C++的流basic_streambuf

发布: 2008-4-22 18:25 | 作者: 不详 | 来源: http://dev.csdn.net/author/linweixuan/index.html | 查看: 157次 | 进入软件测试论坛讨论

关键字：basic_streambufC++的流basic_streambuf
不是个抽象类,但是他是C++流的基类.它提供了基本的缓冲区管理.它包含六个缓存区指针,三个分别是读指针(开头,结尾,当前),另外三个是写指针(开头,结尾,当前)

    读开始指针                            当前读指针                                    读结尾指针
_M_gbegin                          _M_gnext                      _M_gend

         =========================================================
              ^                                                      ^                                              ^
       _M_pbegin                          _M_pnext                      _M_pend
           写开始指针                            当前写指针                           写结尾指针

template <class_CharT, class_Traits>
classbasic_streambuf
{
friendclassbasic_istream<_CharT, _Traits>;
friendclassbasic_ostream<_CharT, _Traits>;
public:                         // Typedefs.
typedef_CharT                   char_type;
typedeftypename_Traits::int_type        int_type;
typedeftypename_Traits::pos_type     pos_type;
typedeftypename_Traits::off_type       off_type;
typedef_Traits                    traits_type;

public:                         // Destructor.
virtual ~basic_streambuf() {}

public:                         // Locale-related functions.
localepubimbue(constlocale& __loc) {
    this->imbue(__loc);
    locale__tmp = _M_locale;
    _M_locale = __loc;
    return__tmp;
}
localegetloc() const { return_M_locale; }

public:                         // Buffer management.
//设置缓冲区和长度
basic_streambuf* pubsetbuf(char_type* __s, streamsize__n)
    { returnthis->setbuf(__s, __n); }

//设置缓冲区偏移量,简单调用seekoff()函数
pos_typepubseekoff(off_type__offset, ios_base::seekdir__way,
                      ios_base::openmode__mod = ios_base::in | ios_base::out)
    { returnthis->seekoff(__offset, __way, __mod); }
//设置缓冲区位置,简单调用seekpos()函数
pos_typepubseekpos(pos_type__sp,
                      ios_base::openmode__mod = ios_base::in | ios_base::out)
    { returnthis->seekpos(__sp, __mod); }

//放置缓冲区同步,简单调用sync()函数
intpubsync() { returnthis->sync(); }