#ifndef SHSTR_H__
#define SHSTR_H__

#include "util.h"

extern int buf_overflow (const char *buf1, const char *buf2, int bufsize);

struct shstr
{
  static const char *null;

  const char *s;

  static int &refcnt (const char *s)
  {
    return *((int *)s - 1);
  }

  static int &length (const char *s)
  {
    return *((int *)s - 2);
  }

  int &refcnt () const
  {
    return refcnt (s);
  }

  int length () const
  {
    return length (s);
  }

  static const char *find (const char *s);
  static const char *intern (const char *s);

  static void gc (); // garbage collect a few strings

  // this is used for informational messages and the like
  const char *operator &() const { return s; }

  const char &operator [](int i) const { return s[i]; }
  operator const char *() const { return s == null ? 0 : s; }

  shstr ()
  : s (null)
  {
  }

  shstr (const shstr &sh)
  : s (sh.s)
  {
    ++refcnt ();
  }

  explicit shstr (const char *s)
  : s (intern (s))
  {
  }

  ~shstr ()
  {
    --refcnt ();
  }

  const shstr &operator =(const shstr &sh)
  {
    --refcnt ();
    s = sh.s;
    ++refcnt ();

    return *this;
  }

  const shstr &operator =(const char *str)
  {
    --refcnt ();

#if 0
    // this optimises the important case of str == constant 0
    if (is_constant (str))
      s = str ? intern (str) : null;
    else
#endif
      s = intern (str);

    return *this;
  }
};

inline int strlen (const shstr &sh)
{
  return sh.length ();
}

inline bool operator ==(const shstr &a, const shstr &b)
{
  return a.s == b.s;
}

inline bool operator !=(const shstr &a, const shstr &b)
{
  return !(a == b);
}

#endif