iconv encoding conversion problem

Question

I am having trouble converting strings from utf8 to gb2312. My convert function is below

void convert(const char *from_charset,const char *to_charset, char *inptr, char *outptr)
{
    size_t inleft = strlen(inptr);
    size_t outleft = inleft;
    iconv_t cd;     /* conversion descriptor */

    if ((cd = iconv_open(to_charset, from_charset)) == (iconv_t)(-1)) 
    {
            fprintf(stderr, "Cannot open converter from %s to %s\n", from_charset, to_charset);
            exit(8);
    }

    /* return code of iconv() */
    int rc = iconv(cd, &inptr, &inleft, &outptr, &outleft);
    if (rc == -1) 
    {
            fprintf(stderr, "Error in converting characters\n");

            if(errno == E2BIG)
                    printf("errno == E2BIG\n");
            if(errno == EILSEQ)
                    printf("errno == EILSEQ\n");
            if(errno == EINVAL)
                    printf("errno == EINVAL\n");

            iconv_close(cd);
            exit(8);
    }
    iconv_close(cd);
}

This is an example of how I used it:

int len = 1000;
char *result = new char[len];
convert("UTF-8", "GB2312", some_string, result);

edit: I most of the time get a E2BIG error.

Answer 1

outleft should be the size of the output buffer (e.g. 1000 bytes), not the size of the incoming string.

When converting, the string length usually changes in the process and you cannot know how long it is going to be until afterwards. E2BIG means that the output buffer wasn't large enough, in which case you need to give it more output buffer space (notice that it has already converted some of the data and adjusted the four variables passed to it accordingly).