LibreOffice: rtl/stringutils.hxx Source File

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stringutils.hxx
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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
33namespace 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//
49struct 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
98struct 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};
105using OUStringChar = OUStringChar_ const;
106
108#endif
109
110 namespace libreoffice_internal
111{
112/*
113These templates use SFINAE (Substitution failure is not an error) to help distinguish the various
114plain C string types: char*, const char*, char[N], const char[N], char[] and const char[].
115There are 2 cases:
1161) 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 (Note that OUStringChar is also covered by ConstCharArrayDetector's TypeUtf16 check, but
122 provides a pointer to a string that is not NUL-terminated, unlike the char16_t const[N] arrays
123 normally covered by that check, and which are assumed to represent NUL-terminated string
124 literals.)
1252) All plain C string types are wanted, and const char[N] needs to be handled differently.
126 In this case const char[N] would match const char* argument type (not exactly sure why, but it's
127 consistent in all of gcc, clang and msvc). Using a template with a reference to const of the type
128 avoids this problem, and CharPtrDetector ensures that the function is called only with char pointer
129 arguments. The const in the argument is necessary to handle the case when something is explicitly
130 cast to const char*. Additionally (non-const) char[N] needs to be handled, but with the reference
131 being const, it would also match const char[N], so another overload with a reference to non-const
132 and NonConstCharArrayDetector are used to ensure the function is called only with (non-const) char[N].
133Additionally, char[] and const char[] (i.e. size unknown) are rather tricky. Their usage with 'T&' would
134mean it would be 'char(&)[]', which seems to be invalid. But gcc and clang somehow manage when it is
135a template. while msvc complains about no conversion from char[] to char[1]. And the reference cannot
136be avoided, because 'const char[]' as argument type would match also 'const char[N]'
137So char[] and const char[] should always be used with their contents specified (which automatically
138turns them into char[N] or const char[N]), or char* and const char* should be used.
139*/
140 struct Dummy {};
141template< typename T1, typename T2 = void >
142 struct CharPtrDetector
143{
144 static const bool ok = false;
145};
146template< typename T >
147 struct CharPtrDetector< const char*, T >
148{
149 typedef T Type;
150 static const bool ok = true;
151};
152template< typename T >
153 struct CharPtrDetector< char*, T >
154{
155 typedef T Type;
156 static const bool ok = true;
157};
158#if defined LIBO_INTERNAL_ONLY
159template<typename T> struct CharPtrDetector<sal_Unicode *, T> { using TypeUtf16 = T; };
160template<typename T> struct CharPtrDetector<sal_Unicode const *, T> { using TypeUtf16 = T; };
161template<typename T> struct CharPtrDetector<sal_Unicode[], T> { using TypeUtf16 = T; };
162template<typename T> struct CharPtrDetector<sal_Unicode const[], T> { using TypeUtf16 = T; };
163#endif
164
165template< typename T1, typename T2 >
166 struct NonConstCharArrayDetector
167{
168};
169template< typename T, int N >
170 struct NonConstCharArrayDetector< char[ N ], T >
171{
172 typedef T Type;
173};
174#ifdef RTL_STRING_UNITTEST
175// never use, until all compilers handle this
176template< typename T >
177struct NonConstCharArrayDetector< char[], T >
178{
179 typedef T Type;
180};
181template< typename T >
182struct NonConstCharArrayDetector< const char[], T >
183{
184 typedef T Type;
185};
186#endif
187#if defined LIBO_INTERNAL_ONLY
188template<typename T, std::size_t N> struct NonConstCharArrayDetector<sal_Unicode[N], T> {
189 using TypeUtf16 = T;
190};
191#endif
192
193template< typename T1, typename T2 = void >
194 struct ConstCharArrayDetector
195{
196 static const bool ok = false;
197};
