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 "config.h"
  27 #include "obstack.h"
  28
  29
  30 //****************************************************************************
  31 // macros and constants
  32
  33 #define ROUND_UP_OFFSET_TO_EFFICIENT_SIZE(arena,ofs) \
  34     ofs = (sizeint) (dEFFICIENT_SIZE( ((sizeint)(arena)) + ofs ) - ((sizeint)(arena)) )
  35
  36 #define MAX_ALLOC_SIZE \
  37     ((sizeint)(dOBSTACK_ARENA_SIZE - sizeof (Arena) - EFFICIENT_ALIGNMENT + 1))
  38
  39 //****************************************************************************
  40 // dObStack
  41
  42 dObStack::dObStack():
  43     m_first(NULL), m_last(NULL),
  44     m_current_arena(NULL), m_current_ofs(0)
  45 {
  46 }
  47
  48
  49 dObStack::~dObStack()
  50 {
  51     // free all arenas
  52     Arena *a,*nexta;
  53     a = m_first;
  54     while (a) {
  55         nexta = a->m_next;
  56         dFree (a,dOBSTACK_ARENA_SIZE);
  57         a = nexta;
  58     }
  59 }
  60
  61
  62 void *dObStack::alloc (sizeint num_bytes)
  63 {
  64     if (num_bytes > MAX_ALLOC_SIZE) dDebug (0,"num_bytes too large");
  65
  66     bool last_alloc_needed = false, last_init_needed = false;
  67     Arena **last_ptr = NULL;
  68
  69     if (m_last != NULL) {
  70         if ((m_last->m_used + num_bytes) > dOBSTACK_ARENA_SIZE) {
  71             if (m_last->m_next != NULL) {
  72                 m_last = m_last->m_next;
  73                 last_init_needed = true;
  74             } else {
  75                 last_ptr = &m_last->m_next;
  76                 last_alloc_needed = true;
  77             }
  78         }
  79     } else {
  80         last_ptr = &m_last;
  81         last_alloc_needed = true;
  82     }
  83
  84     if (last_alloc_needed) {
  85         Arena *new_last = (Arena *) dAlloc (dOBSTACK_ARENA_SIZE);
  86         new_last->m_next = 0;
  87         *last_ptr = new_last;
  88         if (m_first == NULL) {
  89             m_first = new_last;
  90         }
  91         m_last = new_last;
  92         last_init_needed = true;
  93     }
  94
  95     if (last_init_needed) {
  96         m_last->m_used = sizeof (Arena);
  97         ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (m_last,m_last->m_used);
  98     }
  99
 100     // allocate an area in the arena
 101     char *c = ((char*) m_last) + m_last->m_used;
 102     m_last->m_used += num_bytes;
 103     ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (m_last,m_last->m_used);
 104     return c;
 105 }
 106
 107
 108 void dObStack::freeAll()
 109 {
 110     Arena *current = m_first;
 111     m_last = current;
 112     // It is necessary to reset used sizes in whole arena chain
 113     // otherwise enumeration may proceed to remains of old deleted joints in unused arenas
 114     while (current) {
 115         current->m_used = sizeof(Arena);
 116         ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (current,current->m_used);
 117         current = current->m_next;
 118     }
 119 }
 120
 121
 122 void *dObStack::rewind()
 123 {
 124     return switch_to_arena(m_first);
 125 }
 126
 127 void *dObStack::next (sizeint num_bytes)
 128 {
 129     // this functions like alloc, except that no new storage is ever allocated
 130     if (!m_current_arena) {
 131         return 0;
 132     }
 133
 134     m_current_ofs += num_bytes;
 135     ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (m_current_arena,m_current_ofs);
 136
 137     if (m_current_ofs < m_current_arena->m_used) {
 138         return ((char*) m_current_arena) + m_current_ofs;
 139     }
 140
 141     return switch_to_arena(m_current_arena->m_next);
 142 }
 143
 144 void *dObStack::switch_to_arena(Arena *next_arena)
 145 {
 146     m_current_arena = next_arena;
 147     if (!next_arena) {
 148         return 0;
 149     }
 150     m_current_ofs = sizeof (Arena);
 151     ROUND_UP_OFFSET_TO_EFFICIENT_SIZE (next_arena, m_current_ofs);
 152     // Check if end of allocation has been reached
 153     if (m_current_ofs >= next_arena->m_used) {
 154         return 0;
 155     }
 156     return ((char*) next_arena) + m_current_ofs;
 157 }