/* Copyright (C) 1989, 1992 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC 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 2, or (at your option)
any later version.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* As a special exception, if you link this library with files
   compiled with GCC to produce an executable, this does not cause
   the resulting executable to be covered by the GNU General Public License.
   This exception does not however invalidate any other reasons why
   the executable file might be covered by the GNU General Public License.  */

/* 
  $Header: /home/fsf/rms/c-runtime/dispatch/RCS/hash.h,v 0.11 1992/08/31 21:15:02 dglattin Exp rms $
  $Author: dglattin $
  $Date: 1992/08/31 21:15:02 $
  $Log: hash.h,v $
 * Revision 0.11  1992/08/31  21:15:02  dglattin
 * minor documentation changes.
 *
 * Revision 0.10  1992/08/18  04:46:58  dglattin
 * Saving a working version before release.
 *
 * Revision 0.9  1992/04/13  11:43:08  dennisg
 * Check in after array version of run-time works.
 * Expect more changes as hash version and other changes are made.
 *
 * Revision 0.8  1991/12/10  12:05:28  dennisg
 * Cleaned up file format for a distribution.
 *
 * Revision 0.7  1991/12/03  02:01:23  dennisg
 * fixed assert macro.
 * added memory allocation adjustment macro for hash size allocation.
 *
 * Revision 0.6  1991/11/24  01:20:02  dennisg
 * changed shorts back to ints.
 * the efficiency gained didn't out weight the grossness of the code.
 *
 * Revision 0.5  1991/11/23  22:19:21  dennisg
 * converted some entries in the hash structure from ints to shorts.
 * this was done to use a less expensive division instruction
 * in the hashIndex  routine.
 *
 * Revision 0.4  1991/11/21  22:25:19  dennisg
 * deleted hash mask information from hash struct.
 * changed hashing algorithm.  those values are no longer needed.
 *
 * Revision 0.3  1991/11/07  23:23:40  dennisg
 * implemented hash table expansion as suggested by rms.
 *
 * Revision 0.2  1991/11/07  22:30:54  dennisg
 * added copyleft
 *
 * Revision 0.1  1991/10/24  00:45:39  dennisg
 * Initial check in.  Preliminary development stage.
 *
*/
 

#ifndef _hash_INCLUDE_GNU
#define _hash_INCLUDE_GNU


#include "assert.h"
#include "mutex.h"


/*
 * This data structure is used to hold items
 *  stored in a hash table.  Each node holds 
 *  a key/value pair.
 *
 * Items in the cache are really of type void*.
 */
typedef struct cache_node {
  struct cache_node *nextNode;	/* Pointer to next entry on
				   the list.  NULL indicates
				   end of list. */
  void *theKey;			/* Key used to locate the
				   value.  Used to locate
				   value when more than one
				   key computes the same hash
				   value. */
  void *theValue;		/* Value stored for the
				   key. */
} CacheNode, *CacheNode_t;


/*
 * This data type is the function that computes a hash code given a key.
 * Therefore, the key can be a pointer to anything and the function specific
 * to the key type. 
 *
 * Unfortunately there is a mutual data structure reference problem with this
 * typedef.  Therefore, to remove compiler warnings the functions passed to
 * hash_new will have to be casted to this type. 
 */
typedef unsigned int   (*HashFunc)(void*, void*);

/*
 * This data type is the function that compares two hash keys and returns an
 * integer greater than, equal to, or less than 0, according as the first
 * parameter is lexico-graphically greater than, equal to, or less than the
 * second. 
 */

typedef int     (*CompareFunc)(void*, void*);


/*
 * This data structure is the cache.
 *
 * It must be passed to all of the hashing routines
 *   (except for new).
 */
typedef struct cache {
  /*
   * Variables used to implement the
   *  hash itself.
   */
  CacheNode_t  (*theNodeTable)[]; /* Pointer to an array of
				     hash nodes. */
  /*
   * Variables used to track the size of the hash
   *  table so to determine when to resize it.
   */
  unsigned int sizeOfHash,	/* Number of buckets 
				   allocated for the hash
				   table  (number of array
				   entries allocated for
				   "theNodeTable").  Must be
				   a power of two. */
  unsigned int entriesInHash,	/* Current number of entries
				   in the hash table. */
  unsigned int mask;		/* Precomputed mask. */
  /*
   * Variables used to implement indexing
   *  through the hash table.
   */
  unsigned int lastBucket;	/* Tracks which entry in the
				   array where the last value
				   was returned. */
  /* Function used to compute a hash code given a key. 
     This function is specified when the hash table is created. */
  HashFunc    hashFunc;
  /* Function used to compare two hash keys to determine
     if they are equal. */
  CompareFunc compareFunc;
} Cache, *Cache_t;


/* Allocate and initialize a hash table. */ 
Cache_t 
hash_new (unsigned int sizeOfHash,
	  HashFunc aHashFunc, CompareFunc aCompareFunc);
                       
/* Deallocate all of the hash nodes and the cache itself. */
void 
hash_delete (Cache_t theCache);

/* Add the key/value pair to the hash table.  If the
   hash table reaches a level of fullnes then it will be resized. 
                                                   
   assert if the key is already in the hash. */
void 
hash_add (Cache_t *theCache, void *aKey, void *aValue);
     
/* Remove the key/value pair from the hash table.  
   assert if the key isn't in the table. */
void 
hash_remove (Cache_t theCache, void *aKey);

/* Used to index through the hash table.  Start with NULL
   to get the first entry.
                                                  
   Successive calls pass the value returned previously.
   ** Don't modify the hash during this operation *** 
                                                  
   Cache nodes are returned such that key or value can
   be extracted. */
CacheNode_t 
hash_next (Cache_t theCache, CacheNode_t aCacheNode);

/* Used to return a value from a hash table using a given key.  */
void* 
hash_value_for_key (Cache_t theCache, void *aKey);


/************************************************

        Useful hashing functions.  
        
        Declared inline for your pleaseure. 
        
************************************************/

/* Calculate a hash code by performing some 
   manipulation of the key pointer. */
static inline unsigned int 
intHash(Cache_t theCache, void *aKey)
{


  assert(sizeof (unsigned int) == sizeof (aKey));

  return ((unsigned int)aKey >> (sizeof(void*) - 1)) & theCache->mask ;
}


/* Calculate a hash code by iterating over a NULL 
   terminate string. */
static inline unsigned int 
strHash(Cache_t theCache, void *aKey)
{
  unsigned int ret = 0;
  unsigned int ctr = 0;
        
        
  while(*(char*)aKey) {
    ret ^= *(char*)aKey++ << ctr;
    ctr = (ctr + 1) % sizeof(void*);
  }

  return ret & theCache->mask ;
}


/* Compare two integers. */
static inline int 
intCmp(void *k1, void *k2)
{
  return !((int)k1 - (int)k2);
}


/* Compare two strings. */
static inline int 
strCmp(void *k1, void *k2)
{
  return !strcmp(k1, k2);
}


#endif /* _hash_INCLUDE_GNU */
