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    Types: TextFile
    Names: »bucket.c«

└─⟦a05ed705a⟧ Bits:30007078 DKUUG GNU 2/12/89
    └─⟦847972ed9⟧ »./gdbm0.9.tar.Z« 
        └─⟦e41d67701⟧ 
            └─⟦this⟧ »gdbm/bucket.c« 

TextFile

/* bucket.c - The routines for playing with hash buckets. */

/*  GNU DBM  - DataBase Manager (database subroutines) by Philip A. Nelson
    Copyright (C) 1989  Free Software Foundation, Inc.

    This program 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.

    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., 675 Mass Ave, Cambridge, MA 02139, USA.

    You may contact the author by:
       e-mail:  phil@wwu.edu
      us-mail:  Philip A. Nelson
                Computer Science Department
                Western Washington University
                Bellingham, WA 98226
        phone:  (206) 676-3035
       
*************************************************************************/


#include <stdio.h>
#include <sys/types.h>
#include <sys/file.h>
#include <sys/stat.h>
#include "gdbmdefs.h"
#include "systems.h"


/* Initializing a new hash buckets sets all bucket entries to -1 hash value. */
_gdbm_new_bucket (dbf, bucket, bits)
     gdbm_file_info *dbf;
     hash_bucket *bucket;
     int bits;
{
  int index;
  
  /* Initialize the avail block. */
  bucket->av_count = 0;

  /* Set the information fields first. */
  bucket->bucket_bits = bits;
  bucket->count = 0;
  
  /* Initialize all bucket elements. */
  for (index = 0; index < dbf->header->bucket_elems; index++)
    bucket->h_table[index].hash_value = -1;
}



/* Find a bucket for DBF that is pointed to by the bucket directory from
   location DIR_INDEX.   The bucket cache is first checked to see if it
   is already in memory.  If not, a bucket may be tossed to read the new
   bucket.  In any case, the requested bucket is make the "current" bucket
   and dbf->bucket points to the correct bucket. */
int
_gdbm_get_bucket (dbf, dir_index)
     gdbm_file_info *dbf;
     int dir_index;
{
  int  bucket_adr;	/* The address of the correct hash bucket.  */
  int  num_bytes;	/* The number of bytes read. */
  int  index;		/* Loop index. */

  /* Initial set up. */
  dbf->bucket_dir = dir_index;
  bucket_adr = dbf->dir [dir_index];
  
  /* Is that one is not alread current, we must find it. */
  if (dbf->cache_entry->ca_adr != bucket_adr)
    {
      /* Look in the cache. */
      for (index = 0; index < CACHE_SIZE; index++)
	if (dbf->bucket_cache[index].ca_adr == bucket_adr)
	  {
	    dbf->bucket = dbf->bucket_cache[index].ca_bucket;
	    dbf->cache_entry = &dbf->bucket_cache[index];
	    return;
	  }

      /* It is not in the cache, read it from the disk. */
      dbf->last_read = (dbf->last_read + 1) % CACHE_SIZE;
      dbf->bucket_cache[dbf->last_read].ca_adr = bucket_adr;
      dbf->bucket = dbf->bucket_cache[dbf->last_read].ca_bucket;
      dbf->cache_entry = &dbf->bucket_cache[dbf->last_read];
      dbf->cache_entry->ca_data.elem_loc = -1;
      dbf->cache_entry->ca_changed = FALSE;

      /* Read the bucket. */
      num_bytes = lseek (dbf->desc, bucket_adr, L_SET);
      if (num_bytes != bucket_adr)
	_gdbm_fatal (dbf, "lseek error");

      num_bytes = read (dbf->desc, dbf->bucket, dbf->header->bucket_size);
      if (num_bytes != dbf->header->bucket_size)
	_gdbm_fatal (dbf, "read error");
    }

  return TRUE;
}


/* Split the current bucket.  This includes moving all items in the bucket to
   a new bucket.  This doesn't require any disk reads because all hash values
   are stored in the buckets.  Splitting the current bucket may require
   doubling the size of the hash directory.  */

