util: move fnv1a hash implementation into its own header

Reviewed-by: Eric Anholt <[email protected]>
Reviewed-by: Iago Toral Quiroga <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3475>

1 files changed, 61 insertions, 0 deletions

diff --git a/src/util/fnv1a.h b/src/util/fnv1a.h
new file mode 100644
index 00000000000..0f92d0b0e40
--- /dev/null
+++ b/src/util/fnv1a.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright © 2009,2012 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ *    Eric Anholt <[email protected]>
+ *
+ */
+
+#ifndef _FNV1A_H
+#define _FNV1A_H
+
+enum {
+   _mesa_fnv32_1a_offset_bias = 2166136261u,
+};
+
+/**
+ * Quick FNV-1a hash implementation based on:
+ * http://www.isthe.com/chongo/tech/comp/fnv/
+ *
+ * FNV-1a is not be the best hash out there -- Jenkins's lookup3 is supposed
+ * to be quite good, and it probably beats FNV.  But FNV has the advantage
+ * that it involves almost no code.  For an improvement on both, see Paul
+ * Hsieh's http://www.azillionmonkeys.com/qed/hash.html
+ */
+static inline uint32_t
+_mesa_fnv32_1a_accumulate_block(uint32_t hash, const void *data, size_t size)
+{
+   const uint8_t *bytes = (const uint8_t *)data;
+
+   while (size-- != 0) {
+      hash ^= *bytes;
+      hash = hash * 0x01000193;
+      bytes++;
+   }
+
+   return hash;
+}
+
+#define _mesa_fnv32_1a_accumulate(hash, expr) \
+   _mesa_fnv32_1a_accumulate_block(hash, &(expr), sizeof(expr))
+
+#endif