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added 16-bit hashing

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This commit is contained in:
Logan007 2020-06-29 15:44:51 +05:45
parent c7a8210078
commit a64cfa450e
2 changed files with 22 additions and 0 deletions
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2
include/pearson.h
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@ -19,3 +19,5 @@
void pearson_hash_256 (uint8_t *out, const uint8_t *in, size_t len);
void pearson_hash_128 (uint8_t *out, const uint8_t *in, size_t len);
uint16_t pearson_hash_16 (const uint8_t *in, size_t len);

20
src/pearson.c
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@ -219,3 +219,23 @@ void pearson_hash_128 (uint8_t *out, const uint8_t *in, size_t len) {
o = (uint64_t*)&out[8];
*o = lower_hash;
}
// 16-bit hash: the return value has to be interpreted as uint16_t and
// follows machine-specific endianess in memory
uint16_t pearson_hash_16 (const uint8_t *in, size_t len) {
uint16_t hash = 0;
uint16_t hash_mask = 0x0100;
for (size_t i = 0; i < len; i++) {
// broadcast the character, xor into hash, make them different permutations
uint16_t c = (uint8_t)in[i];
c |= c << 8;
hash ^= c ^ hash_mask;
// table lookup
hash = t[(uint8_t)hash] + (t[hash >> 8] << 8);
}
// output
return hash;
}