_gdbm_split_bucket (dbf, next_insert)
     gdbm_file_info *dbf;
     int next_insert;
{
  hash_bucket *bucket[2]; 	/* Pointers to the new buckets. */

  int          new_bits;	/* The number of bits for the new buckets. */
  int	       cache_0;		/* Location in the cache for the buckets. */
  int	       cache_1;
  int	       adr_0;		/* File address of the new bucket 0. */
  int	       adr_1;		/* File address of the new bucket 1. */
  avail_elem   old_bucket;	/* Avail Struct for the old bucket. */

  int          dir_start0;	/* Used in updating the directory. */
  int          dir_start1;
  int          dir_end;

  int	      *new_dir;		/* Pointer to the new directory. */
  int          dir_adr; 	/* Address of the new directory. */
  int          dir_size;	/* Size of the new directory. */
  int          old_adr[31]; 	/* Address of the old directories. */
  int          old_size[31]; 	/* Size of the old directories. */
  int	       old_count;	/* Number of old directories. */

  int          index;		/* Used in array indexing. */
  int          index1;		/* Used in array indexing. */
  int          elem_loc;	/* Location in new bucket to put element. */
  bucket_element *old_el;	/* Pointer into the old bucket. */
  int	       select;		/* Used to index bucket during movement. */

  int	       num_bytes;	/* For use with write. */

  /* No directories are yet old. */
  old_count = 0;

  while (dbf->bucket->count == dbf->header->bucket_elems)
    {
      /* Initialize the "new" buckets in the cache. */
      do
	{
	  dbf->last_read = (dbf->last_read + 1) % CACHE_SIZE;
	  cache_0 = dbf->last_read;
	}      
      while (dbf->bucket_cache[cache_0].ca_bucket == dbf->bucket);
      bucket[0] = dbf->bucket_cache[cache_0].ca_bucket;
      if (dbf->bucket_cache[cache_0].ca_changed)
	_gdbm_write_bucket (dbf, &dbf->bucket_cache[cache_0]);
      do
	{
	  dbf->last_read = (dbf->last_read + 1) % CACHE_SIZE;
	  cache_1 = dbf->last_read;
	}      
      while (dbf->bucket_cache[cache_1].ca_bucket == dbf->bucket);
      bucket[1] = dbf->bucket_cache[cache_1].ca_bucket;
      if (dbf->bucket_cache[cache_1].ca_changed)
	_gdbm_write_bucket (dbf, &dbf->bucket_cache[cache_1]);
      new_bits = dbf->bucket->bucket_bits+1;
      _gdbm_new_bucket (dbf, bucket[0], new_bits);
      _gdbm_new_bucket (dbf, bucket[1], new_bits);
      adr_0 = _gdbm_alloc (dbf, dbf->header->bucket_size); 
      dbf->bucket_cache[cache_0].ca_adr = adr_0;
      adr_1 = _gdbm_alloc (dbf, dbf->header->bucket_size);
      dbf->bucket_cache[cache_1].ca_adr = adr_1;

      
      
      /* Double the directory size if necessary. */
      if (dbf->header->dir_bits == dbf->bucket->bucket_bits)
	{
	  dir_size = dbf->header->dir_size * 2;
	  dir_adr  = _gdbm_alloc (dbf, dir_size);
	  new_dir  = (int *) malloc (dir_size);
	  if (new_dir == NULL) _gdbm_fatal (dbf, "malloc error");
	  for (index = 0; index < dbf->header->dir_size/sizeof (int); index++)
	    {
	      new_dir[2*index]   = dbf->dir[index];
	      new_dir[2*index+1] = dbf->dir[index];
	    }
	  
	  /* Update header. */
	  old_adr[old_count] = dbf->header->dir;
	  dbf->header->dir = dir_adr;
	  old_size[old_count] = dbf->header->dir_size;
	  dbf->header->dir_size = dir_size;
	  dbf->header->dir_bits = new_bits;
	  old_count++;
	  
	  /* Now update dbf.  */
	  dbf->header_changed = TRUE;
	  dbf->bucket_dir *= 2;
	  free (dbf->dir);
	  dbf->dir = new_dir;
	}

      /* Copy all elements in dbf->bucket into the new buckets. */
      for (index = 0; index < dbf->header->bucket_elems; index++)
	{
	  old_el = & (dbf->bucket->h_table[index]);
	  select = (old_el->hash_value >> (31-new_bits)) & 1;
	  elem_loc = old_el->hash_value % dbf->header->bucket_elems;
	  while (bucket[select]->h_table[elem_loc].hash_value != -1)
	    elem_loc = (elem_loc + 1) % dbf->header->bucket_elems;
	  bucket[select]->h_table[elem_loc] = *old_el;
	  bucket[select]->count += 1;
	}
      
