zoneHeap.hpp

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/* Copyright 1994, LongView Technologies L.L.C. $Revision: 1.8 $ */
/* Copyright (c) 2006, Sun Microsystems, Inc.
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#ifdef DELTA_COMPILER

// Basic heap management
// maintains a map of the heap + free lists to reduce fragmentation
// allocations are in multiples of block size (2**k)

class HeapChunk;
class ChunkKlass;
class FreeList;

class Heap: public CHeapObj {
 protected:
  int size;             // total size in bytes
 public:
  int blockSize;        // allocation unit in bytes (must be power of 2)
  int nfree;            // number of free lists
 protected:
  int log2BS;           // log2(blockSize)
  
  int bytesUsed;        // used bytes (rounded to block size)
  int total;            // total bytes allocated so far
  int ifrag;            // bytes wasted by internal fragmentation
  char* _base;          // for deallocation
  char* base;           // base addr of heap (aligned to block size)
  ChunkKlass* heapKlass;// map of heap (1 byte / block)
  FreeList* freeList;   // array of free lists for different chunk sizes
  FreeList* bigList;    // list of all big free blocks
  ChunkKlass* lastCombine;// result of last block combination
 public:
  Heap* newHeap;        // only set when growing a heap (i.e. replacing it)
  bool combineMode;     // do eager block combination on deallocs?
  
 public:
  // Constructor
  Heap(int s, int bs);
  ~Heap();

  // Initializes the Heap
  void clear();
  
  // Allocation
  void* allocate(int wantedBytes);      // returns NULL if allocation failed
  void  deallocate(void* p, int bytes);

  // Compaction
  char* compact(void move(char* from, char* to, int nbytes));   // returns first free byte  

  // Sizes  
  int capacity()  const { return size; }
  int usedBytes() const { return bytesUsed; }
  int freeBytes() const { return size - bytesUsed; }

  // Fragmentation
  double intFrag() const { return usedBytes() ? (float)ifrag / usedBytes() : 0 ; }
  double extFrag() const { return usedBytes() ? 1.0 - (float)usedBytes() / capacity() : 0; }

  // Location
  char* startAddr() const { return base; }
  char* endAddr()   const { return startAddr() + capacity(); }

  // Queries
  bool  contains(void* p) const { return (void*)base <= p && p < (void*)(base + capacity()); }
  void* firstUsed() const; // Address of first used object
  void* nextUsed(void* prev) const;
  void* findStartOfBlock(void* start) const;
  int   sizeOfBlock(void* nm) const;
  
  // Misc.
  void verify() const;
  void print() const;

 protected:
  int mapSize() const { return size >> log2BS; }
  char*  blockAddr(ChunkKlass* m) const {
    u_char* fm = (u_char*)heapKlass;
    u_char* bm = (u_char*)m;
    assert(bm >= fm && bm < fm + mapSize(), "not a heapKlass entry");
    return base + ((bm - fm) << log2BS);
  }
  ChunkKlass* mapAddr(void* p) const {
    char* pp = (char*)p;
    assert(pp >= base && pp < base + size, "not in this heap");
    assert(int(pp) % blockSize == 0, "must be block-aligned");
    u_char* fm = (u_char*)heapKlass;
    return (ChunkKlass*)(fm + ((pp - base) >> log2BS));
  }

  ChunkKlass* heapEnd() const { return (ChunkKlass*)((u_char*)heapKlass + mapSize()); }

  // Free list management
  void* allocFromLists(int wantedBytes);
  bool  addToFreeList(ChunkKlass* m);
  void  removeFromFreeList(ChunkKlass* m);

  int combineAll();
  int combine(HeapChunk*& m);
};

#endif

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