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

/* This file is part of GDBM, the GNU data base manager.
   Copyright (C) 1990-1991, 1993, 2007, 2011, 2013, 2016-2018 Free
   Software Foundation, Inc.

   GDBM 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 3, or (at your option)
   any later version.

   GDBM 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 GDBM. If not, see <http://www.gnu.org/licenses/>.   */

#include "autoconf.h"
#include "gdbmdefs.h"
#include <limits.h>

#define GDBM_MAX_DIR_SIZE INT_MAX
#define GDBM_MAX_DIR_HALF (GDBM_MAX_DIR_SIZE / 2)

/* Initializing a new hash buckets sets all bucket entries to -1 hash value. */
void
_gdbm_new_bucket (GDBM_FILE 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;
}

/* Return true if the directory entry at DIR_INDEX can be considered
   valid. This means that DIR_INDEX is in the valid range for addressing
   the dir array, and the offset stored in dir[DIR_INDEX] points past
   first two blocks in file. This does not necessarily mean that there's
   a valid bucket or data block at that offset. All this implies is that
   it is safe to use the offset for look up in the bucket cache and to
   attempt to read a block at that offset. */
int
gdbm_dir_entry_valid_p (GDBM_FILE dbf, int dir_index)
{
  return dir_index >= 0
         && dir_index < GDBM_DIR_COUNT (dbf)
         && dbf->dir[dir_index] >= 2*dbf->header->block_size;
}
    
/* 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.  On success, the requested bucket becomes the "current" bucket
   and dbf->bucket points to the correct bucket. On error, the current
   bucket remains unchanged. */

int
_gdbm_get_bucket (GDBM_FILE dbf, int dir_index)
{
  int rc;
  off_t bucket_adr;	/* The address of the correct hash bucket.  */
  off_t	file_pos;	/* The return address for lseek. */
  int   index;		/* Loop index. */

  if (!gdbm_dir_entry_valid_p (dbf, dir_index))
    {
      /* FIXME: negative caching? */
      GDBM_SET_ERRNO (dbf, GDBM_BAD_DIR_ENTRY, TRUE);
      return -1;
    }
  
  /* Initial set up. */
  dbf->bucket_dir = dir_index;
  bucket_adr = dbf->dir[dir_index];
  
  if (dbf->bucket_cache == NULL)
    {
      if (_gdbm_init_cache (dbf, DEFAULT_CACHESIZE) == -1)
	{
	  _gdbm_fatal (dbf, _("couldn't init cache"));
	  return -1;
	}
    }

  /* If that one is not already current, we must find it. */
  if (dbf->cache_entry->ca_adr != bucket_adr)
    {
      size_t lru;
      hash_bucket *bucket;
      
      /* Look in the cache. */
      for (index = 0; index < dbf->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 0;
	    }
        }

      /* It is not in the cache, read it from the disk. */

      /* Position the file pointer */
      file_pos = gdbm_file_seek (dbf, bucket_adr, SEEK_SET);
      if (file_pos != bucket_adr)
	{
	  GDBM_SET_ERRNO (dbf, GDBM_FILE_SEEK_ERROR, TRUE);
	  _gdbm_fatal (dbf, _("lseek error"));
	  return -1;
	}
      
      /* Flush and drop the last recently used cache entry */
      lru = (dbf->last_read + 1) % dbf->cache_size;
      if (dbf->bucket_cache[lru].ca_changed)
	{
	  if (_gdbm_write_bucket (dbf, &dbf->bucket_cache[lru]))
	    return -1;
	}
      _gdbm_cache_entry_invalidate (dbf, lru);
      
      /* Read the bucket. */
      rc = _gdbm_full_read (dbf, dbf->bucket_cache[lru].ca_bucket,
			    dbf->header->bucket_size);
      if (rc)
	{
	  GDBM_DEBUG (GDBM_DEBUG_ERR,
		      "%s: error reading bucket: %s",
		      dbf->name, gdbm_db_strerror (dbf));
	  dbf->need_recovery = TRUE;
	  _gdbm_fatal (dbf, gdbm_db_strerror (dbf));
	  return -1;
	}
      /* Validate the bucket */
      bucket = dbf->bucket_cache[lru].ca_bucket;
      if (!(bucket->count >= 0
	    && bucket->count <= dbf->header->bucket_elems
	    && bucket->bucket_bits >= 0
	    && bucket->bucket_bits <= dbf->header->dir_bits))
	{
	  GDBM_SET_ERRNO (dbf, GDBM_BAD_BUCKET, TRUE);
	  return -1;
	}
      /* Validate bucket_avail table */
      if (gdbm_bucket_avail_table_validate (dbf, bucket))
	return -1;

      /* Finally, store it in cache */
      dbf->last_read = lru;
      dbf->bucket_cache[lru].ca_adr = bucket_adr;
      dbf->bucket = dbf->bucket_cache[lru].ca_bucket;
      dbf->cache_entry = &dbf->bucket_cache[lru];
      dbf->cache_entry->ca_data.elem_loc = -1;
      dbf->cache_entry->ca_changed = FALSE;
    }
  return 0;
}

int
_gdbm_read_bucket_at (GDBM_FILE dbf, off_t off, hash_bucket *bucket,
		      size_t size)
{
  off_t file_pos;
  int i;

  if (dbf->cache_entry && dbf->cache_entry->ca_adr == off)
    {
      memcpy (bucket, dbf->bucket, size);
      return 0;
    }

