2.boost::iostreams分析暂停一段时间

原因：

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：

在真正掌握模版之前尽量少用

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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.

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

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.