LibreOffice
LibreOffice 7.2 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 /*
11  * This file is part of LibreOffice published API.
12  */
13 
14 #ifndef INCLUDED_RTL_STRINGUTILS_HXX
15 #define INCLUDED_RTL_STRINGUTILS_HXX
16 
17 #include "sal/config.h"
18 
19 #include <cassert>
20 #include <cstddef>
21 
22 #include "sal/types.h"
23 
24 // The unittest uses slightly different code to help check that the proper
25 // calls are made. The class is put into a different namespace to make
26 // sure the compiler generates a different (if generating also non-inline)
27 // copy of the function and does not merge them together. The class
28 // is "brought" into the proper rtl namespace by a typedef below.
29 #ifdef RTL_STRING_UNITTEST
30 #define rtl rtlunittest
31 #endif
32 
33 namespace rtl
34 {
35 
36 #ifdef RTL_STRING_UNITTEST
37 #undef rtl
38 #endif
39 
40 #if defined LIBO_INTERNAL_ONLY
42 
43 // A simple wrapper around a single char. Can be useful in string concatenation contexts, like in
44 //
45 // OString s = ...;
46 // char c = ...;
47 // s += OStringChar(c);
48 //
49 struct SAL_WARN_UNUSED OStringChar {
50  constexpr OStringChar(char theC): c(theC) {}
51  template<typename T> OStringChar(T &&) = delete;
52  constexpr operator std::string_view() const { return {&c, 1}; }
53  char const c;
54 };
55 
98 struct SAL_WARN_UNUSED OUStringChar_ {
99  constexpr OUStringChar_(sal_Unicode theC): c(theC) {}
100  constexpr OUStringChar_(char theC): c(theC) { assert(c <= 0x7F); }
101  template<typename T> OUStringChar_(T &&) = delete;
102  constexpr operator std::u16string_view() const { return {&c, 1}; }
103  sal_Unicode const c;
104 };
105 using OUStringChar = OUStringChar_ const;
106 
108 #endif
109 
110 namespace libreoffice_internal
111 {
112 /*
113 These templates use SFINAE (Substitution failure is not an error) to help distinguish the various
114 plain C string types: char*, const char*, char[N], const char[N], char[] and const char[].
115 There are 2 cases:
116 1) Only string literal (i.e. const char[N]) is wanted, not any of the others.
117  In this case it is necessary to distinguish between const char[N] and char[N], as the latter
118  would be automatically converted to the const variant, which is not wanted (not a string literal
119  with known size of the content). In this case ConstCharArrayDetector is used to ensure the function
120  is called only with const char[N] arguments. There's no other plain C string type overload.
121 2) All plain C string types are wanted, and const char[N] needs to be handled differently.
122  In this case const char[N] would match const char* argument type (not exactly sure why, but it's
123  consistent in all of gcc, clang and msvc). Using a template with a reference to const of the type
124  avoids this problem, and CharPtrDetector ensures that the function is called only with char pointer
125  arguments. The const in the argument is necessary to handle the case when something is explicitly
126  cast to const char*. Additionally (non-const) char[N] needs to be handled, but with the reference
127  being const, it would also match const char[N], so another overload with a reference to non-const
128  and NonConstCharArrayDetector are used to ensure the function is called only with (non-const) char[N].
129 Additionally, char[] and const char[] (i.e. size unknown) are rather tricky. Their usage with 'T&' would
130 mean it would be 'char(&)[]', which seems to be invalid. But gcc and clang somehow manage when it is
131 a template. while msvc complains about no conversion from char[] to char[1]. And the reference cannot
132 be avoided, because 'const char[]' as argument type would match also 'const char[N]'
133 So char[] and const char[] should always be used with their contents specified (which automatically
134 turns them into char[N] or const char[N]), or char* and const char* should be used.
