taskrambler  0.1.9
Web server and task management solution.
utils/hash.h File Reference
#include <sys/types.h>
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Functions

unsigned long sdbm (const unsigned char *, size_t)
 

Detailed Description

Functions to handle varios signals send to the application.

Author
Georg Hopp

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

Definition in file utils/hash.h.

Function Documentation

unsigned long sdbm ( const unsigned char *  str,
size_t  len 
)

SDBM hashing algorithm:

this algorithm was created for sdbm (a public-domain reimplementation of ndbm) database library. it was found to do well in scrambling bits, causing better distribution of the keys and fewer splits. it also happens to be a good general hashing function with good distribution. the actual function is hash(i) = hash(i - 1) * 65599 + str[i]; what is included below is the faster version used in gawk. [there is even a faster, duff-device version] the magic constant 65599 was picked out of thin air while experimenting with different constants, and turns out to be a prime. this is one of the algorithms used in berkeley db (see sleepycat) and elsewhere.

Definition at line 45 of file utils/hash.c.

Referenced by assetCtor(), configValueCtor(), hashDelete(), hashGet(), hashValueCtor(), httpCookieCtor(), httpHeaderCtor(), and sessionCtor().

46 {
47  unsigned long hash = 0;
48 
49  for(; 0 < len; str++, len--)
50  hash = tolower(*str) + (hash << 6) + (hash << 16) - hash;
51 
52  return hash;
53 }

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