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LibreOffice 5.2 SDK C/C++ API Reference
stringconcat.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 #ifndef INCLUDED_RTL_STRINGCONCAT_HXX
11 #define INCLUDED_RTL_STRINGCONCAT_HXX
12 
13 #include <rtl/stringutils.hxx>
14 
15 #include <string.h>
16 
17 #ifdef LIBO_INTERNAL_ONLY // "RTL_FAST_STRING"
18 
19 #ifdef RTL_STRING_UNITTEST
20 #define rtl rtlunittest
21 #endif
22 namespace rtl
23 {
24 #ifdef RTL_STRING_UNITTEST
25 #undef rtl
26 #endif
27 
28 /*
29 Implementation of efficient string concatenation.
30 
31 The whole system is built around two basic template classes:
32 - ToStringHelper< T > - for each T it can give the length of the resulting string representation and can write
33  this string representation to a buffer
34 - O(U)StringConcat< T1, T2 > - operator+ now, instead of creating O(U)String object, returns only this helper object,
35  that keeps a reference to both operator+ operands; only when converted to O(U)String it will actually create
36  the resulting string object using ToStringHelper, creating directly the resulting object without any string
37  intermediate objects
38 As all the code is inline methods, it allows for extensive optimization and will usually result in very effective code
39 (even surpassing strlen/strcat and equalling handwritten), while allowing for very easy and intuitive syntax.
40 */
41 
47 template< typename T >
48 struct ToStringHelper
49  {
51  static int length( const T& );
53  static char* addData( char* buffer, const T& );
55  static sal_Unicode* addData( sal_Unicode* buffer, const T& );
57  static const bool allowOStringConcat = false;
59  static const bool allowOUStringConcat = false;
60  };
61 
62 inline
63 char* addDataHelper( char* buffer, const char* data, int length )
64  {
65  memcpy( buffer, data, length );
66  return buffer + length;
67  }
68 
69 inline
70 sal_Unicode* addDataHelper( sal_Unicode* buffer, const sal_Unicode* data, int length )
71  {
72  memcpy( buffer, data, length * sizeof( sal_Unicode ));
73  return buffer + length;
74  }
75 
76 inline
77 sal_Unicode* addDataLiteral( sal_Unicode* buffer, const char* data, int length )
78  {
79  while( length-- > 0 )
80  *buffer++ = *data++;
81  return buffer;
82  }
83 
84 inline
85 char* addDataCString( char* buffer, const char* str )
86  {
87  while( *str != '\0' )
88  *buffer++ = *str++;
89  return buffer;
90  }
91 
92 inline
93 sal_Unicode* addDataUString( sal_Unicode* buffer, const sal_Unicode* str )
94  {
95  while( *str != '\0' )
96  *buffer++ = *str++;
97  return buffer;
98  }
99 
100 template<>
101 struct ToStringHelper< const char* >
102  {
103  static int length( const char* str ) {
104  return sal::static_int_cast<int>(strlen( str ));
105  }
106  static char* addData( char* buffer, const char* str ) { return addDataCString( buffer, str ); }
107  static const bool allowOStringConcat = true;
108  static const bool allowOUStringConcat = false;
109  };
110 
111 template<>
112 struct ToStringHelper< char* >
113  {
114  static int length( const char* str ) {
115  return sal::static_int_cast<int>(strlen( str ));
116  }
117  static char* addData( char* buffer, const char* str ) { return addDataCString( buffer, str ); }
118  static const bool allowOStringConcat = true;
119  static const bool allowOUStringConcat = false;
120  };
121 
122 template< int N >
123 struct ToStringHelper< char[ N ] >
124  {
125  static int length( const char str[ N ] ) {
126  return sal::static_int_cast<int>(strlen( str ));
127  }
128  static char* addData( char* buffer, const char str[ N ] ) { return addDataCString( buffer, str ); }
