source: NonGTP/Boost/boost/format/internals.hpp @ 857

Revision 857, 8.0 KB checked in by igarcia, 19 years ago (diff)
Line 
1// ----------------------------------------------------------------------------
2// internals.hpp :  internal structs : stream_format_state, format_item.
3//                  included by format.hpp
4// ----------------------------------------------------------------------------
5
6//  Copyright Samuel Krempp 2003. Use, modification, and distribution are
7//  subject to the Boost Software License, Version 1.0. (See accompanying
8//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
9
10//  See http://www.boost.org/libs/format for library home page
11
12// ----------------------------------------------------------------------------
13
14#ifndef BOOST_FORMAT_INTERNALS_HPP
15#define BOOST_FORMAT_INTERNALS_HPP
16
17
18#include <string>
19#include <boost/assert.hpp>
20#include <boost/optional.hpp>
21#include <boost/limits.hpp>
22#include <boost/format/detail/compat_workarounds.hpp>
23#include <boost/format/alt_sstream.hpp> // used as a dummy stream
24
25namespace boost {
26namespace io {
27namespace detail {
28
29
30//---- stream_format_state --------------------------------------------------//
31
32//   set of params that define the format state of a stream
33    template<class Ch, class Tr>
34    struct stream_format_state
35    {
36        typedef BOOST_IO_STD basic_ios<Ch, Tr>   basic_ios;
37
38        stream_format_state(Ch fill)                 { reset(fill); }
39//        stream_format_state(const basic_ios& os)     { set_by_stream(os); }
40
41        void reset(Ch fill);                     //- sets to default state.
42        void set_by_stream(const basic_ios& os); //- sets to os's state.
43        void apply_on(basic_ios & os,            //- applies format_state to the stream
44                      boost::io::detail::locale_t * loc_default = 0) const;
45        template<class T>
46        void apply_manip(T manipulator)          //- modifies state by applying manipulator
47            { apply_manip_body<Ch, Tr, T>( *this, manipulator) ; }
48
49        // --- data ---
50        std::streamsize width_;
51        std::streamsize precision_;
52        Ch fill_;
53        std::ios_base::fmtflags flags_;
54        std::ios_base::iostate  rdstate_;
55        std::ios_base::iostate  exceptions_;
56        boost::optional<boost::io::detail::locale_t>  loc_;
57    }; 
58
59
60//---- format_item  ---------------------------------------------------------//
61
62//   stores all parameters that can be specified in format strings
63    template<class Ch, class Tr, class Alloc> 
64    struct format_item
65    {     
66        enum pad_values { zeropad = 1, spacepad =2, centered=4, tabulation = 8 };
67                         // 1. if zeropad is set, all other bits are not,
68                         // 2. if tabulation is set, all others are not.
69                         // centered and spacepad can be mixed freely.
70        enum arg_values { argN_no_posit   = -1, // non-positional directive. will set argN later
71                          argN_tabulation = -2, // tabulation directive. (no argument read)
72                          argN_ignored    = -3  // ignored directive. (no argument read)
73        };
74        typedef BOOST_IO_STD basic_ios<Ch, Tr>                    basic_ios;
75        typedef detail::stream_format_state<Ch, Tr>               stream_format_state;
76        typedef ::std::basic_string<Ch, Tr, Alloc>                string_type;
77
78        format_item(Ch fill) :argN_(argN_no_posit), fmtstate_(fill),
79                              truncate_(max_streamsize()), pad_scheme_(0)  {}
80        void reset(Ch fill);
81        void compute_states(); // sets states  according to truncate and pad_scheme.
