btree.h

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/*-
 * Copyright (c) 1991, 1993, 1994
 * The Regents of the University of California. All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Mike Olson.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 * must display the following acknowledgement:
 * This product includes software developed by the University of
 * California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * @(#)btree.h 8.11 (Berkeley) 8/17/94
 */

/* Macros to set/clear/test flags. */
#define F_SET(p, f) (p)->flags |= (f)
#define F_CLR(p, f) (p)->flags &= ~(f)
#define F_ISSET(p, f) ((p)->flags & (f))

#include <mpool.h>

#define mpool_open __mpool_open
#define mpool_filter __mpool_filter
#define mpool_new __mpool_new
#define mpool_get __mpool_get
#define mpool_put __mpool_put
#define mpool_sync __mpool_sync
#define mpool_close __mpool_close

#define DEFMINKEYPAGE (2) /* Minimum keys per page */
#define MINCACHE (5) /* Minimum cached pages */
#define MINPSIZE (512) /* Minimum page size */

/*
 * Page 0 of a btree file contains a copy of the meta-data. This page is also
 * used as an out-of-band page, i.e. page pointers that point to nowhere point
 * to page 0. Page 1 is the root of the btree.
 */
#define P_INVALID 0 /* Invalid tree page number. */
#define P_META 0 /* Tree metadata page number. */
#define P_ROOT 1 /* Tree root page number. */

/*
 * There are five page layouts in the btree: btree internal pages (BINTERNAL),
 * btree leaf pages (BLEAF), recno internal pages (RINTERNAL), recno leaf pages
 * (RLEAF) and overflow pages. All five page types have a page header (PAGE).
 * This implementation requires that values within structures NOT be padded.
 * (ANSI C permits random padding.) If your compiler pads randomly you'll have
 * to do some work to get this package to run.
 */
typedef struct _page {
 pgno_t pgno; /* this page's page number */
 pgno_t prevpg; /* left sibling */
 pgno_t nextpg; /* right sibling */

#define P_BINTERNAL 0x01 /* btree internal page */
#define P_BLEAF 0x02 /* leaf page */
#define P_OVERFLOW 0x04 /* overflow page */
#define P_RINTERNAL 0x08 /* recno internal page */
#define P_RLEAF 0x10 /* leaf page */
#define P_TYPE 0x1f /* type mask */
#define P_PRESERVE 0x20 /* never delete this chain of pages */
 u_int32_t flags;

 indx_t lower; /* lower bound of free space on page */
 indx_t upper; /* upper bound of free space on page */
 indx_t linp[1]; /* indx_t-aligned VAR. LENGTH DATA */
} PAGE;

/* First and next index. */
#define BTDATAOFF \
 (sizeof(pgno_t) + sizeof(pgno_t) + sizeof(pgno_t) + \
 sizeof(u_int32_t) + sizeof(indx_t) + sizeof(indx_t))
#define NEXTINDEX(p) (((p)->lower - BTDATAOFF) / sizeof(indx_t))

/*
 * For pages other than overflow pages, there is an array of offsets into the
 * rest of the page immediately following the page header. Each offset is to
 * an item which is unique to the type of page. The h_lower offset is just
 * past the last filled-in index. The h_upper offset is the first item on the
 * page. Offsets are from the beginning of the page.
 *
 * If an item is too big to store on a single page, a flag is set and the item
 * is a { page, size } pair such that the page is the first page of an overflow
 * chain with size bytes of item. Overflow pages are simply bytes without any
 * external structure.
 *
 * The page number and size fields in the items are pgno_t-aligned so they can
 * be manipulated without copying. (This presumes that 32 bit items can be
 * manipulated on this system.)
 */
#define LALIGN(n) (((n) + sizeof(pgno_t) - 1) & ~(sizeof(pgno_t) - 1))
#define NOVFLSIZE (sizeof(pgno_t) + sizeof(u_int32_t))

/*
 * For the btree internal pages, the item is a key. BINTERNALs are {key, pgno}
 * pairs, such that the key compares less than or equal to all of the records
 * on that page. For a tree without duplicate keys, an internal page with two
 * consecutive keys, a and b, will have all records greater than or equal to a
 * and less than b stored on the page associated with a. Duplicate keys are
 * somewhat special and can cause duplicate internal and leaf page records and
 * some minor modifications of the above rule.
 */
typedef struct _binternal {
 u_int32_t ksize; /* key size */
 pgno_t pgno; /* page number stored on */
#define P_BIGDATA 0x01 /* overflow data */
#define P_BIGKEY 0x02 /* overflow key */
 u_char flags;
 char bytes[1]; /* data */
} BINTERNAL;

/* Get the page's BINTERNAL structure at index indx. */
#define GETBINTERNAL(pg, indx) \
 ((BINTERNAL *)((char *)(pg) + (pg)->linp[indx]))

/* Get the number of bytes in the entry. */
#define NBINTERNAL(len) \
 LALIGN(sizeof(u_int32_t) + sizeof(pgno_t) + sizeof(u_char) + (len))

