7zip/C/LzHash.h at 26.02 · AIahmedshrf/7zip

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/* LzHash.h -- HASH constants for LZ algorithms

2023-03-05 : Igor Pavlov : Public domain */

#ifndef ZIP7_INC_LZ_HASH_H

#define ZIP7_INC_LZ_HASH_H

(kHash2Size >= (1 << 8)) : Required

(kHash3Size >= (1 << 16)) : Required

#define kHash2Size (1 << 10)

#define kHash3Size (1 << 16)

// #define kHash4Size (1 << 20)

#define kFix3HashSize (kHash2Size)

#define kFix4HashSize (kHash2Size + kHash3Size)

// #define kFix5HashSize (kHash2Size + kHash3Size + kHash4Size)

We use up to 3 crc values for hash:

crc0

crc1 << Shift_1

crc2 << Shift_2

(Shift_1 = 5) and (Shift_2 = 10) is good tradeoff.

Small values for Shift are not good for collision rate.

Big value for Shift_2 increases the minimum size

of hash table, that will be slow for small files.

#define kLzHash_CrcShift_1 5

#define kLzHash_CrcShift_2 10

#endif