1*f6dc9357SAndroid Build Coastguard Worker /* LzHash.h -- HASH constants for LZ algorithms 2*f6dc9357SAndroid Build Coastguard Worker 2023-03-05 : Igor Pavlov : Public domain */ 3*f6dc9357SAndroid Build Coastguard Worker 4*f6dc9357SAndroid Build Coastguard Worker #ifndef ZIP7_INC_LZ_HASH_H 5*f6dc9357SAndroid Build Coastguard Worker #define ZIP7_INC_LZ_HASH_H 6*f6dc9357SAndroid Build Coastguard Worker 7*f6dc9357SAndroid Build Coastguard Worker /* 8*f6dc9357SAndroid Build Coastguard Worker (kHash2Size >= (1 << 8)) : Required 9*f6dc9357SAndroid Build Coastguard Worker (kHash3Size >= (1 << 16)) : Required 10*f6dc9357SAndroid Build Coastguard Worker */ 11*f6dc9357SAndroid Build Coastguard Worker 12*f6dc9357SAndroid Build Coastguard Worker #define kHash2Size (1 << 10) 13*f6dc9357SAndroid Build Coastguard Worker #define kHash3Size (1 << 16) 14*f6dc9357SAndroid Build Coastguard Worker // #define kHash4Size (1 << 20) 15*f6dc9357SAndroid Build Coastguard Worker 16*f6dc9357SAndroid Build Coastguard Worker #define kFix3HashSize (kHash2Size) 17*f6dc9357SAndroid Build Coastguard Worker #define kFix4HashSize (kHash2Size + kHash3Size) 18*f6dc9357SAndroid Build Coastguard Worker // #define kFix5HashSize (kHash2Size + kHash3Size + kHash4Size) 19*f6dc9357SAndroid Build Coastguard Worker 20*f6dc9357SAndroid Build Coastguard Worker /* 21*f6dc9357SAndroid Build Coastguard Worker We use up to 3 crc values for hash: 22*f6dc9357SAndroid Build Coastguard Worker crc0 23*f6dc9357SAndroid Build Coastguard Worker crc1 << Shift_1 24*f6dc9357SAndroid Build Coastguard Worker crc2 << Shift_2 25*f6dc9357SAndroid Build Coastguard Worker (Shift_1 = 5) and (Shift_2 = 10) is good tradeoff. 26*f6dc9357SAndroid Build Coastguard Worker Small values for Shift are not good for collision rate. 27*f6dc9357SAndroid Build Coastguard Worker Big value for Shift_2 increases the minimum size 28*f6dc9357SAndroid Build Coastguard Worker of hash table, that will be slow for small files. 29*f6dc9357SAndroid Build Coastguard Worker */ 30*f6dc9357SAndroid Build Coastguard Worker 31*f6dc9357SAndroid Build Coastguard Worker #define kLzHash_CrcShift_1 5 32*f6dc9357SAndroid Build Coastguard Worker #define kLzHash_CrcShift_2 10 33*f6dc9357SAndroid Build Coastguard Worker 34*f6dc9357SAndroid Build Coastguard Worker #endif 35