memalloc.c

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   /*======================================*/

   newBlock->nextBlock = NULL;
   newBlock->prevBlock = blockPtr;
   newBlock->nextFree = (struct chunkInfo *) (((char *) newBlock) + MemoryData(theEnv)->BlockInfoSize);
   newBlock->size = (long) usableBlockSize;
   blockPtr->nextBlock = newBlock;

   newTopChunk = (struct chunkInfo *) (((char *) newBlock) + MemoryData(theEnv)->BlockInfoSize + MemoryData(theEnv)->ChunkInfoSize + usableBlockSize);
   newTopChunk->nextFree = NULL;
   newTopChunk->lastFree = NULL;
   newTopChunk->size = 0;
   newTopChunk->prevChunk = newBlock->nextFree;

   newBlock->nextFree->nextFree = NULL;
   newBlock->nextFree->lastFree = NULL;
   newBlock->nextFree->prevChunk = NULL;
   newBlock->nextFree->size = (long) usableBlockSize;

   return(1);
  }

/*******************************************************/
/* RequestChunk: Allocates memory by returning a chunk */
/*   of memory from a larger block of memory.          */
/*******************************************************/
globle void *RequestChunk(
  void *theEnv,
  size_t requestSize)
  {
   struct chunkInfo *chunkPtr;
   struct blockInfo *blockPtr;

   /*==================================================*/
   /* Allocate initial memory pool block if it has not */
   /* already been allocated.                          */
   /*==================================================*/

   if (MemoryData(theEnv)->BlockMemoryInitialized == FALSE)
      {
       if (InitializeBlockMemory(theEnv,requestSize) == 0) return(NULL);
      }

   /*====================================================*/
   /* Make sure that the amount of memory requested will */
   /* fall on a boundary of strictest alignment          */
   /*====================================================*/

   requestSize = (((requestSize - 1) / STRICT_ALIGN_SIZE) + 1) * STRICT_ALIGN_SIZE;

   /*=====================================================*/
   /* Search through the list of free memory for a block  */
   /* of the appropriate size.  If a block is found, then */
   /* allocate and return a pointer to it.                */
   /*=====================================================*/

   blockPtr = MemoryData(theEnv)->TopMemoryBlock;

   while (blockPtr != NULL)
     {
      chunkPtr = blockPtr->nextFree;

      while (chunkPtr != NULL)
        {
         if ((chunkPtr->size == requestSize) ||
             (chunkPtr->size > (requestSize + MemoryData(theEnv)->ChunkInfoSize)))
           {
            AllocateChunk(theEnv,blockPtr,chunkPtr,requestSize);

            return((void *) (((char *) chunkPtr) + MemoryData(theEnv)->ChunkInfoSize));
           }
         chunkPtr = chunkPtr->nextFree;
        }

      if (blockPtr->nextBlock == NULL)
        {
         if (AllocateBlock(theEnv,blockPtr,requestSize) == 0)  /* get another block */
           { return(NULL); }
        }
      blockPtr = blockPtr->nextBlock;
     }

   SystemError(theEnv,"MEMORY",2);
   EnvExitRouter(theEnv,EXIT_FAILURE);
   return(NULL); /* Unreachable, but prevents warning. */
  }

/********************************************/
/* AllocateChunk: Allocates a chunk from an */
/*   existing chunk in a block of memory.   */
/********************************************/
static void AllocateChunk(
  void *theEnv,
  struct blockInfo *parentBlock,
  struct chunkInfo *chunkPtr,
  size_t requestSize)
  {
   struct chunkInfo *splitChunk, *nextChunk;

   /*=============================================================*/
   /* If the size of the memory chunk is an exact match for the   */
   /* requested amount of memory, then the chunk can be allocated */
   /* without splitting it.                                       */
   /*=============================================================*/

   if (requestSize == chunkPtr->size)
     {
      chunkPtr->size = - (long int) requestSize;
      if (chunkPtr->lastFree == NULL)
        {
         if (chunkPtr->nextFree != NULL)
           { parentBlock->nextFree = chunkPtr->nextFree; }
         else
           { parentBlock->nextFree = NULL; }
        }
      else
        { chunkPtr->lastFree->nextFree = chunkPtr->nextFree; }

      if (chunkPtr->nextFree != NULL)
        { chunkPtr->nextFree->lastFree = chunkPtr->lastFree; }

      chunkPtr->lastFree = NULL;
      chunkPtr->nextFree = NULL;
      return;
     }

   /*===========================================================*/
   /* If the size of the memory chunk is larger than the memory */
   /* request, then split the chunk into two pieces.            */
   /*===========================================================*/

   nextChunk = (struct chunkInfo *)
              (((char *) chunkPtr) + MemoryData(theEnv)->ChunkInfoSize + chunkPtr->size);

   splitChunk = (struct chunkInfo *)
                  (((char *) chunkPtr) + (MemoryData(theEnv)->ChunkInfoSize + requestSize));

   splitChunk->size = (long) (chunkPtr->size - (requestSize + MemoryData(theEnv)->ChunkInfoSize));
   splitChunk->prevChunk = chunkPtr;

   splitChunk->nextFree = chunkPtr->nextFree;
   splitChunk->lastFree = chunkPtr->lastFree;

   nextChunk->prevChunk = splitChunk;

   if (splitChunk->lastFree == NULL)
     { parentBlock->nextFree = splitChunk; }
   else
     { splitChunk->lastFree->nextFree = splitChunk; }

   if (splitChunk->nextFree != NULL)
     { splitChunk->nextFree->lastFree = splitChunk; }

   chunkPtr->size = - (long int) requestSize;
   chunkPtr->lastFree = NULL;
   chunkPtr->nextFree = NULL;

   return;
  }

/***********************************************************/
/* ReturnChunk: Frees memory allocated using RequestChunk. */
/***********************************************************/
globle int ReturnChunk(
  void *theEnv,
  void *memPtr,
  size_t size)
  {
   struct chunkInfo *chunkPtr, *lastChunk, *nextChunk, *topChunk;
   struct blockInfo *blockPtr;

