path: root/lib/erl_interface/src/registry/hash_dohash.c

/*
 * %CopyrightBegin%
 * 
 * Copyright Ericsson AB 1998-2009. All Rights Reserved.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * %CopyrightEnd%
 *

 */
#include "hash.h"

/* This is hashpjw, from the dragon book */
/* Note that this function is only used as a default hash function.
 * All calls are made through the hash pointer in the tab structure.
 * The only place this function is explicitly referenced is in
 * hash_newtab(); Users can use hash_setfunc() to change the hash function.
 */
int ei_dohash(const char *key) 
{
  const char *s;
  unsigned h = 0;
  unsigned g;
  
  for (s=key; *s; s++) {
    h = (h << 4) + *s;
    if ((g = (h & 0xf0000000))) { /* assumes 32-bit int */
      h = h^(g >> 24);
      h = h^g;
    }
  }
  return h;
}