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btree.h

/*-
 * 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     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) __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"

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