STL stl_alloc.h

# // Comment By:  凝霜  
# // E-mail:      mdl2009@vip.qq.com  
# // Blog:        http://blog.csdn.net/mdl13412  
#   
# // 特别说明: SGI STL的allocator在我的编译环境下不使用内存池  
# //          而其内存池不进行内存释放操作, 其释放时机为程序退出或者stack unwinding  
# //          由操作系统保证内存的回收  
#   
# /* 
#  * Copyright (c) 1996-1997 
#  * Silicon Graphics Computer Systems, Inc. 
#  * 
#  * Permission to use, copy, modify, distribute and sell this software 
#  * and its documentation for any purpose is hereby granted without fee, 
#  * provided that the above copyright notice appear in all copies and 
#  * that both that copyright notice and this permission notice appear 
#  * in supporting documentation.  Silicon Graphics makes no 
#  * representations about the suitability of this software for any 
#  * purpose.  It is provided "as is" without express or implied warranty. 
#  */  
#   
# /* NOTE: This is an internal header file, included by other STL headers. 
#  *   You should not attempt to use it directly. 
#  */  
#   
# #ifndef __SGI_STL_INTERNAL_ALLOC_H  
# #define __SGI_STL_INTERNAL_ALLOC_H  
#   
# #ifdef __SUNPRO_CC  
# #  define __PRIVATE public  
# // SUN编译器对private限制过多, 需要开放权限  
# #else  
# #  define __PRIVATE private  
# #endif  
#   
# // 为了保证兼容性, 对于不支持模板类静态成员的情况, 使用malloc()进行内存分配  
# #ifdef __STL_STATIC_TEMPLATE_MEMBER_BUG  
# #  define __USE_MALLOC  
# #endif  
#   
# // 实现了一些标准的node allocator  
# // 但是不同于C++标准或者STL原始STL标准  
# // 这些allocator没有封装不同指针类型  
# // 事实上我们假定只有一种指针理性  
# // allocation primitives意在分配不大于原始STL allocator分配的独立的对象  
#   
# #if 0  
# #   include <new>  
# #   define __THROW_BAD_ALLOC throw bad_alloc  
# #elif !defined(__THROW_BAD_ALLOC)  
# #   include <iostream.h>  
# #   define __THROW_BAD_ALLOC cerr << "out of memory" << endl; exit(1)  
# #endif  
#   
# #ifndef __ALLOC  
# #   define __ALLOC alloc  
# #endif  
# #ifdef __STL_WIN32THREADS  
# #   include <windows.h>  
# #endif  
#   
# #include <stddef.h>  
# #include <stdlib.h>  
# #include <string.h>  
# #include <assert.h>  
# #ifndef __RESTRICT  
# #  define __RESTRICT  
# #endif  
#   
# // 多线程支持  
# // __STL_PTHREADS       // GCC编译器  
# // _NOTHREADS           // 不支持多线程  
# // __STL_SGI_THREADS    // SGI机器专用  
# // __STL_WIN32THREADS   // MSVC编译器  
# #if !defined(__STL_PTHREADS) && !defined(_NOTHREADS)   
#  && !defined(__STL_SGI_THREADS) && !defined(__STL_WIN32THREADS)  
# #   define _NOTHREADS  
# #endif  
#   
# # ifdef __STL_PTHREADS  
#     // POSIX Threads  
#     // This is dubious, since this is likely to be a high contention  
#     // lock.   Performance may not be adequate.  
# #   include <pthread.h>  
# #   define __NODE_ALLOCATOR_LOCK   
#         if (threads) pthread_mutex_lock(&__node_allocator_lock)  
# #   define __NODE_ALLOCATOR_UNLOCK   
#         if (threads) pthread_mutex_unlock(&__node_allocator_lock)  
# #   define __NODE_ALLOCATOR_THREADS true  
# #   define __VOLATILE volatile  // Needed at -O3 on SGI  
# # endif  
# # ifdef __STL_WIN32THREADS  
#     // The lock needs to be initialized by constructing an allocator  
#     // objects of the right type.  We do that here explicitly for alloc.  
