1    	// Components for manipulating sequences of characters -*- C++ -*-
2    	
3    	// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
4    	// Free Software Foundation, Inc.
5    	//
6    	// This file is part of the GNU ISO C++ Library.  This library is free
7    	// software; you can redistribute it and/or modify it under the
8    	// terms of the GNU General Public License as published by the
9    	// Free Software Foundation; either version 2, or (at your option)
10   	// any later version.
11   	
12   	// This library is distributed in the hope that it will be useful,
13   	// but WITHOUT ANY WARRANTY; without even the implied warranty of
14   	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15   	// GNU General Public License for more details.
16   	
17   	// You should have received a copy of the GNU General Public License along
18   	// with this library; see the file COPYING.  If not, write to the Free
19   	// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
20   	// USA.
21   	
22   	// As a special exception, you may use this file as part of a free software
23   	// library without restriction.  Specifically, if other files instantiate
24   	// templates or use macros or inline functions from this file, or you compile
25   	// this file and link it with other files to produce an executable, this
26   	// file does not by itself cause the resulting executable to be covered by
27   	// the GNU General Public License.  This exception does not however
28   	// invalidate any other reasons why the executable file might be covered by
29   	// the GNU General Public License.
30   	
31   	/** @file basic_string.tcc
32   	 *  This is an internal header file, included by other library headers.
33   	 *  You should not attempt to use it directly.
34   	 */
35   	
36   	//
37   	// ISO C++ 14882: 21  Strings library
38   	//
39   	
40   	// Written by Jason Merrill based upon the specification by Takanori Adachi
41   	// in ANSI X3J16/94-0013R2.  Rewritten by Nathan Myers to ISO-14882.
42   	
43   	#ifndef _BASIC_STRING_TCC
44   	#define _BASIC_STRING_TCC 1
45   	
46   	#pragma GCC system_header
47   	
48   	namespace std
49   	{
50   	  template<typename _Type>
51   	    inline bool
52   	    __is_null_pointer(_Type* __ptr)
53   	    { return __ptr == 0; }
54   	
55   	  template<typename _Type>
56   	    inline bool
57   	    __is_null_pointer(_Type)
58   	    { return false; }
59   	
60   	  template<typename _CharT, typename _Traits, typename _Alloc>
61   	    const typename basic_string<_CharT, _Traits, _Alloc>::size_type
62   	    basic_string<_CharT, _Traits, _Alloc>::
63   	    _Rep::_S_max_size = (((npos - sizeof(_Rep_base))/sizeof(_CharT)) - 1) / 4;
64   	
65   	  template<typename _CharT, typename _Traits, typename _Alloc>
66   	    const _CharT
67   	    basic_string<_CharT, _Traits, _Alloc>::
68   	    _Rep::_S_terminal = _CharT();
69   	
70   	  template<typename _CharT, typename _Traits, typename _Alloc>
71   	    const typename basic_string<_CharT, _Traits, _Alloc>::size_type
72   	    basic_string<_CharT, _Traits, _Alloc>::npos;
73   	
74   	  // Linker sets _S_empty_rep_storage to all 0s (one reference, empty string)
75   	  // at static init time (before static ctors are run).
76   	  template<typename _CharT, typename _Traits, typename _Alloc>
77   	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
78   	    basic_string<_CharT, _Traits, _Alloc>::_Rep::_S_empty_rep_storage[
79   	    (sizeof(_Rep_base) + sizeof(_CharT) + sizeof(size_type) - 1) /
80   	      sizeof(size_type)];
81   	
82   	  // NB: This is the special case for Input Iterators, used in
83   	  // istreambuf_iterators, etc.
84   	  // Input Iterators have a cost structure very different from
85   	  // pointers, calling for a different coding style.
86   	  template<typename _CharT, typename _Traits, typename _Alloc>
87   	    template<typename _InIterator>
88   	      _CharT*
89   	      basic_string<_CharT, _Traits, _Alloc>::
90   	      _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
91   			   input_iterator_tag)
92   	      {
93   	#ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
94   		if (__beg == __end && __a == _Alloc())
95   		  return _S_empty_rep()._M_refdata();
96   	#endif
97   		// Avoid reallocation for common case.
