1 /* MDB Tools - A library for reading MS Access database file
2 * Copyright (C) 2000 Brian Bruns
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Library General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Library General Public License for more details.
13 *
14 * You should have received a copy of the GNU Library General Public
15 * License along with this library; if not, write to the
16 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
17 * Boston, MA 02110-1301, USA.
18 */
19
20 #include "mdbtools.h"
21
22 #ifdef DMALLOC
23 #include "dmalloc.h"
24 #endif
25
26 static guint32
mdb_map_find_next0(MdbHandle * mdb,unsigned char * map,unsigned int map_sz,guint32 start_pg)27 mdb_map_find_next0(MdbHandle *mdb, unsigned char *map, unsigned int map_sz, guint32 start_pg)
28 {
29 guint32 pgnum, i, usage_bitlen;
30 unsigned char *usage_bitmap;
31
32 pgnum = mdb_get_int32(map, 1);
33 usage_bitmap = map + 5;
34 usage_bitlen = (map_sz - 5) * 8;
35
36 i = (start_pg >= pgnum) ? start_pg-pgnum+1 : 0;
37 for (; i<usage_bitlen; i++) {
38 if (usage_bitmap[i/8] & (1 << (i%8))) {
39 return pgnum + i;
40 }
41 }
42 /* didn't find anything */
43 return 0;
44 }
45 static int
mdb_map_find_next1(MdbHandle * mdb,unsigned char * map,unsigned int map_sz,guint32 start_pg)46 mdb_map_find_next1(MdbHandle *mdb, unsigned char *map, unsigned int map_sz, guint32 start_pg)
47 {
48 guint32 map_ind, max_map_pgs, offset, usage_bitlen;
49
50 /*
51 * start_pg will tell us where to (re)start the scan
52 * for the next data page. each usage_map entry points to a
53 * 0x05 page which bitmaps (mdb->fmt->pg_size - 4) * 8 pages.
54 *
55 * map_ind gives us the starting usage_map entry
56 * offset gives us a page offset into the bitmap
57 */
58 usage_bitlen = (mdb->fmt->pg_size - 4) * 8;
59 max_map_pgs = (map_sz - 1) / 4;
60 map_ind = (start_pg + 1) / usage_bitlen;
61 offset = (start_pg + 1) % usage_bitlen;
62
63 for (; map_ind<max_map_pgs; map_ind++) {
64 unsigned char *usage_bitmap;
65 guint32 i, map_pg;
66
67 if (!(map_pg = mdb_get_int32(map, (map_ind*4)+1))) {
68 continue;
69 }
70 if(mdb_read_alt_pg(mdb, map_pg) != mdb->fmt->pg_size) {
71 fprintf(stderr, "Oops! didn't get a full page at %d\n", map_pg);
72 exit(1);
73 }
74
75 usage_bitmap = mdb->alt_pg_buf + 4;
76 for (i=offset; i<usage_bitlen; i++) {
77 if (usage_bitmap[i/8] & (1 << (i%8))) {
78 return map_ind*usage_bitlen + i;
79 }
80 }
81 offset = 0;
82 }
83 /* didn't find anything */
84 return 0;
85 }
86 guint32
mdb_map_find_next(MdbHandle * mdb,unsigned char * map,unsigned int map_sz,guint32 start_pg)87 mdb_map_find_next(MdbHandle *mdb, unsigned char *map, unsigned int map_sz, guint32 start_pg)
88 {
89 if (map[0] == 0) {
90 return mdb_map_find_next0(mdb, map, map_sz, start_pg);
91 } else if (map[0] == 1) {
92 return mdb_map_find_next1(mdb, map, map_sz, start_pg);
93 }
94
95 fprintf(stderr, "Warning: unrecognized usage map type: %d\n", map[0]);
96 return -1;
97 }
98 guint32
mdb_alloc_page(MdbTableDef * table)99 mdb_alloc_page(MdbTableDef *table)
100 {
101 printf("Allocating new page\n");
102 return 0;
103 }
104 guint32
mdb_map_find_next_freepage(MdbTableDef * table,int row_size)105 mdb_map_find_next_freepage(MdbTableDef *table, int row_size)
106 {
107 MdbCatalogEntry *entry = table->entry;
108 MdbHandle *mdb = entry->mdb;
109 guint32 pgnum;
110 guint32 cur_pg = 0;
111 int free_space;
112
113 do {
114 pgnum = mdb_map_find_next(mdb,
115 table->free_usage_map,
116 table->freemap_sz, cur_pg);
117 //printf("looking at page %d\n", pgnum);
118 if (!pgnum) {
119 /* allocate new page */
120 pgnum = mdb_alloc_page(table);
121 return pgnum;
122 }
123 cur_pg = pgnum;
124
125 mdb_read_pg(mdb, pgnum);
126 free_space = mdb_pg_get_freespace(mdb);
127
128 } while (free_space < row_size);
129
130 //printf("page %d has %d bytes left\n", pgnum, free_space);
131
132 return pgnum;
133 }
134