db/btree/btree.h

   1 /*-
   2  * Copyright (c) 1991, 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Mike Olson.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  *      @(#)btree.h     8.11 (Berkeley) 8/17/94
  37  */
  38
  39 /* Macros to set/clear/test flags. */
  40 #define F_SET(p, f)     (p)->flags |= (f)
  41 #define F_CLR(p, f)     (p)->flags &= ~(f)
  42 #define F_ISSET(p, f)   ((p)->flags & (f))
  43
  44 #include <mpool.h>
  45
  46 #ifdef _LIBC
  47 /* In the GNU C library we must not pollute the namespace because libdb is
  48    needed by libnss_db.  */
  49 #define mpool_open __mpool_open
  50 #define mpool_filter __mpool_filter
  51 #define mpool_new __mpool_new
  52 #define mpool_get __mpool_get
  53 #define mpool_put __mpool_put
  54 #define mpool_sync __mpool_sync
  55 #define mpool_close __mpool_close
  56 #endif
  57
  58 #define DEFMINKEYPAGE   (2)             /* Minimum keys per page */
  59 #define MINCACHE        (5)             /* Minimum cached pages */
  60 #define MINPSIZE        (512)           /* Minimum page size */
  61
  62 /*
  63  * Page 0 of a btree file contains a copy of the meta-data.  This page is also
  64  * used as an out-of-band page, i.e. page pointers that point to nowhere point
  65  * to page 0.  Page 1 is the root of the btree.
  66  */
  67 #define P_INVALID        0              /* Invalid tree page number. */
  68 #define P_META           0              /* Tree metadata page number. */
  69 #define P_ROOT           1              /* Tree root page number. */
  70
  71 /*
  72  * There are five page layouts in the btree: btree internal pages (BINTERNAL),
  73  * btree leaf pages (BLEAF), recno internal pages (RINTERNAL), recno leaf pages
  74  * (RLEAF) and overflow pages.  All five page types have a page header (PAGE).
  75  * This implementation requires that values within structures NOT be padded.
  76  * (ANSI C permits random padding.)  If your compiler pads randomly you'll have
  77  * to do some work to get this package to run.
  78  */
  79 typedef struct _page {
  80         pgno_t  pgno;                   /* this page's page number */
  81         pgno_t  prevpg;                 /* left sibling */
  82         pgno_t  nextpg;                 /* right sibling */
  83
  84 #define P_BINTERNAL     0x01            /* btree internal page */
  85 #define P_BLEAF         0x02            /* leaf page */
  86 #define P_OVERFLOW      0x04            /* overflow page */
  87 #define P_RINTERNAL     0x08            /* recno internal page */
  88 #define P_RLEAF         0x10            /* leaf page */
  89 #define P_TYPE          0x1f            /* type mask */
  90 #define P_PRESERVE      0x20            /* never delete this chain of pages */
  91         u_int32_t flags;
  92
  93         indx_t  lower;                  /* lower bound of free space on page */
  94         indx_t  upper;                  /* upper bound of free space on page */
  95         indx_t  linp[1];                /* indx_t-aligned VAR. LENGTH DATA */
  96 } PAGE;
  97
  98 /* First and next index. */
  99 #define BTDATAOFF                                                       \
 100         (sizeof(pgno_t) + sizeof(pgno_t) + sizeof(pgno_t) +             \
 101             sizeof(u_int32_t) + sizeof(indx_t) + sizeof(indx_t))
 102 #define NEXTINDEX(p)    (((p)->lower - BTDATAOFF) / sizeof(indx_t))
 103
 104 /*
 105  * For pages other than overflow pages, there is an array of offsets into the
 106  * rest of the page immediately following the page header.  Each offset is to
 107  * an item which is unique to the type of page.  The h_lower offset is just
 108  * past the last filled-in index.  The h_upper offset is the first item on the
 109  * page.  Offsets are from the beginning of the page.
 110  *
 111  * If an item is too big to store on a single page, a flag is set and the item
 112  * is a { page, size } pair such that the page is the first page of an overflow
 113  * chain with size bytes of item.  Overflow pages are simply bytes without any
 114  * external structure.
 115  *
 116  * The page number and size fields in the items are pgno_t-aligned so they can
 117  * be manipulated without copying.  (This presumes that 32 bit items can be
 118  * manipulated on this system.)
