#define CHARSET_MAX 41

static const char *

getTok(const char **pp)

{

  enum { inAtom, inString, init, inComment };

  int state = init;

  const char *tokStart = 0;

  for (;;) {

    switch (**pp) {

    case '\0':

      return 0;

    case ' ':

    case '\r':

    case '\t':

    case '\n':

      if (state == inAtom)

        return tokStart;

      break;

    case '(':

      if (state == inAtom)

        return tokStart;

      if (state != inString)

        state++;

      break;

    case ')':

      if (state > init)

        --state;

      else if (state != inString)

        return 0;

      break;

    case ';':

    case '/':

    case '=':

      if (state == inAtom)

        return tokStart;

      if (state == init)

        return (*pp)++;

      break;

    case '\\':

      ++*pp;

      if (**pp == '\0')

        return 0;

      break;

    case '"':

      switch (state) {

      case inString:

        ++*pp;

        return tokStart;

      case inAtom:

        return tokStart;

      case init:

        tokStart = *pp;

        state = inString;

        break;

      }

      break;

    default:

      if (state == init) {

        tokStart = *pp;

        state = inAtom;

      }

      break;

    }

    ++*pp;

  }

  /* not reached */

}

/* key must be lowercase ASCII */

static int

matchkey(const char *start, const char *end, const char *key)

{

  if (!start)

    return 0;

  for (; start != end; start++, key++)

    if (*start != *key && *start != 'A' + (*key - 'a'))

      return 0;

  return *key == '\0';

}

void

getXMLCharset(const char *buf, char *charset)

{

  const char *next, *p;

  charset[0] = '\0';

  next = buf;

  p = getTok(&next);

  if (matchkey(p, next, "text"))

    strcpy(charset, "us-ascii");

  else if (!matchkey(p, next, "application"))

    return;

  p = getTok(&next);

  if (!p || *p != '/')

    return;

  p = getTok(&next);

  if (matchkey(p, next, "xml"))

    isXml = 1;

  p = getTok(&next);

  while (p) {

    if (*p == ';') {

      p = getTok(&next);

      if (matchkey(p, next, "charset")) {

        p = getTok(&next);

        if (p && *p == '=') {

          p = getTok(&next);

          if (p) {

            char *s = charset;

            if (*p == '"') {

              while (++p != next - 1) {

                if (*p == '\\')

                  ++p;

                if (s == charset + CHARSET_MAX - 1) {

                  charset[0] = '\0';

                  break;

                }

                *s++ = *p;

              }

              *s++ = '\0';

            }

            else {

              if (next - p > CHARSET_MAX - 1)

                break;

              while (p != next)

                *s++ = *p++;

              *s = 0;

              break;

            }

          }

        }

      }

    }

  else

    p = getTok(&next);

  }

}

int

main(int argc, char **argv)

{

  char buf[CHARSET_MAX];

  getXMLCharset(argv[1], buf);

  printf("charset = \"%s\"\n", buf);

  return 0;

}