| 1 | #ifndef NU_MPH_H |
|---|---|
| 2 | #define NU_MPH_H |
| 3 | |
| 4 | /* Intentionally undocumented |
| 5 | * |
| 6 | * http://iswsa.acm.org/mphf/index.html |
| 7 | */ |
| 8 | |
| 9 | #include <stdint.h> |
| 10 | #include <sys/types.h> |
| 11 | |
| 12 | #include <libnu/config.h> |
| 13 | |
| 14 | #if defined (__cplusplus) || defined (c_plusplus) |
| 15 | extern "C"{ |
| 16 | #endif |
| 17 | |
| 18 | #ifdef NU_WITH_UDB |
| 19 | |
| 20 | /* those need to be the same values as used in MPH generation */ |
| 21 | #define PRIME 0x01000193 |
| 22 | |
| 23 | /** Calculate G offset from codepoint |
| 24 | */ |
| 25 | static inline |
| 26 | uint32_t _nu_hash(uint32_t hash, uint32_t codepoint) { |
| 27 | if (hash == 0) { |
| 28 | hash = PRIME; |
| 29 | } |
| 30 | |
| 31 | return hash ^ codepoint; |
| 32 | } |
| 33 | |
| 34 | /** Get hash value of Unicode codepoint |
| 35 | */ |
| 36 | static inline |
| 37 | uint32_t nu_mph_hash(const int16_t *G, size_t G_SIZE, |
| 38 | uint32_t codepoint) { |
| 39 | |
| 40 | uint32_t h = _nu_hash(hash: 0, codepoint); |
| 41 | int16_t offset = G[h % G_SIZE]; |
| 42 | if (offset < 0) { |
| 43 | return (uint32_t)(-offset - 1); |
| 44 | } |
| 45 | return (_nu_hash(hash: offset, codepoint) % G_SIZE); |
| 46 | } |
| 47 | |
| 48 | /** Lookup value in MPH |
| 49 | */ |
| 50 | static inline |
| 51 | uint32_t nu_mph_lookup(const uint32_t *V_C, const uint16_t *V_I, |
| 52 | uint32_t codepoint, uint32_t hash) { |
| 53 | |
| 54 | const uint32_t *c = (V_C + hash); |
| 55 | const uint16_t *i = (V_I + hash); |
| 56 | |
| 57 | /* due to nature of minimal perfect hash, it will always |
| 58 | * produce collision for codepoints outside of MPH original set. |
| 59 | * thus VALUES_C contain original codepoint to check if |
| 60 | * collision occurred */ |
| 61 | |
| 62 | return (*c != codepoint ? 0 : *i); |
| 63 | } |
| 64 | |
| 65 | #endif /* NU_WITH_UDB */ |
| 66 | |
| 67 | #if defined (__cplusplus) || defined (c_plusplus) |
| 68 | } |
| 69 | #endif |
| 70 | |
| 71 | #endif /* NU_MPH_H */ |
| 72 |