 119  */
 120 #define LALIGN(n)       (((n) + sizeof(pgno_t) - 1) & ~(sizeof(pgno_t) - 1))
 121 #define NOVFLSIZE       (sizeof(pgno_t) + sizeof(u_int32_t))
 122
 123 /*
 124  * For the btree internal pages, the item is a key.  BINTERNALs are {key, pgno}
 125  * pairs, such that the key compares less than or equal to all of the records
 126  * on that page.  For a tree without duplicate keys, an internal page with two
 127  * consecutive keys, a and b, will have all records greater than or equal to a
 128  * and less than b stored on the page associated with a.  Duplicate keys are
 129  * somewhat special and can cause duplicate internal and leaf page records and
 130  * some minor modifications of the above rule.
 131  */
 132 typedef struct _binternal {
 133         u_int32_t ksize;                /* key size */
 134         pgno_t  pgno;                   /* page number stored on */
 135 #define P_BIGDATA       0x01            /* overflow data */
 136 #define P_BIGKEY        0x02            /* overflow key */
 137         u_char  flags;
 138         char    bytes[1];               /* data */
 139 } BINTERNAL;
 140
 141 /* Get the page's BINTERNAL structure at index indx. */
 142 #define GETBINTERNAL(pg, indx)                                          \
 143         ((BINTERNAL *)((char *)(pg) + (pg)->linp[indx]))
 144
 145 /* Get the number of bytes in the entry. */
 146 #define NBINTERNAL(len)                                                 \
 147         LALIGN(sizeof(u_int32_t) + sizeof(pgno_t) + sizeof(u_char) + (len))
 148
 149 /* Copy a BINTERNAL entry to the page. */
 150 #define WR_BINTERNAL(p, size, pgno, flags) {                            \
 151         *(u_int32_t *)p = size;                                         \
 152         p += sizeof(u_int32_t);                                         \
 153         *(pgno_t *)p = pgno;                                            \
 154         p += sizeof(pgno_t);                                            \
 155         *(u_char *)p = flags;                                           \
 156         p += sizeof(u_char);                                            \
 157 }
 158
 159 /*
 160  * For the recno internal pages, the item is a page number with the number of
 161  * keys found on that page and below.
 162  */
 163 typedef struct _rinternal {
 164         recno_t nrecs;                  /* number of records */
 165         pgno_t  pgno;                   /* page number stored below */
 166 } RINTERNAL;
 167
 168 /* Get the page's RINTERNAL structure at index indx. */
 169 #define GETRINTERNAL(pg, indx)                                          \
 170         ((RINTERNAL *)((char *)(pg) + (pg)->linp[indx]))
 171
 172 /* Get the number of bytes in the entry. */
 173 #define NRINTERNAL                                                      \
 174         LALIGN(sizeof(recno_t) + sizeof(pgno_t))
 175
 176 /* Copy a RINTERNAL entry to the page. */
 177 #define WR_RINTERNAL(p, nrecs, pgno) {                                  \
 178         *(recno_t *)p = nrecs;                                          \
 179         p += sizeof(recno_t);                                           \
 180         *(pgno_t *)p = pgno;                                            \
 181 }
 182
 183 /* For the btree leaf pages, the item is a key and data pair. */
 184 typedef struct _bleaf {
 185         u_int32_t       ksize;          /* size of key */
 186         u_int32_t       dsize;          /* size of data */
 187         u_char  flags;                  /* P_BIGDATA, P_BIGKEY */
 188         char    bytes[1];               /* data */
 189 } BLEAF;
 190
 191 /* Get the page's BLEAF structure at index indx. */
 192 #define GETBLEAF(pg, indx)                                              \
 193         ((BLEAF *)((char *)(pg) + (pg)->linp[indx]))
 194
 195 /* Get the number of bytes in the entry. */
 196 #define NBLEAF(p)       NBLEAFDBT((p)->ksize, (p)->dsize)
 197
 198 /* Get the number of bytes in the user's key/data pair. */
 199 #define NBLEAFDBT(ksize, dsize)                                         \
 200         LALIGN(sizeof(u_int32_t) + sizeof(u_int32_t) + sizeof(u_char) + \
 201             (ksize) + (dsize))
 202
 203 /* Copy a BLEAF entry to the page. */
 204 #define WR_BLEAF(p, key, data, flags) {                                 \
 205         *(u_int32_t *)p = key->size;                                    \
 206         p += sizeof(u_int32_t);                                         \
 207         *(u_int32_t *)p = data->size;                                   \
 208         p += sizeof(u_int32_t);                                         \
 209         *(u_char *)p = flags;                                           \
 210         p += sizeof(u_char);                                            \