98   		_CharT __buf[128];
99   		size_type __len = 0;
100  		while (__beg != __end && __len < sizeof(__buf) / sizeof(_CharT))
101  		  {
102  		    __buf[__len++] = *__beg;
103  		    ++__beg;
104  		  }
105  		_Rep* __r = _Rep::_S_create(__len, size_type(0), __a);
106  		_M_copy(__r->_M_refdata(), __buf, __len);
107  		try
108  		  {
109  		    while (__beg != __end)
110  		      {
111  			if (__len == __r->_M_capacity)
112  			  {
113  			    // Allocate more space.
114  			    _Rep* __another = _Rep::_S_create(__len + 1, __len, __a);
115  			    _M_copy(__another->_M_refdata(), __r->_M_refdata(), __len);
116  			    __r->_M_destroy(__a);
117  			    __r = __another;
118  			  }
119  			__r->_M_refdata()[__len++] = *__beg;
120  			++__beg;
121  		      }
122  		  }
123  		catch(...)
124  		  {
125  		    __r->_M_destroy(__a);
126  		    __throw_exception_again;
127  		  }
128  		__r->_M_set_length_and_sharable(__len);
129  		return __r->_M_refdata();
130  	      }
131  	
132  	  template<typename _CharT, typename _Traits, typename _Alloc>
133  	    template <typename _InIterator>
134  	      _CharT*
135  	      basic_string<_CharT, _Traits, _Alloc>::
136  	      _S_construct(_InIterator __beg, _InIterator __end, const _Alloc& __a,
137  			   forward_iterator_tag)
138  	      {
139  	#ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
140  		if (__beg == __end && __a == _Alloc())
141  		  return _S_empty_rep()._M_refdata();
142  	#endif
143  		// NB: Not required, but considered best practice.
144  		if (__builtin_expect(__is_null_pointer(__beg) && __beg != __end, 0))
145  		  __throw_logic_error(__N("basic_string::_S_construct NULL not valid"));
146  	
147  		const size_type __dnew = static_cast<size_type>(std::distance(__beg,
148  									      __end));
149  		// Check for out_of_range and length_error exceptions.
150  		_Rep* __r = _Rep::_S_create(__dnew, size_type(0), __a);
151  		try
152  		  { _S_copy_chars(__r->_M_refdata(), __beg, __end); }
153  		catch(...)
154  		  {
155  		    __r->_M_destroy(__a);
156  		    __throw_exception_again;
157  		  }
158  		__r->_M_set_length_and_sharable(__dnew);
159  		return __r->_M_refdata();
160  	      }
161  	
162  	  template<typename _CharT, typename _Traits, typename _Alloc>
163  	    _CharT*
164  	    basic_string<_CharT, _Traits, _Alloc>::
165  	    _S_construct(size_type __n, _CharT __c, const _Alloc& __a)
166  	    {
167  	#ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
168  	      if (__n == 0 && __a == _Alloc())
169  		return _S_empty_rep()._M_refdata();
170  	#endif
171  	      // Check for out_of_range and length_error exceptions.
