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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2004 IEEE and The Open Group, All Rights Reserved --><title>mbtowc</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="mbtowc"></a> <a name="tag_03_364"></a><!-- mbtowc --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2004 Edition<br>Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_364_01"></a>NAME</h4><blockquote>mbtowc - convert a character to a wide-character code</blockquote><h4><a name="tag_03_364_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/stdlib.h.html">stdlib.h</a>><br><br> int mbtowc(wchar_t *restrict</tt> <i>pwc</i><tt>, const char *restrict</tt> <i>s</i><tt>, size_t</tt> <i>n</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_364_03"></a>DESCRIPTION</h4><blockquote><div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"border="0"> The functionality described on this reference page is aligned with the ISO C standard. Any conflict between therequirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers tothe ISO C standard. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div><p>If <i>s</i> is not a null pointer, <i>mbtowc</i>() shall determine the number of bytes that constitute the character pointed toby <i>s</i>. It shall then determine the wide-character code for the value of type <b>wchar_t</b> that corresponds to thatcharacter. (The value of the wide-character code corresponding to the null byte is 0.) If the character is valid and <i>pwc</i> isnot a null pointer, <i>mbtowc</i>() shall store the wide-character code in the object pointed to by <i>pwc</i>.</p><p>The behavior of this function is affected by the <i>LC_CTYPE</i> category of the current locale. For a state-dependent encoding,this function is placed into its initial state by a call for which its character pointer argument, <i>s</i>, is a null pointer.Subsequent calls with <i>s</i> as other than a null pointer shall cause the internal state of the function to be altered asnecessary. A call with <i>s</i> as a null pointer shall cause this function to return a non-zero value if encodings have statedependency, and 0 otherwise. If the implementation employs special bytes to change the shift state, these bytes shall not produceseparate wide-character codes, but shall be grouped with an adjacent character. Changing the <i>LC_CTYPE</i> category causes theshift state of this function to be unspecified. At most <i>n</i> bytes of the array pointed to by <i>s</i> shall be examined.</p><p>The implementation shall behave as if no function defined in this volume of IEEE Std 1003.1-2001 calls<i>mbtowc</i>().</p></blockquote><h4><a name="tag_03_364_04"></a>RETURN VALUE</h4><blockquote><p>If <i>s</i> is a null pointer, <i>mbtowc</i>() shall return a non-zero or 0 value, if character encodings, respectively, do ordo not have state-dependent encodings. If <i>s</i> is not a null pointer, <i>mbtowc</i>() shall either return 0 (if <i>s</i> pointsto the null byte), or return the number of bytes that constitute the converted character (if the next <i>n</i> or fewer bytes forma valid character), or return -1 <sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> and may set <i>errno</i> to indicate the error <img src="../images/opt-end.gif" alt="[Option End]" border="0"> (if they do not form a valid character).</p><p>In no case shall the value returned be greater than <i>n</i> or the value of the {MB_CUR_MAX} macro.</p></blockquote><h4><a name="tag_03_364_05"></a>ERRORS</h4><blockquote><p>The <i>mbtowc</i>() function may fail if:</p><dl compact><dt>[EILSEQ]</dt><dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Invalid character sequence is detected. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_364_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_364_07"></a>APPLICATION USAGE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_364_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_364_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_364_10"></a>SEE ALSO</h4><blockquote><p><a href="mblen.html"><i>mblen</i>()</a>, <a href="mbstowcs.html"><i>mbstowcs</i>()</a>, <a href="wctomb.html"><i>wctomb</i>()</a>, <a href="wcstombs.html"><i>wcstombs</i>()</a>, the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/stdlib.h.html"><i><stdlib.h></i></a></p></blockquote><h4><a name="tag_03_364_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 4. Aligned with the ISO C standard.</p></blockquote><h4><a name="tag_03_364_12"></a>Issue 6</h4><blockquote><p>The <i>mbtowc</i>() prototype is updated for alignment with the ISO/IEC 9899:1999 standard.</p><p>Extensions beyond the ISO C standard are marked.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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