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// -*-c++-*-
/* $Id: union.h,v 1.7 1999/09/16 00:49:50 dm Exp $ */
/*
*
* Copyright (C) 1998 David Mazieres (dm@uun.org)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
* USA
*
*/
#ifndef _ARPC_TAGUNION_INCLUDED_
#define _ARPC_TAGUNION_INCLUDED_ 1
#include "opnew.h"
#include "array.h"
#include <typeinfo>
#ifndef TUNION_DEBUG
# if defined (CHECK_BOUNDS) || defined (DMALLOC)
# define TUNION_DEBUG 1
# endif /* CHECK_BOUNDS || DMALLOC */
#endif /* !TUNION_DEBUG */
#if 0
/* For a contant n, C++ defines sizeof (T[n]) to be n * sizeof (T).
* Assuming 8 is the maximum alignment requirement, this means any
* object T's maximum alignment requirment is sizeof (T) % 8.
* AlignmentHack (T) can be used to declare a primitive type with the
* same alignment requirements. */
template<size_t n> struct __alignment_hack;
template<> struct __alignment_hack<0> { typedef double type; };
template<> struct __alignment_hack<1> { typedef char type; };
template<> struct __alignment_hack<2> { typedef u_int16_t type; };
template<> struct __alignment_hack<3> { typedef char type; };
template<> struct __alignment_hack<4> { typedef u_int32_t type; };
template<> struct __alignment_hack<5> { typedef char type; };
template<> struct __alignment_hack<6> { typedef u_int16_t type; };
template<> struct __alignment_hack<7> { typedef char type; };
#define AlignmentHack(T) typename ::__alignment_hack<(sizeof(T)%8)>::type
#else
#define AlignmentHack(T) u_int64_t
#endif
class union_entry_base {
protected:
struct vtbl {
const std::type_info *type;
void (*destructor) (union_entry_base *);
void (*assignop) (union_entry_base *, const union_entry_base *);
size_t size;
};
const vtbl *vptr;
public:
void init () { vptr = NULL; }
void init (const union_entry_base &b) { init (); assign (b); }
void destroy () { if (vptr) vptr->destructor (this); init (); }
void assign (const union_entry_base &b) {
if (b.vptr)
b.vptr->assignop (this, &b);
else
destroy ();
}
const std::type_info *type () const { return vptr ? vptr->type : NULL; }
};
template<class T> class union_entry : public union_entry_base {
union {
AlignmentHack(T) _hack;
char m[sizeof (T)];
};
static const vtbl *getvptr () {
static const vtbl vt = { &typeid (T), &destructor, &assignop, sizeof (T) };
return &vt;
}
static void destructor (union_entry_base *tb) {
union_entry *te = static_cast<union_entry *> (tb);
te->_addr ()->~T ();
}
static void assignop (union_entry_base *dstb,
const union_entry_base *srcb) {
union_entry *dst = static_cast<union_entry *> (dstb);
const union_entry *src = static_cast<const union_entry *> (srcb);
dst->select ();
(void) (*dst->_addr () = *src->_addr ()); // XXX - cast required by egcs
}
T *_addr () { return reinterpret_cast<T *> (m); }
const T *_addr () const { return reinterpret_cast<const T *> (m); }
void verify () const {
#if TUNION_DEBUG
if (!vptr || *vptr->type != typeid (T))
panic ("union_entry<%s>::verify: accessed when %s selected\n",
typeid (T).name (), vptr ? vptr->type->name () : "NULL");
#endif /* TUNION_DEBUG */
}
public:
T *addr () { verify (); return _addr (); }
const T *addr () const { verify (); return _addr (); }
T *operator-> () { return addr (); }
const T *operator-> () const { return addr (); }
T &operator *() { return *addr (); }
const T &operator *() const { return *addr (); }
operator T *() { return addr (); }
operator const T *() const { return addr (); }
void select () {
if (!vptr || *vptr->type != typeid (T)) {
destroy ();
vptr = getvptr ();
new (static_cast<void *> (m)) T;
}
}
void Xstompcast () {
#if TUNION_DEBUG
if (!vptr || vptr->size != sizeof (T))
panic ("union_entry<%s>::Xstompcast: cast changes object size\n",
typeid (T).name ());
#endif /* TUNION_DEBUG */
vptr = getvptr ();
}
};
template<> class union_entry<void> : public union_entry_base {
static const vtbl *getvptr () {
static const vtbl vt = { &typeid (void), &destructor, &assignop, 0 };
return &vt;
}
static void destructor (union_entry_base *tb) {}
static void assignop (union_entry_base *dstb,
const union_entry_base *srcb) {
union_entry *dst = static_cast<union_entry *> (dstb);
dst->select ();
}
public:
void select () {
if (!vptr || *vptr->type != typeid (void)) {
destroy ();
vptr = getvptr ();
}
}
/* It's okay to cast anything to void. */
void Xstompcast () { select (); }
};
template<class T, size_t n> class union_entry<T[n]>
: public union_entry<toarray (T[n])> {
// typedef toarray (T[n]) array_t;
toarray (T) &operator[] (ptrdiff_t i) { return (**this)[i]; }
const toarray (T) &operator[] (ptrdiff_t i) const { return (**this)[i]; }
};
#endif /* !_ARPC_TAGUNION_INCLUDED_ */
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