129  static sal_Unicode* addData( sal_Unicode* buffer, const char str[ N ] ) { return addDataLiteral( buffer, str, N - 1 ); }
130  static const bool allowOStringConcat = true;
131  static const bool allowOUStringConcat = false;
132  };
133 
134 template< int N >
135 struct ToStringHelper< const char[ N ] >
136  {
137  static int length( const char str[ N ] ) { (void)str; assert( strlen( str ) == N - 1 ); return N - 1; }
138  static char* addData( char* buffer, const char str[ N ] ) { return addDataHelper( buffer, str, N - 1 ); }
139  static sal_Unicode* addData( sal_Unicode* buffer, const char str[ N ] ) { return addDataLiteral( buffer, str, N - 1 ); }
140  static const bool allowOStringConcat = true;
141  static const bool allowOUStringConcat = true;
142  };
143 
144 template<char C> struct ToStringHelper<OUStringLiteral1_<C>> {
145  static int length(OUStringLiteral1_<C>) { return 1; }
146  static char * addData(char * buffer, OUStringLiteral1_<C> literal)
147  { return addDataHelper(buffer, &literal.c, 1); }
148  static sal_Unicode * addData(
149  sal_Unicode * buffer, OUStringLiteral1_<C> literal)
150  { return addDataLiteral(buffer, &literal.c, 1); }
151  static bool const allowOStringConcat = false;
152  static bool const allowOUStringConcat = true;
153 };
154 
161 template< typename T1, typename T2 >
162 struct OStringConcat
163  {
164  public:
165  OStringConcat( const T1& left_, const T2& right_ ) : left( left_ ), right( right_ ) {}
166  int length() const { return ToStringHelper< T1 >::length( left ) + ToStringHelper< T2 >::length( right ); }
167  char* addData( char* buffer ) const { return ToStringHelper< T2 >::addData( ToStringHelper< T1 >::addData( buffer, left ), right ); }
168  // NOTE here could be functions that would forward to the "real" temporary OString. Note however that e.g. getStr()
169  // is not so simple, as the OString temporary must live long enough (i.e. can't be created here in a function, a wrapper
170  // temporary object containing it must be returned instead).
171  private:
172  const T1& left;
173  const T2& right;
174  };
175 
182 template< typename T1, typename T2 >
183 struct OUStringConcat
184  {
185  public:
186  OUStringConcat( const T1& left_, const T2& right_ ) : left( left_ ), right( right_ ) {}
187  int length() const { return ToStringHelper< T1 >::length( left ) + ToStringHelper< T2 >::length( right ); }
188  sal_Unicode* addData( sal_Unicode* buffer ) const { return ToStringHelper< T2 >::addData( ToStringHelper< T1 >::addData( buffer, left ), right ); }
189  private:
190  const T1& left;
191  const T2& right;
192  };
193 
194 template< typename T1, typename T2 >
195 struct ToStringHelper< OStringConcat< T1, T2 > >
196  {
197  static int length( const OStringConcat< T1, T2 >& c ) { return c.length(); }
198  static char* addData( char* buffer, const OStringConcat< T1, T2 >& c ) { return c.addData( buffer ); }
199  static const bool allowOStringConcat = ToStringHelper< T1 >::allowOStringConcat && ToStringHelper< T2 >::allowOStringConcat;
200  static const bool allowOUStringConcat = false;
201  };
202 
203 template< typename T1, typename T2 >
204 struct ToStringHelper< OUStringConcat< T1, T2 > >
205  {
206  static int length( const OUStringConcat< T1, T2 >& c ) { return c.length(); }
207  static sal_Unicode* addData( sal_Unicode* buffer, const OUStringConcat< T1, T2 >& c ) { return c.addData( buffer ); }
208  static const bool allowOStringConcat = false;
209  static const bool allowOUStringConcat = ToStringHelper< T1 >::allowOUStringConcat && ToStringHelper< T2 >::allowOUStringConcat;
210  };
211 
212 template< typename T1, typename T2 >
213 inline
