root/libdb/btree.h(53.html)

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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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