manual/examples/mbstouwcs.c

   1 #include <stdbool.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4 #include <wchar.h>
   5
   6 /* Do not include the above headers in the example.
   7 */
   8 wchar_t *
   9 mbstouwcs (const char *s)
  10 {
  11   /* Include the null terminator in the conversion.  */
  12   size_t len = strlen (s) + 1;
  13   wchar_t *result = reallocarray (NULL, len, sizeof (wchar_t));
  14   if (result == NULL)
  15     return NULL;
  16
  17   wchar_t *wcp = result;
  18   mbstate_t state;
  19   memset (&state, '\0', sizeof (state));
  20
  21   while (true)
  22     {
  23       wchar_t wc;
  24       size_t nbytes = mbrtowc (&wc, s, len, &state);
  25       if (nbytes == 0)
  26         {
  27           /* Terminate the result string.  */
  28           *wcp = L'\0';
  29           break;
  30         }
  31       else if (nbytes == (size_t) -2)
  32         {
  33           /* Truncated input string.  */
  34           errno = EILSEQ;
  35           free (result);
  36           return NULL;
  37         }
  38       else if (nbytes == (size_t) -1)
  39         {
  40           /* Some other error (including EILSEQ).  */
  41           free (result);
  42           return NULL;
  43         }
  44       else
  45         {
  46           /* A character was converted.  */
  47           *wcp++ = towupper (wc);
  48           len -= nbytes;
  49           s += nbytes;
  50         }
  51     }
  52   return result;
  53 }