172  	      _Rep* __r = _Rep::_S_create(__n, size_type(0), __a);
173  	      if (__n)
174  		_M_assign(__r->_M_refdata(), __n, __c);
175  	
176  	      __r->_M_set_length_and_sharable(__n);
177  	      return __r->_M_refdata();
178  	    }
179  	
180  	  template<typename _CharT, typename _Traits, typename _Alloc>
181  	    basic_string<_CharT, _Traits, _Alloc>::
182  	    basic_string(const basic_string& __str)
183  	    : _M_dataplus(__str._M_rep()->_M_grab(_Alloc(__str.get_allocator()),
184  						  __str.get_allocator()),
185  			  __str.get_allocator())
186  	    { }
187  	
188  	  template<typename _CharT, typename _Traits, typename _Alloc>
189  	    basic_string<_CharT, _Traits, _Alloc>::
190  	    basic_string(const _Alloc& __a)
191  	    : _M_dataplus(_S_construct(size_type(), _CharT(), __a), __a)
192  	    { }
193  	
194  	  template<typename _CharT, typename _Traits, typename _Alloc>
195  	    basic_string<_CharT, _Traits, _Alloc>::
196  	    basic_string(const basic_string& __str, size_type __pos, size_type __n)
197  	    : _M_dataplus(_S_construct(__str._M_data()
198  				       + __str._M_check(__pos,
199  							"basic_string::basic_string"),
200  				       __str._M_data() + __str._M_limit(__pos, __n)
201  				       + __pos, _Alloc()), _Alloc())
202  	    { }
203  	
204  	  template<typename _CharT, typename _Traits, typename _Alloc>
205  	    basic_string<_CharT, _Traits, _Alloc>::
206  	    basic_string(const basic_string& __str, size_type __pos,
207  			 size_type __n, const _Alloc& __a)
208  	    : _M_dataplus(_S_construct(__str._M_data()
209  				       + __str._M_check(__pos,
210  							"basic_string::basic_string"),
211  				       __str._M_data() + __str._M_limit(__pos, __n)
212  				       + __pos, __a), __a)
213  	    { }
214  	
215  	  // TBD: DPG annotate
216  	  template<typename _CharT, typename _Traits, typename _Alloc>
217  	    basic_string<_CharT, _Traits, _Alloc>::
218  	    basic_string(const _CharT* __s, size_type __n, const _Alloc& __a)
219  	    : _M_dataplus(_S_construct(__s, __s + __n, __a), __a)
220  	    { }
221  	
222  	  // TBD: DPG annotate
223  	  template<typename _CharT, typename _Traits, typename _Alloc>
224  	    basic_string<_CharT, _Traits, _Alloc>::
225  	    basic_string(const _CharT* __s, const _Alloc& __a)
226  	    : _M_dataplus(_S_construct(__s, __s ? __s + traits_type::length(__s) :
227  				       __s + npos, __a), __a)
Event string_null_sink_parm_call: Passing parameter "__s" to "std::char_traits<char>::length(char const *)" which expects a null-terminated string. [details]
At conditional (1): "__s": Taking true branch.
228  	    { }
229  	
230  	  template<typename _CharT, typename _Traits, typename _Alloc>
231  	    basic_string<_CharT, _Traits, _Alloc>::
232  	    basic_string(size_type __n, _CharT __c, const _Alloc& __a)
233  	    : _M_dataplus(_S_construct(__n, __c, __a), __a)
234  	    { }
235  	
236  	  // TBD: DPG annotate
237  	  template<typename _CharT, typename _Traits, typename _Alloc>
238  	    template<typename _InputIterator>
239  	    basic_string<_CharT, _Traits, _Alloc>::
240  	    basic_string(_InputIterator __beg, _InputIterator __end, const _Alloc& __a)
241  	    : _M_dataplus(_S_construct(__beg, __end, __a), __a)
242  	    { }
243  	
244  	  template<typename _CharT, typename _Traits, typename _Alloc>
245  	    basic_string<_CharT, _Traits, _Alloc>&
246  	    basic_string<_CharT, _Traits, _Alloc>::
247  	    assign(const basic_string& __str)
248  	    {
249  	      if (_M_rep() != __str._M_rep())
250  		{
251  		  // XXX MT
252  		  const allocator_type __a = this->get_allocator();
253  		  _CharT* __tmp = __str._M_rep()->_M_grab(__a, __str.get_allocator());
254  		  _M_rep()->_M_dispose(__a);
255  		  _M_data(__tmp);
256  		}
257  	      return *this;
258  	    }
259  	
260  	  template<typename _CharT, typename _Traits, typename _Alloc>
261  	    basic_string<_CharT, _Traits, _Alloc>&
262  	    basic_string<_CharT, _Traits, _Alloc>::
263  	    assign(const _CharT* __s, size_type __n)
264  	    {
265  	      __glibcxx_requires_string_len(__s, __n);
266  	      _M_check_length(this->size(), __n, "basic_string::assign");
267  	      if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
268  		return _M_replace_safe(size_type(0), this->size(), __s, __n);
269  	      else
270  		{
271  		  // Work in-place.
