Class Template `filter`

Description
Headers
Reference

Description

The class template filter, its subcass wfilter and their specializations input_filter, output_filter, input_wfilter and output_wfilter are provided by the Iostreams Library to ease the definitions of new models of the various Filter concepts. These templates and typedefs supply the member types char_type and category required by the Iostreams Library; they are inteded to be used as base classes for user-defined Filters.

The supplied category member is convertible to closable_tag and to localizable_tag. This allows users to define models of the concepts Closable and Localizable simply by providing definitions of member functions close and imbue.

Headers

<boost/iostreams/concepts.hpp>

Reference

Synopsis

namespace boost{ namespace iostreams {

template<typename Mode, typename Ch = char>
struct filter;

template<typename Mode, typename Ch = wchar_t>
struct wfilter : filter<Mode, Ch> { };

typedef filter<input>    input_filter;
typedef filter<output>   output_filter;
typedef wfilter<input>   input_wfilter;
typedef wfilter<output>  output_wfilter;

template<typename Mode, typename Ch = char>
struct filter {
    typedef Ch         char_type;
    typedef see below  category;

    template<typename Device>
    void close(Device&);

    template<typename Device>
    void close(std::ios_base::openmode, Device&);

    void imbue(const std::locale&);
};

} } // End namespace boost::io

Template parameters

Mode	-	A mode tag.
Ch	-	The character type

`filter::category`

    typedef see below category;

A category tag convertible to Mode, filter_tag, closable_tag and localizable_tag.

`filter::close`

    template<typename Device>
    void close(Device&);

    template<typename Device>
    void close(std::ios_base::openmode, Device&);

Both overloads are implemented as no-ops. The second is available only if Mode is convertible to bidirectional. The first is available only if Mode is not convertible to bidirectional.

Required by Closable.

`filter::imbue`

    void imbue(const std::locale&);

Implemented as a no-op. Required by Localizable.

Revised 20 May, 2004

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

Class Template filter