# #   define __NODE_ALLOCATOR_LOCK   
#         EnterCriticalSection(&__node_allocator_lock)  
# #   define __NODE_ALLOCATOR_UNLOCK   
#         LeaveCriticalSection(&__node_allocator_lock)  
# #   define __NODE_ALLOCATOR_THREADS true  
# #   define __VOLATILE volatile  // may not be needed  
# # endif /* WIN32THREADS */  
# # ifdef __STL_SGI_THREADS  
#     // This should work without threads, with sproc threads, or with  
#     // pthreads.  It is suboptimal in all cases.  
#     // It is unlikely to even compile on nonSGI machines.  
#   
#     extern "C" {  
#       extern int __us_rsthread_malloc;  
#     }  
#     // The above is copied from malloc.h.  Including <malloc.h>  
#     // would be cleaner but fails with certain levels of standard  
#     // conformance.  
# #   define __NODE_ALLOCATOR_LOCK if (threads && __us_rsthread_malloc)   
#                 { __lock(&__node_allocator_lock); }  
# #   define __NODE_ALLOCATOR_UNLOCK if (threads && __us_rsthread_malloc)   
#                 { __unlock(&__node_allocator_lock); }  
# #   define __NODE_ALLOCATOR_THREADS true  
# #   define __VOLATILE volatile  // Needed at -O3 on SGI  
# # endif  
# # ifdef _NOTHREADS  
# //  Thread-unsafe  
# #   define __NODE_ALLOCATOR_LOCK  
# #   define __NODE_ALLOCATOR_UNLOCK  
# #   define __NODE_ALLOCATOR_THREADS false  
# #   define __VOLATILE  
# # endif  
#   
# __STL_BEGIN_NAMESPACE  
#   
# #if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)  
# #pragma set woff 1174  
# #endif  
#   
# // Malloc-based allocator.  Typically slower than default alloc below.  
# // Typically thread-safe and more storage efficient.  
# #ifdef __STL_STATIC_TEMPLATE_MEMBER_BUG  
# # ifdef __DECLARE_GLOBALS_HERE  
#     void (* __malloc_alloc_oom_handler)() = 0;  
#     // g++ 2.7.2 does not handle static template data members.  
# # else  
#     extern void (* __malloc_alloc_oom_handler)();  
# # endif  
# #endif  
#   
# // 一级配置器  
# template <int inst>  
# class __malloc_alloc_template  
# {  
# private:  
#     // 用于在设置了__malloc_alloc_oom_handler情况下循环分配内存,  
#     // 直到成功分配  
#     static void *oom_malloc(size_t);  
#     static void *oom_realloc(void *, size_t);  
#   
#     // 如果编译器支持模板类静态成员, 则使用错误处理函数, 类似C++的set_new_handler()  
#     // 默认值为0, 如果不设置, 则内存分配失败时直接__THROW_BAD_ALLOC  
# #ifndef __STL_STATIC_TEMPLATE_MEMBER_BUG  
#     static void (* __malloc_alloc_oom_handler)();  
# #endif  
#   
# public:  
#     // 分配指定大小的内存(size_t n)， 如果分配失败, 则进入循环分配阶段  
#     // 循环分配前提是要保证正确设置了__malloc_alloc_oom_handler  
#     static void * allocate(size_t n)  
#     {  
#         void *result = malloc(n);  
#         if (0 == result) result = oom_malloc(n);  
#         return result;  
#     }  
#   
#     // 后面的size_t是为了兼容operator delele  
#     static void deallocate(void *p, size_t /* n */)  
#     { free(p); }  
#   
#     // 重新分配内存大小, 第二个参数是为了兼容operator new  
#     static void * reallocate(void *p, size_t /* old_sz */, size_t new_sz)  
#     {  
#         void * result = realloc(p, new_sz);  
#         if (0 == result) result = oom_realloc(p, new_sz);  
#         return result;  
#     }  
#   
#     // 设置错误处理函数, 返回原来的函数指针  
#     // 不属于C++标准规定的接口  
#     static void (* set_malloc_handler(void (*f)()))()  
#     {  
#         void (* old)() = __malloc_alloc_oom_handler;  
#         __malloc_alloc_oom_handler = f;  
#         return(old);  
#     }  
# };  
#   
# // malloc_alloc out-of-memory handling  
#   
# #ifndef __STL_STATIC_TEMPLATE_MEMBER_BUG  
