MemoryAllocator.h

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/* SPDX-FileCopyrightText: 2011-2023 Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */
 
#ifndef __MEMORYALLOCATOR_H__
#define __MEMORYALLOCATOR_H__
 
#include <cstdio>
#include <cstdlib>
 
#include "MEM_guardedalloc.h"
 
#define HEAP_BASE 16
#define UCHAR unsigned char


class VirtualMemoryAllocator {
 public:
  virtual ~VirtualMemoryAllocator() = default;
 
  virtual void *allocate() = 0;
  virtual void deallocate(void *obj) = 0;
  virtual void destroy() = 0;
  virtual void printInfo() = 0;
 
  virtual int getAllocated() = 0;
  virtual int getAll() = 0;
  virtual int getBytes() = 0;
 
  MEM_CXX_CLASS_ALLOC_FUNCS("DUALCON:VirtualMemoryAllocator")
};

template<int N> class MemoryAllocator : public VirtualMemoryAllocator {
 private:
  int HEAP_UNIT, HEAP_MASK;

  UCHAR **data;

  UCHAR ***stack;

  int datablocknum;

  int stackblocknum;

  int stacksize;

  int available;

  void allocateDataBlock()
  {
    // Allocate a data block
    datablocknum += 1;
    data = (UCHAR **)realloc(data, sizeof(UCHAR *) * datablocknum);
    data[datablocknum - 1] = (UCHAR *)malloc(HEAP_UNIT * N);
 
    // Update allocation stack
    for (int i = 0; i < HEAP_UNIT; i++) {
      stack[0][i] = (data[datablocknum - 1] + i * N);
    }
    available = HEAP_UNIT;
  }

  void allocateStackBlock()
  {
    // Allocate a stack block
    stackblocknum += 1;
    stacksize += HEAP_UNIT;
    stack = (UCHAR ***)realloc(stack, sizeof(UCHAR **) * stackblocknum);
    stack[stackblocknum - 1] = (UCHAR **)malloc(HEAP_UNIT * sizeof(UCHAR *));
  }
 
 public:
  MemoryAllocator()
  {
    HEAP_UNIT = 1 << HEAP_BASE;
    HEAP_MASK = (1 << HEAP_BASE) - 1;
 
    data = (UCHAR **)malloc(sizeof(UCHAR *));
    data[0] = (UCHAR *)malloc(HEAP_UNIT * N);
    datablocknum = 1;
 
    stack = (UCHAR ***)malloc(sizeof(UCHAR **));
    stack[0] = (UCHAR **)malloc(HEAP_UNIT * sizeof(UCHAR *));
    stackblocknum = 1;
    stacksize = HEAP_UNIT;
    available = HEAP_UNIT;
 
    for (int i = 0; i < HEAP_UNIT; i++) {
      stack[0][i] = (data[0] + i * N);
    }
  }

  void destroy() override
  {
    int i;
    for (i = 0; i < datablocknum; i++) {
      free(data[i]);
    }
    for (i = 0; i < stackblocknum; i++) {
      free(stack[i]);
    }
    free(data);
    free(stack);
  }

  void *allocate() override
  {
    if (available == 0) {
      allocateDataBlock();
    }
 
    // printf("Allocating %d\n", header[ allocated ]) ;
    available--;
    return (void *)stack[available >> HEAP_BASE][available & HEAP_MASK];
  }

  void deallocate(void *obj) override
  {
    if (available == stacksize) {
      allocateStackBlock();
    }
 
    // printf("De-allocating %d\n", ( obj - data ) / N ) ;
    stack[available >> HEAP_BASE][available & HEAP_MASK] = (UCHAR *)obj;
    available++;
    // printf("%d %d\n", allocated, header[ allocated ]) ;
  }

  void printInfo() override
  {
    printf("Bytes: %d Used: %d Allocated: %d Maxfree: %d\n",
           getBytes(),
           getAllocated(),
           getAll(),
           stacksize);
  }

  int getAllocated() override
  {
    return HEAP_UNIT * datablocknum - available;
  };
 
  int getAll() override
  {
    return HEAP_UNIT * datablocknum;
  };
 
  int getBytes() override
  {
    return N;
  };
 
  MEM_CXX_CLASS_ALLOC_FUNCS("DUALCON:MemoryAllocator")
};
 
#endif /* __MEMORYALLOCATOR_H__ */