/* Copy a BINTERNAL entry to the page. */
#define WR_BINTERNAL(p, size, pgno, flags) { \
 *(u_int32_t *)p = size; \
 p += sizeof(u_int32_t); \
 *(pgno_t *)p = pgno; \
 p += sizeof(pgno_t); \
 *(u_char *)p = flags; \
 p += sizeof(u_char); \
}

/*
 * For the recno internal pages, the item is a page number with the number of
 * keys found on that page and below.
 */
typedef struct _rinternal {
 recno_t nrecs; /* number of records */
 pgno_t pgno; /* page number stored below */
} RINTERNAL;

/* Get the page's RINTERNAL structure at index indx. */
#define GETRINTERNAL(pg, indx) \
 ((RINTERNAL *)((char *)(pg) + (pg)->linp[indx]))

/* Get the number of bytes in the entry. */
#define NRINTERNAL \
 LALIGN(sizeof(recno_t) + sizeof(pgno_t))

/* Copy a RINTERNAL entry to the page. */
#define WR_RINTERNAL(p, nrecs, pgno) { \
 *(recno_t *)p = nrecs; \
 p += sizeof(recno_t); \
 *(pgno_t *)p = pgno; \
}

/* For the btree leaf pages, the item is a key and data pair. */
typedef struct _bleaf {
 u_int32_t ksize; /* size of key */
 u_int32_t dsize; /* size of data */
 u_char flags; /* P_BIGDATA, P_BIGKEY */
 char bytes[1]; /* data */
} BLEAF;

/* Get the page's BLEAF structure at index indx. */
#define GETBLEAF(pg, indx) \
 ((BLEAF *)((char *)(pg) + (pg)->linp[indx]))

/* Get the number of bytes in the entry. */
#define NBLEAF(p) NBLEAFDBT((p)->ksize, (p)->dsize)

/* Get the number of bytes in the user's key/data pair. */
#define NBLEAFDBT(ksize, dsize) \
 LALIGN(sizeof(u_int32_t) + sizeof(u_int32_t) + sizeof(u_char) + \
 (ksize) + (dsize))

/* Copy a BLEAF entry to the page. */
#define WR_BLEAF(p, key, data, flags) { \
 *(u_int32_t *)p = key->size; \
 p += sizeof(u_int32_t); \
 *(u_int32_t *)p = data->size; \
 p += sizeof(u_int32_t); \
 *(u_char *)p = flags; \
 p += sizeof(u_char); \
 memmove(p, key->data, key->size); \
 p += key->size; \
 memmove(p, data->data, data->size); \
}

/* For the recno leaf pages, the item is a data entry. */
typedef struct _rleaf {
 u_int32_t dsize; /* size of data */
 u_char flags; /* P_BIGDATA */
 char bytes[1];
} RLEAF;

/* Get the page's RLEAF structure at index indx. */
#define GETRLEAF(pg, indx) \
 ((RLEAF *)((char *)(pg) + (pg)->linp[indx]))

/* Get the number of bytes in the entry. */
#define NRLEAF(p) NRLEAFDBT((p)->dsize)

/* Get the number of bytes from the user's data. */
#define NRLEAFDBT(dsize) \
 LALIGN(sizeof(u_int32_t) + sizeof(u_char) + (dsize))

/* Copy a RLEAF entry to the page. */
#define WR_RLEAF(p, data, flags) { \
 *(u_int32_t *)p = data->size; \
 p += sizeof(u_int32_t); \
 *(u_char *)p = flags; \
 p += sizeof(u_char); \
 memmove(p, data->data, data->size); \
}

/*
 * A record in the tree is either a pointer to a page and an index in the page
 * or a page number and an index. These structures are used as a cursor, stack
 * entry and search returns as well as to pass records to other routines.
 *
 * One comment about searches. Internal page searches must find the largest
 * record less than key in the tree so that descents work. Leaf page searches
 * must find the smallest record greater than key so that the returned index
 * is the record's correct position for insertion.
 */
typedef struct _epgno {
 pgno_t pgno; /* the page number */
 indx_t index; /* the index on the page */
} EPGNO;

typedef struct _epg {
 PAGE *page; /* the (pinned) page */
 indx_t index; /* the index on the page */
} EPG;

/*
 * About cursors. The cursor (and the page that contained the key/data pair
 * that it referenced) can be deleted, which makes things a bit tricky. If
 * there are no duplicates of the cursor key in the tree (i.e. B_NODUPS is set
 * or there simply aren't any duplicates of the key) we copy the key that it
 * referenced when it's deleted, and reacquire a new cursor key if the cursor
 * is used again. If there are duplicates keys, we move to the next/previous
 * key, and set a flag so that we know what happened. NOTE: if duplicate (to
 * the cursor) keys are added to the tree during this process, it is undefined
 * if they will be returned or not in a cursor scan.
 *
 * The flags determine the possible states of the cursor:
 *
 * CURS_INIT The cursor references *something*.
 * CURS_ACQUIRE The cursor was deleted, and a key has been saved so that
 * we can reacquire the right position in the tree.
 * CURS_AFTER, CURS_BEFORE
 * The cursor was deleted, and now references a key/data pair
 * that has not yet been returned, either before or after the
 * deleted key/data pair.
 * XXX
 * This structure is broken out so that we can eventually offer multiple
 * cursors as part of the DB interface.
 */
typedef struct _cursor {
 EPGNO pg; /* B: Saved tree reference. */
 DBT key; /* B: Saved key, or key.data == NULL. */
 recno_t rcursor; /* R: recno cursor (1-based) */

