2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
226 lines
6 KiB
Groff
226 lines
6 KiB
Groff
.\" $NetBSD: mpool.3,v 1.10 2010/12/16 11:49:35 jruoho Exp $
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.\"
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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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.\" 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. 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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.\" @(#)mpool.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd December 16, 2010
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.Dt MPOOL 3
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.Os
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.Sh NAME
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.Nm mpool ,
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.Nm mpool_open ,
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.Nm mpool_filter ,
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.Nm mpool_new ,
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.Nm mpool_get ,
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.Nm mpool_put ,
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.Nm mpool_sync ,
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.Nm mpool_close
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.Nd shared memory buffer pool
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.Sh SYNOPSIS
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.In db.h
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.In mpool.h
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.Ft MPOOL *
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.Fn mpool_open "DBT *key" "int fd" "pgno_t pagesize" "pgno_t maxcache"
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.Ft void
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.Fn mpool_filter "MPOOL *mp" "void (*pgin)(void *, pgno_t, void *)" \
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"void (*pgout)(void *, pgno_t, void *)" "void *pgcookie"
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.Ft void *
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.Fn mpool_new "MPOOL *mp" "pgno_t *pgnoaddr"
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.Ft void *
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.Fn mpool_get "MPOOL *mp" "pgno_t pgno" "u_int flags"
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.Ft int
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.Fn mpool_put "MPOOL *mp" "void *pgaddr" "u_int flags"
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.Ft int
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.Fn mpool_sync "MPOOL *mp"
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.Ft int
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.Fn mpool_close "MPOOL *mp"
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.Sh DESCRIPTION
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.Nm
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is the library interface intended to provide page oriented buffer
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management of files.
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The buffers may be shared between processes.
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.Pp
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The function
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.Fn mpool_open
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initializes a memory pool.
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The
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.Fa key
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argument is the byte string used to negotiate between multiple
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processes wishing to share buffers.
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If the file buffers are mapped in shared memory, all processes using
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the same key will share the buffers.
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If
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.Fa key
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is
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.Dv NULL ,
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the buffers are mapped into private memory.
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The
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.Fa fd
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argument is a file descriptor for the underlying file, which must be
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seekable.
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If
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.Fa key
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is
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.No non- Ns Dv NULL
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and matches a file already being mapped, the
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.Fa fd
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argument is ignored.
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.Pp
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The
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.Fa pagesize
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argument is the size, in bytes, of the pages into which the file is
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broken up.
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The
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.Fa maxcache
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argument is the maximum number of pages from the underlying file to
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cache at any one time.
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This value is not relative to the number of processes which share a
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file's buffers, but will be the largest value specified by any of the
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processes sharing the file.
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.Pp
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The
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.Fn mpool_filter
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function is intended to make transparent input and output processing
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of the pages possible.
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If the
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.Fa pgin
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function is specified, it is called each time a buffer is read into
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the memory pool from the backing file.
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If the
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.Fa pgout
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function is specified, it is called each time a buffer is written into
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the backing file.
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Both functions are are called with the
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.Fa pgcookie
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pointer, the page number and a pointer to the page to being read or
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written.
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.Pp
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The function
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.Fn mpool_new
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takes an MPOOL pointer and an address as arguments.
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If a new page can be allocated, a pointer to the page is returned and
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the page number is stored into the
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.Fa pgnoaddr
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address.
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Otherwise,
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.Dv NULL
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is returned and errno is set.
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.Pp
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The function
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.Fn mpool_get
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takes a MPOOL pointer and a page number as arguments.
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If the page exists, a pointer to the page is returned.
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Otherwise,
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.Dv NULL
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is returned and errno is set.
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The flags parameter is not currently used.
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.Pp
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The function
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.Fn mpool_put
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unpins the page referenced by
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.Fa pgaddr .
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.Fa pgaddr
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must be an address previously returned by
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.Fn mpool_get
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or
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.Fn mpool_new .
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The flag value is specified by or'ing any of the following values:
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.Bl -tag -width MPOOL_DIRTYX -offset indent
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.It Dv MPOOL_DIRTY
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The page has been modified and needs to be written to the backing
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file.
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.El
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.Pp
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.Fn mpool_put
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returns 0 on success and \-1 if an error occurs.
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.Pp
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The function
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.Fn mpool_sync
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writes all modified pages associated with the MPOOL pointer to the
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backing file.
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.Fn mpool_sync
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returns 0 on success and \-1 if an error occurs.
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.Pp
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The
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.Fn mpool_close
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function frees up any allocated memory associated with the memory pool
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cookie.
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Modified pages are
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.Em not
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written to the backing file.
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.Fn mpool_close
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returns 0 on success and \-1 if an error occurs.
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.Sh ERRORS
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The
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.Fn mpool_open
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function may fail and set
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.Va errno
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for any of the errors specified for the library routine
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.Xr malloc 3 .
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.Pp
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The
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.Fn mpool_get
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function may fail and set
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.Va errno
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for the following:
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.Bl -tag -width Er -offset indent
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.It Er EINVAL
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The requested record doesn't exist.
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.El
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.Pp
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The
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.Fn mpool_new
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and
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.Fn mpool_get
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functions may fail and set
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.Va errno
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for any of the errors specified for the library routines
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.Xr read 2 ,
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.Xr write 2 ,
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and
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.Xr malloc 3 .
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.Pp
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The
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.Fn mpool_sync
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function may fail and set
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.Va errno
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for any of the errors specified for the library routine
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.Xr write 2 .
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.Pp
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The
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.Fn mpool_close
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function may fail and set
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.Va errno
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for any of the errors specified for the library routine
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.Xr free 3 .
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.Sh SEE ALSO
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.Xr btree 3 ,
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.Xr dbopen 3 ,
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.Xr hash 3 ,
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.Xr recno 3
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