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/* objalloc.h -- routines to allocate memory for objects

   Copyright 1997 Free Software Foundation, Inc.

   Written by Ian Lance Taylor, Cygnus Solutions.

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, 59 Temple Place - Suite 330,

Boston, MA 02111-1307, USA.  */

#ifndef OBJALLOC_H

#define OBJALLOC_H

#include "ansidecl.h"

/* These routines allocate space for an object.  The assumption is

   that the object will want to allocate space as it goes along, but

   will never want to free any particular block.  There is a function

   to free a block, which also frees all more recently allocated

   blocks.  There is also a function to free all the allocated space.

   This is essentially a specialization of obstacks.  The main

   difference is that a block may not be allocated a bit at a time.

   Another difference is that these routines are always built on top

   of malloc, and always pass an malloc failure back to the caller,

   unlike more recent versions of obstacks.  */

/* This is what an objalloc structure looks like.  Callers should not

   refer to these fields, nor should they allocate these structure

   themselves.  Instead, they should only create them via

   objalloc_init, and only access them via the functions and macros

   listed below.  The structure is only defined here so that we can

   access it via macros.  */

struct objalloc

{

  char *current_ptr;

  unsigned int current_space;

  PTR chunks;

};

/* Work out the required alignment.  */

struct objalloc_align { char x; double d; };

#if defined (__STDC__) && __STDC__

#ifndef offsetof

#include <stddef.h>

#endif

#define OBJALLOC_ALIGN \

  ((ptrdiff_t) ((char *) &((struct objalloc_align *) 0)->d - (char *) 0))

#else

#define OBJALLOC_ALIGN \

  ((long) ((char *) &((struct objalloc_align *) 0)->d - (char *) 0))

#endif

/* Create an objalloc structure.  Returns NULL if malloc fails.  */

extern struct objalloc *objalloc_create PARAMS ((void));

/* Allocate space from an objalloc structure.  Returns NULL if malloc

   fails.  */

extern PTR _objalloc_alloc PARAMS ((struct objalloc *, unsigned long));

/* The macro version of objalloc_alloc.  We only define this if using

   gcc, because otherwise we would have to evaluate the arguments

   multiple times, or use a temporary field as obstack.h does.  */

#if defined (__GNUC__) && defined (__STDC__) && __STDC__

/* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and

   does not implement __extension__.  But that compiler doesn't define

   __GNUC_MINOR__.  */

#if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)

#define __extension__

#endif

#define objalloc_alloc(o, l)                                            \

  __extension__                                                         \

  ({ struct objalloc *__o = (o);                                        \

     unsigned long __len = (l);                                         \

     if (__len == 0)                                                     \

       __len = 1;                                                       \

     __len = (__len + OBJALLOC_ALIGN - 1) &~ (OBJALLOC_ALIGN - 1);      \

     (__len <= __o->current_space                                       \

      ? (__o->current_ptr += __len,                                     \

         __o->current_space -= __len,                                   \

         (PTR) (__o->current_ptr - __len))                              \

      : _objalloc_alloc (__o, __len)); })

#else /* ! __GNUC__ */

#define objalloc_alloc(o, l) _objalloc_alloc ((o), (l))

#endif /* ! __GNUC__ */

/* Free an entire objalloc structure.  */

extern void objalloc_free PARAMS ((struct objalloc *));

/* Free a block allocated by objalloc_alloc.  This also frees all more

   recently allocated blocks.  */

extern void objalloc_free_block PARAMS ((struct objalloc *, PTR));

#endif /* OBJALLOC_H */