# template <int inst>  
# void (* __malloc_alloc_template<inst>::__malloc_alloc_oom_handler)() = 0;  
# #endif  
#   
# // 如果设置了__malloc_alloc_oom_handler, 则首先执行错误处理函数, 然后循环分配直到成功  
# // 如果未设置__malloc_alloc_oom_handler, __THROW_BAD_ALLOC  
# template <int inst>  
# void * __malloc_alloc_template<inst>::oom_malloc(size_t n)  
# {  
#     void (* my_malloc_handler)();  
#     void *result;  
#   
#     for (;;) {  
#         my_malloc_handler = __malloc_alloc_oom_handler;  
#         if (0 == my_malloc_handler) { __THROW_BAD_ALLOC; }  
#         (*my_malloc_handler)();  
#         result = malloc(n);  
#         if (result) return(result);  
#     }  
# }  
#   
# template <int inst>  
# void * __malloc_alloc_template<inst>::oom_realloc(void *p, size_t n)  
# {  
#     void (* my_malloc_handler)();  
#     void *result;  
#   
#     for (;;) {  
#         my_malloc_handler = __malloc_alloc_oom_handler;  
#         if (0 == my_malloc_handler) { __THROW_BAD_ALLOC; }  
#         (*my_malloc_handler)();  
#         result = realloc(p, n);  
#         if (result) return(result);  
#     }  
# }  
#   
# // 这个版本的STL并没有使用non-type模板参数  
# typedef __malloc_alloc_template<0> malloc_alloc;  
#   
# // 这个类中的接口其实就是STL标准中的allocator的接口  
# // 实际上所有的SGI STL都使用这个进行内存配置  
# // 例如: stl_vector.h中  
# // template <class T, class Alloc = alloc>  
# // class vector  
# // {  
# //      ...  
# // protected:  
# //      typedef simple_alloc<value_type, Alloc> data_allocator;  
# //      ...  
# //};  
# template<class T, class Alloc>  
# class simple_alloc  
# {  
# public:  
#     static T *allocate(size_t n)  
#                 { return 0 == n? 0 : (T*) Alloc::allocate(n * sizeof (T)); }  
#     static T *allocate(void)  
#                 { return (T*) Alloc::allocate(sizeof (T)); }  
#     static void deallocate(T *p, size_t n)  
#                 { if (0 != n) Alloc::deallocate(p, n * sizeof (T)); }  
#     static void deallocate(T *p)  
#                 { Alloc::deallocate(p, sizeof (T)); }  
# };  
#   
# // Allocator adaptor to check size arguments for debugging.  
# // Reports errors using assert.  Checking can be disabled with  
# // NDEBUG, but it's far better to just use the underlying allocator  
# // instead when no checking is desired.  
# // There is some evidence that this can confuse Purify.  
# template <class Alloc>  
# class debug_alloc  
# {  
# private:  
#     enum {extra = 8};       // Size of space used to store size.  Note  
#                             // that this must be large enough to preserve  
#                             // alignment.  
#   
# public:  
#   
#     // extra 保证不会分配为0的内存空间, 而且要保证内存对齐  
#     // 把分配内存的最前面设置成n的大小, 用于后面校验  
#     // 内存对齐的作用就是保护前面extra大小的数据不被修改  
#     static void * allocate(size_t n)  
#     {  
#         char *result = (char *)Alloc::allocate(n + extra);  
#         *(size_t *)result = n;  
#         return result + extra;  
#     }  
#   
#     // 如果*(size_t *)real_p != n则肯定发生向前越界  
#     static void deallocate(void *p, size_t n)  
#     {  
#         char * real_p = (char *)p - extra;  
#         assert(*(size_t *)real_p == n);  
#         Alloc::deallocate(real_p, n + extra);  
#     }  
#   
#     static void * reallocate(void *p, size_t old_sz, size_t new_sz)  
#     {  
#         char * real_p = (char *)p - extra;  
