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| author | Andres Freund | 2017-08-22 22:36:49 +0000 |
|---|---|---|
| committer | Andres Freund | 2017-08-22 22:36:49 +0000 |
| commit | 0052a0243d9c979a06ef273af965508103c456e0 (patch) | |
| tree | 0919e3a3994c692bc763e78eb4667efa1bd4ed4e | |
| parent | 2bfd1b1ee562c4e4fd065c7f7d1beaa9b9852070 (diff) | |
Add a hash_combine function for mixing hash values.
This hash function is derived from Boost's function of the same name.
Author: Andres Freund, Thomas Munro
Discussion: https://postgr.es/m/CAEepm%3D3rdgjfxW4cKvJ0OEmya2-34B0qHNG1xV0vK7TGPJGMUQ%40mail.gmail.com
Discussion: https://postgr.es/m/20170731210844.3cwrkmsmbbpt4rjc%40alap3.anarazel.de
| -rw-r--r-- | src/include/utils/hashutils.h | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/src/include/utils/hashutils.h b/src/include/utils/hashutils.h new file mode 100644 index 0000000000..56b7bfc9cb --- /dev/null +++ b/src/include/utils/hashutils.h @@ -0,0 +1,23 @@ +/* + * Utilities for working with hash values. + * + * Portions Copyright (c) 2017, PostgreSQL Global Development Group + */ + +#ifndef HASHUTILS_H +#define HASHUTILS_H + +/* + * Combine two hash values, resulting in another hash value, with decent bit + * mixing. + * + * Similar to boost's hash_combine(). + */ +static inline uint32 +hash_combine(uint32 a, uint32 b) +{ + a ^= b + 0x9e3779b9 + (a << 6) + (a >> 2); + return a; +} + +#endif /* HASHUTILS_H */ |