path: root/mysql/libmariadb/ma_hash.c

/************************************************************************************
    Copyright (C) 2000, 2012 MySQL AB & MySQL Finland AB & TCX DataKonsult AB,
                 Monty Program AB, 2016 MariaDB Corporation AB
   
   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.
   
   This library 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
   Library General Public License for more details.
   
   You should have received a copy of the GNU Library General Public
   License along with this library; if not see <http://www.gnu.org/licenses>
   or write to the Free Software Foundation, Inc., 
   51 Franklin St., Fifth Floor, Boston, MA 02110, USA

   Part of this code includes code from the PHP project which
   is freely available from http://www.php.net
*************************************************************************************/

/* The hash functions used for saveing keys */
/* One of key_length or key_length_offset must be given */
/* Key length of 0 isn't allowed */

#include <ma_global.h>
#include <ma_sys.h>
#include <ma_string.h>
#include <mariadb_ctype.h>
#include "ma_hash.h"

#define NO_RECORD	((uint) -1)
#define LOWFIND 1
#define LOWUSED 2
#define HIGHFIND 4
#define HIGHUSED 8

static uint hash_mask(uint hashnr,uint buffmax,uint maxlength);
static void movelink(HASH_LINK *array,uint pos,uint next_link,uint newlink);
static uint calc_hashnr(const uchar *key,uint length);
static uint calc_hashnr_caseup(const uchar *key,uint length);
static int hashcmp(HASH *hash,HASH_LINK *pos,const uchar *key,uint length);


my_bool _hash_init(HASH *hash,uint size,uint key_offset,uint key_length,
		  hash_get_key get_key,
		  void (*free_element)(void*),uint flags CALLER_INFO_PROTO)
{
  hash->records=0;
  if (ma_init_dynamic_array_ci(&hash->array,sizeof(HASH_LINK),size,0))
  {
    hash->free=0;				/* Allow call to hash_free */
    return(TRUE);
  }
  hash->key_offset=key_offset;
  hash->key_length=key_length;
  hash->blength=1;
  hash->current_record= NO_RECORD;		/* For the future */
  hash->get_key=get_key;
  hash->free=free_element;
  hash->flags=flags;
  if (flags & HASH_CASE_INSENSITIVE)
    hash->calc_hashnr=calc_hashnr_caseup;
  else
    hash->calc_hashnr=calc_hashnr;
  return(0);
}


void hash_free(HASH *hash)
{
  if (hash->free)
  {
    uint i,records;
    HASH_LINK *data=dynamic_element(&hash->array,0,HASH_LINK*);
    for (i=0,records=hash->records ; i < records ; i++)
      (*hash->free)(data[i].data);
    hash->free=0;
  }
  ma_delete_dynamic(&hash->array);
  hash->records=0;
  return;
}

	/* some helper functions */

/*
  This function is char* instead of uchar* as HPUX11 compiler can't
  handle inline functions that are not defined as native types
*/

static inline char*
hash_key(HASH *hash,const uchar *record,uint *length,my_bool first)
{
  if (hash->get_key)
    return (char *)(*hash->get_key)(record,(uint *)length,first);
  *length=hash->key_length;
  return (char*) record+hash->key_offset;
}

	/* Calculate pos according to keys */

static uint hash_mask(uint hashnr,uint buffmax,uint maxlength)
{
  if ((hashnr & (buffmax-1)) < maxlength) return (hashnr & (buffmax-1));
  return (hashnr & ((buffmax >> 1) -1));
}

static uint hash_rec_mask(HASH *hash,HASH_LINK *pos,uint buffmax,
			  uint maxlength)
{
  uint length;
  uchar *key= (uchar*) hash_key(hash,pos->data,&length,0);
  return hash_mask((*hash->calc_hashnr)(key,length),buffmax,maxlength);
}

#ifndef NEW_HASH_FUNCTION

	/* Calc hashvalue for a key */

static uint calc_hashnr(const uchar *key,uint length)
{
  register uint nr=1, nr2=4;
  while (length--)
  {
    nr^= (((nr & 63)+nr2)*((uint) (uchar) *key++))+ (nr << 8);
    nr2+=3;
  }
  return((uint) nr);
}

	/* Calc hashvalue for a key, case indepenently */

static uint calc_hashnr_caseup(const uchar *key,uint length)
{
  register uint nr=1, nr2=4;
  while (length--)
  {
    nr^= (((nr & 63)+nr2)*((uint) (uchar) toupper(*key++)))+ (nr << 8);
    nr2+=3;
  }
  return((uint) nr);
}

#else

/*
 * Fowler/Noll/Vo hash
 *
 * The basis of the hash algorithm was taken from an idea sent by email to the
 * IEEE Posix P1003.2 mailing list from Phong Vo (kpv@research.att.com) and
 * Glenn Fowler (gsf@research.att.com).  Landon Curt Noll (chongo@toad.com)
 * later improved on their algorithm.
 *
 * The magic is in the interesting relationship between the special prime
 * 16777619 (2^24 + 403) and 2^32 and 2^8.
 *
 * This hash produces the fewest collisions of any function that we've seen so
 * far, and works well on both numbers and strings.
 */

uint calc_hashnr(const uchar *key, uint len)
{
  const uchar *end=key+len;
  uint hash;
  for (hash = 0; key < end; key++)
  {
    hash *= 16777619;
    hash ^= (uint) *(uchar*) key;
  }
  return (hash);
}

uint calc_hashnr_caseup(const uchar *key, uint len)
{
  const uchar *end=key+len;
  uint hash;
  for (hash = 0; key < end; key++)
  {
    hash *= 16777619;
    hash ^= (uint) (uchar) toupper(*key);
  }
  return (hash);
}

#endif


#ifndef __SUNPRO_C				/* SUNPRO can't handle this */
static inline
#endif
unsigned int rec_hashnr(HASH *hash,const uchar *record)
{
  uint length;
  uchar *key= (uchar*) hash_key(hash,record,&length,0);
  return (*hash->calc_hashnr)(key,length);
}


	/* Search after a record based on a key */
	/* Sets info->current_ptr to found record */

void* hash_search(HASH *hash,const uchar *key,uint length)
{
  HASH_LINK *pos;
  uint flag,idx;

  flag=1;
  if (hash->records)
  {
    idx=hash_mask((*hash->calc_hashnr)(key,length ? length :
					 hash->key_length),
		    hash->blength,hash->records);
    do
    {
      pos= dynamic_element(&hash->array,idx,HASH_LINK*);
      if (!hashcmp(hash,pos,key,length))
      {
	hash->current_record= idx;
	return (pos->data);
      }
      if (flag)
      {
	flag=0;					/* Reset flag */
	if (hash_rec_mask(hash,pos,hash->blength,hash->records) != idx)
	  break;				/* Wrong link */
      }
    }
    while ((idx=pos->next) != NO_RECORD);
  }
  hash->current_record= NO_RECORD;
  return(0);
}

	/* Get next record with identical key */
	/* Can only be called if previous calls was hash_search */

void *hash_next(HASH *hash,const uchar *key,uint length)
{
  HASH_LINK *pos;
  uint idx;

  if (hash->current_record != NO_RECORD)
  {
    HASH_LINK *data=dynamic_element(&hash->array,0,HASH_LINK*);
    for (idx=data[hash->current_record].next; idx != NO_RECORD ; idx=pos->next)
    {
      pos=data+idx;
      if (!hashcmp(hash,pos,key,length))
      {
	hash->current_record= idx;
	return pos->data;
      }
    }
    hash->current_record=NO_RECORD;
  }
  return 0;
}


	/* Change link from pos to new_link */

static void movelink(HASH_LINK *array,uint find,uint next_link,uint newlink)
{
  HASH_LINK *old_link;
  do
  {
    old_link=array+next_link;
  }
  while ((next_link=old_link->next) != find);
  old_link->next= newlink;
  return;
}

	/* Compare a key in a record to a whole key. Return 0 if identical */

static int hashcmp(HASH *hash,HASH_LINK *pos,const uchar *key,uint length)
{
  uint rec_keylength;
  uchar *rec_key= (uchar*) hash_key(hash,pos->data,&rec_keylength,1);
  return (length && length != rec_keylength) ||
     memcmp(rec_key,key,rec_keylength);
}


	/* Write a hash-key to the hash-index */

my_bool hash_insert(HASH *info,const uchar *record)
{
  int flag;
  uint halfbuff,hash_nr,first_index,idx;
  uchar *ptr_to_rec= NULL,*ptr_to_rec2= NULL;
  HASH_LINK *data,*empty,*gpos= NULL,*gpos2 = NULL,*pos;