#         assert(*(size_t *)real_p == old_sz);  
#         char * result = (char *)  
#                       Alloc::reallocate(real_p, old_sz + extra, new_sz + extra);  
#         *(size_t *)result = new_sz;  
#         return result + extra;  
#     }  
# };  
#   
# # ifdef __USE_MALLOC  
#   
# typedef malloc_alloc alloc;  
# typedef malloc_alloc single_client_alloc;  
#   
# # else  
#   
# // 默认的node allocator  
# // 如果有合适的编译器, 速度上与原始的STL class-specific allocators大致等价  
# // 但是具有产生更少内存碎片的优点  
# // Default_alloc_template参数是用于实验性质的, 在未来可能会消失  
# // 客户只能在当下使用alloc  
# //  
# // 重要的实现属性:  
# // 1. 如果客户请求一个size > __MAX_BYTE的对象, 则直接使用malloc()分配  
# // 2. 对于其它情况下, 我们将请求对象的大小按照内存对齐向上舍入ROUND_UP(requested_size)  
# // TODO: 待翻译  
# // 2. In all other cases, we allocate an object of size exactly  
# //    ROUND_UP(requested_size).  Thus the client has enough size  
# //    information that we can return the object to the proper free list  
# //    without permanently losing part of the object.  
# //  
#   
# // 第一个模板参数指定是否有多于一个线程使用本allocator  
# // 在一个default_alloc实例中分配对象, 在另一个deallocate实例中释放对象, 是安全的  
# // 这有效的转换其所有权到另一个对象  
# // 这可能导致对我们引用的区域产生不良影响  
# // 第二个模板参数仅仅用于创建多个default_alloc实例  
# // 不同容器使用不同allocator实例创建的node拥有不同类型, 这限制了此方法的通用性  
#   
# // Sun C++ compiler需要在类外定义这些枚举  
# #ifdef __SUNPRO_CC  
# // breaks if we make these template class members:  
#   enum {__ALIGN = 8};  
#   enum {__MAX_BYTES = 128};  
#   enum {__NFREELISTS = __MAX_BYTES/__ALIGN};  
# #endif  
#   
# template <bool threads, int inst>  
# class __default_alloc_template  
# {  
# private:  
#   // Really we should use static const int x = N  
#   // instead of enum { x = N }, but few compilers accept the former.  
# # ifndef __SUNPRO_CC  
#     enum {__ALIGN = 8};  
#     enum {__MAX_BYTES = 128};  
#     enum {__NFREELISTS = __MAX_BYTES/__ALIGN};  
# # endif  
#     // 向上舍入操作  
#     // 解释一下, __ALIGN - 1指明的是实际内存对齐的粒度  
#     // 例如__ALIGN = 8时, 我们只需要7就可以实际表示8个数(0~7)  
#     // 那么~(__ALIGN - 1)就是进行舍入的粒度  
#     // 我们将(bytes) + __ALIGN-1)就是先进行进位, 然后截断  
#     // 这就保证了我是向上舍入的  
#     // 例如byte = 100, __ALIGN = 8的情况  
#     // ~(__ALIGN - 1) = (1 000)B  
#     // ((bytes) + __ALIGN-1) = (1 101 011)B  
#     // (((bytes) + __ALIGN-1) & ~(__ALIGN - 1)) = (1 101 000 )B = (104)D  
#     // 104 / 8 = 13, 这就实现了向上舍入  
#     // 对于byte刚好满足内存对齐的情况下, 结果保持byte大小不变  
#     // 记得《Hacker's Delight》上面有相关的计算  
#     // 这个表达式与下面给出的等价  
#     // ((((bytes) + _ALIGN - 1) * _ALIGN) / _ALIGN)  
#     // 但是SGI STL使用的方法效率非常高  
#     static size_t ROUND_UP(size_t bytes)  
#     {  
#         return (((bytes) + __ALIGN-1) & ~(__ALIGN - 1));  
#     }  
# __PRIVATE:  
#     // 管理内存链表用  
#     // 为了尽最大可能减少内存的使用, 这里使用一个union  
#     // 如果使用第一个成员, 则指向另一个相同的union obj  
#     // 而如果使用第二个成员, 则指向实际的内存区域  
#     // 这样就实现了链表结点只使用一个指针的大小空间, 却能同时做索引和指向内存区域  
#     // 这个技巧性非常强, 值得学习  
#     union obj  
#     {  
#         union obj * free_list_link;  
#         char client_data[1];    /* The client sees this.        */  
#     };  
# private:  
# # ifdef __SUNPRO_CC  
#     static obj * __VOLATILE free_list[];  
#         // Specifying a size results in duplicate def for 4.1  
# # else  
#     // 这里分配的free_list为16  
#     // 对应的内存链容量分别为8, 16, 32 ... 