PHP哈希算法设计

[php]代码库

static inline ulong zend_inline_hash_func(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;
}


  hashing function used in Perl 5.005:
  # Return the hashed value of a string: $hash = perlhash("key")
  # (Defined by the PERL_HASH macro in hv.h)
  sub perlhash
  {
      $hash = 0;
      foreach (split //, shift) {
          $hash = $hash*33 + ord($_);
      }
      return $hash;
  }