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"