   /*=====================================================*/
   /* Determine if the expected size of the chunk matches */
   /* the size stored in the chunk's information record.  */
   /*=====================================================*/

   size = (((size - 1) / STRICT_ALIGN_SIZE) + 1) * STRICT_ALIGN_SIZE;

   chunkPtr = (struct chunkInfo *) (((char *) memPtr) - MemoryData(theEnv)->ChunkInfoSize);

   if (chunkPtr == NULL)
     { return(FALSE); }

   if (chunkPtr->size >= 0)
     { return(FALSE); }

   if (chunkPtr->size != - (long int) size)
     { return(FALSE); }

   chunkPtr->size = - chunkPtr->size;

   /*=============================================*/
   /* Determine in which block the chunk resides. */
   /*=============================================*/

   topChunk = chunkPtr;
   while (topChunk->prevChunk != NULL)
     { topChunk = topChunk->prevChunk; }
   blockPtr = (struct blockInfo *) (((char *) topChunk) - MemoryData(theEnv)->BlockInfoSize);

   /*===========================================*/
   /* Determine the chunks physically preceding */
   /* and following the returned chunk.         */
   /*===========================================*/

   lastChunk = chunkPtr->prevChunk;
   nextChunk = (struct chunkInfo *) (((char *) memPtr) + size);

   /*=========================================================*/
   /* Add the chunk to the list of free chunks for the block. */
   /*=========================================================*/

   if (blockPtr->nextFree != NULL)
     { blockPtr->nextFree->lastFree = chunkPtr; }

   chunkPtr->nextFree = blockPtr->nextFree;
   chunkPtr->lastFree = NULL;

   blockPtr->nextFree = chunkPtr;

   /*=====================================================*/
   /* Combine this chunk with previous chunk if possible. */
   /*=====================================================*/

   if (lastChunk != NULL)
     {
      if (lastChunk->size > 0)
        {
         lastChunk->size += (MemoryData(theEnv)->ChunkInfoSize + chunkPtr->size);

         if (nextChunk != NULL)
           { nextChunk->prevChunk = lastChunk; }
         else
           { return(FALSE); }

         if (lastChunk->lastFree != NULL)
           { lastChunk->lastFree->nextFree = lastChunk->nextFree; }

         if (lastChunk->nextFree != NULL)
           { lastChunk->nextFree->lastFree = lastChunk->lastFree; }

         lastChunk->nextFree = chunkPtr->nextFree;
         if (chunkPtr->nextFree != NULL)
           { chunkPtr->nextFree->lastFree = lastChunk; }
         lastChunk->lastFree = NULL;

         blockPtr->nextFree = lastChunk;
         chunkPtr->lastFree = NULL;
         chunkPtr->nextFree = NULL;
         chunkPtr = lastChunk;
        }
     }

   /*=====================================================*/
   /* Combine this chunk with the next chunk if possible. */
   /*=====================================================*/

   if (nextChunk == NULL) return(FALSE);
   if (chunkPtr == NULL) return(FALSE);

   if (nextChunk->size > 0)
     {
      chunkPtr->size += (MemoryData(theEnv)->ChunkInfoSize + nextChunk->size);

      topChunk = (struct chunkInfo *) (((char *) nextChunk) + nextChunk->size + MemoryData(theEnv)->ChunkInfoSize);
      if (topChunk != NULL)
        { topChunk->prevChunk = chunkPtr; }
      else
        { return(FALSE); }

      if (nextChunk->lastFree != NULL)
        { nextChunk->lastFree->nextFree = nextChunk->nextFree; }

      if (nextChunk->nextFree != NULL)
        { nextChunk->nextFree->lastFree = nextChunk->lastFree; }

     }

   /*===========================================*/
   /* Free the buffer if we can, but don't free */
   /* the first buffer if it's the only one.    */
   /*===========================================*/

   if ((chunkPtr->prevChunk == NULL) &&
       (chunkPtr->size == blockPtr->size))
     {
      if (blockPtr->prevBlock != NULL)
        {
         blockPtr->prevBlock->nextBlock = blockPtr->nextBlock;
         if (blockPtr->nextBlock != NULL)
           { blockPtr->nextBlock->prevBlock = blockPtr->prevBlock; }
         free((char *) blockPtr);
        }
      else
        {
         if (blockPtr->nextBlock != NULL)
           {
            blockPtr->nextBlock->prevBlock = NULL;
            MemoryData(theEnv)->TopMemoryBlock = blockPtr->nextBlock;
            free((char *) blockPtr);
           }
        }
     }

   return(TRUE);
  }

/***********************************************/
/* ReturnAllBlocks: Frees all allocated blocks */
/*   back to the operating system.             */
/***********************************************/
globle void ReturnAllBlocks(
  void *theEnv)
  {
   struct blockInfo *theBlock, *nextBlock;

   /*======================================*/
   /* Free up int based memory allocation. */
   /*======================================*/

   theBlock = MemoryData(theEnv)->TopMemoryBlock;
   while (theBlock != NULL)
     {
      nextBlock = theBlock->nextBlock;
      free((char *) theBlock);
      theBlock = nextBlock;
     }

   MemoryData(theEnv)->TopMemoryBlock = NULL;
  }
#endif