LibreOffice
LibreOffice 4.4 SDK C/C++ API Reference
stringutils.hxx
Go to the documentation of this file.
1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2 /*
3  * This file is part of the LibreOffice project.
4  *
5  * This Source Code Form is subject to the terms of the Mozilla Public
6  * License, v. 2.0. If a copy of the MPL was not distributed with this
7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
8  */
9 
10 #ifndef INCLUDED_RTL_STRINGUTILS_HXX
11 #define INCLUDED_RTL_STRINGUTILS_HXX
12 
13 #include <sal/config.h>
14 #include <sal/types.h>
15 
16 // Manually defining RTL_DISABLE_FAST_STRING allows to force turning fast string concatenation off
17 // (e.g. for debugging).
18 #ifndef RTL_DISABLE_FAST_STRING
19 // This feature is not part of public API and is meant to be used only internally by LibreOffice.
20 #ifdef LIBO_INTERNAL_ONLY
21 // Enable fast string concatenation.
22 #define RTL_FAST_STRING
23 #endif
24 #endif
25 
26 // The unittest uses slightly different code to help check that the proper
27 // calls are made. The class is put into a different namespace to make
28 // sure the compiler generates a different (if generating also non-inline)
29 // copy of the function and does not merge them together. The class
30 // is "brought" into the proper rtl namespace by a typedef below.
31 #ifdef RTL_STRING_UNITTEST
32 #define rtl rtlunittest
33 #endif
34 
35 namespace rtl
36 {
37 
38 #ifdef RTL_STRING_UNITTEST
39 #undef rtl
40 #endif
41 
42 namespace libreoffice_internal
43 {
44 /*
45 These templates use SFINAE (Substitution failure is not an error) to help distinguish the various
46 plain C string types: char*, const char*, char[N], const char[N], char[] and const char[].
47 There are 2 cases:
48 1) Only string literal (i.e. const char[N]) is wanted, not any of the others.
49  In this case it is necessary to distinguish between const char[N] and char[N], as the latter
50  would be automatically converted to the const variant, which is not wanted (not a string literal
51  with known size of the content). In this case ConstCharArrayDetector is used to ensure the function
52  is called only with const char[N] arguments. There's no other plain C string type overload.
53 2) All plain C string types are wanted, and const char[N] needs to be handled differently.
54  In this case const char[N] would match const char* argument type (not exactly sure why, but it's
55  consistent in all of gcc, clang and msvc). Using a template with a reference to const of the type
56  avoids this problem, and CharPtrDetector ensures that the function is called only with char pointer
57  arguments. The const in the argument is necessary to handle the case when something is explicitly
58  cast to const char*. Additionally (non-const) char[N] needs to be handled, but with the reference
59  being const, it would also match const char[N], so another overload with a reference to non-const
60  and NonConstCharArrayDetector are used to ensure the function is called only with (non-const) char[N].
61 Additionally, char[] and const char[] (i.e. size unknown) are rather tricky. Their usage with 'T&' would
62 mean it would be 'char(&)[]', which seems to be invalid. But gcc and clang somehow manage when it is
63 a template. while msvc complains about no conversion from char[] to char[1]. And the reference cannot
64 be avoided, because 'const char[]' as argument type would match also 'const char[N]'
65 So char[] and const char[] should always be used with their contents specified (which automatically
66 turns them into char[N] or const char[N]), or char* and const char* should be used.
67 */
68 struct Dummy {};
69 template< typename T1, typename T2 = void >
71 {
72  static const bool ok = false;
73 };
74 template< typename T >
75 struct CharPtrDetector< const char*, T >
76 {
77  typedef T Type;
78  static const bool ok = true;
79 };
80 template< typename T >
81 struct CharPtrDetector< char*, T >
82 {
83  typedef T Type;
84  static const bool ok = true;
85 };
86 
87 template< typename T1, typename T2 >
89 {
90 };
91 template< typename T, int N >
92 struct NonConstCharArrayDetector< char[ N ], T >
93 {
94  typedef T Type;
95 };
96 #ifdef RTL_STRING_UNITTEST
97 // never use, until all compilers handle this
98 template< typename T >
99 struct NonConstCharArrayDetector< char[], T >
100 {
101  typedef T Type;
102 };
103 template< typename T >
104 struct NonConstCharArrayDetector< const char[], T >
105 {
106  typedef T Type;
107 };
108 #endif
109 
110 template< typename T1, typename T2 = void >
112 {
113  static const bool ok = false;
114 };
115 template< int N, typename T >
116 struct ConstCharArrayDetector< const char[ N ], T >
117 {
118  typedef T Type;
119  static const int size = N;
120  static const bool ok = true;
121 };
122 
123 // this one is used to rule out only const char[N]
124 template< typename T >
126 {
127  typedef Dummy Type;
128 };
129 template< int N >
130 struct ExceptConstCharArrayDetector< const char[ N ] >
131 {
132 };
133 // this one is used to rule out only const char[N]
134 // (const will be brought in by 'const T&' in the function call)
135 // msvc needs const char[N] here (not sure whether gcc or msvc
136 // are right, it doesn't matter).
137 template< typename T >
139 {
140  typedef Dummy Type;
141 };
142 template< int N >
143 struct ExceptCharArrayDetector< char[ N ] >
144 {
145 };
146 template< int N >
147 struct ExceptCharArrayDetector< const char[ N ] >
148 {
149 };
150 
151 template< typename T1, typename T2 = void >
153 {
154  static const bool ok = false;
155 };
156 template< typename T >
158 {
159  typedef T Type;
160  static const bool ok = true;
161 };
162 template< typename T >
164 {
165  typedef T Type;
166  static const bool ok = true;
167 };
168 
169 // SFINAE helper class
170 template< typename T, bool >
171 struct Enable
172  {
173  };
174 
175 template< typename T >
176 struct Enable< T, true >
177  {
178  typedef T Type;
179  };
180 
181 
182 } /* Namespace */
183 
184 } /* Namespace */
185 
186 #endif // INCLUDED_RTL_STRINGUTILS_HXX
187 
188 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
Definition: stringutils.hxx:68
static const bool ok
Definition: stringutils.hxx:72
Definition: bootstrap.hxx:24
T Type
Definition: stringutils.hxx:178
Definition: stringutils.hxx:171
Definition: stringutils.hxx:70
sal_uInt16 sal_Unicode
Definition: types.h:152
Dummy Type
Definition: stringutils.hxx:127
static const bool ok
Definition: stringutils.hxx:113
Dummy Type
Definition: stringutils.hxx:140
static const bool ok
Definition: stringutils.hxx:154