93 lines
3.5 KiB
C
93 lines
3.5 KiB
C
/*-
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Margo Seltzer.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)page.h 8.1 (Berkeley) 6/6/93
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*/
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/*
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* Definitions for hashing page file format.
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*/
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/*
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* routines dealing with a data page
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*
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* page format:
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* +------------------------------+
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* p | n | keyoff | datoff | keyoff |
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* +------------+--------+--------+
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* | datoff | free | ptr | --> |
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* +--------+---------------------+
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* | F R E E A R E A |
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* +--------------+---------------+
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* | <---- - - - | data |
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* +--------+-----+----+----------+
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* | key | data | key |
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* +--------+----------+----------+
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*
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* Pointer to the free space is always: p[p[0] + 2]
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* Amount of free space on the page is: p[p[0] + 1]
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*/
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/*
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* How many bytes required for this pair?
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* 2 shorts in the table at the top of the page + room for the
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* key and room for the data
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*
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* We prohibit entering a pair on a page unless there is also room to append
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* an overflow page. The reason for this it that you can get in a situation
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* where a single key/data pair fits on a page, but you can't append an
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* overflow page and later you'd have to split the key/data and handle like
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* a big pair.
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* You might as well do this up front.
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*/
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#define PAIRSIZE(K,D) (2*sizeof(u_short) + (K)->size + (D)->size)
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#define BIGOVERHEAD (4*sizeof(u_short))
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#define KEYSIZE(K) (4*sizeof(u_short) + (K)->size);
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#define OVFLSIZE (2*sizeof(u_short))
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#define FREESPACE(P) ((P)[(P)[0]+1])
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#define OFFSET(P) ((P)[(P)[0]+2])
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#define PAIRFITS(P,K,D) \
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(((P)[2] >= REAL_KEY) && \
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(PAIRSIZE((K),(D)) + OVFLSIZE) <= FREESPACE((P)))
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#define PAGE_META(N) (((N)+3) * sizeof(u_short))
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typedef struct {
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BUFHEAD *newp;
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BUFHEAD *oldp;
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BUFHEAD *nextp;
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u_short next_addr;
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} SPLIT_RETURN;
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