187 lines
6.9 KiB
HTML
187 lines
6.9 KiB
HTML
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>mbrtowc</title>
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<basefont size="3"> <a name="mbrtowc"></a> <a name="tag_03_360"></a><!-- mbrtowc -->
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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_360_01"></a>NAME</h4>
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<blockquote>mbrtowc - convert a character to a wide-character code (restartable)</blockquote>
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<h4><a name="tag_03_360_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/wchar.h.html">wchar.h</a>><br>
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<br>
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size_t mbrtowc(wchar_t *restrict</tt> <i>pwc</i><tt>, const char *restrict</tt> <i>s</i><tt>,<br>
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size_t</tt> <i>n</i><tt>, mbstate_t *restrict</tt> <i>ps</i><tt>);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_360_03"></a>DESCRIPTION</h4>
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<blockquote>
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<div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"
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border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the
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requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to
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the ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div>
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<p>If <i>s</i> is a null pointer, the <i>mbrtowc</i>() function shall be equivalent to the call:</p>
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<pre>
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<tt>mbrtowc(NULL, "", 1, ps)
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</tt>
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</pre>
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<p>In this case, the values of the arguments <i>pwc</i> and <i>n</i> are ignored.</p>
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<p>If <i>s</i> is not a null pointer, the <i>mbrtowc</i>() function shall inspect at most <i>n</i> bytes beginning at the byte
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pointed to by <i>s</i> to determine the number of bytes needed to complete the next character (including any shift sequences). If
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the function determines that the next character is completed, it shall determine the value of the corresponding wide character and
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then, if <i>pwc</i> is not a null pointer, shall store that value in the object pointed to by <i>pwc</i>. If the corresponding wide
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character is the null wide character, the resulting state described shall be the initial conversion state.</p>
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<p>If <i>ps</i> is a null pointer, the <i>mbrtowc</i>() function shall use its own internal <b>mbstate_t</b> object, which shall be
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initialized at program start-up to the initial conversion state. Otherwise, the <b>mbstate_t</b> object pointed to by <i>ps</i>
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shall be used to completely describe the current conversion state of the associated character sequence. The implementation shall
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behave as if no function defined in this volume of IEEE Std 1003.1-2001 calls <i>mbrtowc</i>().</p>
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<p>The behavior of this function is affected by the <i>LC_CTYPE</i> category of the current locale.</p>
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</blockquote>
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<h4><a name="tag_03_360_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>The <i>mbrtowc</i>() function shall return the first of the following that applies:</p>
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<dl compact>
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<dt>0</dt>
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<dd>If the next <i>n</i> or fewer bytes complete the character that corresponds to the null wide character (which is the value
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stored).</dd>
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<dt>between 1 and <i>n</i> inclusive</dt>
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<dd><br>
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If the next <i>n</i> or fewer bytes complete a valid character (which is the value stored); the value returned shall be the number
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of bytes that complete the character.</dd>
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<dt>(<b>size_t</b>)-2</dt>
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<dd>If the next <i>n</i> bytes contribute to an incomplete but potentially valid character, and all <i>n</i> bytes have been
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processed (no value is stored). When <i>n</i> has at least the value of the {MB_CUR_MAX} macro, this case can only occur if
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<i>s</i> points at a sequence of redundant shift sequences (for implementations with state-dependent encodings).</dd>
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<dt>(<b>size_t</b>)-1</dt>
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<dd>If an encoding error occurs, in which case the next <i>n</i> or fewer bytes do not contribute to a complete and valid character
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(no value is stored). In this case, [EILSEQ] shall be stored in <i>errno</i> and the conversion state is undefined.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_03_360_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>mbrtowc</i>() function may fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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<i>ps</i> points to an object that contains an invalid conversion state. <img src="../images/opt-end.gif" alt="[Option End]"
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border="0"></dd>
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<dt>[EILSEQ]</dt>
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<dd>Invalid character sequence is detected.</dd>
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</dl>
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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_360_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_360_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_360_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_360_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_360_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="mbsinit.html"><i>mbsinit</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/wchar.h.html"><i><wchar.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_360_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 5. Included for alignment with ISO/IEC 9899:1990/Amendment 1:1995 (E).</p>
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</blockquote>
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<h4><a name="tag_03_360_12"></a>Issue 6</h4>
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<blockquote>
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<p>The <i>mbrtowc</i>() prototype is updated for alignment with the ISO/IEC 9899:1999 standard.</p>
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<p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p>
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<ul>
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<li>
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<p>The [EINVAL] error condition is added.</p>
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</li>
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</ul>
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<p>ISO/IEC 9899:1999 standard, Technical Corrigendum No. 1 is incorporated.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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