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Diffstat (limited to 'dbm/include/page.h')
| -rw-r--r-- | dbm/include/page.h | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/dbm/include/page.h b/dbm/include/page.h new file mode 100644 index 000000000..faf2b815b --- /dev/null +++ b/dbm/include/page.h @@ -0,0 +1,96 @@ +/*- + * Copyright (c) 1990, 1993, 1994 + * The Regents of the University of California. All rights reserved. + * + * This code is derived from software contributed to Berkeley by + * Margo Seltzer. + * + * 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. + * + * @(#)page.h 8.2 (Berkeley) 5/31/94 + */ + +/* + * Definitions for hashing page file format. + */ + +/* + * routines dealing with a data page + * + * page format: + * +------------------------------+ + * p | n | keyoff | datoff | keyoff | + * +------------+--------+--------+ + * | datoff | free | ptr | --> | + * +--------+---------------------+ + * | F R E E A R E A | + * +--------------+---------------+ + * | <---- - - - | data | + * +--------+-----+----+----------+ + * | key | data | key | + * +--------+----------+----------+ + * + * Pointer to the free space is always: p[p[0] + 2] + * Amount of free space on the page is: p[p[0] + 1] + */ + +/* + * How many bytes required for this pair? + * 2 shorts in the table at the top of the page + room for the + * key and room for the data + * + * We prohibit entering a pair on a page unless there is also room to append + * an overflow page. The reason for this it that you can get in a situation + * where a single key/data pair fits on a page, but you can't append an + * overflow page and later you'd have to split the key/data and handle like + * a big pair. + * You might as well do this up front. + */ +#ifndef PAGE_H +#define PAGE_H + +#define PAIRSIZE(K,D) (2*sizeof(uint16) + (K)->size + (D)->size) +#define BIGOVERHEAD (4*sizeof(uint16)) +#define KEYSIZE(K) (4*sizeof(uint16) + (K)->size); +#define OVFLSIZE (2*sizeof(uint16)) +#define FREESPACE(P) ((P)[(P)[0]+1]) +#define OFFSET(P) ((P)[(P)[0]+2]) +#define PAIRFITS(P,K,D) \ + (((P)[2] >= REAL_KEY) && \ + (PAIRSIZE((K),(D)) + OVFLSIZE) <= FREESPACE((P))) +#define PAGE_META(N) (((N)+3) * sizeof(uint16)) + +typedef struct { + BUFHEAD *newp; + BUFHEAD *oldp; + BUFHEAD *nextp; + uint16 next_addr; +} SPLIT_RETURN; +#endif + |