128  
#     static obj * __VOLATILE free_list[__NFREELISTS];  
# # endif  
#     // 根据待待分配的空间大小, 在free_list中选择合适的大小  
#     static  size_t FREELIST_INDEX(size_t bytes)  
#     {  
#         return (((bytes) + __ALIGN-1)/__ALIGN - 1);  
#     }  
#   
#   // Returns an object of size n, and optionally adds to size n free list.  
#   static void *refill(size_t n);  
#   // Allocates a chunk for nobjs of size "size".  nobjs may be reduced  
#   // if it is inconvenient to allocate the requested number.  
#   static char *chunk_alloc(size_t size, int &nobjs);  
#   
#   // 内存池  
#   static char *start_free;      // 内存池起始点  
#   static char *end_free;        // 内存池结束点  
#   static size_t heap_size;      // 已经在堆上分配的空间大小  
#   
# // 下面三个条件编译给多线程条件下使用的锁提供必要支持  
# # ifdef __STL_SGI_THREADS  
#     static volatile unsigned long __node_allocator_lock;  
#     static void __lock(volatile unsigned long *);  
#     static inline void __unlock(volatile unsigned long *);  
# # endif  
#   
# # ifdef __STL_PTHREADS  
#     static pthread_mutex_t __node_allocator_lock;  
# # endif  
#   
# # ifdef __STL_WIN32THREADS  
#     static CRITICAL_SECTION __node_allocator_lock;  
#     static bool __node_allocator_lock_initialized;  
#   
#   public:  
#     __default_alloc_template() {  
#     // This assumes the first constructor is called before threads  
#     // are started.  
#         if (!__node_allocator_lock_initialized) {  
#             InitializeCriticalSection(&__node_allocator_lock);  
#             __node_allocator_lock_initialized = true;  
#         }  
#     }  
#   private:  
# # endif  
#   
#     // 用于多线程环境下锁定操作用  
#     class lock  
#     {  
#     public:  
#         lock() { __NODE_ALLOCATOR_LOCK; }  
#         ~lock() { __NODE_ALLOCATOR_UNLOCK; }  
#     };  
#     friend class lock;  
#   
# public:  
#   /* n must be > 0      */  
#   static void * allocate(size_t n)  
#   {  
#     obj * __VOLATILE * my_free_list;  
#     obj * __RESTRICT result;  
#   
#     // 如果待分配对象大于__MAX_BYTES, 使用一级配置器分配  
#     if (n > (size_t) __MAX_BYTES) {  
#         return(malloc_alloc::allocate(n));  
#     }  
#     my_free_list = free_list + FREELIST_INDEX(n);  
#     // Acquire the lock here with a constructor call.  
#     // This ensures that it is released in exit or during stack  
#     // unwinding.  
# #       ifndef _NOTHREADS  
#         /*REFERENCED*/  
#         lock lock_instance;  
# #       endif  
#     result = *my_free_list;  
#     // 如果是第一次使用这个容量的链表, 则分配此链表需要的内存  
#     // 如果不是, 则判断内存吃容量, 不够则分配  
#     if (result == 0) {  
#         void *r = refill(ROUND_UP(n));  
#         return r;  
#     }  
#     *my_free_list = result -> free_list_link;  
#     return (result);  
#   };  
#   
#   /* p may not be 0 */  
#   static void deallocate(void *p, size_t n)  
#   {  
#     obj *q = (obj *)p;  
#     obj * __VOLATILE * my_free_list;  
#   
#     // 对于大于__MAX_BYTES的对象, 因为采用的是一级配置器分配, 所以同样使用一级配置器释放  
#     if (n > (size_t) __MAX_BYTES) {  
#         malloc_alloc::deallocate(p, n);  
#         return;  
#     }  
#     my_free_list = free_list + FREELIST_INDEX(n);  
#     // acquire lock  
# #       ifndef _NOTHREADS  
#         /*REFERENCED*/  
#         lock lock_instance;  
# #       endif /* _NOTHREADS */  
#     q -> free_list_link = *my_free_list;  
#     *my_free_list = q;  
#     // lock is released here  
#   }  
#   
#   static