libstdc++: postypes.h Source File

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postypes.h
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1// Position types -*- C++ -*-
2
3// Copyright (C) 1997-2026 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#ifdef _GLIBCXX_SYSHDR
39#pragma GCC system_header
40#endif
41
42#include <cwchar> // For mbstate_t
43
44namespace std _GLIBCXX_VISIBILITY(default)
45{
46_GLIBCXX_BEGIN_NAMESPACE_VERSION
47
48 // The types streamoff, streampos and wstreampos and the class
49 // template fpos<> are described in clauses 21.1.2, 21.1.3, 27.1.2,
50 // 27.2, 27.4.1, 27.4.3 and D.6. Despite all this verbiage, the
51 // behaviour of these types is mostly implementation defined or
52 // unspecified. The behaviour in this implementation is as noted
53 // below.
54
55#pragma GCC diagnostic push
56#pragma GCC diagnostic ignored "-Wlong-long"
57 /**
58 * @brief Type used by fpos, char_traits<char>, and char_traits<wchar_t>.
59 *
60 * In clauses 21.1.3.1 and 27.4.1 streamoff is described as an
61 * implementation defined type.
62 * Note: In versions of GCC up to and including GCC 3.3, streamoff
63 * was typedef long.
64 */
65#ifdef __INT64_TYPE__
66 typedef __INT64_TYPE__ streamoff;
67#else
68 typedef long long streamoff;
69#endif
70#pragma GCC diagnostic pop
71
72 /// Integral type for I/O operation counts and buffer sizes.
73 typedef ptrdiff_t streamsize; // Signed integral type
74
75 /**
76 * @brief Class representing stream positions.
77 *
78 * The standard places no requirements upon the template parameter StateT.
79 * In this implementation StateT must be DefaultConstructible,
80 * CopyConstructible and Assignable. The standard only requires that fpos
81 * should contain a member of type StateT. In this implementation it also
82 * contains an offset stored as a signed integer.
83 *
84 * @param StateT Type passed to and returned from state().
85 */
86 template<typename _StateT>
87 class fpos
88 {
89 private:
90 streamoff _M_off;
91 _StateT _M_state;
92
93 public:
94 // The standard doesn't require that fpos objects can be default
95 // constructed. This implementation provides a default
96 // constructor that initializes the offset to 0 and default
97 // constructs the state.
98 fpos()
99 : _M_off(0), _M_state() { }
100
101 // The standard requires that fpos objects can be constructed
102 // from streamoff objects using the constructor syntax, and
103 // fails to give any meaningful semantics. In this
104 // implementation implicit conversion is also allowed, and this
105 // constructor stores the streamoff as the offset and default
106 // constructs the state.
107 /// Construct position from offset.
108 fpos(streamoff __off)
109 : _M_off(__off), _M_state() { }
110
111#if __cplusplus >= 201103L
112 fpos(const fpos&) = default;
113 fpos& operator=(const fpos&) = default;
114 ~fpos() = default;
115#endif
116
117 /// Convert to streamoff.
118 operator streamoff() const { return _M_off; }
119
120 /// Remember the value of @a st.
121 void
122 state(_StateT __st)
123 { _M_state = __st; }
124
125 /// Return the last set value of @a st.
126 _StateT
127 state() const
128 { return _M_state; }
129
130 // The standard requires that this operator must be defined, but
131 // gives no semantics. In this implementation it just adds its
132 // argument to the stored offset and returns *this.
133 /// Add offset to this position.
134 fpos&
135 operator+=(streamoff __off)
136 {
137 _M_off += __off;
138 return *this;
139 }
140
141 // The standard requires that this operator must be defined, but
142 // gives no semantics. In this implementation it just subtracts
143 // its argument from the stored offset and returns *this.
144 /// Subtract offset from this position.
145 fpos&
146 operator-=(streamoff __off)
147 {
148 _M_off -= __off;
149 return *this;
150 }
151
152 // The standard requires that this operator must be defined, but
153 // defines its semantics only in terms of operator-. In this
154 // implementation it constructs a copy of *this, adds the
155 // argument to that copy using operator+= and then returns the
156 // copy.
