xref: /csrg-svn/lib/libc/db/btree/btree.h (revision 51969)

/*-
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Mike Olson.
 *
 * %sccs.include.redist.c%
 *
 *	@(#)btree.h	5.6 (Berkeley) 12/16/91
 */

#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 longs within structures are NOT 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_long	flags;

	index_t	lower;			/* lower bound of free space on page */
	index_t	upper;			/* upper bound of free space on page */
	index_t	linp[1];		/* long-aligned VARIABLE LENGTH DATA */
} PAGE;

/* First and next index. */
#define	BTDATAOFF	(sizeof(pgno_t) + sizeof(pgno_t) + sizeof(pgno_t) + \
			    sizeof(u_long) + sizeof(index_t) + sizeof(index_t))
#define	NEXTINDEX(p)	(((p)->lower - BTDATAOFF) / sizeof(index_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 size and page number fields in the items are long aligned so they can be
 * manipulated without copying.
 */
#define	LALIGN(n)	(((n) + sizeof(u_long) - 1) & ~(sizeof(u_long) - 1))
#define	NOVFLSIZE	(sizeof(pgno_t) + sizeof(size_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 {
	size_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(size_t) + sizeof(pgno_t) + sizeof(u_char) + (len))

/* Copy a BINTERNAL entry to the page. */
#define	WR_BINTERNAL(p, size, pgno, flags) { \
	*(size_t *)p = size; \
	p += sizeof(size_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 {
	size_t	ksize;			/* size of key */
	size_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(size_t) + sizeof(size_t) + sizeof(u_char) + \
	    (ksize) + (dsize))

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

/* For the recno leaf pages, the item is a data entry. */
typedef struct RLEAF {
	size_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(size_t) + sizeof(u_char) + (dsize))

/* Copy a RLEAF entry to the page. */
#define	WR_RLEAF(p, data, flags) { \
	*(size_t *)p = data->size; \
	p += sizeof(size_t); \
	*(u_char *)p = flags; \
	p += sizeof(u_char); \
	bcopy(data->data, p, 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.
 *
 * One comment about cursors.  The cursor key is never removed from the tree,
 * even if deleted.  This is because it is quite difficult to decide where the
 * cursor should be when other keys have been inserted/deleted in the tree;
 * duplicate keys make it impossible.  This scheme does require extra work
 * though, to make sure that we don't perform an operation on a deleted key.
 */
typedef struct EPGNO {
	pgno_t	pgno;			/* the page number */
	index_t	index;			/* the index on the page */
} EPGNO;

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

/*
 * The metadata of the tree.  The m_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_long	m_magic;		/* magic number */
	u_long	m_version;		/* version */
	u_long	m_psize;		/* page size */
	u_long	m_free;			/* page number of first free page */
	u_long	m_nrecs;		/* R: number of records */
#define	SAVEMETA	(BTF_NODUPS | BTF_RECNO)
	u_long	m_flags;		/* bt_flags & SAVEMETA */
	u_long	m_lorder;		/* byte order */
} BTMETA;

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

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

	EPGNO	bt_bcursor;		/* B: btree cursor */
	recno_t	bt_rcursor;		/* R: recno cursor (1-based) */

#define	BT_POP(t)	(t->bt_sp ? t->bt_stack + --t->bt_sp : NULL)
#define	BT_CLR(t)	(t->bt_sp = 0)
	EPGNO	*bt_stack;		/* stack of parent pages */
	u_int	bt_sp;			/* current stack pointer */
	u_int	bt_maxstack;		/* largest stack */

	char	*bt_kbuf;		/* key buffer */
	size_t	bt_kbufsz;		/* key buffer size */
	char	*bt_dbuf;		/* data buffer */
	size_t	bt_dbufsz;		/* data buffer size */

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

	pgno_t	bt_free;		/* XXX next free page */
	index_t	bt_psize;		/* page size */
	index_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 */
	int	(*bt_pfx) __P((const DBT *, const DBT *));
					/* R: recno input function */
	int	(*bt_irec) __P((struct BTREE *, recno_t));
	recno_t	bt_nrecs;		/* R: number of records */
	caddr_t	bt_smap;		/* R: start of mapped space */
	caddr_t bt_emap;		/* R: end of mapped space */
	size_t	bt_reclen;		/* R: fixed record length */
	u_char	bt_bval;		/* R: delimiting byte/pad character */

#define	BTF_DELCRSR	0x001		/* cursor has been deleted */
#define	BTF_FIXEDLEN	0x002		/* fixed length records */
#define	BTF_INMEM	0x004		/* in-memory tree */
#define	BTF_METADIRTY	0x008		/* B: need to write metadata */
#define	BTF_MODIFIED	0x010		/* tree modified */
#define	BTF_NODUPS	0x020		/* B: no duplicate keys permitted */
#define	BTF_RDONLY	0x040		/* read-only tree */
#define	BTF_RECNO	0x080		/* record oriented tree */
#define	BTF_SEQINIT	0x100		/* sequential scan initialized */
	u_long		bt_flags;	/* btree state */
} BTREE;

#define	ISSET(t, f)	((t)->bt_flags & (f))
#define	NOTSET(t, f)	(!((t)->bt_flags & (f)))
#define	SET(t, f)	((t)->bt_flags |= (f))
#define	UNSET(t, f)	((t)->bt_flags &= ~(f))

#include "extern.h"