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/core/ignore_unused.hpp>
21#include <boost/optional.hpp>
22#include <boost/limits.hpp>
23#include <boost/format/detail/compat_workarounds.hpp>
24#include <boost/format/alt_sstream.hpp> // used as a dummy stream
25
26namespace boost {
27namespace io {
28namespace detail {
29
30
31//---- stream_format_state --------------------------------------------------//
32
33// set of params that define the format state of a stream
34 template<class Ch, class Tr>
35 struct stream_format_state
36 {
37 typedef BOOST_IO_STD basic_ios<Ch, Tr> basic_ios;
38
39 stream_format_state(Ch fill) { reset(fill); }
40// stream_format_state(const basic_ios& os) { set_by_stream(os); }
41
42 void reset(Ch fill); //- sets to default state.
43 void set_by_stream(const basic_ios& os); //- sets to os's state.
44 void apply_on(basic_ios & os, //- applies format_state to the stream
45 boost::io::detail::locale_t * loc_default = 0) const;
46 template<class T>
47 void apply_manip(T manipulator) //- modifies state by applying manipulator
48 { apply_manip_body<Ch, Tr, T>( *this, manipulator) ; }
49
50 // --- data ---
51 std::streamsize width_;
52 std::streamsize precision_;
53 Ch fill_;
54 std::ios_base::fmtflags flags_;
55 std::ios_base::iostate rdstate_;
56 std::ios_base::iostate exceptions_;
57 boost::optional<boost::io::detail::locale_t> loc_;
58 };
59
60
61//---- format_item ---------------------------------------------------------//
62
63// stores all parameters that can be specified in format strings
64 template<class Ch, class Tr, class Alloc>
65 struct format_item
66 {
67 enum pad_values { zeropad = 1, spacepad =2, centered=4, tabulation = 8 };
68 // 1. if zeropad is set, all other bits are not,
69 // 2. if tabulation is set, all others are not.
70 // centered and spacepad can be mixed freely.
71 enum arg_values { argN_no_posit = -1, // non-positional directive. will set argN later
72 argN_tabulation = -2, // tabulation directive. (no argument read)
73 argN_ignored = -3 // ignored directive. (no argument read)
74 };
75 typedef BOOST_IO_STD basic_ios<Ch, Tr> basic_ios;
76 typedef detail::stream_format_state<Ch, Tr> stream_format_state;
77 typedef ::std::basic_string<Ch, Tr, Alloc> string_type;
78
79 format_item(Ch fill) :argN_(argN_no_posit), fmtstate_(fill),
80 truncate_(max_streamsize()), pad_scheme_(0) {}
81 void reset(Ch fill);
82 void compute_states(); // sets states according to truncate and pad_scheme.
83
84 static std::streamsize max_streamsize() {
85 return (std::numeric_limits<std::streamsize>::max)();
86 }
87
88 // --- data ---
89 int argN_; //- argument number (starts at 0, eg : %1 => argN=0)
90 // negative values for items that don't process an argument
91 string_type res_; //- result of the formatting of this item
92 string_type appendix_; //- piece of string between this item and the next
93
94 stream_format_state fmtstate_;// set by parsing, is only affected by modify_item
95
96 std::streamsize truncate_;//- is set for directives like %.5s that ask truncation
97 unsigned int pad_scheme_;//- several possible padding schemes can mix. see pad_values
98 };
99
100
101
102//--- Definitions ------------------------------------------------------------
103
104// - stream_format_state:: -------------------------------------------------
105 template<class Ch, class Tr>
106 void stream_format_state<Ch,Tr>:: apply_on (basic_ios & os,
107 boost::io::detail::locale_t * loc_default) const {
108 // If a locale is available, set it first. "os.fill(fill_);" may chrash otherwise.
109#if !defined(BOOST_NO_STD_LOCALE)
110 if(loc_)
111 os.imbue(loc_.get());
112 else if(loc_default)
113 os.imbue(*loc_default);
114#else
115 ignore_unused(loc_default);
116#endif
117 // set the state of this stream according to our params
118 if(width_ != -1)
119 os.width(width_);
120 if(precision_ != -1)
121 os.precision(precision_);
122 if(fill_ != 0)
123 os.fill(fill_);
124 os.flags(flags_);
125 os.clear(rdstate_);
126 os.exceptions(exceptions_);
127 }
128
129 template<class Ch, class Tr>
130 void stream_format_state<Ch,Tr>:: set_by_stream(const basic_ios& os) {
131 // set our params according to the state of this stream
132 flags_ = os.flags();
133 width_ = os.width();
134 precision_ = os.precision();
135 fill_ = os.fill();
136 rdstate_ = os.rdstate();
137 exceptions_ = os.exceptions();
138 }
139
140
141 template<class Ch, class Tr, class T>
142 void apply_manip_body( stream_format_state<Ch, Tr>& self,
143 T manipulator) {
144 // modify our params according to the manipulator
145 basic_oaltstringstream<Ch, Tr> ss;
146 self.apply_on( ss );
147 ss << manipulator;
148 self.set_by_stream( ss );
149 }
150
151 template<class Ch, class Tr> inline
152 void stream_format_state<Ch,Tr>:: reset(Ch fill) {
153 // set our params to standard's default state. cf 27.4.4.1 of the C++ norm
154 width_=0; precision_=6;
155 fill_=fill; // default is widen(' '), but we cant compute it without the locale
156 flags_ = std::ios_base::dec | std::ios_base::skipws;
157 // the adjust_field part is left equal to 0, which means right.
158 exceptions_ = std::ios_base::goodbit;
159 rdstate_ = std::ios_base::goodbit;
160 }
161
162
163// --- format_item:: --------------------------------------------------------
164
165 template<class Ch, class Tr, class Alloc>
166 void format_item<Ch, Tr, Alloc>::
167 reset (Ch fill) {
168 argN_=argN_no_posit; truncate_ = max_streamsize(); pad_scheme_ =0;
169 res_.resize(0); appendix_.resize(0);
170 fmtstate_.reset(fill);
171 }
172
173 template<class Ch, class Tr, class Alloc>
174 void format_item<Ch, Tr, Alloc>::
175 compute_states() {
176 // reflect pad_scheme_ on fmt_state_
177 // because some pad_schemes has complex consequences on several state params.
178 if(pad_scheme_ & zeropad) {
179 // ignore zeropad in left alignment :
180 if(fmtstate_.flags_ & std::ios_base::left) {
181 BOOST_ASSERT(!(fmtstate_.flags_ &(std::ios_base::adjustfield ^std::ios_base::left)));
182 // only left bit might be set. (not right, nor internal)
183 pad_scheme_ = pad_scheme_ & (~zeropad);
184 }
185 else {
186 pad_scheme_ &= ~spacepad; // printf ignores spacepad when zeropadding
187 fmtstate_.fill_='0';
188 fmtstate_.flags_ = (fmtstate_.flags_ & ~std::ios_base::adjustfield)
189 | std::ios_base::internal;
190 // removes all adjustfield bits, and adds internal.
191 }
192 }
193 if(pad_scheme_ & spacepad) {
194 if(fmtstate_.flags_ & std::ios_base::showpos)
195 pad_scheme_ &= ~spacepad;
196 }
197 }
198
199
200} } } // namespaces boost :: io :: detail
201
202
203#endif // BOOST_FORMAT_INTERNALS_HPP
204

source code of include/boost/format/internals.hpp