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<h4 class="subsection">6.4.2 Non-reentrant Conversion of Strings</h4>

<p>For convenience the ISO&nbsp;C90<!-- /@w --> standard also defines functions to
convert entire strings instead of single characters.  These functions
suffer from the same problems as their reentrant counterparts from
Amendment&nbsp;1<!-- /@w --> to ISO&nbsp;C90<!-- /@w -->; see <a href="Converting-Strings.html#Converting-Strings">Converting Strings</a>.

<!-- stdlib.h -->
<!-- ISO -->
<div class="defun">
&mdash; Function: size_t <b>mbstowcs</b> (<var>wchar_t *wstring, const char *string, size_t size</var>)<var><a name="index-mbstowcs-666"></a></var><br>
<blockquote><p>The <code>mbstowcs</code> (&ldquo;multibyte string to wide character string&rdquo;)
function converts the null-terminated string of multibyte characters
<var>string</var> to an array of wide character codes, storing not more than
<var>size</var> wide characters into the array beginning at <var>wstring</var>. 
The terminating null character counts towards the size, so if <var>size</var>
is less than the actual number of wide characters resulting from
<var>string</var>, no terminating null character is stored.

        <p>The conversion of characters from <var>string</var> begins in the initial
shift state.

        <p>If an invalid multibyte character sequence is found, the <code>mbstowcs</code>
function returns a value of -1.  Otherwise, it returns the number
of wide characters stored in the array <var>wstring</var>.  This number does
not include the terminating null character, which is present if the
number is less than <var>size</var>.

        <p>Here is an example showing how to convert a string of multibyte
characters, allocating enough space for the result.

     <pre class="smallexample">          wchar_t *
          mbstowcs_alloc (const char *string)
          {
            size_t size = strlen (string) + 1;
            wchar_t *buf = xmalloc (size * sizeof (wchar_t));
          
            size = mbstowcs (buf, string, size);
            if (size == (size_t) -1)
              return NULL;
            buf = xrealloc (buf, (size + 1) * sizeof (wchar_t));
            return buf;
          }
</pre>
        </blockquote></div>

<!-- stdlib.h -->
<!-- ISO -->
<div class="defun">
&mdash; Function: size_t <b>wcstombs</b> (<var>char *string, const wchar_t *wstring, size_t size</var>)<var><a name="index-wcstombs-667"></a></var><br>
<blockquote><p>The <code>wcstombs</code> (&ldquo;wide character string to multibyte string&rdquo;)
function converts the null-terminated wide character array <var>wstring</var>
into a string containing multibyte characters, storing not more than
<var>size</var> bytes starting at <var>string</var>, followed by a terminating
null character if there is room.  The conversion of characters begins in
the initial shift state.

        <p>The terminating null character counts towards the size, so if <var>size</var>
is less than or equal to the number of bytes needed in <var>wstring</var>, no
terminating null character is stored.

        <p>If a code that does not correspond to a valid multibyte character is
found, the <code>wcstombs</code> function returns a value of -1. 
Otherwise, the return value is the number of bytes stored in the array
<var>string</var>.  This number does not include the terminating null character,
which is present if the number is less than <var>size</var>. 
</p></blockquote></div>

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