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      1 /* objalloc.h -- routines to allocate memory for objects
      2    Copyright 1997-2012 Free Software Foundation, Inc.
      3    Written by Ian Lance Taylor, Cygnus Solutions.
      4 
      5 This program is free software; you can redistribute it and/or modify it
      6 under the terms of the GNU General Public License as published by the
      7 Free Software Foundation; either version 2, or (at your option) any
      8 later version.
      9 
     10 This program is distributed in the hope that it will be useful,
     11 but WITHOUT ANY WARRANTY; without even the implied warranty of
     12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     13 GNU General Public License for more details.
     14 
     15 You should have received a copy of the GNU General Public License
     16 along with this program; if not, write to the Free Software
     17 Foundation, 51 Franklin Street - Fifth Floor,
     18 Boston, MA 02110-1301, USA.  */
     19 
     20 #ifndef OBJALLOC_H
     21 #define OBJALLOC_H
     22 
     23 #include "ansidecl.h"
     24 
     25 /* These routines allocate space for an object.  The assumption is
     26    that the object will want to allocate space as it goes along, but
     27    will never want to free any particular block.  There is a function
     28    to free a block, which also frees all more recently allocated
     29    blocks.  There is also a function to free all the allocated space.
     30 
     31    This is essentially a specialization of obstacks.  The main
     32    difference is that a block may not be allocated a bit at a time.
     33    Another difference is that these routines are always built on top
     34    of malloc, and always pass an malloc failure back to the caller,
     35    unlike more recent versions of obstacks.  */
     36 
     37 /* This is what an objalloc structure looks like.  Callers should not
     38    refer to these fields, nor should they allocate these structure
     39    themselves.  Instead, they should only create them via
     40    objalloc_init, and only access them via the functions and macros
     41    listed below.  The structure is only defined here so that we can
     42    access it via macros.  */
     43 
     44 struct objalloc
     45 {
     46   char *current_ptr;
     47   unsigned int current_space;
     48   void *chunks;
     49 };
     50 
     51 /* Work out the required alignment.  */
     52 
     53 struct objalloc_align { char x; double d; };
     54 
     55 #if defined (__STDC__) && __STDC__
     56 #ifndef offsetof
     57 #include <stddef.h>
     58 #endif
     59 #endif
     60 #ifndef offsetof
     61 #define offsetof(TYPE, MEMBER) ((unsigned long) &((TYPE *)0)->MEMBER)
     62 #endif
     63 #define OBJALLOC_ALIGN offsetof (struct objalloc_align, d)
     64 
     65 /* Create an objalloc structure.  Returns NULL if malloc fails.  */
     66 
     67 extern struct objalloc *objalloc_create (void);
     68 
     69 /* Allocate space from an objalloc structure.  Returns NULL if malloc
     70    fails.  */
     71 
     72 extern void *_objalloc_alloc (struct objalloc *, unsigned long);
     73 
     74 /* The macro version of objalloc_alloc.  We only define this if using
     75    gcc, because otherwise we would have to evaluate the arguments
     76    multiple times, or use a temporary field as obstack.h does.  */
     77 
     78 #if defined (__GNUC__) && defined (__STDC__) && __STDC__
     79 
     80 /* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
     81    does not implement __extension__.  But that compiler doesn't define
     82    __GNUC_MINOR__.  */
     83 #if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
     84 #define __extension__
     85 #endif
     86 
     87 #define objalloc_alloc(o, l)						\
     88   __extension__								\
     89   ({ struct objalloc *__o = (o);					\
     90      unsigned long __len = (l);						\
     91      if (__len == 0)							\
     92        __len = 1;							\
     93      __len = (__len + OBJALLOC_ALIGN - 1) &~ (OBJALLOC_ALIGN - 1);	\
     94      (__len != 0 && __len <= __o->current_space				\
     95       ? (__o->current_ptr += __len,					\
     96 	 __o->current_space -= __len,					\
     97 	 (void *) (__o->current_ptr - __len))				\
     98       : _objalloc_alloc (__o, __len)); })
     99 
    100 #else /* ! __GNUC__ */
    101 
    102 #define objalloc_alloc(o, l) _objalloc_alloc ((o), (l))
    103 
    104 #endif /* ! __GNUC__ */
    105 
    106 /* Free an entire objalloc structure.  */
    107 
    108 extern void objalloc_free (struct objalloc *);
    109 
    110 /* Free a block allocated by objalloc_alloc.  This also frees all more
    111    recently allocated blocks.  */
    112 
    113 extern void objalloc_free_block (struct objalloc *, void *);
    114 
    115 #endif /* OBJALLOC_H */
    116