mdw@git.distorted.org.uk Git - mLib/blob - mem/arena.h

   1 /* -*-c-*-
   2  *
   3  * Abstraction for memory allocation arenas
   4  *
   5  * (c) 2000 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of the mLib utilities library.
  11  *
  12  * mLib is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * mLib is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with mLib; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 #ifndef MLIB_ARENA_H
  29 #define MLIB_ARENA_H
  30
  31 #ifdef __cplusplus
  32   extern "C" {
  33 #endif
  34
  35 /*----- Header files ------------------------------------------------------*/
  36
  37 #include <stdlib.h>
  38
  39 /*----- Data structures ---------------------------------------------------*/
  40
  41 /* --- An arena structure --- */
  42
  43 typedef struct arena {
  44   const struct arena_ops *ops;
  45 } arena;
  46
  47 typedef struct arena_ops {
  48   void *(*alloc)(arena */*a*/, size_t /*sz*/);
  49   void *(*realloc)(arena */*a*/, void */*p*/, size_t /*sz*/, size_t /*osz*/);
  50   void (*free)(arena */*a*/, void */*p*/);
  51   void (*purge)(arena */*a*/);
  52 } arena_ops;
  53
  54 /*----- Global variables --------------------------------------------------*/
  55
  56 extern arena *arena_global;             /* Standard global arena */
  57 extern arena arena_stdlib;              /* Arena based on @malloc@/@free@ */
  58
  59 /*----- Functions provided ------------------------------------------------*/
  60
  61 /* --- @ALLOCV_SAFE_P@, @NEWV_SAFE_P@ ---
  62  *
  63  * Arguments:   @type *p@ = pointer to a vector (for @NEWV_SAFE_P@; not
  64  *                      evaluated)
  65  *              @size_t n@ = number of elements
  66  *              @size_t sz@ = element size (for @ALLOCV_SAFE_P@)
  67  *
  68  * Returns:     Nonzero if the product of @n@ and @sz@ (or @sizeof(*p)@) is
  69  *              representable in type @size_t@.
  70  */
  71
  72 #define ALLOCV_SAFE_P(n, sz) ((n) <= (size_t)-1/(sz))
  73 #define NEWV_SAFE_P(p, n) (ALLOCV_SAFE_P((n), sizeof(*(p))))
  74
  75 /* --- @arena_fakerealloc@ --- *
  76  *
  77  * Arguments:   @arena *a@ = pointer to arena block
  78  *              @void *p@ = pointer to memory block to resize
  79  *              @size_t sz@ = size desired for the block
  80  *              @size_t osz@ = size of the old block
  81  *
  82  * Returns:     ---
  83  *
  84  * Use:         Standard fake @realloc@ function, for use if you don't
  85  *              support @realloc@ properly.
  86  */
  87
  88 extern void *arena_fakerealloc(arena */*a*/, void */*p*/,
  89                                size_t /*sz*/, size_t /*osz*/);
  90
  91 /* --- Useful macros --- */
  92
  93 #define A_ALLOC(a, sz) (((a)->ops->alloc)((a), (sz)))
  94 #define A_ALLOCV(a, n, sz)                                              \
  95         (ALLOCV_SAFE_P((n), (sz)) ? ((a)->ops->alloc)((a), (n)*(sz)) : 0)
  96 #define A_NEW(p, a) do { (p) = A_ALLOC((a), sizeof(*(p))); } while (0)
  97 #define A_NEWV(p, a, n)                                                 \
  98         do { (p) = A_ALLOCV((a), (n), sizeof(*(p))); } while (0)
  99 #define A_REALLOC(a, p, sz, osz)                                        \
 100         (((a)->ops->realloc)((a), (p), (sz), (osz)))
 101 #define A_REALLOCV(a, p, n, on, sz)                                     \
 102         (ALLOCV_SAFE_P((n), (sz)) ?                                     \
 103                 ((a)->ops->realloc)((a), (p), (n)*(sz), (on)*(sz)) : 0)
 104 #define A_RENEWV(q, p, a, n, on) do {                                   \
 105         (q) = !sizeof((*(p)) = (*(q))) +                                \
 106               A_REALLOCV((a), (p), (n), (on), sizeof(*(p)));            \
 107 } while (0)
 108 #define A_FREE(a, p) (((a)->ops->free)((a), (p)))
 109
 110 /* --- Simple function equivalents --- */
 111
 112 extern void *a_alloc(arena */*a*/, size_t /*sz*/);
 113 extern void *a_allocv(arena */*a*/, size_t /*n*/, size_t /*sz*/);
 114 extern void *a_realloc(arena */*a*/, void */*p*/,
 115                        size_t /*sz*/, size_t /*osz*/);
 116 extern void *a_reallocv(arena */*a*/, void */*p*/,
 117                         size_t /*n*/, size_t /*on*/, size_t /*sz*/);
 118 extern void a_free(arena */*a*/, void */*p*/);
 119
 120 /*----- That's all, folks -------------------------------------------------*/
 121
 122 #ifdef __cplusplus
 123   }
 124 #endif
 125
 126 #endif