135 */
136 struct Dummy {};
137 template< typename T1, typename T2 = void >
139 {
140  static const bool ok = false;
141 };
142 template< typename T >
143 struct CharPtrDetector< const char*, T >
144 {
145  typedef T Type;
146  static const bool ok = true;
147 };
148 template< typename T >
149 struct CharPtrDetector< char*, T >
150 {
151  typedef T Type;
152  static const bool ok = true;
153 };
154 #if defined LIBO_INTERNAL_ONLY
155 template<typename T> struct CharPtrDetector<sal_Unicode *, T> { using TypeUtf16 = T; };
156 template<typename T> struct CharPtrDetector<sal_Unicode const *, T> { using TypeUtf16 = T; };
157 template<typename T> struct CharPtrDetector<sal_Unicode[], T> { using TypeUtf16 = T; };
158 template<typename T> struct CharPtrDetector<sal_Unicode const[], T> { using TypeUtf16 = T; };
159 #endif
160 
161 template< typename T1, typename T2 >
163 {
164 };
165 template< typename T, int N >
166 struct NonConstCharArrayDetector< char[ N ], T >
167 {
168  typedef T Type;
169 };
170 #ifdef RTL_STRING_UNITTEST
171 // never use, until all compilers handle this
172 template< typename T >
173 struct NonConstCharArrayDetector< char[], T >
174 {
175  typedef T Type;
176 };
177 template< typename T >
178 struct NonConstCharArrayDetector< const char[], T >
179 {
180  typedef T Type;
181 };
182 #endif
183 #if defined LIBO_INTERNAL_ONLY
184 template<typename T, std::size_t N> struct NonConstCharArrayDetector<sal_Unicode[N], T> {
185  using TypeUtf16 = T;
186 };
187 #endif
188 
189 template< typename T1, typename T2 = void >
191 {
192  static const bool ok = false;
193 };
194 template< std::size_t N, typename T >
195 struct ConstCharArrayDetector< const char[ N ], T >
196 {
197  typedef T Type;
198  static const std::size_t length = N - 1;
199  static const bool ok = true;
200 #if defined LIBO_INTERNAL_ONLY
201  constexpr
202 #endif
203  static bool isValid(char const (& literal)[N]) {
204  for (std::size_t i = 0; i != N - 1; ++i) {
205  if (literal[i] == '\0') {
206  return false;
207  }
208  }
209  return literal[N - 1] == '\0';
210  }
211 #if defined LIBO_INTERNAL_ONLY
212  constexpr
213 #endif
214  static char const * toPointer(char const (& literal)[N]) { return literal; }
215 };
216 
217 #if defined(__COVERITY__)
218 //to silence over zealous warnings that the loop is logically dead
219 //for the single char case
220 template< typename T >
221 struct ConstCharArrayDetector< const char[ 1 ], T >
222 {
223  typedef T Type;
224  static const std::size_t length = 0;
225  static const bool ok = true;
226 #if defined LIBO_INTERNAL_ONLY
227  constexpr
228 #endif
229  static bool isValid(char const (& literal)[1]) {
230  return literal[0] == '\0';
231  }
232 #if defined LIBO_INTERNAL_ONLY
233  constexpr
234 #endif
235  static char const * toPointer(char const (& literal)[1]) { return literal; }
236 };
237 #endif
238 
239 #if defined LIBO_INTERNAL_ONLY && defined __cpp_char8_t
240 template<std::size_t N, typename T>
241 struct ConstCharArrayDetector<char8_t const [N], T> {
242  using Type = T;
243  static constexpr bool const ok = true;
244  static constexpr std::size_t const length = N - 1;
245  static constexpr bool isValid(char8_t const (& literal)[N]) {
246  for (std::size_t i = 0; i != N - 1; ++i) {
247  if (literal[i] == u8'\0') {
248  return false;
249  }
250  }
251  return literal[N - 1] == u8'\0';
252  }
253  static constexpr char const * toPointer(char8_t const (& literal)[N])
254  { return reinterpret_cast<char const *>(literal); }
255 };
256 #endif
257 
258 #if defined LIBO_INTERNAL_ONLY
259 template<std::size_t N, typename T>
260 struct ConstCharArrayDetector<sal_Unicode const [N], T> {
261  using TypeUtf16 = T;
262  static constexpr bool const ok = true;
263  static constexpr std::size_t const length = N - 1;
264  static constexpr bool isValid(sal_Unicode const (& literal)[N]) {