 211         memmove(p, key->data, key->size);                               \
 212         p += key->size;                                                 \
 213         memmove(p, data->data, data->size);                             \
 214 }
 215
 216 /* For the recno leaf pages, the item is a data entry. */
 217 typedef struct _rleaf {
 218         u_int32_t       dsize;          /* size of data */
 219         u_char  flags;                  /* P_BIGDATA */
 220         char    bytes[1];
 221 } RLEAF;
 222
 223 /* Get the page's RLEAF structure at index indx. */
 224 #define GETRLEAF(pg, indx)                                              \
 225         ((RLEAF *)((char *)(pg) + (pg)->linp[indx]))
 226
 227 /* Get the number of bytes in the entry. */
 228 #define NRLEAF(p)       NRLEAFDBT((p)->dsize)
 229
 230 /* Get the number of bytes from the user's data. */
 231 #define NRLEAFDBT(dsize)                                                \
 232         LALIGN(sizeof(u_int32_t) + sizeof(u_char) + (dsize))
 233
 234 /* Copy a RLEAF entry to the page. */
 235 #define WR_RLEAF(p, data, flags) {                                      \
 236         *(u_int32_t *)p = data->size;                                   \
 237         p += sizeof(u_int32_t);                                         \
 238         *(u_char *)p = flags;                                           \
 239         p += sizeof(u_char);                                            \
 240         memmove(p, data->data, data->size);                             \
 241 }
 242
 243 /*
 244  * A record in the tree is either a pointer to a page and an index in the page
 245  * or a page number and an index.  These structures are used as a cursor, stack
 246  * entry and search returns as well as to pass records to other routines.
 247  *
 248  * One comment about searches.  Internal page searches must find the largest
 249  * record less than key in the tree so that descents work.  Leaf page searches
 250  * must find the smallest record greater than key so that the returned index
 251  * is the record's correct position for insertion.
 252  */
 253 typedef struct _epgno {
 254         pgno_t  pgno;                   /* the page number */
 255         indx_t  index;                  /* the index on the page */
 256 } EPGNO;
 257
 258 typedef struct _epg {
 259         PAGE    *page;                  /* the (pinned) page */
 260         indx_t   index;                 /* the index on the page */
 261 } EPG;
 262
 263 /*
 264  * About cursors.  The cursor (and the page that contained the key/data pair
 265  * that it referenced) can be deleted, which makes things a bit tricky.  If
 266  * there are no duplicates of the cursor key in the tree (i.e. B_NODUPS is set
 267  * or there simply aren't any duplicates of the key) we copy the key that it
 268  * referenced when it's deleted, and reacquire a new cursor key if the cursor
 269  * is used again.  If there are duplicates keys, we move to the next/previous
 270  * key, and set a flag so that we know what happened.  NOTE: if duplicate (to
 271  * the cursor) keys are added to the tree during this process, it is undefined
 272  * if they will be returned or not in a cursor scan.
 273  *
 274  * The flags determine the possible states of the cursor:
 275  *
 276  * CURS_INIT    The cursor references *something*.
 277  * CURS_ACQUIRE The cursor was deleted, and a key has been saved so that
 278  *              we can reacquire the right position in the tree.
 279  * CURS_AFTER, CURS_BEFORE
 280  *              The cursor was deleted, and now references a key/data pair
 281  *              that has not yet been returned, either before or after the
 282  *              deleted key/data pair.
 283  * XXX
 284  * This structure is broken out so that we can eventually offer multiple
 285  * cursors as part of the DB interface.
 286  */
 287 typedef struct _cursor {
 288         EPGNO    pg;                    /* B: Saved tree reference. */
 289         DBT      key;                   /* B: Saved key, or key.data == NULL. */
 290         recno_t  rcursor;               /* R: recno cursor (1-based) */
 291
 292 #define CURS_ACQUIRE    0x01            /*  B: Cursor needs to be reacquired. */
 293 #define CURS_AFTER      0x02            /*  B: Unreturned cursor after key. */
 294 #define CURS_BEFORE     0x04            /*  B: Unreturned cursor before key. */
 295 #define CURS_INIT       0x08            /* RB: Cursor initialized. */
 296         u_int8_t flags;
 297 } CURSOR;
 298
 299 /*
 300  * The metadata of the tree.  The nrecs field is used only by the RECNO code.
 301  * This is because the btree doesn't really need it and it requires that every
 302  * put or delete call modify the metadata.
