MemoryPool< T, chunkSize > Class Template Reference

Class to provide a constant access time memory pool for one kind of objects. More...

#include <MemoryPool.h>

Collaboration diagram for MemoryPool< T, chunkSize >:

Public Member Functions
	MemoryPool (int n=0)
	Constructor.
	~MemoryPool ()
	Free allocated memory.
size_t	size () const
	Return number of elements currently stored.
T *	operator[] (size_t i)
	Return pointer to memory segment for element i, no range check.
T *	at (size_t i)
	Return pointer to memory segment for element i, including range check.
void	clear ()
	Clear number of entries, does not free memory or call destructors.
T *	add ()
	Returns an pointer to the next free memory segment, allocating additional memory if necessary.
void	reserve (size_t n)
	Make sure there is enough memory allocated for n elements.
void	release_memory ()
	Release all allocated memory, called automatically upon destruction.

Protected Attributes
size_t	m_entries
	Number of occupied entries.
std::vector< T * >	m_chunks
	Pointers to all allocated memory chunks.

Detailed Description

template<class T, int chunkSize = 128>
class Belle2::MemoryPool< T, chunkSize >

Class to provide a constant access time memory pool for one kind of objects.

It is similar to TClonesArray but uses Templates and is also suited for non TObject classes. The Memory will be allocated in chunks, each large enough to hold chunkSize objects of type T.

This class will not initialize the memory, it is the responsibility of the user to call new(pool.add()) T(...) when adding an element to initialize the memory. This is required to make the Pool usable for classes without default constructor

Definition at line 33 of file MemoryPool.h.

Constructor & Destructor Documentation

MemoryPool()

MemoryPool ( int  n = 0 )

inlineexplicit

Constructor.

Parameters

n	Reserve space for n elements on construction

Definition at line 40 of file MemoryPool.h.

: m_entries(0) { reserve(n); }

~MemoryPool()

~MemoryPool ( )

inline

Free allocated memory.

Definition at line 43 of file MemoryPool.h.

{ release_memory(); }

Member Function Documentation

add()

T * add ( )

inline

Returns an pointer to the next free memory segment, allocating additional memory if necessary.

Returns

Pointer to the next free memory segment.

Definition at line 74 of file MemoryPool.h.

    {
      if (m_entries / chunkSize >= m_chunks.size()) {
        m_chunks.push_back(reinterpret_cast<T*>(malloc(chunkSize * sizeof(T))));
      }
      return (*this)[m_entries++];
    }

at()

T * at ( size_t  i )

inline

Return pointer to memory segment for element i, including range check.

Parameters

i	The index of the memory segment.

Returns

Pointer to the memory segment.

Definition at line 63 of file MemoryPool.h.

{ return (i >= m_entries) ? 0 : (*this)[i]; }

clear()

void clear ( )

inline

Clear number of entries, does not free memory or call destructors.

Definition at line 68 of file MemoryPool.h.

{ m_entries = 0; }

operator[]()

T * operator[] ( size_t  i )

inline

Return pointer to memory segment for element i, no range check.

Parameters

i	The index of the memory segment.

Returns

Pointer to the memory segment.

Definition at line 56 of file MemoryPool.h.

{ return m_chunks[i / chunkSize] + i % chunkSize; }

release_memory()

void release_memory ( )

inline

Release all allocated memory, called automatically upon destruction.

Definition at line 98 of file MemoryPool.h.

    {
      for (T* ptr : m_chunks) {
        free(reinterpret_cast<void*>(ptr));
      }
      m_chunks.clear();
    }

reserve()

void reserve ( size_t  n )

inline

Make sure there is enough memory allocated for n elements.

Parameters

n	The number of elements for which memory should be made available.

Definition at line 86 of file MemoryPool.h.

    {
      size_t needed_chunks = n / chunkSize + 1;
      m_chunks.reserve(needed_chunks);
      while (m_chunks.size() < needed_chunks) {
        m_chunks.push_back(reinterpret_cast<T*>(malloc(chunkSize * sizeof(T))));
      }
    }

size()

size_t size ( ) const

inline

Return number of elements currently stored.

Returns

The number of elements currently stored

Definition at line 49 of file MemoryPool.h.

{ return m_entries; }

Member Data Documentation

m_chunks

std::vector<T*> m_chunks

protected

Pointers to all allocated memory chunks.

Definition at line 109 of file MemoryPool.h.

m_entries

size_t m_entries

protected

Number of occupied entries.

Definition at line 108 of file MemoryPool.h.

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The documentation for this class was generated from the following file:

• framework/core/include/MemoryPool.h