157 /// Add position and offset.
158 fpos
159 operator+(streamoff __off) const
160 {
161 fpos __pos(*this);
162 __pos += __off;
163 return __pos;
164 }
165
166 // The standard requires that this operator must be defined, but
167 // defines its semantics only in terms of operator+. In this
168 // implementation it constructs a copy of *this, subtracts the
169 // argument from that copy using operator-= and then returns the
170 // copy.
171 /// Subtract offset from position.
172 fpos
173 operator-(streamoff __off) const
174 {
175 fpos __pos(*this);
176 __pos -= __off;
177 return __pos;
178 }
179
180 // The standard requires that this operator must be defined, but
181 // defines its semantics only in terms of operator+. In this
182 // implementation it returns the difference between the offset
183 // stored in *this and in the argument.
184 /// Subtract position to return offset.
185 streamoff
186 operator-(const fpos& __other) const
187 { return _M_off - __other._M_off; }
188 };
189
190 // The standard only requires that operator== must be an
191 // equivalence relation. In this implementation two fpos<StateT>
192 // objects belong to the same equivalence class if the contained
193 // offsets compare equal.
194 /// Test if equivalent to another position.
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 template<typename _StateT>
201 inline bool
202 operator!=(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
203 { return streamoff(__lhs) != streamoff(__rhs); }
204
205 // Clauses 21.1.3.1 and 21.1.3.2 describe streampos and wstreampos
206 // as implementation defined types, but clause 27.2 requires that
207 // they must both be typedefs for fpos<mbstate_t>
208 /// File position for char streams.
209 typedef fpos<mbstate_t> streampos;
210 /// File position for wchar_t streams.
211 typedef fpos<mbstate_t> wstreampos;
212
213#ifdef _GLIBCXX_USE_CHAR8_T
214 /// File position for char8_t streams.
215 typedef fpos<mbstate_t> u8streampos;
216#endif
217
218#if __cplusplus >= 201103L
219 /// File position for char16_t streams.
220 typedef fpos<mbstate_t> u16streampos;
221 /// File position for char32_t streams.
222 typedef fpos<mbstate_t> u32streampos;
223#endif
224
225_GLIBCXX_END_NAMESPACE_VERSION
226} // namespace
227
228#endif
cwchar
std
ISO C++ entities toplevel namespace is std.
std::streamsize
ptrdiff_t streamsize
Integral type for I/O operation counts and buffer sizes.
Definition postypes.h:73
std::u32streampos
fpos< mbstate_t > u32streampos
File position for char32_t streams.
Definition postypes.h:222
std::streamoff
long long streamoff
Type used by fpos, char_traits<char>, and char_traits<wchar_t>.
Definition postypes.h:68
std::wstreampos
fpos< mbstate_t > wstreampos
File position for wchar_t streams.
Definition postypes.h:211
std::streampos
fpos< mbstate_t > streampos
File position for char streams.
Definition postypes.h:209
std::u16streampos
fpos< mbstate_t > u16streampos
File position for char16_t streams.
Definition postypes.h:220
std::fpos
Class representing stream positions.
Definition postypes.h:88
std::fpos::operator-=
fpos & operator-=(streamoff __off)
Subtract offset from this position.
Definition postypes.h:146
std::fpos::state
void state(_StateT __st)
Remember the value of st.
Definition postypes.h:122
std::fpos::operator+
fpos operator+(streamoff __off) const
Add position and offset.
Definition postypes.h:159
std::fpos::fpos
fpos(streamoff __off)
Construct position from offset.
Definition postypes.h:108
std::fpos::operator+=
fpos & operator+=(streamoff __off)
Add offset to this position.
Definition postypes.h:135
std::fpos::operator-
streamoff operator-(const fpos &__other) const
Subtract position to return offset.
Definition postypes.h:186
std::fpos::state
_StateT state() const
Return the last set value of st.
Definition postypes.h:127
std::fpos::operator-
fpos operator-(streamoff __off) const
Subtract offset from position.
Definition postypes.h:173