140 lines
5.5 KiB
HTML
140 lines
5.5 KiB
HTML
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<title>posix_mem_offset</title>
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<basefont size="3"> <a name="posix_mem_offset"></a> <a name="tag_03_424"></a><!-- posix_mem_offset -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_424_01"></a>NAME</h4>
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<blockquote>posix_mem_offset - find offset and length of a mapped typed memory block (<b>ADVANCED REALTIME</b>)</blockquote>
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<h4><a name="tag_03_424_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('TYM')">TYM</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> #include <<a href="../basedefs/sys/mman.h.html">sys/mman.h</a>><br>
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<br>
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int posix_mem_offset(const void *restrict</tt> <i>addr</i><tt>, size_t</tt> <i>len</i><tt>,<br>
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off_t *restrict</tt> <i>off</i><tt>, size_t *restrict</tt> <i>contig_len</i><tt>,<br>
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int *restrict</tt> <i>fildes</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]"
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border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_424_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>posix_mem_offset</i>() function shall return in the variable pointed to by <i>off</i> a value that identifies the offset
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(or location), within a memory object, of the memory block currently mapped at <i>addr</i>. The function shall return in the
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variable pointed to by <i>fildes</i>, the descriptor used (via <a href="../functions/mmap.html"><i>mmap</i>()</a>) to establish the
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mapping which contains <i>addr</i>. If that descriptor was closed since the mapping was established, the returned value of
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<i>fildes</i> shall be -1. The <i>len</i> argument specifies the length of the block of the memory object the user wishes the
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offset for; upon return, the value pointed to by <i>contig_len</i> shall equal either <i>len</i>, or the length of the largest
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contiguous block of the memory object that is currently mapped to the calling process starting at <i>addr</i>, whichever is
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smaller.</p>
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<p>If the memory object mapped at <i>addr</i> is a typed memory object, then if the <i>off</i> and <i>contig_len</i> values
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obtained by calling <i>posix_mem_offset</i>() are used in a call to <a href="../functions/mmap.html"><i>mmap</i>()</a> with a file
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descriptor that refers to the same memory pool as <i>fildes</i> (either through the same port or through a different port), and
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that was opened with neither the POSIX_TYPED_MEM_ALLOCATE nor the POSIX_TYPED_MEM_ALLOCATE_CONTIG flag, the typed memory area that
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is mapped shall be exactly the same area that was mapped at <i>addr</i> in the address space of the process that called
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<i>posix_mem_offset</i>().</p>
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<p>If the memory object specified by <i>fildes</i> is not a typed memory object, then the behavior of this function is
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implementation-defined.</p>
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</blockquote>
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<h4><a name="tag_03_424_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, the <i>posix_mem_offset</i>() function shall return zero; otherwise, the corresponding error status
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value shall be returned.</p>
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</blockquote>
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<h4><a name="tag_03_424_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>posix_mem_offset</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EACCES]</dt>
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<dd>The process has not mapped a memory object supported by this function at the given address <i>addr</i>.</dd>
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</dl>
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<p>This function shall not return an error code of [EINTR].</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_424_06"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_424_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_424_08"></a>RATIONALE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_424_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_424_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="mmap.html"><i>mmap</i>()</a> , <a href="posix_typed_mem_open.html"><i>posix_typed_mem_open</i>()</a> , the Base
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Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/sys/mman.h.html"><i><sys/mman.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_424_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 6. Derived from IEEE Std 1003.1j-2000.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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