82
83        static std::streamsize max_streamsize() {
84            return (std::numeric_limits<std::streamsize>::max)();
85        }
86
87        // --- data ---
88        int         argN_;  //- argument number (starts at 0,  eg : %1 => argN=0)
89                            //  negative values for items that don't process an argument
90        string_type  res_;      //- result of the formatting of this item
91        string_type  appendix_; //- piece of string between this item and the next
92
93        stream_format_state fmtstate_;// set by parsing, is only affected by modify_item
94
95        std::streamsize truncate_;//- is set for directives like %.5s that ask truncation
96        unsigned int pad_scheme_;//- several possible padding schemes can mix. see pad_values
97    };
98
99
100
101//--- Definitions  ------------------------------------------------------------
102
103// -   stream_format_state:: -------------------------------------------------
104    template<class Ch, class Tr>
105    void stream_format_state<Ch,Tr>:: apply_on (basic_ios & os,
106                      boost::io::detail::locale_t * loc_default) const {
107        // set the state of this stream according to our params
108        if(width_ != -1)
109            os.width(width_);
110        if(precision_ != -1)
111            os.precision(precision_);
112        if(fill_ != 0)
113            os.fill(fill_);
114        os.flags(flags_);
115        os.clear(rdstate_);
116        os.exceptions(exceptions_);
117#if !defined(BOOST_NO_STD_LOCALE)
118        if(loc_)
119            os.imbue(loc_.get());
120        else if(loc_default)
121            os.imbue(*loc_default);
122#endif       
123    }
124
125    template<class Ch, class Tr>
126    void stream_format_state<Ch,Tr>:: set_by_stream(const basic_ios& os) {
127        // set our params according to the state of this stream
128        flags_ = os.flags();
129        width_ = os.width();
130        precision_ = os.precision();
131        fill_ = os.fill();
132        rdstate_ = os.rdstate();
133        exceptions_ = os.exceptions();
134    }
135
136
137    template<class Ch, class Tr, class T>
138    void apply_manip_body( stream_format_state<Ch, Tr>& self,
139                           T manipulator) {
140        // modify our params according to the manipulator
141        basic_oaltstringstream<Ch, Tr>  ss;
142        self.apply_on( ss );
143        ss << manipulator;
144        self.set_by_stream( ss );
145    }
146
147    template<class Ch, class Tr> inline
148    void stream_format_state<Ch,Tr>:: reset(Ch fill) {
149        // set our params to standard's default state.   cf § 27.4.4.1 of the C++ norm
150        width_=0; precision_=6;
151        fill_=fill; // default is widen(' '), but we cant compute it without the locale
152        flags_ = std::ios_base::dec | std::ios_base::skipws;
153        // the adjust_field part is left equal to 0, which means right.
154        exceptions_ = std::ios_base::goodbit;
155        rdstate_ = std::ios_base::goodbit;
156    }
157
158
159// ---   format_item:: --------------------------------------------------------
160
161    template<class Ch, class Tr, class Alloc>
162    void format_item<Ch, Tr, Alloc>::
163    reset (Ch fill) {
164        argN_=argN_no_posit; truncate_ = max_streamsize(); pad_scheme_ =0;
165        res_.resize(0); appendix_.resize(0);
166        fmtstate_.reset(fill);
167    }
168
169    template<class Ch, class Tr, class Alloc>
170    void format_item<Ch, Tr, Alloc>::
171    compute_states() {
172        // reflect pad_scheme_   on  fmt_state_
173        //   because some pad_schemes has complex consequences on several state params.
174        if(pad_scheme_ & zeropad) {
175            // ignore zeropad in left alignment :
176            if(fmtstate_.flags_ & std::ios_base::left) {
177              BOOST_ASSERT(!(fmtstate_.flags_ &(std::ios_base::adjustfield ^std::ios_base::left)));
178              // only left bit might be set. (not right, nor internal)
179              pad_scheme_ = pad_scheme_ & (~zeropad);
180            }
181            else {
182                pad_scheme_ &= ~spacepad; // printf ignores spacepad when zeropadding
183                fmtstate_.fill_='0';
184                fmtstate_.flags_ = (fmtstate_.flags_ & ~std::ios_base::adjustfield)
185                    | std::ios_base::internal;
186                // removes all adjustfield bits, and adds internal.
187            }
188        }
189        if(pad_scheme_ & spacepad) {
190            if(fmtstate_.flags_ & std::ios_base::showpos)
191                pad_scheme_ &= ~spacepad;
192        }
193    }
194
195
196} } } // namespaces boost :: io :: detail
197
198
199#endif // BOOST_FORMAT_INTERNALS_HPP
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