ode/src/obstack.cpp

   1 /*************************************************************************
   2  *                                                                       *
   3  * Open Dynamics Engine, Copyright (C) 2001,2002 Russell L. Smith.       *
   4  * All rights reserved.  Email: russ@q12.org   Web: www.q12.org          *
   5  *                                                                       *
   6  * This library is free software; you can redistribute it and/or         *
   7  * modify it under the terms of EITHER:                                  *
   8  *   (1) The GNU Lesser General Public License as published by the Free  *
   9  *       Software Foundation; either version 2.1 of the License, or (at  *
  10  *       your option) any later version. The text of the GNU Lesser      *
  11  *       General Public License is included with this library in the     *
  12  *       file LICENSE.TXT.                                               *
  13  *   (2) The BSD-style license that is included with this library in     *
  14  *       the file LICENSE-BSD.TXT.                                       *
  15  *                                                                       *
  16  * This library is distributed in the hope that it will be useful,       *
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the files    *
  19  * LICENSE.TXT and LICENSE-BSD.TXT for more details.                     *
  20  *                                                                       *
  21  *************************************************************************/
  22
  23 #include <ode/common.h>
  24 #include <ode/error.h>
  25 #include <ode/memory.h>
  26 #include "obstack.h"
  27
  28 //****************************************************************************
  29 // macros and constants
  30
  31 #define ROUND_UP_OFFSET_TO_EFFICIENT_SIZE(arena,ofs) \
  32   ofs = (size_t) (dEFFICIENT_SIZE( ((intP)(arena)) + ofs ) - ((intP)(arena)) );
  33
  34 #define MAX_ALLOC_SIZE \
  35   ((size_t)(dOBSTACK_ARENA_SIZE - sizeof (Arena) - EFFICIENT_ALIGNMENT + 1))
  36
  37 //****************************************************************************
  38 // dObStack
  39
  40 dObStack::dObStack()
  41 {
  42   first = 0;
  43   last = 0;
  44   current_arena = 0;
  45   current_ofs = 0;
  46 }
  47
  48
  49 dObStack::~dObStack()
  50 {
  51   // free all arenas
  52   Arena *a,*nexta;
  53   a = first;
  54   while (a) {
  55     nexta = a->next;
  56     dFree (a,dOBSTACK_ARENA_SIZE);
  57     a = nexta;
  58   }
  59 }
  60
  61
  62 void *dObStack::alloc (int num_bytes)
  63 {
  64   if ((size_t)num_bytes > MAX_ALLOC_SIZE) dDebug (0,"num_bytes too large");
  65
  66   // allocate or move to a new arena if necessary
  67   if (!first) {
  68     // allocate the first arena if necessary
  69     first = last = (Arena *) dAlloc (dOBSTACK_ARENA_SIZE);
  70     first->next = 0;
  71     first->used = sizeof (Arena);
  72     ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (first,first->used);
  73   }
  74   else {
  75     // we already have one or more arenas, see if a new arena must be used
  76     if ((last->used + num_bytes) > dOBSTACK_ARENA_SIZE) {
  77       if (!last->next) {
  78         last->next = (Arena *) dAlloc (dOBSTACK_ARENA_SIZE);
  79         last->next->next = 0;
  80       }
  81       last = last->next;
  82       last->used = sizeof (Arena);
  83       ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (last,last->used);
  84     }
  85   }
  86
  87   // allocate an area in the arena
  88   char *c = ((char*) last) + last->used;
  89   last->used += num_bytes;
  90   ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (last,last->used);
  91   return c;
  92 }
  93
  94
  95 void dObStack::freeAll()
  96 {
  97   last = first;
  98   if (first) {
  99     first->used = sizeof(Arena);
 100     ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (first,first->used);
 101   }
 102 }
 103
 104
 105 void *dObStack::rewind()
 106 {
 107   current_arena = first;
 108   current_ofs = sizeof (Arena);
 109   if (current_arena) {
 110     ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (current_arena,current_ofs)
 111     return ((char*) current_arena) + current_ofs;
 112   }
 113   else return 0;
 114 }
 115
 116
 117 void *dObStack::next (int num_bytes)
 118 {
 119   // this functions like alloc, except that no new storage is ever allocated
 120   if (!current_arena) return 0;
 121   current_ofs += num_bytes;
 122   ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (current_arena,current_ofs);
 123   if (current_ofs >= current_arena->used) {
 124     current_arena = current_arena->next;
 125     if (!current_arena) return 0;
 126     current_ofs = sizeof (Arena);
 127     ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (current_arena,current_ofs);
 128   }
 129   return ((char*) current_arena) + current_ofs;
 130 }