Add Murmur2A hashing feature to BLI

Murmur2a is a very fast hashing function generation int32 hashes.
It also features a very good distribution of generated hashes.

However, it is not endianness-agnostic, meaning it will usually generate
different hashes for a same key on big- and little-endian architectures.
Consequently, **it shall not be used to generate persistent hashes**
(never store them in .blend file e.g.).

This implementation supports incremental hashing, and is a direct
adaptation of reference implementation (in c++):
https://smhasher.googlecode.com/svn-history/r130/trunk/MurmurHash2.cpp

That cpp code was also used to generate reference values in gtests file.

Reviewers: sergey, campbellbarton

Reviewed By: campbellbarton

Projects: #bf_blender

Differential Revision: https://developer.blender.org/D892

1 files changed, 45 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_hash_mm2a.h b/source/blender/blenlib/BLI_hash_mm2a.h
new file mode 100644
index 00000000000..503eb5e96d9
--- /dev/null
+++ b/source/blender/blenlib/BLI_hash_mm2a.h
@@ -0,0 +1,45 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * 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.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+#ifndef __BLI_MM2A_H__
+#define __BLI_MM2A_H__
+
+/** \file BLI_hash_mm2a.h
+ *  \ingroup bli
+ */
+
+#include "BLI_sys_types.h"
+
+typedef struct BLI_HashMurmur2A {
+	uint32_t hash;
+	uint32_t tail;
+	uint32_t count;
+	uint32_t size;
+} BLI_HashMurmur2A;
+
+void BLI_hash_mm2a_init(BLI_HashMurmur2A *mm2, uint32_t seed);
+
+void BLI_hash_mm2a_add(BLI_HashMurmur2A *mm2, const unsigned char *data, size_t len);
+
+void BLI_hash_mm2a_add_int(BLI_HashMurmur2A *mm2, int data);
+
+uint32_t BLI_hash_mm2a_end(BLI_HashMurmur2A *mm2);
+
+#endif  /* __BLI_MM2A_H__ */