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| <h4 class="subsection">6.4.1 Non-reentrant Conversion of Single Characters</h4> |
| |
| <!-- stdlib.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: int <b>mbtowc</b> (<var>wchar_t *restrict result, const char *restrict string, size_t size</var>)<var><a name="index-mbtowc-662"></a></var><br> |
| <blockquote><p>The <code>mbtowc</code> (“multibyte to wide character”) function when called |
| with non-null <var>string</var> converts the first multibyte character |
| beginning at <var>string</var> to its corresponding wide character code. It |
| stores the result in <code>*</code><var>result</var>. |
| |
| <p><code>mbtowc</code> never examines more than <var>size</var> bytes. (The idea is |
| to supply for <var>size</var> the number of bytes of data you have in hand.) |
| |
| <p><code>mbtowc</code> with non-null <var>string</var> distinguishes three |
| possibilities: the first <var>size</var> bytes at <var>string</var> start with |
| valid multibyte characters, they start with an invalid byte sequence or |
| just part of a character, or <var>string</var> points to an empty string (a |
| null character). |
| |
| <p>For a valid multibyte character, <code>mbtowc</code> converts it to a wide |
| character and stores that in <code>*</code><var>result</var>, and returns the |
| number of bytes in that character (always at least 1 and never |
| more than <var>size</var>). |
| |
| <p>For an invalid byte sequence, <code>mbtowc</code> returns -1. For an |
| empty string, it returns 0, also storing <code>'\0'</code> in |
| <code>*</code><var>result</var>. |
| |
| <p>If the multibyte character code uses shift characters, then |
| <code>mbtowc</code> maintains and updates a shift state as it scans. If you |
| call <code>mbtowc</code> with a null pointer for <var>string</var>, that |
| initializes the shift state to its standard initial value. It also |
| returns nonzero if the multibyte character code in use actually has a |
| shift state. See <a href="Shift-State.html#Shift-State">Shift State</a>. |
| </p></blockquote></div> |
| |
| <!-- stdlib.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: int <b>wctomb</b> (<var>char *string, wchar_t wchar</var>)<var><a name="index-wctomb-663"></a></var><br> |
| <blockquote><p>The <code>wctomb</code> (“wide character to multibyte”) function converts |
| the wide character code <var>wchar</var> to its corresponding multibyte |
| character sequence, and stores the result in bytes starting at |
| <var>string</var>. At most <code>MB_CUR_MAX</code> characters are stored. |
| |
| <p><code>wctomb</code> with non-null <var>string</var> distinguishes three |
| possibilities for <var>wchar</var>: a valid wide character code (one that can |
| be translated to a multibyte character), an invalid code, and |
| <code>L'\0'</code>. |
| |
| <p>Given a valid code, <code>wctomb</code> converts it to a multibyte character, |
| storing the bytes starting at <var>string</var>. Then it returns the number |
| of bytes in that character (always at least 1 and never more |
| than <code>MB_CUR_MAX</code>). |
| |
| <p>If <var>wchar</var> is an invalid wide character code, <code>wctomb</code> returns |
| -1. If <var>wchar</var> is <code>L'\0'</code>, it returns <code>0</code>, also |
| storing <code>'\0'</code> in <code>*</code><var>string</var>. |
| |
| <p>If the multibyte character code uses shift characters, then |
| <code>wctomb</code> maintains and updates a shift state as it scans. If you |
| call <code>wctomb</code> with a null pointer for <var>string</var>, that |
| initializes the shift state to its standard initial value. It also |
| returns nonzero if the multibyte character code in use actually has a |
| shift state. See <a href="Shift-State.html#Shift-State">Shift State</a>. |
| |
| <p>Calling this function with a <var>wchar</var> argument of zero when |
| <var>string</var> is not null has the side-effect of reinitializing the |
| stored shift state <em>as well as</em> storing the multibyte character |
| <code>'\0'</code> and returning 0. |
| </p></blockquote></div> |
| |
| <p>Similar to <code>mbrlen</code> there is also a non-reentrant function that |
| computes the length of a multibyte character. It can be defined in |
| terms of <code>mbtowc</code>. |
| |
| <!-- stdlib.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: int <b>mblen</b> (<var>const char *string, size_t size</var>)<var><a name="index-mblen-664"></a></var><br> |
| <blockquote><p>The <code>mblen</code> function with a non-null <var>string</var> argument returns |
| the number of bytes that make up the multibyte character beginning at |
| <var>string</var>, never examining more than <var>size</var> bytes. (The idea is |
| to supply for <var>size</var> the number of bytes of data you have in hand.) |
| |
| <p>The return value of <code>mblen</code> distinguishes three possibilities: the |
| first <var>size</var> bytes at <var>string</var> start with valid multibyte |
| characters, they start with an invalid byte sequence or just part of a |
| character, or <var>string</var> points to an empty string (a null character). |
| |
| <p>For a valid multibyte character, <code>mblen</code> returns the number of |
| bytes in that character (always at least <code>1</code> and never more than |
| <var>size</var>). For an invalid byte sequence, <code>mblen</code> returns |
| -1. For an empty string, it returns 0. |
| |
| <p>If the multibyte character code uses shift characters, then <code>mblen</code> |
| maintains and updates a shift state as it scans. If you call |
| <code>mblen</code> with a null pointer for <var>string</var>, that initializes the |
| shift state to its standard initial value. It also returns a nonzero |
| value if the multibyte character code in use actually has a shift state. |
| See <a href="Shift-State.html#Shift-State">Shift State</a>. |
| |
| <p><a name="index-stdlib_002eh-665"></a>The function <code>mblen</code> is declared in <samp><span class="file">stdlib.h</span></samp>. |
| </p></blockquote></div> |
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