multibyte_conversion_ex.c

int
file_mbsrtowcs (int input, int output)
{
    /* Note the use of MB_LEN_MAX.
     * MB_CUR_MAX cannot portably be used here */
    char buffer[BUFSIZE + MB_LEN_MAX];
    mbstate_t state;
    int filled = 0;
    int eof = 0;

    /* Initialize the state  */
    memset (&state, '\0, sizeof (state));

    while (!eof)
    {
        ssize_t nread;
        ssize_t nwrite;
        char *inp = buffer;
        wchar_t outbuf[BUFSIZ];
        wchar_t *outp = outbuf;

        /* Fill up the buffer from the input file.  */
        nread = read (input, buffer + filled, BUFSIZ);
        if (nread < 0)
        {
            perror("read");
            return 0;
        }
        /* If we reach end of file, make a note to read no more.  */
        if (nread == 0)
            eof = 1;

        /* filled is now the number of bytes in buffer.  */
        filled += nread;

        /* Convert those bytes to wide characters--as many as we can */
        while (1)
        {
            size_t thislen = mbrtowc (outp, inp, filled, &state);
            /* stop converting at invalid character;
             * this can mean we have read just the first part
             * of a valid character.  */
            if (thislen == (size_t) -1)
                break;
            /* we want to handle embedded NUL bytes
             * but the return value is 0. Correct this.  */
            if (thislen == 0)
                thislen = 1;
            /* Advance past this character. */
            inp += thislen;
            filled -= thislen;
            ++outp;
        }

        /* Write the wide characters we just made.  */
        nwrite = write(output, outbuf,
                (outp - outbuf) * sizeof (wchar_t));
        if (nwrite < 0)
        {
            perror ("write");
            return 0;
        }

        /* see if we have a real invalid character. */
        if ((eol && filled > 0) || filled >= MB_CUR_MAX)
        {
            error (0, 0, "invalid multibyte character");
            return 0;
        }

        /* if any characters must be carried forward,
         * put them at the beginning of the buffer. */

        if (filled > 0)
            memmove (buffer, inp, filled);
    }
    return 1;
}