include/objalloc.h

   1 /* objalloc.h -- routines to allocate memory for objects
   2    Copyright 1997, 2001 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 <= __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 */