Since a pointer is basically just an int we can use integer hashing.
This one is taken from https://gist.github.com/badboy/6267743
A google search seems to suggest this is a common and good algorithm.
Since it operates 32 bits at a time it is really effective.
assert that we are hashing 32bit aligned pointers.
Signed-off-by: Thomas Helland <thomashellan...@gmail.com>
---
src/util/hash_table.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)
diff --git a/src/util/hash_table.c b/src/util/hash_table.c
index 24184c0..54d04ef 100644
--- a/src/util/hash_table.c
+++ b/src/util/hash_table.c
@@ -393,6 +393,15 @@ _mesa_hash_table_random_entry(struct hash_table *ht,
return NULL;
}
+static inline uint32_t
+hash_32bit_int(uint32_t a) {
+ a = (a ^ 61) ^ (a >> 16);
+ a = a + (a << 3);
+ a = a ^ (a >> 4);
+ a = a * 0x27d4eb2d;
+ a = a ^ (a >> 15);
+ return a;
+}
/**
* Quick FNV-1a hash implementation based on:
@@ -406,8 +415,19 @@ _mesa_hash_table_random_entry(struct hash_table *ht,
uint32_t
_mesa_hash_data(const void *data, size_t size)
{
- return _mesa_fnv32_1a_accumulate_block(_mesa_fnv32_1a_offset_bias,
- data, size);
+ uint32_t hash = _mesa_fnv32_1a_offset_bias;
+ const uint32_t *ints = (const uint32_t *) data;
+
+ assert((size % 4) == 0);
+
+ uint32_t i = size / 4;
+
+ while (i-- != 0) {
+ hash ^= hash_32bit_int(*ints);
+ ints++;
+ }
+
+ return hash;
}
/** FNV-1a string hash implementation */
--
2.3.4
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