272  		  const size_type __pos = __s - _M_data();
273  		  if (__pos >= __n)
274  		    _M_copy(_M_data(), __s, __n);
275  		  else if (__pos)
276  		    _M_move(_M_data(), __s, __n);
277  		  _M_rep()->_M_set_length_and_sharable(__n);
278  		  return *this;
279  		}
280  	     }
281  	
282  	  template<typename _CharT, typename _Traits, typename _Alloc>
283  	    basic_string<_CharT, _Traits, _Alloc>&
284  	    basic_string<_CharT, _Traits, _Alloc>::
285  	    append(size_type __n, _CharT __c)
286  	    {
287  	      if (__n)
288  		{
289  		  _M_check_length(size_type(0), __n, "basic_string::append");	  
290  		  const size_type __len = __n + this->size();
291  		  if (__len > this->capacity() || _M_rep()->_M_is_shared())
292  		    this->reserve(__len);
293  		  _M_assign(_M_data() + this->size(), __n, __c);
294  		  _M_rep()->_M_set_length_and_sharable(__len);
295  		}
296  	      return *this;
297  	    }
298  	
299  	  template<typename _CharT, typename _Traits, typename _Alloc>
300  	    basic_string<_CharT, _Traits, _Alloc>&
301  	    basic_string<_CharT, _Traits, _Alloc>::
302  	    append(const _CharT* __s, size_type __n)
303  	    {
304  	      __glibcxx_requires_string_len(__s, __n);
305  	      if (__n)
306  		{
307  		  _M_check_length(size_type(0), __n, "basic_string::append");
308  		  const size_type __len = __n + this->size();
309  		  if (__len > this->capacity() || _M_rep()->_M_is_shared())
310  		    {
311  		      if (_M_disjunct(__s))
312  			this->reserve(__len);
313  		      else
314  			{
315  			  const size_type __off = __s - _M_data();
316  			  this->reserve(__len);
317  			  __s = _M_data() + __off;
318  			}
319  		    }
320  		  _M_copy(_M_data() + this->size(), __s, __n);
321  		  _M_rep()->_M_set_length_and_sharable(__len);
322  		}
323  	      return *this;
324  	    }
325  	
326  	  template<typename _CharT, typename _Traits, typename _Alloc>
327  	    basic_string<_CharT, _Traits, _Alloc>&
328  	    basic_string<_CharT, _Traits, _Alloc>::
329  	    append(const basic_string& __str)
330  	    {
331  	      const size_type __size = __str.size();
332  	      if (__size)
333  		{
334  		  const size_type __len = __size + this->size();
335  		  if (__len > this->capacity() || _M_rep()->_M_is_shared())
336  		    this->reserve(__len);
337  		  _M_copy(_M_data() + this->size(), __str._M_data(), __size);
338  		  _M_rep()->_M_set_length_and_sharable(__len);
339  		}
340  	      return *this;
341  	    }    
342  	
343  	  template<typename _CharT, typename _Traits, typename _Alloc>
344  	    basic_string<_CharT, _Traits, _Alloc>&
345  	    basic_string<_CharT, _Traits, _Alloc>::
346  	    append(const basic_string& __str, size_type __pos, size_type __n)
347  	    {
348  	      __str._M_check(__pos, "basic_string::append");
349  	      __n = __str._M_limit(__pos, __n);
350  	      if (__n)
351  		{
352  		  const size_type __len = __n + this->size();
353  		  if (__len > this->capacity() || _M_rep()->_M_is_shared())
354  		    this->reserve(__len);
355  		  _M_copy(_M_data() + this->size(), __str._M_data() + __pos, __n);
356  		  _M_rep()->_M_set_length_and_sharable(__len);	  
357  		}
358  	      return *this;
359  	    }
360  	
361  	   template<typename _CharT, typename _Traits, typename _Alloc>
362  	     basic_string<_CharT, _Traits, _Alloc>&
363  	     basic_string<_CharT, _Traits, _Alloc>::
364  	     insert(size_type __pos, const _CharT* __s, size_type __n)
365  	     {
366  	       __glibcxx_requires_string_len(__s, __n);
367  	       _M_check(__pos, "basic_string::insert");
368  	       _M_check_length(size_type(0), __n, "basic_string::insert");
369  	       if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
370  	         return _M_replace_safe(__pos, size_type(0), __s, __n);
371  	       else
372  	         {
373  	           // Work in-place.
