| [/============================================================================== |
| Copyright (C) 2001-2010 Hartmut Kaiser |
| Copyright (C) 2001-2010 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] |
| |
| 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 (`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::hold_any`]] |
| ] |
| |
| [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::hold_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] |