如何基于basic_streambuf构建filtered_streambuf？
我有一个项目，要求我将过滤器插入流中，以便根据过滤器修改传出数据。经过一番研究，我似乎想要做的是创建一个像这样的filtered_streambuf：
template <class StreamBuf>
class filtered_streambuf: public StreamBuf
{ ... }
然后将filtered_streambuf<>插入到我需要过滤的任何流中。我的问题是，我不知道在过滤流时需要维护哪些不变量，以确保
- 派生类可以按预期工作。特别是，我可能会发现我已经在其他filtered_streambufs上构建了filtered_streambufs。
- 所有各种流插入器、提取器和操纵器都按预期工作。
问题是我似乎无法弄清楚我需要提供什么最小接口才能保证 iostream 拥有正常工作所需的功能。
特别是，我是否需要伪造受保护指针变量的移动？我是否需要一个假数据缓冲区？我可以重写公共函数，根据基本streambuf重写它们吗？还是这太简单了？
I have a project that requires me to insert a filter into a stream so that outgoing data will be modified according to the filter. After some research, it seems that what I want to do is create a filtered_streambuf like this:
template <class StreamBuf>
class filtered_streambuf: public StreamBuf
{ ... }
And then insert a filtered_streambuf<> into whichever stream I need to be filtered. My problem is that I don't know what invariants I need to maintain while filtering a stream, in order to ensure that
- Derived classes can work as expected. In particular, I may find I have filtered_streambufs built over other filtered_streambufs.
- All the various stream inserters, extractors and manipulators work as expected.
The trouble is that I just can't seem to work out what the minimal interface is that I need to supply in order to guarantee that an iostream will have what it needs to work correctly.
In particular, do I need to fake the movement of the protected pointer variables, or not? Do I need a fake data buffer, or not? Can I just override the public functions, rewriting them in terms of the base streambuf, or is that too simplistic?
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Boost.Iostreams 可能对您有用。
从文档中：
我自己几乎没有使用过该库，所以我无法进一步发表评论。
Boost.Iostreams may be useful to you.
From the documentation:
I've barely used that libary myself, so I can't comment any further.