src/kits/support/BlockCache.cpp

   1 /*
   2  * Copyright (c) 2003 Marcus Overhagen
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included in
  12  * all copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  17  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  18  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  19  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  20  * DEALINGS IN THE SOFTWARE.
  21  */
  22
  23 #include <BlockCache.h>
  24 #include <Debug.h>
  25 #include <string.h>
  26 #include <stdlib.h>
  27 #include <new>
  28
  29
  30 #define MAGIC1          0x9183f4d9
  31 #define MAGIC2          0xa6b3c87d
  32
  33
  34 struct BBlockCache::_FreeBlock {
  35         DEBUG_ONLY(     uint32          magic1; )
  36                                 _FreeBlock *next;
  37         DEBUG_ONLY(     uint32          magic2; )
  38 };
  39
  40
  41 // The requirements set by the BeBook's description of the destructor,
  42 // as well as Get() function, allowing the caller to dispose of the
  43 // memory, do not allow to allocate one large block to be used as pool.
  44 // Thus we need to create multiple small ones.
  45 // We maintain a list of free blocks.
  46
  47 BBlockCache::BBlockCache(uint32 blockCount, size_t blockSize,
  48         uint32 allocationType)
  49         :
  50         fFreeList(0),
  51         fBlockSize(blockSize),
  52         fFreeBlocks(0),
  53         fBlockCount(blockCount),
  54         fLocker("some BBlockCache lock"),
  55         fAlloc(0),
  56         fFree(0)
  57 {
  58         switch (allocationType) {
  59                 case B_OBJECT_CACHE:
  60                         fAlloc = &operator new[];
  61                         fFree = &operator delete[];
  62                         break;
  63                 case B_MALLOC_CACHE:
  64                 default:
  65                         fAlloc = &malloc;
  66                         fFree = &free;
  67                         break;
  68         }
  69
  70         // To properly maintain a list of free buffers, a buffer must be
  71         // large enough to contain the _FreeBlock struct that is used.
  72         if (blockSize < sizeof(_FreeBlock))
  73                 blockSize = sizeof(_FreeBlock);
  74
  75         // should have at least one block
  76         if (blockCount == 0)
  77                 blockCount = 1;
  78
  79         // create blocks and put them into the free list
  80         while (blockCount--) {
  81                 _FreeBlock *block = reinterpret_cast<_FreeBlock *>(fAlloc(blockSize));
  82                 if (!block)
  83                         break;
  84                 fFreeBlocks++;
  85                 block->next = fFreeList;
  86                 fFreeList = block;
  87                 DEBUG_ONLY(block->magic1 = MAGIC1);
  88                 DEBUG_ONLY(block->magic2 = MAGIC2 + (uint32)(addr_t)block->next);
  89         }
  90 }
  91
  92
  93 BBlockCache::~BBlockCache()
  94 {
  95         // walk the free list and deallocate all blocks
  96         fLocker.Lock();
  97         while (fFreeList) {
  98                 ASSERT(fFreeList->magic1 == MAGIC1);
  99                 ASSERT(fFreeList->magic2 == MAGIC2 + (uint32)(addr_t)fFreeList->next);
 100                 void *pointer = fFreeList;
 101                 fFreeList = fFreeList->next;
 102                 DEBUG_ONLY(memset(pointer, 0xCC, sizeof(_FreeBlock)));
 103                 fFree(pointer);
 104         }
 105         fLocker.Unlock();
 106 }
 107
 108
 109 void *
 110 BBlockCache::Get(size_t blockSize)
 111 {
 112         if (!fLocker.Lock())
 113                 return 0;
 114         void *pointer;
 115         if (blockSize == fBlockSize && fFreeList != 0) {
 116                 // we can take a block from the list
 117                 ASSERT(fFreeList->magic1 == MAGIC1);
 118                 ASSERT(fFreeList->magic2 == MAGIC2 + (uint32)(addr_t)fFreeList->next);
 119                 pointer = fFreeList;
 120                 fFreeList = fFreeList->next;
 121                 fFreeBlocks--;
 122                 DEBUG_ONLY(memset(pointer, 0xCC, sizeof(_FreeBlock)));
 123         } else {
 124                 if (blockSize < sizeof(_FreeBlock))
 125                         blockSize = sizeof(_FreeBlock);
 126                 pointer = fAlloc(blockSize);
 127                 DEBUG_ONLY(if (pointer) memset(pointer, 0xCC, sizeof(_FreeBlock)));
 128         }
 129         fLocker.Unlock();
 130         return pointer;
 131 }
 132
 133
 134 void
 135 BBlockCache::Save(void *pointer, size_t blockSize)
 136 {
 137         if (!fLocker.Lock())
 138                 return;
 139         if (blockSize == fBlockSize && fFreeBlocks < fBlockCount) {
 140                 // the block needs to be returned to the cache
 141                 _FreeBlock *block = reinterpret_cast<_FreeBlock *>(pointer);
 142                 block->next = fFreeList;
 143                 fFreeList = block;
 144                 fFreeBlocks++;
 145                 DEBUG_ONLY(block->magic1 = MAGIC1);
 146                 DEBUG_ONLY(block->magic2 = MAGIC2 + (uint32)(addr_t)block->next);
 147         } else {
 148                 DEBUG_ONLY(memset(pointer, 0xCC, sizeof(_FreeBlock)));
 149                 fFree(pointer);
 150         }
 151         fLocker.Unlock();
 152 }
 153
 154
 155 void BBlockCache::_ReservedBlockCache1() {}
 156 void BBlockCache::_ReservedBlockCache2() {}