| 1 | /* LzHash.h -- HASH constants for LZ algorithms |
| 2 | 2023-03-05 : Igor Pavlov : Public domain */ |
| 3 | |
| 4 | #ifndef ZIP7_INC_LZ_HASH_H |
| 5 | #define ZIP7_INC_LZ_HASH_H |
| 6 | |
| 7 | /* |
| 8 | (kHash2Size >= (1 << 8)) : Required |
| 9 | (kHash3Size >= (1 << 16)) : Required |
| 10 | */ |
| 11 | |
| 12 | #define kHash2Size (1 << 10) |
| 13 | #define kHash3Size (1 << 16) |
| 14 | // #define kHash4Size (1 << 20) |
| 15 | |
| 16 | #define kFix3HashSize (kHash2Size) |
| 17 | #define kFix4HashSize (kHash2Size + kHash3Size) |
| 18 | // #define kFix5HashSize (kHash2Size + kHash3Size + kHash4Size) |
| 19 | |
| 20 | /* |
| 21 | We use up to 3 crc values for hash: |
| 22 | crc0 |
| 23 | crc1 << Shift_1 |
| 24 | crc2 << Shift_2 |
| 25 | (Shift_1 = 5) and (Shift_2 = 10) is good tradeoff. |
| 26 | Small values for Shift are not good for collision rate. |
| 27 | Big value for Shift_2 increases the minimum size |
| 28 | of hash table, that will be slow for small files. |
| 29 | */ |
| 30 | |
| 31 | #define kLzHash_CrcShift_1 5 |
| 32 | #define kLzHash_CrcShift_2 10 |
| 33 | |
| 34 | #endif |