374  	           const size_type __off = __s - _M_data();
375  	           _M_mutate(__pos, 0, __n);
376  	           __s = _M_data() + __off;
377  	           _CharT* __p = _M_data() + __pos;
378  	           if (__s  + __n <= __p)
379  	             _M_copy(__p, __s, __n);
380  	           else if (__s >= __p)
381  	             _M_copy(__p, __s + __n, __n);
382  	           else
383  	             {
384  		       const size_type __nleft = __p - __s;
385  	               _M_copy(__p, __s, __nleft);
386  	               _M_copy(__p + __nleft, __p + __n, __n - __nleft);
387  	             }
388  	           return *this;
389  	         }
390  	     }
391  	
392  	   template<typename _CharT, typename _Traits, typename _Alloc>
393  	     basic_string<_CharT, _Traits, _Alloc>&
394  	     basic_string<_CharT, _Traits, _Alloc>::
395  	     replace(size_type __pos, size_type __n1, const _CharT* __s,
396  		     size_type __n2)
397  	     {
398  	       __glibcxx_requires_string_len(__s, __n2);
399  	       _M_check(__pos, "basic_string::replace");
400  	       __n1 = _M_limit(__pos, __n1);
401  	       _M_check_length(__n1, __n2, "basic_string::replace");
402  	       bool __left;
403  	       if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
404  	         return _M_replace_safe(__pos, __n1, __s, __n2);
405  	       else if ((__left = __s + __n2 <= _M_data() + __pos)
406  			|| _M_data() + __pos + __n1 <= __s)
407  		 {
408  		   // Work in-place: non-overlapping case.
409  		   size_type __off = __s - _M_data();
410  		   __left ? __off : (__off += __n2 - __n1);
411  		   _M_mutate(__pos, __n1, __n2);
412  		   _M_copy(_M_data() + __pos, _M_data() + __off, __n2);
413  		   return *this;
414  		 }
415  	       else
416  		 {
417  		   // Todo: overlapping case.
418  		   const basic_string __tmp(__s, __n2);
419  		   return _M_replace_safe(__pos, __n1, __tmp._M_data(), __n2);
420  		 }
421  	     }
422  	
423  	  template<typename _CharT, typename _Traits, typename _Alloc>
424  	    void
425  	    basic_string<_CharT, _Traits, _Alloc>::_Rep::
426  	    _M_destroy(const _Alloc& __a) throw ()
427  	    {
428  	      const size_type __size = sizeof(_Rep_base) +
429  		                       (this->_M_capacity + 1) * sizeof(_CharT);
430  	      _Raw_bytes_alloc(__a).deallocate(reinterpret_cast<char*>(this), __size);
431  	    }
432  	
433  	  template<typename _CharT, typename _Traits, typename _Alloc>
434  	    void
435  	    basic_string<_CharT, _Traits, _Alloc>::
436  	    _M_leak_hard()
437  	    {
438  	#ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
439  	      if (_M_rep() == &_S_empty_rep())
440  		return;
441  	#endif
442  	      if (_M_rep()->_M_is_shared())
443  		_M_mutate(0, 0, 0);
444  	      _M_rep()->_M_set_leaked();
445  	    }
446  	
447  	  template<typename _CharT, typename _Traits, typename _Alloc>
448  	    void
449  	    basic_string<_CharT, _Traits, _Alloc>::
450  	    _M_mutate(size_type __pos, size_type __len1, size_type __len2)
451  	    {
452  	      const size_type __old_size = this->size();
453  	      const size_type __new_size = __old_size + __len2 - __len1;
454  	      const size_type __how_much = __old_size - __pos - __len1;
455  	
456  	      if (__new_size > this->capacity() || _M_rep()->_M_is_shared())
457  		{
458  		  // Must reallocate.
459  		  const allocator_type __a = get_allocator();
460  		  _Rep* __r = _Rep::_S_create(__new_size, this->capacity(), __a);
461  	
462  		  if (__pos)
463  		    _M_copy(__r->_M_refdata(), _M_data(), __pos);
464  		  if (__how_much)
465  		    _M_copy(__r->_M_refdata() + __pos + __len2,
466  			    _M_data() + __pos + __len1, __how_much);
467  	
468  		  _M_rep()->_M_dispose(__a);
469  		  _M_data(__r->_M_refdata());
470  		}
471  	      else if (__how_much && __len1 != __len2)
472  		{
473  		  // Work in-place.
