text: /*-
   * 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
   * $DragonFly: src/lib/libc/db/btree/btree.h,v 1.4 2005/09/19 09:20:37 asmodai Exp $
   */
  
  /* 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"
  