198template< std::size_t N, typename T >
199 struct ConstCharArrayDetector< const char[ N ], T >
200{
201 typedef T Type;
202 static const std::size_t length = N - 1;
203 static const bool ok = true;
204#if defined LIBO_INTERNAL_ONLY
205 constexpr
206#endif
207 static bool isValid(char const (& literal)[N]) {
208 for (std::size_t i = 0; i != N - 1; ++i) {
209 if (literal[i] == '\0') {
210 return false;
211 }
212 }
213 return literal[N - 1] == '\0';
214 }
215#if defined LIBO_INTERNAL_ONLY
216 constexpr
217#endif
218 static char const * toPointer(char const (& literal)[N]) { return literal; }
219};
220
221#if defined(__COVERITY__)
222//to silence over zealous warnings that the loop is logically dead
223//for the single char case
224template< typename T >
225struct ConstCharArrayDetector< const char[ 1 ], T >
226{
227 typedef T Type;
228 static const std::size_t length = 0;
229 static const bool ok = true;
230#if defined LIBO_INTERNAL_ONLY
231 constexpr
232#endif
233 static bool isValid(char const (& literal)[1]) {
234 return literal[0] == '\0';
235 }
236#if defined LIBO_INTERNAL_ONLY
237 constexpr
238#endif
239 static char const * toPointer(char const (& literal)[1]) { return literal; }
240};
241#endif
242
243#if defined LIBO_INTERNAL_ONLY && defined __cpp_char8_t
244template<std::size_t N, typename T>
245struct ConstCharArrayDetector<char8_t const [N], T> {
246 using Type = T;
247 static constexpr bool const ok = true;
248 static constexpr std::size_t const length = N - 1;
249 static constexpr bool isValid(char8_t const (& literal)[N]) {
250 for (std::size_t i = 0; i != N - 1; ++i) {
251 if (literal[i] == u8'\0') {
252 return false;
253 }
254 }
255 return literal[N - 1] == u8'\0';
256 }
257 static constexpr char const * toPointer(char8_t const (& literal)[N])
258 { return reinterpret_cast<char const *>(literal); }
259};
260#endif
261
262#if defined LIBO_INTERNAL_ONLY
263template<std::size_t N, typename T>
264struct ConstCharArrayDetector<sal_Unicode const [N], T> {
265 using TypeUtf16 = T;
266 static constexpr bool const ok = true;
267 static constexpr std::size_t const length = N - 1;
268 static constexpr bool isValid(sal_Unicode const (& literal)[N]) {
269 for (std::size_t i = 0; i != N - 1; ++i) {
270 if (literal[i] == '\0') {
271 return false;
272 }
273 }
274 return literal[N - 1] == '\0';
275 }
276 static constexpr sal_Unicode const * toPointer(
277 sal_Unicode const (& literal)[N])
278 { return literal; }
279};
280
281#if defined(__COVERITY__)
282//to silence over zealous warnings that the loop is logically dead
283//for the single char case
284template<typename T>
285struct ConstCharArrayDetector<sal_Unicode const [1], T> {
286 using TypeUtf16 = T;
287 static constexpr bool const ok = true;
288 static constexpr std::size_t const length = 0;
289 static constexpr bool isValid(sal_Unicode const (& literal)[1]) {
290 return literal[0] == '\0';
291 }
292 static constexpr sal_Unicode const * toPointer(
293 sal_Unicode const (& literal)[1])
294 { return literal; }
295};
296#endif
297
298template<typename T> struct ConstCharArrayDetector<
299 OUStringChar,
300 T>
301{
302 using TypeUtf16 = T;
303 static constexpr bool const ok = true;
304 static constexpr std::size_t const length = 1;
305 static constexpr bool isValid(OUStringChar) { return true; }
306 static constexpr sal_Unicode const * toPointer(
307 OUStringChar_ const & literal)
308 { return &literal.c; }
309};
310#endif
311
312#if defined LIBO_INTERNAL_ONLY && defined RTL_STRING_UNITTEST
313
314// this one is used to rule out only const char[N]
315template< typename T >
316struct ExceptConstCharArrayDetector
317{
318 typedef Dummy Type;
319};
320template< int N >
321struct ExceptConstCharArrayDetector< const char[ N ] >
322{
323};
324template<std::size_t N>
325struct ExceptConstCharArrayDetector<sal_Unicode const[N]> {};
326template<> struct ExceptConstCharArrayDetector<
327 OUStringChar
328 >
329{};
330
331// this one is used to rule out only const char[N]
332// (const will be brought in by 'const T&' in the function call)
333// msvc needs const char[N] here (not sure whether gcc or msvc
334// are right, it doesn't matter).
