objalloc.h revision 33965
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, 675 Mass Ave, Cambridge, MA 02139, USA. */ 18 19#ifndef OBJALLOC_H 20#define OBJALLOC_H 21 22#include "ansidecl.h" 23 24/* These routines allocate space for an object. The assumption is 25 that the object will want to allocate space as it goes along, but 26 will never want to free any particular block. There is a function 27 to free a block, which also frees all more recently allocated 28 blocks. There is also a function to free all the allocated space. 29 30 This is essentially a specialization of obstacks. The main 31 difference is that a block may not be allocated a bit at a time. 32 Another difference is that these routines are always built on top 33 of malloc, and always pass an malloc failure back to the caller, 34 unlike more recent versions of obstacks. */ 35 36/* This is what an objalloc structure looks like. Callers should not 37 refer to these fields, nor should they allocate these structure 38 themselves. Instead, they should only create them via 39 objalloc_init, and only access them via the functions and macros 40 listed below. The structure is only defined here so that we can 41 access it via macros. */ 42 43struct objalloc 44{ 45 char *current_ptr; 46 unsigned int current_space; 47 PTR chunks; 48}; 49 50/* Work out the required alignment. */ 51 52struct objalloc_align { char x; double d; }; 53 54#if defined (__STDC__) && __STDC__ 55#ifndef offsetof 56#include <stddef.h> 57#endif 58#define OBJALLOC_ALIGN \ 59 ((ptrdiff_t) ((char *) &((struct objalloc_align *) 0)->d - (char *) 0)) 60#else 61#define OBJALLOC_ALIGN \ 62 ((long) ((char *) &((struct objalloc_align *) 0)->d - (char *) 0)) 63#endif 64 65/* Create an objalloc structure. Returns NULL if malloc fails. */ 66 67extern struct objalloc *objalloc_create PARAMS ((void)); 68 69/* Allocate space from an objalloc structure. Returns NULL if malloc 70 fails. */ 71 72extern PTR _objalloc_alloc PARAMS ((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 (PTR) (__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 108extern void objalloc_free PARAMS ((struct objalloc *)); 109 110/* Free a block allocated by objalloc_alloc. This also frees all more 111 recently allocated blocks. */ 112 113extern void objalloc_free_block PARAMS ((struct objalloc *, PTR)); 114 115#endif /* OBJALLOC_H */ 116