/*
 *  Bacula hash table routines
 *
 *  htable is a hash table of items (pointers). This code is
 *    adapted and enhanced from code I wrote in 1982 for a
 *    relocatable linker.  At that time, the hash table size
 *    was fixed and a primary number, which essentially provides
 *    the randomness. In this program, the hash table can grow when
 *    it gets too full, so the table size here is a binary number. The
 *    hashing is provided using an idea from Tcl where the initial
 *    hash code is "randomized" using a simple calculation from
 *    a random number generator that multiplies by a big number
 *    (I multiply by a prime number, while Tcl did not)
 *    then shifts the result down and does the binary division
 *    by masking.  Increasing the size of the hash table is simple.
 *    Just create a new larger table, walk the old table and
 *    re-hash insert each entry into the new table.
 *
 *
 *   Kern Sibbald, July MMIII
 *
 *   Version $Id: htable.c 5012 2007-06-14 16:54:30Z kerns $
 *
 */
/*
   Bacula® - The Network Backup Solution

   Copyright (C) 2003-2006 Free Software Foundation Europe e.V.

   The main author of Bacula is Kern Sibbald, with contributions from
   many others, a complete list can be found in the file AUTHORS.
   This program is Free Software; you can redistribute it and/or
   modify it under the terms of version two of the GNU General Public
   License as published by the Free Software Foundation and included
   in the file LICENSE.

   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, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
   02110-1301, USA.

   Bacula® is a registered trademark of John Walker.
   The licensor of Bacula is the Free Software Foundation Europe
   (FSFE), Fiduciary Program, Sumatrastrasse 25, 8006 Zürich,
   Switzerland, email:ftf@fsfeurope.org.
*/

#include "bacula.h"

#include "htable.h"

/* ===================================================================
 *    htable
 */

/*
 * Create hash of key, stored in hash then
 *  create and return the pseudo random bucket index
 */
void htable::hash_index(char *key)
{
   hash = 0;
   for (char *p=key; *p; p++) {
      hash += (hash << 3) + (uint32_t)*p;
   }
   /* Multiply by large prime number, take top bits, mask for remainder */
   index = ((hash * 1103515249) >> rshift) & mask;
   Dmsg2(100, "Leave hash_index hash=0x%x index=%d\n", hash, index);
}

htable::htable(void *item, void *link, int tsize)
{
   init(item, link, tsize);
}

void htable::init(void *item, void *link, int tsize)
{
   int pwr;
   tsize >>= 2;
   for (pwr=0; tsize; pwr++) {
      tsize >>= 1;
   }
   loffset = (char *)link - (char *)item;
   mask = ~((~0)<<pwr);               /* 3 bits => table size = 8 */
   rshift = 30 - pwr;                 /* start using bits 28, 29, 30 */
   num_items = 0;                     /* number of entries in table */
   buckets = 1<<pwr;                  /* hash table size -- power of two */
   max_items = buckets * 4;           /* allow average 4 entries per chain */
   table = (hlink **)malloc(buckets * sizeof(hlink *));
   memset(table, 0, buckets * sizeof(hlink *));
   walkptr = NULL;
   walk_index = 0;
}

uint32_t htable::size()
{
   return num_items;
}

/*
 * Take each hash link and walk down the chain of items
 *  that hash there counting them (i.e. the hits), 
 *  then report that number.
 *  Obiously, the more hits in a chain, the more time
 *  it takes to reference them. Empty chains are not so
 *  hot either -- as it means unused or wasted space.
 */
#define MAX_COUNT 20
void htable::stats()
{
   int hits[MAX_COUNT];
   int max = 0;
   int i, j;
   hlink *p;
   printf("\n\nNumItems=%d\nTotal buckets=%d\n", num_items, buckets);
   printf("Hits/bucket: buckets\n");
   for (i=0; i < MAX_COUNT; i++) {
      hits[i] = 0;
   }
   for (i=0; i<(int)buckets; i++) {
      p = table[i];
      j = 0;
      while (p) {
         p = (hlink *)(p->next);
         j++;
      }
      if (j > max) {
         max = j;
      }
      if (j < MAX_COUNT) {
         hits[j]++;
      }
   }
   for (i=0; i < MAX_COUNT; i++) {
      printf("%2d:           %d\n",i, hits[i]);
   }
   printf("max hits in a bucket = %d\n", max);
}

void htable::grow_table()
{
   Dmsg1(100, "Grow called old size = %d\n", buckets);
   /* Setup a bigger table */
   htable *big = (htable *)malloc(sizeof(htable));
   big->loffset = loffset;
   big->mask = mask<<1 | 1;
   big->rshift = rshift - 1;
   big->num_items = 0;
   big->buckets = buckets * 2;
   big->max_items = big->buckets * 4;
   big->table = (hlink **)malloc(big->buckets * sizeof(hlink *));
   memset(big->table, 0, big->buckets * sizeof(hlink *));
   big->walkptr = NULL;
   big->walk_index = 0;
   /* Insert all the items in the new hash table */
   Dmsg1(100, "Before copy num_items=%d\n", num_items);
   /*
    * We walk through the old smaller tree getting items,
    * but since we are overwriting the colision links, we must
    * explicitly save the item->next pointer and walk each
    * colision chain ourselves.  We do use next() for getting
    * to the next bucket.
    */
   for (void *item=first(); item; ) {
      void *ni = ((hlink *)((char *)item+loffset))->next;  /* save link overwritten by insert */
      Dmsg1(100, "Grow insert: %s\n", ((hlink *)((char *)item+loffset))->key);
      big->insert(((hlink *)((char *)item+loffset))->key, item);
      if (ni) {
         item = (void *)((char *)ni-loffset);
      } else {
         walkptr = NULL;
         item = next();
      }
   }
   Dmsg1(100, "After copy new num_items=%d\n", big->num_items);
   if (num_items != big->num_items) {
      Dmsg0(000, "****** Big problems num_items mismatch ******\n");
   }
   free(table);
   memcpy(this, big, sizeof(htable));  /* move everything across */
   free(big);
   Dmsg0(100, "Exit grow.\n");
}