335template< typename T >
336struct ExceptCharArrayDetector
337{
338 typedef Dummy Type;
339};
340template< int N >
341struct ExceptCharArrayDetector< char[ N ] >
342{
343};
344template< int N >
345struct ExceptCharArrayDetector< const char[ N ] >
346{
347};
348template<std::size_t N> struct ExceptCharArrayDetector<sal_Unicode[N]> {};
349template<std::size_t N> struct ExceptCharArrayDetector<sal_Unicode const[N]> {};
350template<> struct ExceptCharArrayDetector<OUStringChar_> {};
351
352#endif
353
354template< typename T1, typename T2 = void >
355 struct SalUnicodePtrDetector
356{
357 static const bool ok = false;
358};
359template< typename T >
360 struct SalUnicodePtrDetector< const sal_Unicode*, T >
361{
362 typedef T Type;
363 static const bool ok = true;
364};
365template< typename T >
366 struct SalUnicodePtrDetector< sal_Unicode*, T >
367{
368 typedef T Type;
369 static const bool ok = true;
370};
371
372// SFINAE helper class
373template< typename T, bool >
374 struct Enable
375 {
376 };
377
378template< typename T >
379 struct Enable< T, true >
380 {
381 typedef T Type;
382 };
383
384
385} /* Namespace */
386
387} /* Namespace */
388
389#endif // INCLUDED_RTL_STRINGUTILS_HXX
390
391/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
types.h
sal_Unicode
sal_uInt16 sal_Unicode
Definition types.h:123
SAL_WARN_UNUSED
#define SAL_WARN_UNUSED
Annotate classes where a compiler should warn if an instance is unused.
Definition types.h:587
config.h
rtl
Definition bootstrap.hxx:34
rtl::libreoffice_internal::Dummy
Definition stringutils.hxx:140
rtl::libreoffice_internal::CharPtrDetector
Definition stringutils.hxx:143
rtl::libreoffice_internal::CharPtrDetector::ok
static const bool ok
Definition stringutils.hxx:144
rtl::libreoffice_internal::CharPtrDetector< const char *, T >::Type
T Type
Definition stringutils.hxx:149
rtl::libreoffice_internal::CharPtrDetector< char *, T >::Type
T Type
Definition stringutils.hxx:155
rtl::libreoffice_internal::NonConstCharArrayDetector
Definition stringutils.hxx:167
rtl::libreoffice_internal::NonConstCharArrayDetector< char[N], T >::Type
T Type
Definition stringutils.hxx:172
rtl::libreoffice_internal::ConstCharArrayDetector
Definition stringutils.hxx:195
rtl::libreoffice_internal::ConstCharArrayDetector::ok
static const bool ok
Definition stringutils.hxx:196
rtl::libreoffice_internal::ConstCharArrayDetector< const char[N], T >::toPointer
static char const * toPointer(char const (&literal)[N])
Definition stringutils.hxx:218
rtl::libreoffice_internal::ConstCharArrayDetector< const char[N], T >::Type
T Type
Definition stringutils.hxx:201
rtl::libreoffice_internal::ConstCharArrayDetector< const char[N], T >::isValid
static bool isValid(char const (&literal)[N])
Definition stringutils.hxx:207
rtl::libreoffice_internal::SalUnicodePtrDetector
Definition stringutils.hxx:356
rtl::libreoffice_internal::SalUnicodePtrDetector::ok
static const bool ok
Definition stringutils.hxx:357
rtl::libreoffice_internal::SalUnicodePtrDetector< const sal_Unicode *, T >::Type
T Type
Definition stringutils.hxx:362
rtl::libreoffice_internal::SalUnicodePtrDetector< sal_Unicode *, T >::Type
T Type
Definition stringutils.hxx:368
rtl::libreoffice_internal::Enable
Definition stringutils.hxx:375
rtl::libreoffice_internal::Enable< T, true >::Type
T Type
Definition stringutils.hxx:381