f535537f |
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 |