apps/plugins/doom/z_bmalloc.c

   1 /* Emacs style mode select   -*- C++ -*-
   2  *-----------------------------------------------------------------------------
   3  *
   4  *
   5  *  PrBoom a Doom port merged with LxDoom and LSDLDoom
   6  *  based on BOOM, a modified and improved DOOM engine
   7  *  Copyright (C) 1999 by
   8  *  id Software, Chi Hoang, Lee Killough, Jim Flynn, Rand Phares, Ty Halderman
   9  *  Copyright (C) 1999-2000 by
  10  *  Jess Haas, Nicolas Kalkhof, Colin Phipps, Florian Schulze
  11  *
  12  *  This program is free software; you can redistribute it and/or
  13  *  modify it under the terms of the GNU General Public License
  14  *  as published by the Free Software Foundation; either version 2
  15  *  of the License, or (at your option) any later version.
  16  *
  17  *  This program 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 General Public License for more details.
  21  *
  22  *  You should have received a copy of the GNU General Public License
  23  *  along with this program; if not, write to the Free Software
  24  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  25  *  02111-1307, USA.
  26  *
  27  * DESCRIPTION:
  28  * This is designed to be a fast allocator for small, regularly used block sizes
  29  *-----------------------------------------------------------------------------
  30  */
  31 #include "doomtype.h"
  32 #include "z_zone.h"
  33 #include "z_bmalloc.h"
  34 #include "i_system.h"
  35 #include "rockmacros.h"
  36
  37 typedef struct bmalpool_s {
  38    struct bmalpool_s *nextpool;
  39    size_t             blocks;
  40    byte               used[0];
  41 } bmalpool_t;
  42
  43 inline static void* getelem(bmalpool_t *p, size_t size, size_t n)
  44 {
  45    return (((byte*)p) + sizeof(bmalpool_t) + sizeof(byte)*(p->blocks) + size*n);
  46 }
  47
  48 inline static int iselem(const bmalpool_t *pool, size_t size, const void* p)
  49 {
  50    // CPhipps - need portable # of bytes between pointers
  51    int dif = (const char*)p - (const char*)pool;
  52
  53    dif -= sizeof(bmalpool_t);
  54    dif -= pool->blocks;
  55    if (dif<0) return -1;
  56    dif /= size;
  57    return (((size_t)dif >= pool->blocks) ? -1 : dif);
  58 }
  59
  60 enum { unused_block = 0, used_block = 1};
  61
  62 void* Z_BMalloc(struct block_memory_alloc_s *pzone)
  63 {
  64    register bmalpool_t **pool = (bmalpool_t **)&(pzone->firstpool);
  65    while (*pool != NULL) {
  66       byte *p = memchr((*pool)->used, unused_block, (*pool)->blocks); // Scan for unused marker
  67       if (p) {
  68          int n = p - (*pool)->used;
  69 #ifdef SIMPLECHECKS
  70          if ((n<0) || ((size_t)n>=(*pool)->blocks))
  71             I_Error("Z_BMalloc: memchr returned pointer outside of array");
  72 #endif
  73          (*pool)->used[n] = used_block;
  74          return getelem(*pool, pzone->size, n);
  75       } else
  76          pool = &((*pool)->nextpool);
  77    }
  78    {
  79       // Nothing available, must allocate a new pool
  80       bmalpool_t *newpool;
  81
  82       // CPhipps: Allocate new memory, initialised to 0
  83
  84       *pool = newpool = Z_Calloc(sizeof(*newpool) + (sizeof(byte) + pzone->size)*(pzone->perpool),
  85                                  1,  pzone->tag, NULL);
  86       newpool->nextpool = NULL; // NULL = (void*)0 so this is redundant
  87
  88       // Return element 0 from this pool to satisfy the request
  89       newpool->used[0] = used_block;
  90       newpool->blocks = pzone->perpool;
  91       return getelem(newpool, pzone->size, 0);
  92    }
  93 }
  94
  95 void Z_BFree(struct block_memory_alloc_s *pzone, void* p)
  96 {
  97    register bmalpool_t **pool = (bmalpool_t**)&(pzone->firstpool);
  98
  99    while (*pool != NULL) {
 100       int n = iselem(*pool, pzone->size, p);
 101       if (n >= 0) {
 102 #ifdef SIMPLECHECKS
 103          if ((*pool)->used[n] == unused_block)
 104             I_Error("Z_BFree: Refree in zone %s", pzone->desc);
 105 #endif
 106          (*pool)->used[n] = unused_block;
 107          if (memchr(((*pool)->used), used_block, (*pool)->blocks) == NULL) {
 108             // Block is all unused, can be freed
 109             bmalpool_t *oldpool = *pool;
 110             *pool = (*pool)->nextpool;
 111             Z_Free(oldpool);
 112          }
 113          return;
 114       } else pool = &((*pool)->nextpool);
 115    }
 116    I_Error("Z_BFree: Free not in zone %s", pzone->desc);
 117 }