1// Position types -*- C++ -*-
2
3// Copyright (C) 1997-2024 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file bits/postypes.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{iosfwd}
28 */
29
30//
31// ISO C++ 14882: 27.4.1 - Types
32// ISO C++ 14882: 27.4.3 - Template class fpos
33//
34
35#ifndef _GLIBCXX_POSTYPES_H
36#define _GLIBCXX_POSTYPES_H 1
37
38#pragma GCC system_header
39
40#include <cwchar> // For mbstate_t
41
42namespace std _GLIBCXX_VISIBILITY(default)
43{
44_GLIBCXX_BEGIN_NAMESPACE_VERSION
45
46 // The types streamoff, streampos and wstreampos and the class
47 // template fpos<> are described in clauses 21.1.2, 21.1.3, 27.1.2,
48 // 27.2, 27.4.1, 27.4.3 and D.6. Despite all this verbiage, the
49 // behaviour of these types is mostly implementation defined or
50 // unspecified. The behaviour in this implementation is as noted
51 // below.
52
53 /**
54 * @brief Type used by fpos, char_traits<char>, and char_traits<wchar_t>.
55 *
56 * In clauses 21.1.3.1 and 27.4.1 streamoff is described as an
57 * implementation defined type.
58 * Note: In versions of GCC up to and including GCC 3.3, streamoff
59 * was typedef long.
60 */
61#ifdef __INT64_TYPE__
62 typedef __INT64_TYPE__ streamoff;
63#else
64 typedef long long streamoff;
65#endif
66
67 /// Integral type for I/O operation counts and buffer sizes.
68 typedef ptrdiff_t streamsize; // Signed integral type
69
70 /**
71 * @brief Class representing stream positions.
72 *
73 * The standard places no requirements upon the template parameter StateT.
74 * In this implementation StateT must be DefaultConstructible,
75 * CopyConstructible and Assignable. The standard only requires that fpos
76 * should contain a member of type StateT. In this implementation it also
77 * contains an offset stored as a signed integer.
78 *
79 * @param StateT Type passed to and returned from state().
80 */
81 template<typename _StateT>
82 class fpos
83 {
84 private:
85 streamoff _M_off;
86 _StateT _M_state;
87
88 public:
89 // The standard doesn't require that fpos objects can be default
90 // constructed. This implementation provides a default
91 // constructor that initializes the offset to 0 and default
92 // constructs the state.
93 fpos()
94 : _M_off(0), _M_state() { }
95
96 // The standard requires that fpos objects can be constructed
97 // from streamoff objects using the constructor syntax, and
98 // fails to give any meaningful semantics. In this
99 // implementation implicit conversion is also allowed, and this
100 // constructor stores the streamoff as the offset and default
101 // constructs the state.
102 /// Construct position from offset.
103 fpos(streamoff __off)
104 : _M_off(__off), _M_state() { }
105
106#if __cplusplus >= 201103L
107 fpos(const fpos&) = default;
108 fpos& operator=(const fpos&) = default;
109 ~fpos() = default;
110#endif
111
112 /// Convert to streamoff.
113 operator streamoff() const { return _M_off; }
114
115 /// Remember the value of @a st.
116 void
117 state(_StateT __st)
118 { _M_state = __st; }
119
120 /// Return the last set value of @a st.
121 _StateT
122 state() const
123 { return _M_state; }
124
125 // The standard requires that this operator must be defined, but
126 // gives no semantics. In this implementation it just adds its
127 // argument to the stored offset and returns *this.
128 /// Add offset to this position.
129 fpos&
130 operator+=(streamoff __off)
131 {
132 _M_off += __off;
133 return *this;
134 }
135
136 // The standard requires that this operator must be defined, but
137 // gives no semantics. In this implementation it just subtracts
138 // its argument from the stored offset and returns *this.
139 /// Subtract offset from this position.
140 fpos&
141 operator-=(streamoff __off)
142 {
143 _M_off -= __off;
144 return *this;
145 }
146
147 // The standard requires that this operator must be defined, but
148 // defines its semantics only in terms of operator-. In this
149 // implementation it constructs a copy of *this, adds the
150 // argument to that copy using operator+= and then returns the
151 // copy.
152 /// Add position and offset.
153 fpos
154 operator+(streamoff __off) const
155 {
156 fpos __pos(*this);
157 __pos += __off;
158 return __pos;
159 }
160
161 // The standard requires that this operator must be defined, but
162 // defines its semantics only in terms of operator+. In this
163 // implementation it constructs a copy of *this, subtracts the
164 // argument from that copy using operator-= and then returns the
165 // copy.
166 /// Subtract offset from position.
167 fpos
168 operator-(streamoff __off) const
169 {
170 fpos __pos(*this);
171 __pos -= __off;
172 return __pos;
173 }
174
175 // The standard requires that this operator must be defined, but
176 // defines its semantics only in terms of operator+. In this
177 // implementation it returns the difference between the offset
178 // stored in *this and in the argument.
179 /// Subtract position to return offset.
180 streamoff
181 operator-(const fpos& __other) const
182 { return _M_off - __other._M_off; }
183 };
184
185 // The standard only requires that operator== must be an
186 // equivalence relation. In this implementation two fpos<StateT>
187 // objects belong to the same equivalence class if the contained
188 // offsets compare equal.
189 /// Test if equivalent to another position.
190 template<typename _StateT>
191 inline bool
192 operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
193 { return streamoff(__lhs) == streamoff(__rhs); }
194
195 template<typename _StateT>
196 inline bool
197 operator!=(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
198 { return streamoff(__lhs) != streamoff(__rhs); }
199
200 // Clauses 21.1.3.1 and 21.1.3.2 describe streampos and wstreampos
201 // as implementation defined types, but clause 27.2 requires that
202 // they must both be typedefs for fpos<mbstate_t>
203 /// File position for char streams.
204 typedef fpos<mbstate_t> streampos;
205 /// File position for wchar_t streams.
206 typedef fpos<mbstate_t> wstreampos;
207
208#ifdef _GLIBCXX_USE_CHAR8_T
209 /// File position for char8_t streams.
210 typedef fpos<mbstate_t> u8streampos;
211#endif
212
213#if __cplusplus >= 201103L
214 /// File position for char16_t streams.
215 typedef fpos<mbstate_t> u16streampos;
216 /// File position for char32_t streams.
217 typedef fpos<mbstate_t> u32streampos;
218#endif
219
220_GLIBCXX_END_NAMESPACE_VERSION
221} // namespace
222
223#endif
224