/* MDB Tools - A library for reading MS Access database file

 * Copyright (C) 2000 Brian Bruns

 *

 * 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, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

 */

#include "mdbtools.h"

static gint32

mdb_map_find_next0(MdbHandle *mdb, unsigned char *map, unsigned int map_sz, guint32 start_pg)

{

  guint32 pgnum, i, usage_bitlen;

  unsigned char *usage_bitmap;

  if (map_sz < 5) {

    return 0;

  }

  pgnum = mdb_get_int32(map, 1);

  usage_bitmap = map + 5;

  usage_bitlen = (map_sz - 5) * 8;

  i = (start_pg >= pgnum) ? start_pg-pgnum+1 : 0;

  for (; i<usage_bitlen; i++) {

    if (usage_bitmap[i/8] & (1 << (i%8))) {

      return pgnum + i;

    }

  }

  /* didn't find anything */

  return 0;

}

static gint32

mdb_map_find_next1(MdbHandle *mdb, unsigned char *map, unsigned int map_sz, guint32 start_pg)

{

  guint32 map_ind, max_map_pgs, offset, usage_bitlen;

  /*

  * start_pg will tell us where to (re)start the scan

  * for the next data page.  each usage_map entry points to a

  * 0x05 page which bitmaps (mdb->fmt->pg_size - 4) * 8 pages.

  *

  * map_ind gives us the starting usage_map entry

  * offset gives us a page offset into the bitmap

  */

  usage_bitlen = (mdb->fmt->pg_size - 4) * 8;

  max_map_pgs = (map_sz - 1) / 4;

  map_ind = (start_pg + 1) / usage_bitlen;

  offset = (start_pg + 1) % usage_bitlen;

  for (; map_ind<max_map_pgs; map_ind++) {

    unsigned char *usage_bitmap;

    guint32 i, map_pg;

    if (!(map_pg = mdb_get_int32(map, (map_ind*4)+1))) {

      continue;

    }

    if(mdb_read_alt_pg(mdb, map_pg) != mdb->fmt->pg_size) {

      fprintf(stderr, "Oops! didn't get a full page at %d\n", map_pg);

      return -1;

    } 

    usage_bitmap = mdb->alt_pg_buf + 4;

    for (i=offset; i<usage_bitlen; i++) {

      if (usage_bitmap[i/8] & (1 << (i%8))) {

        return map_ind*usage_bitlen + i;

      }

    }

    offset = 0;

  }

  /* didn't find anything */

  return 0;

}

/* returns 0 on EOF */

/* returns -1 on error (unsupported map type) */

gint32

mdb_map_find_next(MdbHandle *mdb, unsigned char *map, unsigned int map_sz, guint32 start_pg)

{

  if (map[0] == 0) {

    return mdb_map_find_next0(mdb, map, map_sz, start_pg);

  } else if (map[0] == 1) {

    return mdb_map_find_next1(mdb, map, map_sz, start_pg);

  }

  fprintf(stderr, "Warning: unrecognized usage map type: %d\n", map[0]);

  return -1;

}

gint32

mdb_alloc_page(MdbTableDef *table)

{

  printf("Allocating new page\n");

  return 0;

}

gint32

mdb_map_find_next_freepage(MdbTableDef *table, int row_size)

{

  MdbCatalogEntry *entry = table->entry;

  MdbHandle *mdb = entry->mdb;

  gint32 pgnum;

  guint32 cur_pg = 0;

  int free_space;

  do {

    pgnum = mdb_map_find_next(mdb, 

        table->free_usage_map, 

        table->freemap_sz, cur_pg);

    //printf("looking at page %d\n", pgnum);

    if (!pgnum) {

      /* allocate new page */

      return mdb_alloc_page(table);

    } else if (pgnum==-1) {

      fprintf(stderr, "Error: mdb_map_find_next_freepage error while reading maps.\n");

      return -1;

    }

    cur_pg = pgnum;

    mdb_read_pg(mdb, pgnum);

    free_space = mdb_pg_get_freespace(mdb);

  } while (free_space < row_size);

  //printf("page %d has %d bytes left\n", pgnum, free_space);

  return pgnum;

}