// zend_inline_hash_func 实现在文件“php-5.6.26\Zend\zend_hash.h”h = zend_inline_hash_func(arKey, nKeyLength); {// zend_hash_add 定义在文件“php-5.6.26\Zend\zend_hash.h”/** DJBX33A (Daniel J. Bernstein, Times 33 with Addition)** This is Daniel J. Bernstein's popular `times 33' hash function as* posted by him years ago on comp.lang.c. It basically uses a function* like ``hash(i) = hash(i-1) * 33 + str[i]''. This is one of the best* known hash functions for strings. Because it is both computed very* fast and distributes very well.** The magic of number 33, i.e. why it works better than many other* constants, prime or not, has never been adequately explained by* anyone. So I try an explanation: if one experimentally tests all* multipliers between 1 and 256 (as RSE did now) one detects that even* numbers are not useable at all. The remaining 128 odd numbers* (except for the number 1) work more or less all equally well. They* all distribute in an acceptable way and this way fill a hash table* with an average percent of approx. 86%. ** If one compares the Chi^2 values of the variants, the number 33 not* even has the best value. But the number 33 and a few other equally* good numbers like 17, 31, 63, 127 and 129 have nevertheless a great* advantage to the remaining numbers in the large set of possible* multipliers: their multiply operation can be replaced by a faster* operation based on just one shift plus either a single addition* or subtraction operation. And because a hash function has to both* distribute good _and_ has to be very fast to compute, those few* numbers should be preferred and seems to be the reason why Daniel J.* Bernstein also preferred it.*** -- Ralf S. Engelschall <rse@>*/static inline ulong zend_inline_hash_func(const char *arKey, uint nKeyLength){register ulong hash = 5381;/* variant with the hash unrolled eight times */for (; nKeyLength >= 8; nKeyLength -= 8) {hash = ((hash << 5) + hash) + *arKey++;hash = ((hash << 5) + hash) + *arKey++;hash = ((hash << 5) + hash) + *arKey++;hash = ((hash << 5) + hash) + *arKey++;hash = ((hash << 5) + hash) + *arKey++;hash = ((hash << 5) + hash) + *arKey++;hash = ((hash << 5) + hash) + *arKey++;hash = ((hash << 5) + hash) + *arKey++;}switch (nKeyLength) {case 7: hash = ((hash << 5) + hash) + *arKey++; /* fallthrough... */case 6: hash = ((hash << 5) + hash) + *arKey++; /* fallthrough... */case 5: hash = ((hash << 5) + hash) + *arKey++; /* fallthrough... */case 4: hash = ((hash << 5) + hash) + *arKey++; /* fallthrough... */case 3: hash = ((hash << 5) + hash) + *arKey++; /* fallthrough... */case 2: hash = ((hash << 5) + hash) + *arKey++; /* fallthrough... */case 1: hash = ((hash << 5) + hash) + *arKey++; break;case 0: break;EMPTY_SWITCH_DEFAULT_CASE()}return hash;}}