474  		  _M_move(_M_data() + __pos + __len2,
475  			  _M_data() + __pos + __len1, __how_much);
476  		}
477  	      _M_rep()->_M_set_length_and_sharable(__new_size);
478  	    }
479  	
480  	  template<typename _CharT, typename _Traits, typename _Alloc>
481  	    void
482  	    basic_string<_CharT, _Traits, _Alloc>::
483  	    reserve(size_type __res)
484  	    {
485  	      if (__res != this->capacity() || _M_rep()->_M_is_shared())
486  	        {
487  		  // Make sure we don't shrink below the current size
488  		  if (__res < this->size())
489  		    __res = this->size();
490  		  const allocator_type __a = get_allocator();
491  		  _CharT* __tmp = _M_rep()->_M_clone(__a, __res - this->size());
492  		  _M_rep()->_M_dispose(__a);
493  		  _M_data(__tmp);
494  	        }
495  	    }
496  	
497  	  template<typename _CharT, typename _Traits, typename _Alloc>
498  	    void
499  	    basic_string<_CharT, _Traits, _Alloc>::
500  	    swap(basic_string& __s)
501  	    {
502  	      if (_M_rep()->_M_is_leaked())
503  		_M_rep()->_M_set_sharable();
504  	      if (__s._M_rep()->_M_is_leaked())
505  		__s._M_rep()->_M_set_sharable();
506  	      if (this->get_allocator() == __s.get_allocator())
507  		{
508  		  _CharT* __tmp = _M_data();
509  		  _M_data(__s._M_data());
510  		  __s._M_data(__tmp);
511  		}
512  	      // The code below can usually be optimized away.
513  	      else
514  		{
515  		  const basic_string __tmp1(_M_ibegin(), _M_iend(),
516  					    __s.get_allocator());
517  		  const basic_string __tmp2(__s._M_ibegin(), __s._M_iend(),
518  					    this->get_allocator());
519  		  *this = __tmp2;
520  		  __s = __tmp1;
521  		}
522  	    }
523  	
524  	  template<typename _CharT, typename _Traits, typename _Alloc>
525  	    typename basic_string<_CharT, _Traits, _Alloc>::_Rep*
526  	    basic_string<_CharT, _Traits, _Alloc>::_Rep::
527  	    _S_create(size_type __capacity, size_type __old_capacity,
528  		      const _Alloc& __alloc)
529  	    {
530  	      // _GLIBCXX_RESOLVE_LIB_DEFECTS
531  	      // 83.  String::npos vs. string::max_size()
532  	      if (__capacity > _S_max_size)
533  		__throw_length_error(__N("basic_string::_S_create"));
534  	
535  	      // The standard places no restriction on allocating more memory
536  	      // than is strictly needed within this layer at the moment or as
537  	      // requested by an explicit application call to reserve().
538  	
539  	      // Many malloc implementations perform quite poorly when an
540  	      // application attempts to allocate memory in a stepwise fashion
541  	      // growing each allocation size by only 1 char.  Additionally,
542  	      // it makes little sense to allocate less linear memory than the
543  	      // natural blocking size of the malloc implementation.
544  	      // Unfortunately, we would need a somewhat low-level calculation
545  	      // with tuned parameters to get this perfect for any particular
546  	      // malloc implementation.  Fortunately, generalizations about
547  	      // common features seen among implementations seems to suffice.
548  	
549  	      // __pagesize need not match the actual VM page size for good
550  	      // results in practice, thus we pick a common value on the low
551  	      // side.  __malloc_header_size is an estimate of the amount of
552  	      // overhead per memory allocation (in practice seen N * sizeof
553  	      // (void*) where N is 0, 2 or 4).  According to folklore,
554  	      // picking this value on the high side is better than
555  	      // low-balling it (especially when this algorithm is used with
556  	      // malloc implementations that allocate memory blocks rounded up
557  	      // to a size which is a power of 2).
