LibreOffice
LibreOffice 4.2 SDK C/C++ API Reference
 All Classes Namespaces Files Functions Variables Typedefs Enumerations Enumerator Friends Macros Pages
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 
15 // Manually defining RTL_DISABLE_FAST_STRING allows to force turning fast string concatenation off
16 // (e.g. for debugging).
17 #ifndef RTL_DISABLE_FAST_STRING
18 // This feature is not part of public API and is meant to be used only internally by LibreOffice.
19 #ifdef LIBO_INTERNAL_ONLY
20 // Enable fast string concatenation.
21 #define RTL_FAST_STRING
22 #endif
23 #endif
24 
25 // The unittest uses slightly different code to help check that the proper
26 // calls are made. The class is put into a different namespace to make
27 // sure the compiler generates a different (if generating also non-inline)
28 // copy of the function and does not merge them together. The class
29 // is "brought" into the proper rtl namespace by a typedef below.
30 #ifdef RTL_STRING_UNITTEST
31 #define rtl rtlunittest
32 #endif
33 
34 namespace rtl
35 {
36 
37 #ifdef RTL_STRING_UNITTEST
38 #undef rtl
39 #endif
40 
41 namespace internal
42 {
43 /*
44 These templates use SFINAE (Substitution failure is not an error) to help distinguish the various
45 plain C string types: char*, const char*, char[N], const char[N], char[] and const char[].
46 There are 2 cases:
47 1) Only string literal (i.e. const char[N]) is wanted, not any of the others.
48  In this case it is necessary to distinguish between const char[N] and char[N], as the latter
49  would be automatically converted to the const variant, which is not wanted (not a string literal
50  with known size of the content). In this case ConstCharArrayDetector is used to ensure the function
51  is called only with const char[N] arguments. There's no other plain C string type overload.
52 2) All plain C string types are wanted, and const char[N] needs to be handled differently.
53  In this case const char[N] would match const char* argument type (not exactly sure why, but it's
54  consistent in all of gcc, clang and msvc). Using a template with a reference to const of the type
55  avoids this problem, and CharPtrDetector ensures that the function is called only with char pointer
56  arguments. The const in the argument is necessary to handle the case when something is explicitly
57  cast to const char*. Additionally (non-const) char[N] needs to be handled, but with the reference
58  being const, it would also match const char[N], so another overload with a reference to non-const
59  and NonConstCharArrayDetector are used to ensure the function is called only with (non-const) char[N].
60 Additionally, char[] and const char[] (i.e. size unknown) are rather tricky. Their usage with 'T&' would
61 mean it would be 'char(&)[]', which seems to be invalid. But gcc and clang somehow manage when it is
62 a template. while msvc complains about no conversion from char[] to char[1]. And the reference cannot
63 be avoided, because 'const char[]' as argument type would match also 'const char[N]'
64 So char[] and const char[] should always be used with their contents specified (which automatically
65 turns them into char[N] or const char[N]), or char* and const char* should be used.
66 */
67 struct Dummy {};
68 template< typename T1, typename T2 = void >
70 {
71  static const bool ok = false;
72 };
73 template< typename T >
74 struct CharPtrDetector< const char*, T >
75 {
76  typedef T Type;
77  static const bool ok = true;
78 };
79 template< typename T >
80 struct CharPtrDetector< char*, T >
81 {
82  typedef T Type;
83  static const bool ok = true;
84 };
85 
86 template< typename T1, typename T2 >
88 {
89 };
90 template< typename T, int N >
91 struct NonConstCharArrayDetector< char[ N ], T >
92 {
93  typedef T Type;
94 };
95 #ifdef RTL_STRING_UNITTEST
96 // never use, until all compilers handle this
97 template< typename T >
98 struct NonConstCharArrayDetector< char[], T >
99 {
100  typedef T Type;
101 };
102 template< typename T >
103 struct NonConstCharArrayDetector< const char[], T >
104 {
105  typedef T Type;
106 };
107 #endif
108 
109 template< typename T1, typename T2 = void >
111 {
112  static const bool ok = false;
113 };
114 template< int N, typename T >
115 struct ConstCharArrayDetector< const char[ N ], T >
116 {
117  typedef T Type;
118  static const int size = N;
119  static const bool ok = true;
120 };
121 
122 // this one is used to rule out only const char[N]
123 template< typename T >
125 {
126  typedef Dummy Type;
127 };
128 template< int N >
129 struct ExceptConstCharArrayDetector< const char[ N ] >
130 {
131 };
132 // this one is used to rule out only const char[N]
133 // (const will be brought in by 'const T&' in the function call)
134 // msvc needs const char[N] here (not sure whether gcc or msvc
135 // are right, it doesn't matter).
136 template< typename T >
138 {
139  typedef Dummy Type;
140 };
141 template< int N >
142 struct ExceptCharArrayDetector< char[ N ] >
143 {
144 };
145 template< int N >
146 struct ExceptCharArrayDetector< const char[ N ] >
147 {
148 };
149 
150 template< typename T1, typename T2 = void >
152 {
153  static const bool ok = false;
154 };
155 template< typename T >
157 {
158  typedef T Type;
159  static const bool ok = true;
160 };
161 template< typename T >
163 {
164  typedef T Type;
165  static const bool ok = true;
166 };
167 
168 // SFINAE helper class
169 template< typename T, bool >
170 struct Enable
171  {
172  };
173 
174 template< typename T >
175 struct Enable< T, true >
176  {
177  typedef T Type;
178  };
179 
180 
181 } /* Namespace */
182 
183 } /* Namespace */
184 
185 #endif // INCLUDED_RTL_STRINGUTILS_HXX
186 
187 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
Definition: stringutils.hxx:87
Definition: stringutils.hxx:67
T Type
Definition: stringutils.hxx:177
sal_uInt16 sal_Unicode
Definition: types.h:136
static const bool ok
Definition: stringutils.hxx:112
Definition: stringutils.hxx:137
Definition: stringutils.hxx:124
Definition: stringutils.hxx:170
Definition: stringutils.hxx:151
Dummy Type
Definition: stringutils.hxx:126
T Type
Definition: stringutils.hxx:82
Dummy Type
Definition: stringutils.hxx:139
static const bool ok
Definition: stringutils.hxx:71
Definition: stringutils.hxx:110
Definition: stringutils.hxx:69
static const bool ok
Definition: stringutils.hxx:153