实现一个内存池管理的类方法

模拟STL中的freelist,有这个思想在内。

union obj
{
union obj* next;
char p[1];
};
class MemoryPool
{
public:
MemoryPool()
{
union obj* temp;
m_memory.assign(5,(union obj*)NULL);
for(int i=0;i<m_memory.size();i++)
{
for(int j=0;j<m_memory.size();j++)
{
temp = (obj*)malloc(sizeof(char)*(1<<(i+3)));
temp->next = m_memory[i];
m_memory[i] = temp;
}
}
}
char* mem_get(int size)
{
int j;
if( size > 128)
{
char* start = (char*)malloc(sizeof(char)*size);
return start;
}
int index = freelist_index(size);
obj* temp = m_memory[index];
if(temp == NULL) //
{
for(j = index+1;j<m_memory.size();j++)
{
temp = m_memory[j];
if(temp != NULL)
{
m_memory[j] = temp->next;
break;
}
}
if(j>= m_memory.size())
{
for(int j=0;j<m_memory.size();j++)
{
temp = (obj*)malloc(sizeof(char)*(1<<(index+3)));
temp->next = m_memory[index];
m_memory[index] = temp;
}
temp = m_memory[index];
m_memory[index] = temp->next;
return (char*)temp;
}
else
{
obj* cur;
int up_size = round_up(size);
for(int i=0;i<(1<<(j-index));i++)
{
cur = temp;
cur->next = m_memory[index];
m_memory[index] = cur;
temp = cur+up_size;
}
temp = m_memory[index];
m_memory[index] = temp->next;
return (char*)temp;
}
}
else
{
m_memory[index] = temp->next;
return (char*)temp;
}
}
void mem_free(void* p,int size)
{
if(size > 128)
{
free(p);
return ;
}
obj* temp = (obj*)p;
int index = freelist_index(size);
temp->next = m_memory[index];
m_memory[index] = temp;
}
private:
enum {_ALIGN = 8};//
int freelist_index(int __bytes)
{
return (((__bytes) + (int)_ALIGN-1)/(size_t)_ALIGN - 1);
}
int round_up(int __bytes)
{
return (((__bytes) + (int) _ALIGN-1) & ~((int) _ALIGN - 1));
}
vector<union obj*> m_memory;
};

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