root/libdb/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. 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 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 RINTERAL 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)(const DBT *, const DBT *);
                                        /* B: prefix comparison function */
        size_t  (*bt_pfx)(const DBT *, const DBT *);
                                        /* R: recno input function */
        int     (*bt_irec)(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"

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