULT_INT_HASH(uint16_t);
+TRIVIAL_DEFAULT_INT_HASH(int32_t);
+TRIVIAL_DEFAULT_INT_HASH(uint32_t);
+TRIVIAL_DEFAULT_INT_HASH(int64_t);
+TRIVIAL_DEFAULT_INT_HASH(uint64_t);
+
+template<> struct DefaultHash<float> {
+  uint32_t operator()(float value) const
+  {
+    return *(uint32_t *)&value;
+  }
+};
+
+template<> struct DefaultHash<std::string> {
+  uint32_t operator()(const std::string &value) const
+  {
+    uint32_t hash = 5381;
+    for (char c : value) {
+      hash = hash * 33 + c;
+    }
+    return hash;
+  }
+};
+
+/**
+ * While we cannot guarantee that the lower 3 bits or a pointer are zero, it is safe to assume
+ * this in the general case. MEM_malloc only returns 8 byte aligned addresses on 64-bit systems.
+ */
+template<typename T> struct DefaultHash<T *> {
+  uint32_t operator()(const T *value) const
+  {
+    uintptr_t ptr = POINTER_AS_UINT(value);
+    uint32_t hash = (uint32_t)(ptr >> 3);
+    return hash;
+  }
+};
+
+template<typename T> struct DefaultHash<std::unique_ptr<T>> {
+  uint32_t operator()(const std::unique_ptr<T> &value) const
+  {
+    return DefaultHash<T *>{}(value.get());
+  }
+};
+
+template<typename T1, typename T2> struct DefaultHash<std::pair<T1, T2>> {
+  uint32_t operator()(const std::pair<T1, T2> &value) const
+  {
+    uint32_t hash1 = DefaultHash<T1>{}(value.first);
+    uint32_t hash2 = DefaultHash<T2>{}(value.second);
+    return hash1 ^ (hash2 * 33);
+  }
+};
+
+}  // namespace BLI
+
+#endif /* __BLI_HASH_HH__ */
-- 
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