215 typename libreoffice_internal::Enable< OStringConcat< T1, T2 >, ToStringHelper< T1 >::allowOStringConcat && ToStringHelper< T2 >::allowOStringConcat >::Type operator+( const T1& left, const T2& right )
216  {
217  return OStringConcat< T1, T2 >( left, right );
218  }
219 
220 // char[N] and const char[N] need to be done explicitly, otherwise the compiler likes to treat them the same way for some reason
221 template< typename T, int N >
222 inline
224 typename libreoffice_internal::Enable< OStringConcat< T, const char[ N ] >, ToStringHelper< T >::allowOStringConcat >::Type operator+( const T& left, const char (&right)[ N ] )
225  {
226  return OStringConcat< T, const char[ N ] >( left, right );
227  }
228 
229 template< typename T, int N >
230 inline
232 typename libreoffice_internal::Enable< OStringConcat< const char[ N ], T >, ToStringHelper< T >::allowOStringConcat >::Type operator+( const char (&left)[ N ], const T& right )
233  {
234  return OStringConcat< const char[ N ], T >( left, right );
235  }
236 
237 template< typename T, int N >
238 inline
240 typename libreoffice_internal::Enable< OStringConcat< T, char[ N ] >, ToStringHelper< T >::allowOStringConcat >::Type operator+( const T& left, char (&right)[ N ] )
241  {
242  return OStringConcat< T, char[ N ] >( left, right );
243  }
244 
245 template< typename T, int N >
246 inline
248 typename libreoffice_internal::Enable< OStringConcat< char[ N ], T >, ToStringHelper< T >::allowOStringConcat >::Type operator+( char (&left)[ N ], const T& right )
249  {
250  return OStringConcat< char[ N ], T >( left, right );
251  }
252 
253 template< typename T1, typename T2 >
254 inline
256 typename libreoffice_internal::Enable< OUStringConcat< T1, T2 >, ToStringHelper< T1 >::allowOUStringConcat && ToStringHelper< T2 >::allowOUStringConcat >::Type operator+( const T1& left, const T2& right )
257  {
258  return OUStringConcat< T1, T2 >( left, right );
259  }
260 
261 template< typename T1, typename T2 >
262 inline
264 typename libreoffice_internal::Enable< OUStringConcat< T1, T2 >, ToStringHelper< T1 >::allowOUStringConcat && ToStringHelper< T2 >::allowOUStringConcat && libreoffice_internal::ConstCharArrayDetector< T1, void >::ok >::Type operator+( T1& left, const T2& right )
265  {
266  return OUStringConcat< T1, T2 >( left, right );
267  }
268 
269 template< typename T1, typename T2 >
270 inline
272 typename libreoffice_internal::Enable< OUStringConcat< T1, T2 >, ToStringHelper< T1 >::allowOUStringConcat && ToStringHelper< T2 >::allowOUStringConcat && libreoffice_internal::ConstCharArrayDetector< T2, void >::ok >::Type operator+( const T1& left, T2& right )
273  {
274  return OUStringConcat< T1, T2 >( left, right );
275  }
276 
277 #ifdef RTL_STRING_UNITTEST_CONCAT
278 // Special overload to catch the remaining invalid combinations. The helper struct must
279 // be used to make this operator+ overload a worse choice than all the existing overloads above.
280 struct StringConcatInvalid
281  {
282  template< typename T >
283  StringConcatInvalid( const T& ) {}
284  };
285 template< typename T >
286 inline
287 int operator+( const StringConcatInvalid&, const T& )
288  {
289  rtl_string_unittest_invalid_concat = true;
290  return 0; // doesn't matter
291  }
292 #endif
293 
294 } // namespace
295 
296 #endif
297 
298 #endif
sal_uInt16 sal_Unicode
Definition: types.h:155
static const bool ok
Definition: stringutils.hxx:162
T1 static_int_cast(T2 n)
A static_cast between integral types, to avoid C++ compiler warnings.
Definition: types.h:473
#define SAL_WARN_UNUSED_RESULT
Use this as markup for functions and methods whose return value must be checked.
Definition: types.h:325
Definition: bootstrap.hxx:29