void * reallocate(void *p, size_t old_sz, size_t new_sz);  
# } ;  
#   
# typedef __default_alloc_template<__NODE_ALLOCATOR_THREADS, 0> alloc;  
# typedef __default_alloc_template<false, 0> single_client_alloc;  
#   
# // 每次分配一大块内存, 防止多次分配小内存块带来的内存碎片  
# // 进行分配操作时, 根据具体环境决定是否加锁  
# // 我们假定要分配的内存满足内存对齐要求  
# template <bool threads, int inst>  
# char*  
# __default_alloc_template<threads, inst>::chunk_alloc(size_t size, int& nobjs)  
# {  
#     char * result;  
#     size_t total_bytes = size * nobjs;  
#     size_t bytes_left = end_free - start_free;  // 计算内存池剩余容量  
#   
#     // 如果内存池中剩余内存>=需要分配的内内存, 返回start_free指向的内存块,  
#     // 并且重新设置内存池起始点  
#     if (bytes_left >= total_bytes) {  
#         result = start_free;  
#         start_free += total_bytes;  
#         return(result);  
#     }  
#     // 如果内存吃中剩余的容量不够分配, 但是能至少分配一个节点时,  
#     // 返回所能分配的最多的节点, 返回start_free指向的内存块  
#     // 并且重新设置内存池起始点  
#     else if (bytes_left >= size) {  
#         nobjs = bytes_left/size;  
#         total_bytes = size * nobjs;  
#         result = start_free;  
#         start_free += total_bytes;  
#         return(result);  
#     }  
#     // 内存池剩余内存连一个节点也不够分配  
#     else {  
#         size_t bytes_to_get = 2 * total_bytes + ROUND_UP(heap_size >> 4);  
#         // 将剩余的内存分配给指定的free_list[FREELIST_INDEX(bytes_left)]  
#         if (bytes_left > 0) {  
#             obj * __VOLATILE * my_free_list =  
#                         free_list + FREELIST_INDEX(bytes_left);  
#   
#             ((obj *)start_free) -> free_list_link = *my_free_list;  
#             *my_free_list = (obj *)start_free;  
#         }  
#         start_free = (char *)malloc(bytes_to_get);  
#         // 分配失败, 搜索原来已经分配的内存块, 看是否有大于等于当前请求的内存块  
#         if (0 == start_free) {  
#             int i;  
#             obj * __VOLATILE * my_free_list, *p;  
#             // Try to make do with what we have.  That can't  
#             // hurt.  We do not try smaller requests, since that tends  
#             // to result in disaster on multi-process machines.  
#             for (i = size; i <= __MAX_BYTES; i += __ALIGN) {  
#                 my_free_list = free_list + FREELIST_INDEX(i);  
#                 p = *my_free_list;  
#                 // 找到了一个, 将其加入内存池中  
#                 if (0 != p) {  
#                     *my_free_list = p -> free_list_link;  
#                     start_free = (char *)p;  
#                     end_free = start_free + i;  
#                     // 内存池更新完毕, 重新分配需要的内存  
#                     return(chunk_alloc(size, nobjs));  
#                     // Any leftover piece will eventually make it to the  
#                     // right free list.  
#                 }  
#             }  
#   
#             // 再次失败, 直接调用一级配置器分配, 期待异常处理函数能提供帮助  
#             // 不过在我看来, 内存分配失败进行其它尝试已经没什么意义了,  
#             // 最好直接log, 然后让程序崩溃  
#         end_free = 0;   // In case of exception.  