  /* Look in the cache. */
  for (i = 0; i < dbf->cache_size; i++)
    {
      if (dbf->bucket_cache[i].ca_adr == off)
	{
	  memcpy (bucket, dbf->bucket_cache[i].ca_bucket, size);
	  return 0;
	}
    }

  /* Read the bucket. */
  file_pos = gdbm_file_seek (dbf, off, SEEK_SET);
  if (file_pos != off)
    {
      GDBM_SET_ERRNO (dbf, GDBM_FILE_SEEK_ERROR, TRUE);
      return -1;
    }
  if (_gdbm_full_read (dbf, bucket, size))
    {
      GDBM_DEBUG (GDBM_DEBUG_ERR,
		  "%s: error reading bucket: %s",
		  dbf->name, gdbm_db_strerror (dbf));
      return -1;
    }
  return 0;
}

/* 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.  */
int
_gdbm_split_bucket (GDBM_FILE 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;
  off_t        adr_0;		/* File address of the new bucket 0. */
  off_t        adr_1;		/* File address of the new bucket 1. */
  avail_elem   old_bucket;	/* Avail Struct for the old bucket. */

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

  off_t       *new_dir;		/* Pointer to the new directory. */
  off_t        dir_adr; 	/* Address of the new directory. */
  int          dir_size;	/* Size of the new directory. */
  off_t        old_adr[GDBM_HASH_BITS];  /* Address of the old directories. */
  int          old_size[GDBM_HASH_BITS]; /* 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. */
  
  /* No directories are yet old. */
  old_count = 0;

  if (dbf->bucket_cache == NULL)
    {
      if (_gdbm_init_cache (dbf, DEFAULT_CACHESIZE) == -1)
	{
	  _gdbm_fatal (dbf, _("couldn't init cache"));
	  return -1;
	}
    }

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

      /* Double the directory size if necessary. */
      if (dbf->header->dir_bits == dbf->bucket->bucket_bits)
	{
	  if (dbf->header->dir_size >= GDBM_MAX_DIR_HALF)
	    {
	      GDBM_SET_ERRNO (dbf, GDBM_DIR_OVERFLOW, TRUE);
	      _gdbm_fatal (dbf, _("directory overflow"));
	      return -1;
	    }
	  dir_size = dbf->header->dir_size * 2;
	  dir_adr  = _gdbm_alloc (dbf, dir_size);
	  if (dir_adr == 0)
	    return -1;
	  new_dir = malloc (dir_size);
	  if (new_dir == NULL)
	    {
	      GDBM_SET_ERRNO (dbf, GDBM_MALLOC_ERROR, TRUE);
	      _gdbm_fatal (dbf, _("malloc error"));
	      return -1;
	    }

	  for (index = 0; index < GDBM_DIR_COUNT (dbf); 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 >> (GDBM_HASH_BITS - 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++;
	}
      
      /* Allocate avail space for the bucket[1]. */
      bucket[1]->bucket_avail[0].av_adr
	= _gdbm_alloc (dbf, dbf->header->block_size);
      if (bucket[1]->bucket_avail[0].av_adr == 0)
	return -1;
      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, 
                             dbf->coalesce_blocks);
	  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 = _gdbm_bucket_dir (dbf, next_insert);
      
      /* 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, 
                             dbf->coalesce_blocks);
	}
      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, 
                             dbf->coalesce_blocks);
	}
      
    }

  /* Get rid of old directories. */
  for (index = 0; index < old_count; index++)
    if (_gdbm_free (dbf, old_adr[index], old_size[index]))
      return -1;

  return 0;
}


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

int
_gdbm_write_bucket (GDBM_FILE dbf, cache_elem *ca_entry)
{
  int rc;
  off_t file_pos;	/* The return value for lseek. */

  file_pos = gdbm_file_seek (dbf, ca_entry->ca_adr, SEEK_SET);
  if (file_pos != ca_entry->ca_adr)
    {
      GDBM_SET_ERRNO (dbf, GDBM_FILE_SEEK_ERROR, TRUE);
      _gdbm_fatal (dbf, _("lseek error"));
      return -1;
    }
  rc = _gdbm_full_write (dbf, ca_entry->ca_bucket, dbf->header->bucket_size);
  if (rc)
    {
      GDBM_DEBUG (GDBM_DEBUG_STORE|GDBM_DEBUG_ERR,
		  "%s: error writing bucket: %s",
		  dbf->name, gdbm_db_strerror (dbf));	  
      _gdbm_fatal (dbf, gdbm_strerror (rc));
      return -1;
    }

  ca_entry->ca_changed = FALSE;
  ca_entry->ca_data.hash_val = -1;
  ca_entry->ca_data.elem_loc = -1;
  return 0;
}

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