48 lines
1.2 KiB
C
48 lines
1.2 KiB
C
/*
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* sdbm - ndbm work-alike hashed database library
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* based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
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* author: oz@nexus.yorku.ca
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* status: public domain. keep it that way.
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*
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* hashing routine
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*/
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#include "config.h"
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#include "EXTERN.h"
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#include "sdbm.h"
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/*
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* polynomial conversion ignoring overflows
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* [this seems to work remarkably well, in fact better
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* then the ndbm hash function. Replace at your own risk]
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* use: 65599 nice.
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* 65587 even better.
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*/
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long
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sdbm_hash(const char *str, int len)
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{
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unsigned long n = 0;
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#ifdef DUFF
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#define HASHC n = *str++ + 65599 * n
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if (len > 0) {
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int loop = (len + 8 - 1) >> 3;
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switch(len & (8 - 1)) {
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case 0: do {
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HASHC; /* FALLTHROUGH */ case 7: HASHC; /* FALLTHROUGH */
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case 6: HASHC; /* FALLTHROUGH */ case 5: HASHC; /* FALLTHROUGH */
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case 4: HASHC; /* FALLTHROUGH */ case 3: HASHC; /* FALLTHROUGH */
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case 2: HASHC; /* FALLTHROUGH */ case 1: HASHC;
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} while (--loop);
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}
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}
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#else
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while (len--)
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n = *str++ + 65599 * n;
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#endif
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return n;
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}
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