558  	      const size_type __pagesize = 4096;
559  	      const size_type __malloc_header_size = 4 * sizeof(void*);
560  	
561  	      // The below implements an exponential growth policy, necessary to
562  	      // meet amortized linear time requirements of the library: see
563  	      // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
564  	      // It's active for allocations requiring an amount of memory above
565  	      // system pagesize. This is consistent with the requirements of the
566  	      // standard: http://gcc.gnu.org/ml/libstdc++/2001-07/msg00130.html
567  	      if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
568  		__capacity = 2 * __old_capacity;
569  	
570  	      // NB: Need an array of char_type[__capacity], plus a terminating
571  	      // null char_type() element, plus enough for the _Rep data structure.
572  	      // Whew. Seemingly so needy, yet so elemental.
573  	      size_type __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep);
574  	
575  	      const size_type __adj_size = __size + __malloc_header_size;
576  	      if (__adj_size > __pagesize && __capacity > __old_capacity)
577  		{
578  		  const size_type __extra = __pagesize - __adj_size % __pagesize;
579  		  __capacity += __extra / sizeof(_CharT);
580  		  // Never allocate a string bigger than _S_max_size.
581  		  if (__capacity > _S_max_size)
582  		    __capacity = _S_max_size;
583  		  __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep);
584  		}
585  	
586  	      // NB: Might throw, but no worries about a leak, mate: _Rep()
587  	      // does not throw.
588  	      void* __place = _Raw_bytes_alloc(__alloc).allocate(__size);
589  	      _Rep *__p = new (__place) _Rep;
590  	      __p->_M_capacity = __capacity;
591  	      // ABI compatibility - 3.4.x set in _S_create both
592  	      // _M_refcount and _M_length.  All callers of _S_create
593  	      // in basic_string.tcc then set just _M_length.
594  	      // In 4.0.x and later both _M_refcount and _M_length
595  	      // are initialized in the callers, unfortunately we can
596  	      // have 3.4.x compiled code with _S_create callers inlined
597  	      // calling 4.0.x+ _S_create.
598  	      __p->_M_set_sharable();
599  	      return __p;
600  	    }
601  	
602  	  template<typename _CharT, typename _Traits, typename _Alloc>
603  	    _CharT*
604  	    basic_string<_CharT, _Traits, _Alloc>::_Rep::
605  	    _M_clone(const _Alloc& __alloc, size_type __res)
606  	    {
607  	      // Requested capacity of the clone.
608  	      const size_type __requested_cap = this->_M_length + __res;
609  	      _Rep* __r = _Rep::_S_create(__requested_cap, this->_M_capacity,
610  					  __alloc);
611  	      if (this->_M_length)
612  		_M_copy(__r->_M_refdata(), _M_refdata(), this->_M_length);
613  	
614  	      __r->_M_set_length_and_sharable(this->_M_length);
615  	      return __r->_M_refdata();
616  	    }
617  	
618  	  template<typename _CharT, typename _Traits, typename _Alloc>
619  	    void
620  	    basic_string<_CharT, _Traits, _Alloc>::
621  	    resize(size_type __n, _CharT __c)
622  	    {
623  	      const size_type __size = this->size();
624  	      _M_check_length(__size, __n, "basic_string::resize");
625  	      if (__size < __n)
626  		this->append(__n - __size, __c);
627  	      else if (__n < __size)
628  		this->erase(__n);
629  	      // else nothing (in particular, avoid calling _M_mutate() unnecessarily.)
