src/libs/MemoryPool.h

   1 #ifndef _MEMORYPOOL_H
   2 #define _MEMORYPOOL_H
   3
   4 #include <cstdint>
   5 // #include <cstdio>
   6 #include <cstdlib>
   7
   8 #ifdef MEMDEBUG
   9     #define MDEBUG(...) printf(__VA_ARGS__)
  10 #else
  11     #define MDEBUG(...) do {} while (0)
  12 #endif
  13
  14 #include "StreamOutput.h"
  15
  16 /*
  17  * with MUCH thanks to http://www.parashift.com/c++-faq-lite/memory-pools.html
  18  *
  19  * test framework at https://gist.github.com/triffid/5563987
  20  */
  21
  22 class MemoryPool
  23 {
  24 public:
  25     MemoryPool(void* base, uint16_t size);
  26     ~MemoryPool();
  27
  28     void* alloc(size_t);
  29     void  dealloc(void* p);
  30
  31     void  debug(StreamOutput*);
  32
  33     bool  has(void*);
  34
  35     uint32_t free(void);
  36
  37     MemoryPool* next;
  38
  39     static MemoryPool* first;
  40
  41 private:
  42     void* base;
  43     uint16_t size;
  44 };
  45
  46 // this overloads "placement new"
  47 inline void* operator new(size_t nbytes, MemoryPool& pool)
  48 {
  49     return pool.alloc(nbytes);
  50 }
  51
  52 // this allows placement new to free memory if the constructor fails
  53 inline void  operator delete(void* p, MemoryPool& pool)
  54 {
  55     pool.dealloc(p);
  56 }
  57
  58 // this catches all usages of delete blah. The object's destructor is called before we get here
  59 // it first checks if the deleted object is part of a pool, and uses free otherwise.
  60 inline void  operator delete(void* p)
  61 {
  62     MemoryPool* m = MemoryPool::first;
  63     while (m)
  64     {
  65         if (m->has(p))
  66         {
  67             MDEBUG("Pool %p has %p, using dealloc()\n", m, p);
  68             m->dealloc(p);
  69             return;
  70         }
  71         m = m->next;
  72     }
  73
  74     MDEBUG("no pool has %p, using free()\n", p);
  75     free(p);
  76 }
  77
  78 #endif /* _MEMORYPOOL_H */