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<h1>DB_MPOOLFILE->get</h1>
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<h3><pre>
#include <db.h>
<p>
int
DB_MPOOLFILE->get(DB_MPOOLFILE *mpf,
db_pgno_t *pgnoaddr, u_int32_t flags, void **pagep);
</pre></h3>
<h1>Description</h1>
<p>The DB_MPOOLFILE->get method copies a pointer to the page with the page number
specified by <b>pgnoaddr</b>, from the source file in the <a href="../api_c/mempfile_class.html">DB_MPOOLFILE</a>,
into the memory location to which <b>pagep</b> refers. If the page
does not exist or cannot be retrieved, DB_MPOOLFILE->get will fail.
<p><b>Page numbers begin at 0; that is, the first page in the file is page
number 0, not page number 1.</b>
<p>The returned page is <b>size_t</b> type aligned.
<p>The <b>flags</b> value must be set to 0 or by bitwise inclusively <b>OR</b>'ing together one or
more of the following values:
<p><dl compact>
<p><dt><a name="DB_MPOOL_CREATE">DB_MPOOL_CREATE</a><dd>If the specified page does not exist, create it. In this case, the
<a href="memp_register.html#pgin">pgin</a> function, if specified, is
called.
<p><dt><a name="DB_MPOOL_LAST">DB_MPOOL_LAST</a><dd>Return the last page of the source file, and copy its page number into
the memory location to which <b>pgnoaddr</b> refers.
<p><dt><a name="DB_MPOOL_NEW">DB_MPOOL_NEW</a><dd>Create a new page in the file, and copy its page number into the memory
location to which <b>pgnoaddr</b> refers. In this case, the
<a href="memp_register.html#pgin">pgin</a> function, if specified, is
<b>not</b> called.
</dl>
<p>The DB_MPOOL_CREATE, DB_MPOOL_LAST, and
DB_MPOOL_NEW flags are mutually exclusive.
<p>Fully or partially created pages have all their bytes set to a nul byte,
unless the <a href="../api_c/memp_set_clear_len.html">DB_MPOOLFILE->set_clear_len</a> method was called to specify other
behavior before the file was opened.
<p>All pages returned by DB_MPOOLFILE->get will be retained (that is,
<i>pinned</i>), in the pool until a subsequent call to
<a href="../api_c/memp_fput.html">DB_MPOOLFILE->put</a>.
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<p>The DB_MPOOLFILE->get method returns a non-zero error value on failure, 0 on success, and returns DB_PAGE_NOTFOUND if the requested page does not
exist and DB_MPOOL_CREATE was not set.
<h1>Errors</h1>
<p>The DB_MPOOLFILE->get method may fail and return a non-zero error for the following conditions:
<p><dl compact>
<p><dt>EAGAIN<dd>The page reference count has overflowed. (This should never happen unless
there's a bug in the application.)
</dl>
<p><dl compact>
<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
<p>The DB_MPOOL_NEW flag was set, and the source file was not
opened for writing.
<p>More than one of DB_MPOOL_CREATE, DB_MPOOL_LAST, and
DB_MPOOL_NEW was set.
</dl>
<p><dl compact>
<p><dt>ENOMEM<dd>The cache is full, and no more pages will fit in the pool.
</dl>
<p>The DB_MPOOLFILE->get method may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
If a catastrophic error has occurred, the DB_MPOOLFILE->get method may fail and
return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>,
in which case all subsequent Berkeley DB calls will fail in the same way.
<h1>Class</h1>
<a href="../api_c/env_class.html">DB_ENV</a>, <a href="../api_c/mempfile_class.html">DB_MPOOLFILE</a>
<h1>See Also</h1>
<a href="../api_c/memp_list.html">Memory Pools and Related Methods</a>
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