为C 标准库容器写自己的内存分配程序

文章作者 100test 发表时间 2007:09:06 12:48:16
来源 100Test.Com百考试题网


　　根据sgi 的STL源码的二级分配算法改写的内存池分配程序，只要稍微修改就可以实现共享内存方式管理，使用C 标准库容器中的map，set，multimap，multiset测试通过，vector测试通不过，原因是在内存回收的时候考虑的比较简单，vector每次分配内存个数不固定，回收也不固定，这样的话，程序还需要继续完善。

　　内存池管理程序源码如下：

以下是引用片段：
#ifndef MY_ALLOCATOR_H_
#define MY_ALLOCATOR_H_
#include "stdafx.h"
#include
#include
namespace happyever
{
enum { NODENUMS = 2 }.
union _Obj
{
union _Obj* M_free_list_link.
char M_client_data[1].
} .
typedef union _Obj Obj.
struct _Cookie
{
int iShmKey. /* 共享内存键值 */
int iShmID. /* iShmKey对应的shmid */
int iSemKey. /* 锁信号键值 */
int iSemID. /* 锁信号标识 */
int iTotalsize. /* 容器总容量 */
void* pStartall. /* 共享内存自身地址 */
char* pStartfree. /* 自由空间的开始地址*/
char* pEndfree. /* 自由空间的结束地址*/
int iUseNum[NODENUMS].
/*用来存放free_list中节点的size*/
short sFreelistIndex[NODENUMS].
/*存放分配内存节点的链表*/
Obj* uFreelist[NODENUMS].
}.
typedef struct _Cookie Cookie.
//Obj.
//Cookie.
static Cookie *pHead = NULL.
template
class MyAlloc
{
private:
static const int ALIGN = sizeof(Obj).
int round_up(int bytes).
int freelist_index(int bytes).
int freelist_getindex(int bytes).
char* chunk_alloc(int size, int *nobjs).
void* refill(int num,int n).
public:
// type definitions
typedef T value_type.
typedef T* pointer.
typedef const T* const_pointer.
typedef T&. reference.
typedef const T&. const_reference.
typedef std::size_t size_type.
typedef std::ptrdiff_t difference_type.
template
struct rebind
{
typedef MyAlloc other.
}.
pointer address (reference value) const
{
return &.value.
}
const_pointer address (const_reference value) const
{
return &.value.
}
MyAlloc() throw()
{
std::cout<<"MyAlloc"< }
MyAlloc(const MyAlloc&. x) throw()
{
std::cout<<"const MyAlloc"< }
template
MyAlloc (const MyAlloc&. x) throw()
{
std::cout<<"const MyAlloc"< }
~MyAlloc() throw()
{
std::cout<<"~MyAlloc"< }
size_type max_size () const throw()
{
return std::numeric_limits::max() / sizeof(T).
}
//void PrintFreelistAndCookie().
pointer allocate (size_type num, const void* = 0)
{
pointer ret = 0.
Obj** my_free_list.
Obj* result.
int index.
// print message and allocate memory with global new
std::cerr << "allocate " << num << " element(s)"
<< " of size " << sizeof(T) << std::endl.
index = freelist_index(sizeof(T)).
if(index >= NODENUMS)
{
return NULL.
}
my_free_list = pHead->uFreelist index.
//Lock(semid,LOCK_NUM).
result = *my_free_list.
if (result == 0)
{
ret = (pointer)refill((int)num, round_up(sizeof(T))).
}
else
{
*my_free_list = result->M_free_list_link.
ret = (pointer)result.
}
//UnLock(semid,LOCK_NUM).
pHead->iUseNum[index] = pHead->iUseNum[index] (int)num.
if(0 == ret)
{
std::cerr << "alloc memory fail!" << std::endl.
exit(1).
}
std::cerr << " allocated at: " << (void*)ret << std::endl.
PrintFreelistAndCookie().
return ret.
}
void construct (pointer p, const T&. value)
{
// initialize memory with placement new
new((void*)p)T(value).
}
void destroy (pointer p)
{
// destroy objects by calling their destructor
p->~T().
}
void deallocate (pointer p, size_type num)
{
Obj** my_free_list.
Obj* q .
int index.
index = freelist_getindex(sizeof(T)).
if(index >= NODENUMS)
{
std::cerr << "deallocate memory fail!" << std::endl.
exit(1).
}
my_free_list = pHead->uFreelist index.
q = (Obj*) p.
//Lock(semid,LOCK_NUM).
/*这个地方可能会有问题*/
//for(int i=0 .i<(int)num . i )
{
q->M_free_list_link = *my_free_list.
*my_free_list = q.
}
//UnLock(semid,LOCK_NUM).
pHead->iUseNum[index] = pHead->iUseNum[index] - (int)num.

std::cerr << "deallocate " << num << " element(s)"
<< " of size " << sizeof(T)
<< " at: " << (void*)p << std::endl.
PrintFreelistAndCookie().
}
}.
template
int MyAlloc::round_up(int bytes)
{
int i.
i = bytes.
if(bytes < ALIGN)
{
i = ALIGN.
}
std::cout<<"round_up:bytes="<澳大利亚华人论坛
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