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Diffstat (limited to 'lib/libc/db/man/mpool.3')
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diff --git a/lib/libc/db/man/mpool.3 b/lib/libc/db/man/mpool.3 new file mode 100644 index 00000000000..0ad0b6864b5 --- /dev/null +++ b/lib/libc/db/man/mpool.3 @@ -0,0 +1,221 @@ +.\" $NetBSD: mpool.3,v 1.4 1995/02/27 13:23:35 cgd Exp $ +.\" +.\" Copyright (c) 1990, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" 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. +.\" +.\" @(#)mpool.3 8.1 (Berkeley) 6/4/93 +.\" +.TH MPOOL 3 "June 4, 1993" +.UC 7 +.SH NAME +mpool \- shared memory buffer pool +.SH SYNOPSIS +.nf +.ft B +#include <db.h> +#include <mpool.h> + +MPOOL * +mpool_open (DBT *key, int fd, pgno_t pagesize, pgno_t maxcache); + +void +mpool_filter (MPOOL *mp, void (*pgin)(void *, pgno_t, void *), +.ti +5 +void (*pgout)(void *, pgno_t, void *), void *pgcookie); + +void * +mpool_new (MPOOL *mp, pgno_t *pgnoaddr); + +void * +mpool_get (MPOOL *mp, pgno_t pgno, u_int flags); + +int +mpool_put (MPOOL *mp, void *pgaddr, u_int flags); + +int +mpool_sync (MPOOL *mp); + +int +mpool_close (MPOOL *mp); +.ft R +.fi +.SH DESCRIPTION +.IR Mpool +is the library interface intended to provide page oriented buffer management +of files. +The buffers may be shared between processes. +.PP +The function +.I mpool_open +initializes a memory pool. +The +.I key +argument is the byte string used to negotiate between multiple +processes wishing to share buffers. +If the file buffers are mapped in shared memory, all processes using +the same key will share the buffers. +If +.I key +is NULL, the buffers are mapped into private memory. +The +.I fd +argument is a file descriptor for the underlying file, which must be seekable. +If +.I key +is non-NULL and matches a file already being mapped, the +.I fd +argument is ignored. +.PP +The +.I pagesize +argument is the size, in bytes, of the pages into which the file is broken up. +The +.I maxcache +argument is the maximum number of pages from the underlying file to cache +at any one time. +This value is not relative to the number of processes which share a file's +buffers, but will be the largest value specified by any of the processes +sharing the file. +.PP +The +.I mpool_filter +function is intended to make transparent input and output processing of the +pages possible. +If the +.I pgin +function is specified, it is called each time a buffer is read into the memory +pool from the backing file. +If the +.I pgout +function is specified, it is called each time a buffer is written into the +backing file. +Both functions are are called with the +.I pgcookie +pointer, the page number and a pointer to the page to being read or written. +.PP +The function +.I mpool_new +takes an MPOOL pointer and an address as arguments. +If a new page can be allocated, a pointer to the page is returned and +the page number is stored into the +.I pgnoaddr +address. +Otherwise, NULL is returned and errno is set. +.PP +The function +.I mpool_get +takes a MPOOL pointer and a page number as arguments. +If the page exists, a pointer to the page is returned. +Otherwise, NULL is returned and errno is set. +The flags parameter is not currently used. +.PP +The function +.I mpool_put +unpins the page referenced by +.IR pgaddr . +.I Pgaddr +must be an address previously returned by +.I mpool_get +or +.IR mpool_new . +The flag value is specified by +.IR or 'ing +any of the following values: +.TP +MPOOL_DIRTY +The page has been modified and needs to be written to the backing file. +.PP +.I Mpool_put +returns 0 on success and -1 if an error occurs. +.PP +The function +.I mpool_sync +writes all modified pages associated with the MPOOL pointer to the +backing file. +.I Mpool_sync +returns 0 on success and -1 if an error occurs. +.PP +The +.I mpool_close +function free's up any allocated memory associated with the memory pool +cookie. +Modified pages are +.B not +written to the backing file. +.I Mpool_close +returns 0 on success and -1 if an error occurs. +.SH ERRORS +The +.I mpool_open +function may fail and set +.I errno +for any of the errors specified for the library routine +.IR malloc (3). +.PP +The +.I mpool_get +function may fail and set +.I errno +for the following: +.TP 15 +[EINVAL] +The requested record doesn't exist. +.PP +The +.I mpool_new +and +.I mpool_get +functions may fail and set +.I errno +for any of the errors specified for the library routines +.IR read (2) , +.IR write (2) , +and +.IR malloc (3). +.PP +The +.I mpool_sync +function may fail and set +.I errno +for any of the errors specified for the library routine +.IR write (2). +.PP +The +.I mpool_close +function may fail and set +.I errno +for any of the errors specified for the library routine +.IR free (3). +.SH "SEE ALSO" +.IR dbopen (3), +.IR btree (3), +.IR hash (3), +.IR recno (3) |