      /* Allocate avail space for the bucket[1]. */
      bucket[1]->bucket_avail[0].av_adr =
	_gdbm_alloc (dbf, dbf->header->block_size);
      bucket[1]->bucket_avail[0].av_size = dbf->header->block_size;
      bucket[1]->av_count = 1;
      
      /* Copy the avail elements in dbf->bucket to bucket[0]. */
      bucket[0]->av_count = dbf->bucket->av_count;
      index = 0;
      index1 = 0;
      if (bucket[0]->av_count == BUCKET_AVAIL)
	{
	  /* The avail is full, move the first one to bucket[1]. */
	  _gdbm_put_av_elem (dbf->bucket->bucket_avail[0],
			     bucket[1]->bucket_avail,
			     &bucket[1]->av_count);
	  index = 1;
	  bucket[0]->av_count --;
	}
      for (; index < dbf->bucket->av_count; index++)
	{
	  bucket[0]->bucket_avail[index1++] = dbf->bucket->bucket_avail[index];
	}
      
      /* Update the directory.  We have new file addresses for both buckets. */
      dir_start1 = (dbf->bucket_dir >> (dbf->header->dir_bits - new_bits)) | 1;
      dir_end = (dir_start1 + 1) << (dbf->header->dir_bits - new_bits);
      dir_start1 = dir_start1 << (dbf->header->dir_bits - new_bits);
      dir_start0 = dir_start1 - (dir_end - dir_start1);
      for (index = dir_start0; index < dir_start1; index++)
	dbf->dir[index] = adr_0;
      for (index = dir_start1; index < dir_end; index++)
	dbf->dir[index] = adr_1;
      
      
      /* Set changed flags. */
      dbf->bucket_cache[cache_0].ca_changed = TRUE;
      dbf->bucket_cache[cache_1].ca_changed = TRUE;
      dbf->bucket_changed = TRUE;
      dbf->directory_changed = TRUE;
      dbf->second_changed = TRUE;
      
      /* Update the cache! */
      dbf->bucket_dir = next_insert >> (31-dbf->header->dir_bits);
      
      /* Invalidate old cache entry. */
      old_bucket.av_adr  = dbf->cache_entry->ca_adr;
      old_bucket.av_size = dbf->header->bucket_size;
      dbf->cache_entry->ca_adr = 0;
      dbf->cache_entry->ca_changed = FALSE;
      
      /* Set dbf->bucket to the proper bucket. */
      if (dbf->dir[dbf->bucket_dir] == adr_0)
	{
	  dbf->bucket = bucket[0];
	  dbf->cache_entry = &dbf->bucket_cache[cache_0];
	  _gdbm_put_av_elem (old_bucket,
			     bucket[1]->bucket_avail,
			     &bucket[1]->av_count);
	}
      else
	{
	  dbf->bucket = bucket[1];
	  dbf->cache_entry = &dbf->bucket_cache[cache_1];
	  _gdbm_put_av_elem (old_bucket,
			     bucket[0]->bucket_avail,
			     &bucket[0]->av_count);
	}
      
    }

  /* Get rid of old directories. */
  for (index = 0; index < old_count; index++)
    _gdbm_free (dbf, old_adr[index], old_size[index]);
}


/* The only place where a bucket is written.  CA_ENTRY is the
   cache entry containing the bucket to be written. */

_gdbm_write_bucket (dbf, ca_entry)
     gdbm_file_info *dbf;
     cache_elem *ca_entry;
{
  int num_bytes;	/* The return value for lseek and write. */
  
  num_bytes = lseek (dbf->desc, ca_entry->ca_adr, L_SET);
  if (num_bytes != ca_entry->ca_adr )
    _gdbm_fatal (dbf, "lseek error");
  num_bytes = write (dbf->desc, ca_entry->ca_bucket, dbf->header->bucket_size);
  if (num_bytes != dbf->header->bucket_size )
    _gdbm_fatal (dbf, "write error");
  ca_entry->ca_changed = FALSE;
  
}