#define CURS_ACQUIRE 0x01 /* B: Cursor needs to be reacquired. */
#define CURS_AFTER 0x02 /* B: Unreturned cursor after key. */
#define CURS_BEFORE 0x04 /* B: Unreturned cursor before key. */
#define CURS_INIT 0x08 /* RB: Cursor initialized. */
 u_int8_t flags;
} CURSOR;

/*
 * The metadata of the tree. The nrecs field is used only by the RECNO code.
 * This is because the btree doesn't really need it and it requires that every
 * put or delete call modify the metadata.
 */
typedef struct _btmeta {
 u_int32_t magic; /* magic number */
 u_int32_t version; /* version */
 u_int32_t psize; /* page size */
 u_int32_t free; /* page number of first free page */
 u_int32_t nrecs; /* R: number of records */

#define SAVEMETA (B_NODUPS | R_RECNO)
 u_int32_t flags; /* bt_flags & SAVEMETA */
} BTMETA;

/* The in-memory btree/recno data structure. */
typedef struct _btree {
 MPOOL *bt_mp; /* memory pool cookie */

 DB *bt_dbp; /* pointer to enclosing DB */

 EPG bt_cur; /* current (pinned) page */
 PAGE *bt_pinned; /* page pinned across calls */

 CURSOR bt_cursor; /* cursor */

#define BT_PUSH(t, p, i) { \
 t->bt_sp->pgno = p; \
 t->bt_sp->index = i; \
 ++t->bt_sp; \
}
#define BT_POP(t) (t->bt_sp == t->bt_stack ? NULL : --t->bt_sp)
#define BT_CLR(t) (t->bt_sp = t->bt_stack)
 EPGNO bt_stack[50]; /* stack of parent pages */
 EPGNO *bt_sp; /* current stack pointer */

 DBT bt_rkey; /* returned key */
 DBT bt_rdata; /* returned data */

 int bt_fd; /* tree file descriptor */

 pgno_t bt_free; /* next free page */
 u_int32_t bt_psize; /* page size */
 indx_t bt_ovflsize; /* cut-off for key/data overflow */
 int bt_lorder; /* byte order */
 /* sorted order */
 enum { NOT, BACK, FORWARD } bt_order;
 EPGNO bt_last; /* last insert */

 /* B: key comparison function */
 int (*bt_cmp) __P((const DBT *, const DBT *));
 /* B: prefix comparison function */
 size_t (*bt_pfx) __P((const DBT *, const DBT *));
 /* R: recno input function */
 int (*bt_irec) __P((struct _btree *, recno_t));

 FILE *bt_rfp; /* R: record FILE pointer */
 int bt_rfd; /* R: record file descriptor */

 caddr_t bt_cmap; /* R: current point in mapped space */
 caddr_t bt_smap; /* R: start of mapped space */
 caddr_t bt_emap; /* R: end of mapped space */
 size_t bt_msize; /* R: size of mapped region. */

 recno_t bt_nrecs; /* R: number of records */
 size_t bt_reclen; /* R: fixed record length */
 u_char bt_bval; /* R: delimiting byte/pad character */

/*
 * NB:
 * B_NODUPS and R_RECNO are stored on disk, and may not be changed.
 */
#define B_INMEM 0x00001 /* in-memory tree */
#define B_METADIRTY 0x00002 /* need to write metadata */
#define B_MODIFIED 0x00004 /* tree modified */
#define B_NEEDSWAP 0x00008 /* if byte order requires swapping */
#define B_RDONLY 0x00010 /* read-only tree */

#define B_NODUPS 0x00020 /* no duplicate keys permitted */
#define R_RECNO 0x00080 /* record oriented tree */

#define R_CLOSEFP 0x00040 /* opened a file pointer */
#define R_EOF 0x00100 /* end of input file reached. */
#define R_FIXLEN 0x00200 /* fixed length records */
#define R_MEMMAPPED 0x00400 /* memory mapped file. */
#define R_INMEM 0x00800 /* in-memory file */
#define R_MODIFIED 0x01000 /* modified file */
#define R_RDONLY 0x02000 /* read-only file */

#define B_DB_LOCK 0x04000 /* DB_LOCK specified. */
#define B_DB_SHMEM 0x08000 /* DB_SHMEM specified. */
#define B_DB_TXN 0x10000 /* DB_TXN specified. */
 u_int32_t flags;
} BTREE;

#include "extern.h"