bool htable::insert(char *key, void *item)
{
   hlink *hp;
   if (lookup(key)) {
      return false;                   /* already exists */
   }
   sm_check(__FILE__, __LINE__, false);
   ASSERT(index < buckets);
   Dmsg2(100, "Insert: hash=0x%x index=%d\n", (unsigned)hash, index);
   hp = (hlink *)(((char *)item)+loffset);
   Dmsg4(100, "Insert hp=0x%x index=%d item=0x%x offset=%u\n", (unsigned)hp,
      index, (unsigned)item, loffset);
   hp->next = table[index];
   hp->hash = hash;
   hp->key = key;
   table[index] = hp;
   Dmsg3(100, "Insert hp->next=0x%x hp->hash=0x%x hp->key=%s\n",
      (unsigned)hp->next, hp->hash, hp->key);

   if (++num_items >= max_items) {
      Dmsg2(100, "num_items=%d max_items=%d\n", num_items, max_items);
      grow_table();
   }
   sm_check(__FILE__, __LINE__, false);
   Dmsg3(100, "Leave insert index=%d num_items=%d key=%s\n", index, num_items, key);
   return true;
}

void *htable::lookup(char *key)
{
   hash_index(key);
   for (hlink *hp=table[index]; hp; hp=(hlink *)hp->next) {
//    Dmsg2(100, "hp=0x%x key=%s\n", (long)hp, hp->key);
      if (hash == hp->hash && strcmp(key, hp->key) == 0) {
         Dmsg1(100, "lookup return %x\n", ((char *)hp)-loffset);
         return ((char *)hp)-loffset;
      }
   }
   return NULL;
}

void *htable::next()
{
   Dmsg1(100, "Enter next: walkptr=0x%x\n", (unsigned)walkptr);
   if (walkptr) {
      walkptr = (hlink *)(walkptr->next);
   }
   while (!walkptr && walk_index < buckets) {
      walkptr = table[walk_index++];
      if (walkptr) {
         Dmsg3(100, "new walkptr=0x%x next=0x%x inx=%d\n", (unsigned)walkptr,
            (unsigned)(walkptr->next), walk_index-1);
      }
   }
   if (walkptr) {
      Dmsg2(100, "next: rtn 0x%x walk_index=%d\n",
         (unsigned)(((char *)walkptr)-loffset), walk_index);
      return ((char *)walkptr)-loffset;
   }
   Dmsg0(100, "next: return NULL\n");
   return NULL;
}

void *htable::first()
{
   Dmsg0(100, "Enter first\n");
   walkptr = table[0];                /* get first bucket */
   walk_index = 1;                    /* Point to next index */
   while (!walkptr && walk_index < buckets) {
      walkptr = table[walk_index++];  /* go to next bucket */
      if (walkptr) {
         Dmsg3(100, "first new walkptr=0x%x next=0x%x inx=%d\n", (unsigned)walkptr,
            (unsigned)(walkptr->next), walk_index-1);
      }
   }
   if (walkptr) {
      Dmsg1(100, "Leave first walkptr=0x%x\n", (unsigned)walkptr);
      return ((char *)walkptr)-loffset;
   }
   Dmsg0(100, "Leave first walkptr=NULL\n");
   return NULL;
}

/* Destroy the table and its contents */
void htable::destroy()
{
   void *ni;
   void *li = first();
   do {
      ni = next();
      free(li);
      li = ni;
   } while (ni);

   free(table);
   table = NULL;
   Dmsg0(100, "Done destroy.\n");
}



#ifdef TEST_PROGRAM

struct MYJCR {
   char *key;
   hlink link;
};

#define NITEMS 10000

int main()
{
   char mkey[30];
   htable *jcrtbl;
   MYJCR *save_jcr = NULL, *item;
   MYJCR *jcr = NULL;
   int count = 0;

   jcrtbl = (htable *)malloc(sizeof(htable));
   jcrtbl->init(jcr, &jcr->link, NITEMS);

   Dmsg1(000, "Inserting %d items\n", NITEMS);
   for (int i=0; i<NITEMS; i++) {
      sprintf(mkey, "This is htable item %d", i);
      jcr = (MYJCR *)malloc(sizeof(MYJCR));
      Dmsg2(100, "link=0x%x jcr=0x%x\n", (unsigned)&jcr->link, (unsigned)jcr);
      jcr->key = bstrdup(mkey);

      jcrtbl->insert(jcr->key, jcr);
      if (i == 10) {
         save_jcr = jcr;
      }
   }
   if (!(item = (MYJCR *)jcrtbl->lookup(save_jcr->key))) {
      printf("Bad news: %s not found.\n", save_jcr->key);
   } else {
      printf("Item 10's key is: %s\n", item->key);
   }

   jcrtbl->stats();
   printf("Walk the hash table:\n");
   foreach_htable (jcr, jcrtbl) {
//    printf("htable item = %s\n", jcr->key);
      free(jcr->key);
      count++;
   }
   printf("Got %d items -- %s\n", count, count==NITEMS?"OK":"***ERROR***");
   printf("Calling destroy\n");
   jcrtbl->destroy();

   free(jcrtbl);
   printf("Freed jcrtbl\n");

   sm_dump(false);

}
#endif