#             start_free = (char *)malloc_alloc::allocate(bytes_to_get);  
#         }  
#         heap_size += bytes_to_get;  
#         end_free = start_free + bytes_to_get;  
#         // 内存池更新完毕, 重新分配需要的内存  
#         return(chunk_alloc(size, nobjs));  
#     }  
# }  
#   
#   
# // 返回一个大小为n的对象, 并且加入到free_list[FREELIST_INDEX(n)]  
# // 进行分配操作时, 根据具体环境决定是否加锁  
# // 我们假定要分配的内存满足内存对齐要求  
# template <bool threads, int inst>  
# void* __default_alloc_template<threads, inst>::refill(size_t n)  
# {  
#     int nobjs = 20;  
#     char * chunk = chunk_alloc(n, nobjs);  
#     obj * __VOLATILE * my_free_list;  
#     obj * result;  
#     obj * current_obj, * next_obj;  
#     int i;  
#   
#     // 如果内存池仅仅只够分配一个对象的空间, 直接返回即可  
#     if (1 == nobjs) return(chunk);  
#   
#     // 内存池能分配更多的空间  
#     my_free_list = free_list + FREELIST_INDEX(n);  
#   
#     // 在chunk的空间中建立free_list  
#       result = (obj *)chunk;  
#       *my_free_list = next_obj = (obj *)(chunk + n);  
#       for (i = 1; ; i++) {  
#         current_obj = next_obj;  
#         next_obj = (obj *)((char *)next_obj + n);  
#         if (nobjs - 1 == i) {  
#             current_obj -> free_list_link = 0;  
#             break;  
#         } else {  
#             current_obj -> free_list_link = next_obj;  
#         }  
#       }  
#     return(result);  
# }  
#   
# template <bool threads, int inst>  
# void*  
# __default_alloc_template<threads, inst>::reallocate(void *p,  
#                                                     size_t old_sz,  
#                                                     size_t new_sz)  
# {  
#     void * result;  
#     size_t copy_sz;  
#   
#     // 如果old_size和new_size均大于__MAX_BYTES, 则直接调用realloc()  
#     // 因为这部分内存不是经过内存池分配的  
#     if (old_sz > (size_t) __MAX_BYTES && new_sz > (size_t) __MAX_BYTES) {  
#         return(realloc(p, new_sz));  
#     }  
#     // 如果ROUND_UP(old_sz) == ROUND_UP(new_sz), 内存大小没变化, 不进行重新分配  
#     if (ROUND_UP(old_sz) == ROUND_UP(new_sz)) return(p);  
#     // 进行重新分配并拷贝数据  
#     result = allocate(new_sz);  
#     copy_sz = new_sz > old_sz? old_sz : new_sz;  
#     memcpy(result, p, copy_sz);  
#     deallocate(p, old_sz);  
#     return(result);  
# }  
#   
# #ifdef __STL_PTHREADS  
#     template <bool threads, int inst>  
#     pthread_mutex_t  
#     __default_alloc_template<threads, inst>::__node_allocator_lock  
#         = PTHREAD_MUTEX_INITIALIZER;  
# #endif  
#   
# #ifdef __STL_WIN32THREADS  
#     template <bool threads, int inst> CRITICAL_SECTION  
#     __default_alloc_template<threads, inst>::__node_allocator_lock;  
#   
#     template <bool threads, int inst> bool  
#     __default_alloc_template<threads, inst>::__node_allocator_lock_initialized  
#     = false;  
# #endif  
#   
# #ifdef __STL_SGI_THREADS  
# __STL_END_NAMESPACE  
# #include <mutex.h>  
# #include <time.h>  
# __STL_BEGIN_NAMESPACE  
# // Somewhat generic lock implementations.  We need only test-and-set  
# // and some way to sleep.  These should work with both SGI pthreads  
# // and sproc threads.  They may be useful on other systems.  
# template <bool threads, int inst>  
# volatile unsigned long  
# __default_alloc_template<threads, inst>::__node_allocator_lock = 0;  
#   
# #if __mips < 3 || !(defined (_ABIN32) || defined(_ABI64)) || defined(__GNUC__)  
# #   define __test_and_set(l,v) test_and_set(l,v)  
# #endif  
#   
# template <bool threads, int inst>  
# void  
# __default_alloc_template<threads, inst>::__lock(volatile unsigned long *lock)  
# {  
#     const unsigned low_spin_max = 30;  // spin cycles if we suspect uniprocessor  
#     const unsigned high_spin_max = 1000; // spin cycles for multiprocessor  
#     static unsigned spin_max = low_spin_max;  
#     unsigned my_spin_max;  
#     static unsigned last_spins = 0;  
#     unsigned my_last_spins;  
#     static struct timespec ts = {0, 1000};  
#     unsigned junk;  
# #   define __ALLOC_PAUSE junk *= junk; junk *= junk; junk *= junk; junk *= junk  
#     int i;  
#   
#     if (!