Function my_hash_delete

mysys/hash.c:524–605

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

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

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

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

  if ( --(hash->records) < hash->blength >> 1) hash->blength>>=1;
  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 + my_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 + my_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;