 303  */
 304 typedef struct _btmeta {
 305         u_int32_t       magic;          /* magic number */
 306         u_int32_t       version;        /* version */
 307         u_int32_t       psize;          /* page size */
 308         u_int32_t       free;           /* page number of first free page */
 309         u_int32_t       nrecs;          /* R: number of records */
 310
 311 #define SAVEMETA        (B_NODUPS | R_RECNO)
 312         u_int32_t       flags;          /* bt_flags & SAVEMETA */
 313 } BTMETA;
 314
 315 /* The in-memory btree/recno data structure. */
 316 typedef struct _btree {
 317         MPOOL    *bt_mp;                /* memory pool cookie */
 318
 319         DB       *bt_dbp;               /* pointer to enclosing DB */
 320
 321         EPG       bt_cur;               /* current (pinned) page */
 322         PAGE     *bt_pinned;            /* page pinned across calls */
 323
 324         CURSOR    bt_cursor;            /* cursor */
 325
 326 #define BT_PUSH(t, p, i) {                                              \
 327         t->bt_sp->pgno = p;                                             \
 328         t->bt_sp->index = i;                                            \
 329         ++t->bt_sp;                                                     \
 330 }
 331 #define BT_POP(t)       (t->bt_sp == t->bt_stack ? NULL : --t->bt_sp)
 332 #define BT_CLR(t)       (t->bt_sp = t->bt_stack)
 333         EPGNO     bt_stack[50];         /* stack of parent pages */
 334         EPGNO    *bt_sp;                /* current stack pointer */
 335
 336         DBT       bt_rkey;              /* returned key */
 337         DBT       bt_rdata;             /* returned data */
 338
 339         int       bt_fd;                /* tree file descriptor */
 340
 341         pgno_t    bt_free;              /* next free page */
 342         u_int32_t bt_psize;             /* page size */
 343         indx_t    bt_ovflsize;          /* cut-off for key/data overflow */
 344         int       bt_lorder;            /* byte order */
 345                                         /* sorted order */
 346         enum { NOT, BACK, FORWARD } bt_order;
 347         EPGNO     bt_last;              /* last insert */
 348
 349                                         /* B: key comparison function */
 350         int     (*bt_cmp) __P((const DBT *, const DBT *));
 351                                         /* B: prefix comparison function */
 352         size_t  (*bt_pfx) __P((const DBT *, const DBT *));
 353                                         /* R: recno input function */
 354         int     (*bt_irec) __P((struct _btree *, recno_t));
 355
 356         FILE     *bt_rfp;               /* R: record FILE pointer */
 357         int       bt_rfd;               /* R: record file descriptor */
 358
 359         caddr_t   bt_cmap;              /* R: current point in mapped space */
 360         caddr_t   bt_smap;              /* R: start of mapped space */
 361         caddr_t   bt_emap;              /* R: end of mapped space */
 362         size_t    bt_msize;             /* R: size of mapped region. */
 363
 364         recno_t   bt_nrecs;             /* R: number of records */
 365         size_t    bt_reclen;            /* R: fixed record length */
 366         u_char    bt_bval;              /* R: delimiting byte/pad character */
 367
 368 /*
 369  * NB:
 370  * B_NODUPS and R_RECNO are stored on disk, and may not be changed.
 371  */
 372 #define B_INMEM         0x00001         /* in-memory tree */
 373 #define B_METADIRTY     0x00002         /* need to write metadata */
 374 #define B_MODIFIED      0x00004         /* tree modified */
 375 #define B_NEEDSWAP      0x00008         /* if byte order requires swapping */
 376 #define B_RDONLY        0x00010         /* read-only tree */
 377
 378 #define B_NODUPS        0x00020         /* no duplicate keys permitted */
 379 #define R_RECNO         0x00080         /* record oriented tree */
 380
 381 #define R_CLOSEFP       0x00040         /* opened a file pointer */
 382 #define R_EOF           0x00100         /* end of input file reached. */
 383 #define R_FIXLEN        0x00200         /* fixed length records */
 384 #define R_MEMMAPPED     0x00400         /* memory mapped file. */
 385 #define R_INMEM         0x00800         /* in-memory file */
 386 #define R_MODIFIED      0x01000         /* modified file */
 387 #define R_RDONLY        0x02000         /* read-only file */
 388
 389 #define B_DB_LOCK       0x04000         /* DB_LOCK specified. */
 390 #define B_DB_SHMEM      0x08000         /* DB_SHMEM specified. */
 391 #define B_DB_TXN        0x10000         /* DB_TXN specified. */
 392         u_int32_t flags;
 393 } BTREE;
 394
 395 #include "extern.h"