__test_and_set((unsigned long *)lock, 1)) {  
#         return;  
#     }  
#     my_spin_max = spin_max;  
#     my_last_spins = last_spins;  
#     for (i = 0; i < my_spin_max; i++) {  
#         if (i < my_last_spins/2 || *lock) {  
#             __ALLOC_PAUSE;  
#             continue;  
#         }  
#         if (!__test_and_set((unsigned long *)lock, 1)) {  
#             // got it!  
#             // Spinning worked.  Thus we're probably not being scheduled  
#             // against the other process with which we were contending.  
#             // Thus it makes sense to spin longer the next time.  
#             last_spins = i;  
#             spin_max = high_spin_max;  
#             return;  
#         }  
#     }  
#     // We are probably being scheduled against the other process.  Sleep.  
#     spin_max = low_spin_max;  
#     for (;;) {  
#         if (!__test_and_set((unsigned long *)lock, 1)) {  
#             return;  
#         }  
#         nanosleep(&ts, 0);  
#     }  
# }  
#   
# template <bool threads, int inst>  
# inline void  
# __default_alloc_template<threads, inst>::__unlock(volatile unsigned long *lock)  
# {  
# #   if defined(__GNUC__) && __mips >= 3  
#         asm("sync");  
#         *lock = 0;  
# #   elif __mips >= 3 && (defined (_ABIN32) || defined(_ABI64))  
#         __lock_release(lock);  
# #   else  
#         *lock = 0;  
#         // This is not sufficient on many multiprocessors, since  
#         // writes to protected variables and the lock may be reordered.  
# #   endif  
# }  
# #endif  
#   
# // 内存池起始位置  
# template <bool threads, int inst>  
# char *__default_alloc_template<threads, inst>::start_free = 0;  
# // 内存池结束位置  
# template <bool threads, int inst>  
# char *__default_alloc_template<threads, inst>::end_free = 0;  
#   
# template <bool threads, int inst>  
# size_t __default_alloc_template<threads, inst>::heap_size = 0;  
# // 内存池容量索引数组  
# template <bool threads, int inst>  
# __default_alloc_template<threads, inst>::obj * __VOLATILE  
# __default_alloc_template<threads, inst> ::free_list[  
# # ifdef __SUNPRO_CC  
#     __NFREELISTS  
# # else  
#     __default_alloc_template<threads, inst>::__NFREELISTS  
# # endif  
# ] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, };  
# // The 16 zeros are necessary to make version 4.1 of the SunPro  
# // compiler happy.  Otherwise it appears to allocate too little  
# // space for the array.  
#   
# # ifdef __STL_WIN32THREADS  
#   // Create one to get critical section initialized.  
#   // We do this onece per file, but only the first constructor  
#   // does anything.  
#   static alloc __node_allocator_dummy_instance;  
# # endif  
#   
# #endif /* ! __USE_MALLOC */  
#   
# #if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)  
# #pragma reset woff 1174  
# #endif  
#   
# __STL_END_NAMESPACE  
#   
# #undef __PRIVATE  
#   
# #endif /* __SGI_STL_INTERNAL_ALLOC_H */  
#   
# // Local Variables:  
# // mode:C++  
# // End: