模板的世界比较累，先从OOP的视角看看：

咋看一下似乎也没多少东西，是库的作者拿了一堆基础概念在那玩文字游戏好像。

抽象起来应该是这样几个东东：IIOStream IIStream IOStream IInSeek IOutSeek  IIOSeek IStreamInFilter IStreamOutFilter  IStreamIOFilter

看起来确实有点恶心，理论和现实是有差距的，，，唉，，，

接下来让他更恶心一点，应为还缺少一个Filterable的概念

很快出来一张蜘蛛网，，，这也不能说过度设计吧，也许有些系统需要这么细化呢？

不过看到这张蜘蛛网之后果断决定我后面练手绝对不要这么负责，可以考虑v神的做法，接口都是全的，但是功能不一定，使用的不支持的接口就弄个提示啥的。。。

这样看上去是那么回事了，，，seek被提炼到stream里边，filter添加sink的概念，或者直接用delegate更合适？

1.文档不够完善

2.熟悉程度不够，学习曲线比较陡峭，直接用有可能失控

3.实现太过复杂，还需要mpl库的支持

4.如果使用，iostreams将成为底层，整个项目都会对其依赖，有风险

5.说白了，还是能力不够，不过了解了一些iostreams归纳出来的concepts也是非常有收货。

6.网上的一句归纳：

//////////////////////////////////////////////

Device Concepts

The most important Device concepts are these:

• Device: Base for all Device concepts, provides associated character type and category.
• Source: Provides read-only access to a sequence of characters.
• Sink: Provides write-only access to a sequence of characters.
• BidirectionalDevice: Provides access to two separate sequences of characters, one for reading and the other for writing.
• SeekableDevice: Provides read-write access to a single sequence of characters, with a single repositionable read/write head.

Filter Concepts

The most important Filter concepts are these:

• Filter: Base for all Filter concepts, provides associated character type and category.
• InputFilter: Filters characters read from a Source.
• OutputFilter: Filters characters written to a Sink
• BidirectionalFilter: Filters two separate character sequences, one read from a Sink and the other written to a Sink.
• SeekableFilter: Filters a single characters sequence, controlled by a SeekableDevice, providing filtered input, output and random access with a single repositionable read/write head

Optional Behavior

Boost.Iostreams prvides several concepts corresponding to optional behavior that a Filter or Device might implement:

• Blocking: A Device which blocks when it receives a read or write request until all requested characters are available, or until the end of a stream is reached.
• Direct: A Device which provides access to its controlled sequences as regions of memory rather than via a socket-like interface.
• Closable: A Filter or Device which receives notifications immediately before a stream is closed.
• Flushable A Filter or Device which receives notifications when a stream is flushed.
• Localizable: A Filter or Device which receives notifications when the locale of a stream or stream buffer is set using basic_ios::imbue or basic_streambuf::pubimbue.
• Multi-Character: A Filter which provides access to its controlled sequences several characters at a time, via a socket-like interface.
• OptimallyBuffered A Filter or Device which will be fitted with a buffer of custom size if no buffer size is explicitly requested by the user.
• Peekable: A source which allows characters to be put back to the input sequence.
• Pipable: A Filter which can appear in pipelines.

a read request never produces fewer characters than requested unless end-of-stream has been reached or unless a read request to a downsteam Source produces fewer characters than requested, and
a write request never consumes fewer characters than requested unless a write request to a downsteam Sink consumes fewer characters than requested.

*如果熟悉stl应该就了解traits技术（应该是技巧）

<boost/iostreams/traits.hpp>这里是boost::iostream库的traits

还有个模版元函数mod_of