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diff --git a/man3/mpool.3 b/man3/mpool.3 new file mode 100644 index 0000000..20dd313 --- /dev/null +++ b/man3/mpool.3 @@ -0,0 +1,205 @@ +.\" Copyright (c) 1990, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" SPDX-License-Identifier: BSD-4-Clause-UC +.\" +.\" @(#)mpool.3 8.1 (Berkeley) 6/4/93 +.\" +.TH mpool 3 2023-03-30 "Linux man-pages 6.05.01" +.UC 7 +.SH NAME +mpool \- shared memory buffer pool +.SH LIBRARY +Standard C library +.RI ( libc ", " \-lc ) +.SH SYNOPSIS +.nf +.B #include <db.h> +.B #include <mpool.h> +.PP +.BI "MPOOL *mpool_open(DBT *" key ", int " fd ", pgno_t " pagesize \ +", pgno_t " maxcache ); +.PP +.BI "void mpool_filter(MPOOL *" mp ", void (*pgin)(void *, pgno_t, void *)," +.BI " void (*" pgout ")(void *, pgno_t, void *)," +.BI " void *" pgcookie ); +.PP +.BI "void *mpool_new(MPOOL *" mp ", pgno_t *" pgnoaddr ); +.BI "void *mpool_get(MPOOL *" mp ", pgno_t " pgno ", unsigned int " flags ); +.BI "int mpool_put(MPOOL *" mp ", void *" pgaddr ", unsigned int " flags ); +.PP +.BI "int mpool_sync(MPOOL *" mp ); +.BI "int mpool_close(MPOOL *" mp ); +.fi +.SH DESCRIPTION +.IR "Note well" : +This page documents interfaces provided up until glibc 2.1. +Since glibc 2.2, glibc no longer provides these interfaces. +Probably, you are looking for the APIs provided by the +.I libdb +library instead. +.PP +.I Mpool +is the library interface intended to provide page oriented buffer management +of files. +The buffers may be shared between processes. +.PP +The function +.BR 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 +.BR 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 called with the +.I pgcookie +pointer, the page number and a pointer to the page to being read or written. +.PP +The function +.BR mpool_new () +takes an +.I 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 +.I errno +is set. +.PP +The function +.BR mpool_get () +takes an +.I MPOOL +pointer and a page number as arguments. +If the page exists, a pointer to the page is returned. +Otherwise, NULL is returned and +.I errno +is set. +The +.I flags +argument is not currently used. +.PP +The function +.BR mpool_put () +unpins the page referenced by +.IR pgaddr . +.I pgaddr +must be an address previously returned by +.BR mpool_get () +or +.BR mpool_new (). +The flag value is specified by ORing +any of the following values: +.TP +.B MPOOL_DIRTY +The page has been modified and needs to be written to the backing file. +.PP +.BR mpool_put () +returns 0 on success and \-1 if an error occurs. +.PP +The function +.BR mpool_sync () +writes all modified pages associated with the +.I MPOOL +pointer to the +backing file. +.BR mpool_sync () +returns 0 on success and \-1 if an error occurs. +.PP +The +.BR 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. +.BR mpool_close () +returns 0 on success and \-1 if an error occurs. +.SH ERRORS +The +.BR mpool_open () +function may fail and set +.I errno +for any of the errors specified for the library routine +.BR malloc (3). +.PP +The +.BR mpool_get () +function may fail and set +.I errno +for the following: +.TP 15 +.B EINVAL +The requested record doesn't exist. +.PP +The +.BR mpool_new () +and +.BR mpool_get () +functions may fail and set +.I errno +for any of the errors specified for the library routines +.BR read (2), +.BR write (2), +and +.BR malloc (3). +.PP +The +.BR mpool_sync () +function may fail and set +.I errno +for any of the errors specified for the library routine +.BR write (2). +.PP +The +.BR mpool_close () +function may fail and set +.I errno +for any of the errors specified for the library routine +.BR free (3). +.SH STANDARDS +BSD. +.SH SEE ALSO +.BR btree (3), +.BR dbopen (3), +.BR hash (3), +.BR recno (3) |