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<h1>db_env_set_func_seek</h1>
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<h3><pre>
#include <db.h>
<p>
int
db_env_set_func_seek(int (*func_seek)(int fd, size_t pgsize,
db_pgno_t pageno, u_int32_t relative, int rewind, int whence));
</pre></h3>
<h1>Description</h1>
<p>The Berkeley DB library requires the ability to specify that a subsequent read
from or write to a file will occur at a specific location in that file.
The <b>func_seek</b> argument must conform to the following interface:
<p><blockquote><pre>int seek(int fd, size_t pgsize, db_pgno_t pageno,
u_int32_t relative, int rewind, int whence);</pre></blockquote>
<p>The <b>fd</b> argument is an open file descriptor on the file.
<p>The <b>seek</b> function must cause a subsequent read from or write to
the file to occur at a byte offset specified by the calculation:
<p><blockquote><pre>(pgsize * pageno) + relative</pre></blockquote>
<p>If <b>rewind</b> is non-zero, the byte offset is treated as a backward
seek, not a forward one.
<p>The <b>whence</b> argument specifies where in the file the byte offset
is relative to, as described by the IEEE/ANSI Std 1003.1 (POSIX) <b>lseek</b> system
call.
<p>The <b>func_seek</b> interface must return the value of <b>errno</b> on
failure and 0 on success.
<p>The db_env_set_func_seek method configures all operations performed by a process and
all of its threads of control, not operations confined to a single
database environment.
<p>Although the db_env_set_func_seek interface may be called at any time during the
life of the application, it should normally be called before making
calls to the <a href="../api_c/env_create.html">db_env_create</a> or <a href="../api_c/db_create.html">db_create</a> methods.
<p>The db_env_set_func_seek method returns a non-zero error value on failure and 0 on success.
<h1>Errors</h1>
<p>The db_env_set_func_seek method may fail and return a non-zero error for the following conditions:
<p><dl compact>
<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
</dl>
<p>The db_env_set_func_seek 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_env_set_func_seek 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>See Also</h1>
<a href="../ref/program/runtime.html">Run-time configuration</a>
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