objalloc.h revision 60484 
1/* objalloc.h -- routines to allocate memory for objects
2   Copyright 1997 Free Software Foundation, Inc.
3   Written by Ian Lance Taylor, Cygnus Solutions.
4
5This program is free software; you can redistribute it and/or modify it
6under the terms of the GNU General Public License as published by the
7Free Software Foundation; either version 2, or (at your option) any
8later version.
9
10This program is distributed in the hope that it will be useful,
11but WITHOUT ANY WARRANTY; without even the implied warranty of
12MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13GNU General Public License for more details.
14
15You should have received a copy of the GNU General Public License
16along with this program; if not, write to the Free Software
17Foundation, 59 Temple Place - Suite 330,
18Boston, MA 02111-1307, 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
44struct objalloc
45{
46  char *current_ptr;
47  unsigned int current_space;
48  PTR chunks;
49};
50
51/* Work out the required alignment.  */
52
53struct objalloc_align { char x; double d; };
54
55#if defined (__STDC__) && __STDC__
56#ifndef offsetof
57#include <stddef.h>
58#endif
59#define OBJALLOC_ALIGN \
60  ((ptrdiff_t) ((char *) &((struct objalloc_align *) 0)->d - (char *) 0))
61#else
62#define OBJALLOC_ALIGN \
63  ((long) ((char *) &((struct objalloc_align *) 0)->d - (char *) 0))
64#endif
65
66/* Create an objalloc structure.  Returns NULL if malloc fails.  */
67
68extern struct objalloc *objalloc_create PARAMS ((void));
69
70/* Allocate space from an objalloc structure.  Returns NULL if malloc
71   fails.  */
72
73extern PTR _objalloc_alloc PARAMS ((struct objalloc *, unsigned long));
74
75/* The macro version of objalloc_alloc.  We only define this if using
76   gcc, because otherwise we would have to evaluate the arguments
77   multiple times, or use a temporary field as obstack.h does.  */
78
79#if defined (__GNUC__) && defined (__STDC__) && __STDC__
80
81/* NextStep 2.0 cc is really gcc 1.93 but it defines __GNUC__ = 2 and
82   does not implement __extension__.  But that compiler doesn't define
83   __GNUC_MINOR__.  */
84#if __GNUC__ < 2 || (__NeXT__ && !__GNUC_MINOR__)
85#define __extension__
86#endif
87
88#define objalloc_alloc(o, l)						\
89  __extension__								\
90  ({ struct objalloc *__o = (o);					\
91     unsigned long __len = (l);						\
92     if (__len == 0)							\
93       __len = 1;							\
94     __len = (__len + OBJALLOC_ALIGN - 1) &~ (OBJALLOC_ALIGN - 1);	\
95     (__len <= __o->current_space					\
96      ? (__o->current_ptr += __len,					\
97	 __o->current_space -= __len,					\
98	 (PTR) (__o->current_ptr - __len))				\
99      : _objalloc_alloc (__o, __len)); })
100
101#else /* ! __GNUC__ */
102
103#define objalloc_alloc(o, l) _objalloc_alloc ((o), (l))
104
105#endif /* ! __GNUC__ */
106
107/* Free an entire objalloc structure.  */
108
109extern void objalloc_free PARAMS ((struct objalloc *));
110
111/* Free a block allocated by objalloc_alloc.  This also frees all more
112   recently allocated blocks.  */
113
114extern void objalloc_free_block PARAMS ((struct objalloc *, PTR));
115
116#endif /* OBJALLOC_H */
117