265  for (std::size_t i = 0; i != N - 1; ++i) {
266  if (literal[i] == '\0') {
267  return false;
268  }
269  }
270  return literal[N - 1] == '\0';
271  }
272  static constexpr sal_Unicode const * toPointer(
273  sal_Unicode const (& literal)[N])
274  { return literal; }
275 };
276 
277 #if defined(__COVERITY__)
278 //to silence over zealous warnings that the loop is logically dead
279 //for the single char case
280 template<typename T>
281 struct ConstCharArrayDetector<sal_Unicode const [1], T> {
282  using TypeUtf16 = T;
283  static constexpr bool const ok = true;
284  static constexpr std::size_t const length = 0;
285  static constexpr bool isValid(sal_Unicode const (& literal)[1]) {
286  return literal[0] == '\0';
287  }
288  static constexpr sal_Unicode const * toPointer(
289  sal_Unicode const (& literal)[1])
290  { return literal; }
291 };
292 #endif
293 
294 template<typename T> struct ConstCharArrayDetector<
295  OUStringChar,
296  T>
297 {
298  using TypeUtf16 = T;
299  static constexpr bool const ok = true;
300  static constexpr std::size_t const length = 1;
301  static constexpr bool isValid(OUStringChar) { return true; }
302  static constexpr sal_Unicode const * toPointer(
303  OUStringChar_ const & literal)
304  { return &literal.c; }
305 };
306 #endif
307 
308 #if defined LIBO_INTERNAL_ONLY && defined RTL_STRING_UNITTEST
309 
310 // this one is used to rule out only const char[N]
311 template< typename T >
312 struct ExceptConstCharArrayDetector
313 {
314  typedef Dummy Type;
315 };
316 template< int N >
317 struct ExceptConstCharArrayDetector< const char[ N ] >
318 {
319 };
320 template<std::size_t N>
321 struct ExceptConstCharArrayDetector<sal_Unicode const[N]> {};
322 template<> struct ExceptConstCharArrayDetector<
323  OUStringChar
324  >
325 {};
326 
327 // this one is used to rule out only const char[N]
328 // (const will be brought in by 'const T&' in the function call)
329 // msvc needs const char[N] here (not sure whether gcc or msvc
330 // are right, it doesn't matter).
331 template< typename T >
332 struct ExceptCharArrayDetector
333 {
334  typedef Dummy Type;
335 };
336 template< int N >
337 struct ExceptCharArrayDetector< char[ N ] >
338 {
339 };
340 template< int N >
341 struct ExceptCharArrayDetector< const char[ N ] >
342 {
343 };
344 template<std::size_t N> struct ExceptCharArrayDetector<sal_Unicode[N]> {};
345 template<std::size_t N> struct ExceptCharArrayDetector<sal_Unicode const[N]> {};
346 template<> struct ExceptCharArrayDetector<OUStringChar_> {};
347 
348 #endif
349 
350 template< typename T1, typename T2 = void >
352 {
353  static const bool ok = false;
354 };
355 template< typename T >
357 {
358  typedef T Type;
359  static const bool ok = true;
360 };
361 template< typename T >
363 {
364  typedef T Type;
365  static const bool ok = true;
366 };
367 
368 // SFINAE helper class
369 template< typename T, bool >
370 struct Enable
371  {
372  };
373 
374 template< typename T >
375 struct Enable< T, true >
376  {
377  typedef T Type;
378  };
379 
380 
381 } /* Namespace */
382 
383 } /* Namespace */
384 
385 #endif // INCLUDED_RTL_STRINGUTILS_HXX
386 
387 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
sal_uInt16 sal_Unicode
Definition: types.h:123
#define SAL_WARN_UNUSED
Annotate classes where a compiler should warn if an instance is unused.
Definition: types.h:587
Definition: bootstrap.hxx:34
Definition: stringutils.hxx:136
Definition: stringutils.hxx:139
static const bool ok
Definition: stringutils.hxx:140
static const bool ok
Definition: stringutils.hxx:192
static char const * toPointer(char const (&literal)[N])
Definition: stringutils.hxx:214
static bool isValid(char const (&literal)[N])
Definition: stringutils.hxx:203
static const bool ok
Definition: stringutils.hxx:353
Definition: stringutils.hxx:371
T Type
Definition: stringutils.hxx:377