  LINT_INIT(gpos); LINT_INIT(gpos2);
  LINT_INIT(ptr_to_rec); LINT_INIT(ptr_to_rec2);

  flag=0;
  if (!(empty=(HASH_LINK*) ma_alloc_dynamic(&info->array)))
    return(TRUE);				/* No more memory */

  info->current_record= NO_RECORD;
  data=dynamic_element(&info->array,0,HASH_LINK*);
  halfbuff= info->blength >> 1;

  idx=first_index=info->records-halfbuff;
  if (idx != info->records)				/* If some records */
  {
    do
    {
      pos=data+idx;
      hash_nr=rec_hashnr(info,pos->data);
      if (flag == 0)				/* First loop; Check if ok */
	if (hash_mask(hash_nr,info->blength,info->records) != first_index)
	  break;
      if (!(hash_nr & halfbuff))
      {						/* Key will not move */
	if (!(flag & LOWFIND))
	{
	  if (flag & HIGHFIND)
	  {
	    flag=LOWFIND | HIGHFIND;
	    /* key shall be moved to the current empty position */
	    gpos=empty;
	    ptr_to_rec=pos->data;
	    empty=pos;				/* This place is now free */
	  }
	  else
	  {
	    flag=LOWFIND | LOWUSED;		/* key isn't changed */
	    gpos=pos;
	    ptr_to_rec=pos->data;
	  }
	}
	else
	{
	  if (!(flag & LOWUSED))
	  {
	    /* Change link of previous LOW-key */
	    gpos->data=ptr_to_rec;
	    gpos->next=(uint) (pos-data);
	    flag= (flag & HIGHFIND) | (LOWFIND | LOWUSED);
	  }
	  gpos=pos;
	  ptr_to_rec=pos->data;
	}
      }
      else
      {						/* key will be moved */
	if (!(flag & HIGHFIND))
	{
	  flag= (flag & LOWFIND) | HIGHFIND;
	  /* key shall be moved to the last (empty) position */
	  gpos2 = empty; empty=pos;
	  ptr_to_rec2=pos->data;
	}
	else
	{
	  if (!(flag & HIGHUSED))
	  {
	    /* Change link of previous hash-key and save */
	    gpos2->data=ptr_to_rec2;
	    gpos2->next=(uint) (pos-data);
	    flag= (flag & LOWFIND) | (HIGHFIND | HIGHUSED);
	  }
	  gpos2=pos;
	  ptr_to_rec2=pos->data;
	}
      }
    }
    while ((idx=pos->next) != NO_RECORD);

    if ((flag & (LOWFIND | LOWUSED)) == LOWFIND)
    {
      gpos->data=ptr_to_rec;
      gpos->next=NO_RECORD;
    }
    if ((flag & (HIGHFIND | HIGHUSED)) == HIGHFIND)
    {
      gpos2->data=ptr_to_rec2;
      gpos2->next=NO_RECORD;
    }
  }
  /* Check if we are at the empty position */

  idx=hash_mask(rec_hashnr(info,record),info->blength,info->records+1);
  pos=data+idx;
  if (pos == empty)
  {
    pos->data=(uchar*) record;
    pos->next=NO_RECORD;
  }
  else
  {
    /* Check if more records in same hash-nr family */
    empty[0]=pos[0];
    gpos=data+hash_rec_mask(info,pos,info->blength,info->records+1);
    if (pos == gpos)
    {
      pos->data=(uchar*) record;
      pos->next=(uint) (empty - data);
    }
    else
    {
      pos->data=(uchar*) record;
      pos->next=NO_RECORD;
      movelink(data,(uint) (pos-data),(uint) (gpos-data),(uint) (empty-data));
    }
  }
  if (++info->records == info->blength)
    info->blength+= info->blength;
  return(0);
}


/******************************************************************************
** Remove one record from hash-table. The record with the same record
** ptr is removed.
** if there is a free-function it's called for record if found
******************************************************************************/

my_bool hash_delete(HASH *hash,uchar *record)
{
  uint blength,pos2,pos_hashnr,lastpos_hashnr,idx,empty_index;
  HASH_LINK *data,*lastpos,*gpos,*pos,*pos3,*empty;
  if (!hash->records)
    return(1);

  blength=hash->blength;
  data=dynamic_element(&hash->array,0,HASH_LINK*);
  /* Search after record with key */
  pos=data+ hash_mask(rec_hashnr(hash,record),blength,hash->records);
  gpos = 0;

  while (pos->data != record)
  {
    gpos=pos;
    if (pos->next == NO_RECORD)
      return(1);			/* Key not found */
    pos=data+pos->next;
  }

  if ( --(hash->records) < hash->blength >> 1) hash->blength>>=1;
  hash->current_record= NO_RECORD;
  lastpos=data+hash->records;

