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MBSTOWCS(3) Linux Programmer's Manual MBSTOWCS(3)

NAME

     mbstowcs - convert a multibyte string to a wide-character string

SYNOPSIS

     #include <stdlib.h>

     size_t mbstowcs(wchar_t *dest, const char *src, size_t n);

DESCRIPTION

     If  dest  is  not  NULL, the mbstowcs() function converts the multibyte
     string src to a wide-character string starting at dest.  At most n wide
     characters  are  written  to  dest.   The sequence of characters in the
     string src shall begin in the initial shift state.  The conversion  can
     stop for three reasons:

     1. An  invalid  multibyte sequence has been encountered.  In this case,
        (size_t) -1 is returned.

     2. n non-L'\0' wide characters have been stored at dest.  In this case,
        the  number  of wide characters written to dest is returned, but the
        shift state at this point is lost.

     3. The multibyte string has been completely  converted,  including  the
        terminating null character ('\0').  In this case, the number of wide
        characters written to dest,  excluding  the  terminating  null  wide
        character, is returned.

     The programmer must ensure that there is room for at least n wide char-
     acters at dest.

     If dest is NULL, n is ignored, and the conversion  proceeds  as  above,
     except  that  the converted wide characters are not written out to mem-
     ory, and that no length limit exists.

     In order to avoid the case 2 above, the programmer should make  sure  n
     is greater than or equal to mbstowcs(NULL,src,0)+1.

RETURN VALUE

     The mbstowcs() function returns the number of wide characters that make
     up the converted part of the wide-character string, not  including  the
     terminating  null wide character.  If an invalid multibyte sequence was
     encountered, (size_t) -1 is returned.

ATTRIBUTES

     For  an  explanation  of  the  terms  used   in   this   section,   see
     attributes(7).

     +-----------+---------------+---------+
     |Interface  | Attribute     | Value   |
     +-----------+---------------+---------+
     |mbstowcs() | Thread safety | MT-Safe |
     +-----------+---------------+---------+

CONFORMING TO

     POSIX.1-2001, POSIX.1-2008, C99.

NOTES

     The behavior of mbstowcs() depends on the LC_CTYPE category of the cur-
     rent locale.

     The function mbsrtowcs(3) provides a better interface to the same func-
     tionality.

EXAMPLE

     The program below illustrates the use of mbstowcs(), as well as some of
     the wide character classification functions.  An  example  run  is  the
     following:

         $ ./t_mbstowcs de_DE.UTF-8 Gre!  Length of source string (excluding
         terminator):
             8 bytes
             6 multibyte characters

         Wide character string is: Gre! (6 characters)
             G alpha upper
             r alpha lower
              alpha lower
              alpha lower
             e alpha lower
             ! !alpha

 Program source
      #include <wctype.h> #include <locale.h>  #include  <wchar.h>  #include
     <stdio.h> #include <string.h> #include <stdlib.h>

     int main(int argc, char *argv[]) {
         size_t mbslen;      /* Number of multibyte characters in source */
         wchar_t  *wcs;        /* Pointer to converted wide character string
     */
         wchar_t *wp;

         if (argc < 3) {
             fprintf(stderr, "Usage: %s <locale> <string>\n", argv[0]);
             exit(EXIT_FAILURE);
         }

         /* Apply the specified locale */

         if (setlocale(LC_ALL, argv[1]) == NULL) {
             perror("setlocale");
             exit(EXIT_FAILURE);
         }

         /* Calculate the length required to hold argv[2] converted to
            a wide character string */

         mbslen = mbstowcs(NULL, argv[2], 0);
         if (mbslen == (size_t) -1) {
             perror("mbstowcs");
             exit(EXIT_FAILURE);
         }

         /* Describe the source string to the user */

         printf("Length of source string (excluding terminator):\n");
         printf("    %zu bytes\n", strlen(argv[2]));
         printf("    %zu multibyte characters\n\n", mbslen);

         /* Allocate wide character string of the desired size.  Add 1
            to allow for terminating null wide character (L'\0'). */

         wcs = calloc(mbslen + 1, sizeof(wchar_t));
         if (wcs == NULL) {
             perror("calloc");
             exit(EXIT_FAILURE);
         }

         /* Convert the multibyte character string in argv[2] to a
            wide character string */

         if (mbstowcs(wcs, argv[2], mbslen + 1) == (size_t) -1) {
             perror("mbstowcs");
             exit(EXIT_FAILURE);
         }

         printf("Wide character string is: %ls (%zu characters)\n",
                 wcs, mbslen);

         /* Now do some inspection of the classes of the characters in
            the wide character string */

         for (wp = wcs; *wp != 0; wp++) {
             printf("    %lc ", (wint_t) *wp);

             if (!iswalpha(*wp))
                 printf("!");
             printf("alpha ");

             if (iswalpha(*wp)) {
                 if (iswupper(*wp))
                     printf("upper ");

                 if (iswlower(*wp))
                     printf("lower ");
             }

             putchar('\n');
         }

         exit(EXIT_SUCCESS); }