oracular (3) mbstowcs.3.gz

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NAME

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

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <stdlib.h>

       size_t mbstowcs(wchar_t dest[restrict .dsize], const char *restrict src,
                       size_t dsize);

DESCRIPTION

       If  dest  is  not NULL, convert the multibyte string src to a wide-character string starting at dest.  At
       most dsize 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:

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

       •  dsize 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.

       •  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.

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

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

       The programmer must ensure that there is room for at least dsize wide characters at dest.

RETURN VALUE

       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).

       ┌──────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │InterfaceAttributeValue   │
       ├──────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │mbstowcs()                                                                    │ Thread safety │ MT-Safe │
       └──────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

VERSIONS

       The function mbsrtowcs(3) provides a better interface to the same functionality.

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       POSIX.1-2001, C99.

NOTES

       The behavior of mbstowcs() depends on the LC_CTYPE category of the current locale.

EXAMPLES

       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 Grüße!
           Length of source string (excluding terminator):
               8 bytes
               6 multibyte characters

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

   Program source

       #include <locale.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <string.h>
       #include <wchar.h>
       #include <wctype.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 */

           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(*wcs));
           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 (wchar_t *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);
       }

SEE ALSO

       mblen(3), mbsrtowcs(3), mbtowc(3), wcstombs(3), wctomb(3)