  /* Remove link to record */
  empty=pos; empty_index=(uint) (empty-data);
  if (gpos)
    gpos->next=pos->next;		/* unlink current ptr */
  else if (pos->next != NO_RECORD)
  {
    empty=data+(empty_index=pos->next);
    pos->data=empty->data;
    pos->next=empty->next;
  }

  if (empty == lastpos)			/* last key at wrong pos or no next link */
    goto exit;

  /* Move the last key (lastpos) */
  lastpos_hashnr=rec_hashnr(hash,lastpos->data);
  /* pos is where lastpos should be */
  pos=data+hash_mask(lastpos_hashnr,hash->blength,hash->records);
  if (pos == empty)			/* Move to empty position. */
  {
    empty[0]=lastpos[0];
    goto exit;
  }
  pos_hashnr=rec_hashnr(hash,pos->data);
  /* pos3 is where the pos should be */
  pos3= data+hash_mask(pos_hashnr,hash->blength,hash->records);
  if (pos != pos3)
  {					/* pos is on wrong posit */
    empty[0]=pos[0];			/* Save it here */
    pos[0]=lastpos[0];			/* This should be here */
    movelink(data,(uint) (pos-data),(uint) (pos3-data),empty_index);
    goto exit;
  }
  pos2= hash_mask(lastpos_hashnr,blength,hash->records+1);
  if (pos2 == hash_mask(pos_hashnr,blength,hash->records+1))
  {					/* Identical key-positions */
    if (pos2 != hash->records)
    {
      empty[0]=lastpos[0];
      movelink(data,(uint) (lastpos-data),(uint) (pos-data),empty_index);
      goto exit;
    }
    idx= (uint) (pos-data);		/* Link pos->next after lastpos */
  }
  else idx= NO_RECORD;		/* Different positions merge */

  empty[0]=lastpos[0];
  movelink(data,idx,empty_index,pos->next);
  pos->next=empty_index;

exit:
  ma_pop_dynamic(&hash->array);
  if (hash->free)
    (*hash->free)((uchar*) record);
  return(0);
}

	/*
	  Update keys when record has changed.
	  This is much more efficent than using a delete & insert.
	  */

my_bool hash_update(HASH *hash,uchar *record,uchar *old_key,uint old_key_length)
{
  uint idx,new_index,new_pos_index,blength,records,empty;
  HASH_LINK org_link,*data,*previous,*pos;

  data=dynamic_element(&hash->array,0,HASH_LINK*);
  blength=hash->blength; records=hash->records;

  /* Search after record with key */

  idx=hash_mask((*hash->calc_hashnr)(old_key,(old_key_length ?
						old_key_length :
						hash->key_length)),
		  blength,records);
  new_index=hash_mask(rec_hashnr(hash,record),blength,records);
  if (idx == new_index)
    return(0);			/* Nothing to do (No record check) */
  previous=0;
  for (;;)
  {

    if ((pos= data+idx)->data == record)
      break;
    previous=pos;
    if ((idx=pos->next) == NO_RECORD)
      return(1);			/* Not found in links */
  }
  hash->current_record= NO_RECORD;
  org_link= *pos;
  empty=idx;

  /* Relink record from current chain */

  if (!previous)
  {
    if (pos->next != NO_RECORD)
    {
      empty=pos->next;
      *pos= data[pos->next];
    }
  }
  else
    previous->next=pos->next;		/* unlink pos */

  /* Move data to correct position */
  pos=data+new_index;
  new_pos_index=hash_rec_mask(hash,pos,blength,records);
  if (new_index != new_pos_index)
  {					/* Other record in wrong position */
    data[empty] = *pos;
    movelink(data,new_index,new_pos_index,empty);
    org_link.next=NO_RECORD;
    data[new_index]= org_link;
  }
  else
  {					/* Link in chain at right position */
    org_link.next=data[new_index].next;
    data[empty]=org_link;
    data[new_index].next=empty;
  }
  return(0);
}


uchar *hash_element(HASH *hash,uint idx)
{
  if (idx < hash->records)
    return dynamic_element(&hash->array,idx,HASH_LINK*)->data;
  return 0;
}