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28 .\" @(#)mpool.3 8.1 (Berkeley) 6/4/93
29 .\" $FreeBSD: src/lib/libc/db/man/mpool.3,v 1.5.2.5 2003/02/23 19:45:52 trhodes Exp $
30 .\" $DragonFly: src/lib/libc/db/man/mpool.3,v 1.3 2005/09/19 09:20:37 asmodai Exp $
37 .Nd "shared memory buffer pool"
42 .Fn mpool_open "void *key" "int fd" "pgno_t pagesize" "pgno_t maxcache"
46 .Fa "void (*pgin)(void *, pgno_t, void *)"
47 .Fa "void (*pgout)(void *, pgno_t, void *)"
51 .Fn mpool_new "MPOOL *mp" "pgno_t *pgnoaddr"
53 .Fn mpool_get "MPOOL *mp" "pgno_t pgno" "u_int flags"
55 .Fn mpool_put "MPOOL *mp" "void *pgaddr" "u_int flags"
57 .Fn mpool_sync "MPOOL *mp"
59 .Fn mpool_close "MPOOL *mp"
63 library interface is intended to provide page oriented buffer management
65 The buffers may be shared between processes.
69 function initializes a memory pool.
72 argument is the byte string used to negotiate between multiple
73 processes wishing to share buffers.
74 If the file buffers are mapped in shared memory, all processes using
75 the same key will share the buffers.
80 the buffers are mapped into private memory.
83 argument is a file descriptor for the underlying file, which must be seekable.
88 and matches a file already being mapped, the
94 argument is the size, in bytes, of the pages into which the file is broken up.
97 argument is the maximum number of pages from the underlying file to cache
99 This value is not relative to the number of processes which share a file's
100 buffers, but will be the largest value specified by any of the processes
105 function is intended to make transparent input and output processing of the
109 function is specified, it is called each time a buffer is read into the memory
110 pool from the backing file.
113 function is specified, it is called each time a buffer is written into the
115 Both functions are called with the
117 pointer, the page number and a pointer to the page to being read or written.
123 pointer and an address as arguments.
124 If a new page can be allocated, a pointer to the page is returned and
125 the page number is stored into the
138 pointer and a page number as arguments.
139 If the page exists, a pointer to the page is returned.
147 argument is not currently used.
151 function unpins the page referenced by
156 must be an address previously returned by
162 argument is specified by
164 any of the following values:
165 .Bl -tag -width indent
167 The page has been modified and needs to be written to the backing file.
173 returns 0 on success and -1 if an error occurs.
177 function writes all modified pages associated with the
184 returns 0 on success and -1 if an error occurs.
188 function free's up any allocated memory associated with the memory pool
192 written to the backing file.
196 returns 0 on success and -1 if an error occurs.
200 function may fail and set
202 for any of the errors specified for the library routine
207 function may fail and set
212 The requested record doesn't exist.
219 functions may fail and set
221 for any of the errors specified for the library routines
229 function may fail and set
231 for any of the errors specified for the library routine
236 function may fail and set
238 for any of the errors specified for the library routine