c++ 内存池的实现

1、使用内存池的原因

①c/c++的内存分配(malloc或new)可能会花费时间比较多

②随着时间的流逝, 会形成大量的内存碎片

2、代码:

#pragma once

#include <iostream>

#include <assert.h>

#include <typeinfo>

#define GrowValue 16

struct SingleLinkNode

{

SingleLinkNode *next;

void *check;

};

static size_t node_size = sizeof(SingleLinkNode);

static void InsertNode(SingleLinkNode *head, SingleLinkNode *node)

{

assert(head);

node->next = head->next;

head->next = node;

}

static SingleLinkNode *PopNode(SingleLinkNode *head)

{

assert(head->next);

SingleLinkNode *p = head->next;

head->next = p->next;

p->next = nullptr;

return p;

}

template <typename T>

class CObjPool

{

public:

CObjPool(size_t l = 0)

{

head_.next = nullptr;

head_.check = nullptr;

pool_size_ = 0;

Init(l);

}

bool Init(size_t l)

{

if (head_.next != nullptr)

return false;

return Grow(l);

}

void CleanMemory(void)

{

SingleLinkNode *node = head_.next;

while (node)

{

SingleLinkNode *temp = node->next;

delete node;

--pool_size_;

node = temp;

}

head_.next = 0;

}

T *AllocObj(void)

{

if (!head_.next)

{

if (!Grow(GrowValue))

return 0;

}

SingleLinkNode *p = PopNode(&head_);

return (T *)((char *)p + node_size);

}

void FreeObj(T *t)

{

SingleLinkNode *p = (SingleLinkNode *)((char *)t - node_size);

assert(p->check == this);

InsertNode(&head_, p);

}

size_t PoolSize(void)

{

return pool_size_;

}

bool IsAllocByPool(T *t)

{

if (!t)

return;

SingleLinkNode *p = (SingleLinkNode *)((char *)t - node_size);

return p->check == this;

}

private:

bool Grow(size_t l)

{

if (!l)

return true;

for (int i = 0; i < l; ++i)

{

char *ptr = new(std::nothrow) char[node_size + sizeof(T)];

if (!ptr)

return false;

SingleLinkNode *node = (SingleLinkNode *)ptr;

InsertNode(&head_, node);

++pool_size_;

new(ptr + node_size) T;

node->check = this;

}

return true;

}

private:

SingleLinkNode head_;

size_t pool_size_;

};