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- [/==============================================================================
- Copyright (C) 2001-2011 Hartmut Kaiser
- Copyright (C) 2001-2011 Joel de Guzman
- 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)
- ===============================================================================/]
- [section:stream Stream Parsers]
- This module includes the description of the different variants of the `stream`
- parser. It can be used to utilize existing streaming operators
- (`operator>>(std::istream&, ...)`) for input parsing.
- [heading Header]
- // forwards to <boost/spirit/home/qi/stream.hpp>
- #include <boost/spirit/include/qi_stream.hpp>
- Also, see __include_structure__.
- [section:stream Stream Parsers (`stream`, `wstream`, etc.)]
- [heading Description]
- The `stream_parser` is a primitive which allows to use pre-existing standard
- streaming operators for input parsing integrated with __qi__. It
- provides a wrapper parser dispatching the underlying input stream to the stream
- operator of the corresponding attribute type to be parsed. Any value `a` to be
- parsed using the `stream_parser` will result in invoking the standard streaming
- operator for its type `A`, for instance:
- std::istream& operator>> (std::istream&, A&);
- [heading Header]
- // forwards to <boost/spirit/home/qi/stream.hpp>
- #include <boost/spirit/include/qi_stream.hpp>
- Also, see __include_structure__.
- [heading Namespace]
- [table
- [[Name]]
- [[`boost::spirit::stream // alias: boost::spirit::qi::stream`]]
- [[`boost::spirit::wstream // alias: boost::spirit::qi::wstream`]]
- ]
- [heading Synopsis]
- template <typename Char, typename Attrib>
- struct stream_parser;
- [heading Template parameters]
- [table
- [[Parameter] [Description] [Default]]
- [[`Char`] [The character type to use to generate
- the input. This type will be used while
- assigning the generated characters to the
- underlying input iterator.] [`char`]]
- [[`Attrib`] [The type of the attribute the `stream_parser` is
- expected to parse its input into.] [`spirit::basic_hold_any<Char>`]]
- ]
- [heading Model of]
- [:__primitive_parser_concept__]
- [variablelist Notation
- [[`s`] [A variable instance of any type with a defined matching
- streaming `operator>>()` or a __qi_lazy_argument__ that
- evaluates to any type with a defined matching streaming
- `operator>>()`.]]
- ]
- [heading Expression Semantics]
- Semantics of an expression is defined only where it differs from, or is
- not defined in __primitive_parser_concept__.
- [table
- [[Expression] [Description]]
- [[`stream`] [Call the streaming `operator>>()` for the type
- of the mandatory attribute. The input recognized
- by this operator will be the result of the
- `stream` parser. This parser never fails
- (unless the underlying input stream reports an
- error). The character type of the I/O istream
- is assumed to be `char`.]]
- [[`wstream`] [Call the streaming `operator>>()` for the type
- of the mandatory attribute. The input recognized
- by this operator will be the result of the
- `wstream` parser. This parser never fails
- (unless the underlying input stream reports an
- error). The character type of the I/O istream
- is assumed to be `wchar_t`.]]
- ]
- All parsers listed in the table above are predefined specializations of the
- `stream_parser<Char>` basic stream parser type described below. It is
- possible to directly use this type to create stream parsers using an
- arbitrary underlying character type.
- [table
- [[Expression] [Semantics]]
- [
- [``stream_parser<
- Char, Attrib
- >()``] [Call the streaming `operator>>()` for the type
- of the optional attribute, `Attrib`. The input recognized
- by this operator will be the result of the
- `stream_parser<>` parser. This parser never fails
- (unless the underlying input stream reports an
- error). The character type of the I/O istream
- is assumed to be `Char`]]
- ]
- [heading Additional Requirements]
- All of the stream parsers listed above require the type of the value to
- parse (the associated attribute) to implement a streaming operator conforming
- to the usual I/O streams conventions (where `attribute_type` is the type of the
- value to recognize while parse):
- template <typename Istream>
- Istream& operator>> (Istream& os, attribute_type& attr)
- {
- // type specific input parsing
- return os;
- }
- This operator will be called by the stream parsers to gather the input for
- the attribute of type `attribute_type`.
- [note If the `stream` parser is invoked inside a [qi_match `match`]
- (or [qi_match `phrase_match`]) stream manipulator the `Istream`
- passed to the `operator>>()` will have registered (imbued) the same
- standard locale instance as the stream the [qi_match `match`] (or
- [qi_match `phrase_match`]) manipulator has been used with.
- This ensures all facets registered (imbued) with the original I/O
- stream object are used during input parsing.
- ]
- [heading Attributes]
- [table
- [[Expression] [Attribute]]
- [[`stream`] [`spirit::hold_any`]]
- [[`wstream`] [`spirit::whold_any`]]
- [[`stream_parser<Char, Attrib>()`] [`Attrib`]]
- ]
- [important The attribute type `spirit::hold_any` exposed by some of the stream
- parsers is semantically and syntactically equivalent to
- the type implemented by __boost_any__. It has been added to /Spirit/
- as it has better performance and a smaller footprint than
- __boost_any__.
- ]
- [heading Complexity]
- [:O(N), where N is the number of characters consumed by the stream parser]
- [heading Example]
- [note The test harness for the example(s) below is presented in the
- __qi_basics_examples__ section.]
- A class definition used in the examples:
- [reference_qi_complex]
- [reference_qi_stream_complex]
- [reference_qi_stream]
- [endsect]
- [endsect]
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