| 1 | .\" Copyright (c) 1990, 1993
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| 2 | .\" The Regents of the University of California. All rights reserved.
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| 3 | .\"
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| 4 | .\" Redistribution and use in source and binary forms, with or without
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| 5 | .\" modification, are permitted provided that the following conditions
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| 6 | .\" are met:
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| 7 | .\" 1. Redistributions of source code must retain the above copyright
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| 8 | .\" notice, this list of conditions and the following disclaimer.
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| 9 | .\" 2. Redistributions in binary form must reproduce the above copyright
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| 10 | .\" notice, this list of conditions and the following disclaimer in the
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| 11 | .\" documentation and/or other materials provided with the distribution.
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| 12 | .\" 3. All advertising materials mentioning features or use of this software
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| 13 | .\" must display the following acknowledgement:
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| 14 | .\" This product includes software developed by the University of
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| 15 | .\" California, Berkeley and its contributors.
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| 16 | .\" 4. Neither the name of the University nor the names of its contributors
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| 17 | .\" may be used to endorse or promote products derived from this software
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| 18 | .\" without specific prior written permission.
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| 19 | .\"
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| 20 | .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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| 21 | .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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| 22 | .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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| 23 | .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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| 24 | .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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| 25 | .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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| 26 | .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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| 27 | .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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| 28 | .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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| 29 | .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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| 30 | .\" SUCH DAMAGE.
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| 31 | .\"
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| 32 | .\" @(#)mpool.3 8.1 (Berkeley) 6/4/93
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| 33 | .\"
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| 34 | .TH MPOOL 3 "June 4, 1993"
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| 35 | .UC 7
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| 36 | .SH NAME
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| 37 | mpool \- shared memory buffer pool
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| 38 | .SH SYNOPSIS
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| 39 | .nf
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| 40 | .ft B
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| 41 | #include <db.h>
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| 42 | #include <mpool.h>
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| 43 |
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| 44 | MPOOL *
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| 45 | mpool_open (DBT *key, int fd, pgno_t pagesize, pgno_t maxcache);
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| 46 |
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| 47 | void
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| 48 | mpool_filter (MPOOL *mp, void (*pgin)(void *, pgno_t, void *),
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| 49 | .ti +5
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| 50 | void (*pgout)(void *, pgno_t, void *), void *pgcookie);
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| 51 |
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| 52 | void *
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| 53 | mpool_new (MPOOL *mp, pgno_t *pgnoaddr);
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| 54 |
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| 55 | void *
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| 56 | mpool_get (MPOOL *mp, pgno_t pgno, u_int flags);
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| 57 |
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| 58 | int
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| 59 | mpool_put (MPOOL *mp, void *pgaddr, u_int flags);
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| 60 |
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| 61 | int
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| 62 | mpool_sync (MPOOL *mp);
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| 63 |
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| 64 | int
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| 65 | mpool_close (MPOOL *mp);
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| 66 | .ft R
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| 67 | .fi
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| 68 | .SH DESCRIPTION
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| 69 | .IR Mpool
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| 70 | is the library interface intended to provide page oriented buffer management
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| 71 | of files.
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| 72 | The buffers may be shared between processes.
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| 73 | .PP
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| 74 | The function
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| 75 | .I mpool_open
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| 76 | initializes a memory pool.
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| 77 | The
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| 78 | .I key
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| 79 | argument is the byte string used to negotiate between multiple
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| 80 | processes wishing to share buffers.
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| 81 | If the file buffers are mapped in shared memory, all processes using
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| 82 | the same key will share the buffers.
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| 83 | If
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| 84 | .I key
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| 85 | is NULL, the buffers are mapped into private memory.
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| 86 | The
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| 87 | .I fd
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| 88 | argument is a file descriptor for the underlying file, which must be seekable.
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| 89 | If
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| 90 | .I key
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| 91 | is non-NULL and matches a file already being mapped, the
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| 92 | .I fd
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| 93 | argument is ignored.
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| 94 | .PP
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| 95 | The
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| 96 | .I pagesize
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| 97 | argument is the size, in bytes, of the pages into which the file is broken up.
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| 98 | The
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| 99 | .I maxcache
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| 100 | argument is the maximum number of pages from the underlying file to cache
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| 101 | at any one time.
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| 102 | This value is not relative to the number of processes which share a file's
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| 103 | buffers, but will be the largest value specified by any of the processes
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| 104 | sharing the file.
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| 105 | .PP
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| 106 | The
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| 107 | .I mpool_filter
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| 108 | function is intended to make transparent input and output processing of the
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| 109 | pages possible.
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| 110 | If the
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| 111 | .I pgin
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| 112 | function is specified, it is called each time a buffer is read into the memory
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| 113 | pool from the backing file.
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| 114 | If the
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| 115 | .I pgout
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| 116 | function is specified, it is called each time a buffer is written into the
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| 117 | backing file.
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| 118 | Both functions are are called with the
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| 119 | .I pgcookie
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| 120 | pointer, the page number and a pointer to the page to being read or written.
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| 121 | .PP
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| 122 | The function
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| 123 | .I mpool_new
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| 124 | takes an MPOOL pointer and an address as arguments.
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| 125 | If a new page can be allocated, a pointer to the page is returned and
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| 126 | the page number is stored into the
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| 127 | .I pgnoaddr
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| 128 | address.
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