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