630  	    }
631  	
632  	  template<typename _CharT, typename _Traits, typename _Alloc>
633  	    template<typename _InputIterator>
634  	      basic_string<_CharT, _Traits, _Alloc>&
635  	      basic_string<_CharT, _Traits, _Alloc>::
636  	      _M_replace_dispatch(iterator __i1, iterator __i2, _InputIterator __k1,
637  				  _InputIterator __k2, __false_type)
638  	      {
639  		const basic_string __s(__k1, __k2);
640  		const size_type __n1 = __i2 - __i1;
641  		_M_check_length(__n1, __s.size(), "basic_string::_M_replace_dispatch");
642  		return _M_replace_safe(__i1 - _M_ibegin(), __n1, __s._M_data(),
643  				       __s.size());
644  	      }
645  	
646  	  template<typename _CharT, typename _Traits, typename _Alloc>
647  	    basic_string<_CharT, _Traits, _Alloc>&
648  	    basic_string<_CharT, _Traits, _Alloc>::
649  	    _M_replace_aux(size_type __pos1, size_type __n1, size_type __n2,
650  			   _CharT __c)
651  	    {
652  	      _M_check_length(__n1, __n2, "basic_string::_M_replace_aux");
653  	      _M_mutate(__pos1, __n1, __n2);
654  	      if (__n2)
655  		_M_assign(_M_data() + __pos1, __n2, __c);
656  	      return *this;
657  	    }
658  	
659  	  template<typename _CharT, typename _Traits, typename _Alloc>
660  	    basic_string<_CharT, _Traits, _Alloc>&
661  	    basic_string<_CharT, _Traits, _Alloc>::
662  	    _M_replace_safe(size_type __pos1, size_type __n1, const _CharT* __s,
663  			    size_type __n2)
664  	    {
665  	      _M_mutate(__pos1, __n1, __n2);
666  	      if (__n2)
667  		_M_copy(_M_data() + __pos1, __s, __n2);
668  	      return *this;
669  	    }
670  	   
671  	  template<typename _CharT, typename _Traits, typename _Alloc>
672  	    basic_string<_CharT, _Traits, _Alloc>
673  	    operator+(const _CharT* __lhs,
674  		      const basic_string<_CharT, _Traits, _Alloc>& __rhs)
675  	    {
676  	      __glibcxx_requires_string(__lhs);
677  	      typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
678  	      typedef typename __string_type::size_type	  __size_type;
679  	      const __size_type __len = _Traits::length(__lhs);
680  	      __string_type __str;
681  	      __str.reserve(__len + __rhs.size());
682  	      __str.append(__lhs, __len);
683  	      __str.append(__rhs);
684  	      return __str;
685  	    }
686  	
687  	  template<typename _CharT, typename _Traits, typename _Alloc>
688  	    basic_string<_CharT, _Traits, _Alloc>
689  	    operator+(_CharT __lhs, const basic_string<_CharT, _Traits, _Alloc>& __rhs)
690  	    {
691  	      typedef basic_string<_CharT, _Traits, _Alloc> __string_type;
692  	      typedef typename __string_type::size_type	  __size_type;
693  	      __string_type __str;
694  	      const __size_type __len = __rhs.size();
695  	      __str.reserve(__len + 1);
696  	      __str.append(__size_type(1), __lhs);
697  	      __str.append(__rhs);
698  	      return __str;
699  	    }
700  	
701  	  template<typename _CharT, typename _Traits, typename _Alloc>
702  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
703  	    basic_string<_CharT, _Traits, _Alloc>::
704  	    copy(_CharT* __s, size_type __n, size_type __pos) const
705  	    {
706  	      _M_check(__pos, "basic_string::copy");
707  	      __n = _M_limit(__pos, __n);
708  	      __glibcxx_requires_string_len(__s, __n);
709  	      if (__n)
710  		_M_copy(__s, _M_data() + __pos, __n);
711  	      // 21.3.5.7 par 3: do not append null.  (good.)
712  	      return __n;
713  	    }
714  	
715  	  template<typename _CharT, typename _Traits, typename _Alloc>
716  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
717  	    basic_string<_CharT, _Traits, _Alloc>::
718  	    find(const _CharT* __s, size_type __pos, size_type __n) const
719  	    {
720  	      __glibcxx_requires_string_len(__s, __n);
721  	      size_type __ret = npos;
722  	      const size_type __size = this->size();
723  	      if (__pos + __n <= __size)
724  		{
725  		  const _CharT* __data = _M_data();
726  		  const _CharT* __p = std::search(__data + __pos, __data + __size,
727  						  __s, __s + __n, traits_type::eq);
728  		  if (__p != __data + __size || __n == 0)
729  		    __ret = __p - __data;
730  		}
731  	      return __ret;
732  	    }
733  	
734  	  template<typename _CharT, typename _Traits, typename _Alloc>
735  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
736  	    basic_string<_CharT, _Traits, _Alloc>::
737  	    find(_CharT __c, size_type __pos) const
738  	    {
739  	      size_type __ret = npos;
740  	      const size_type __size = this->size();
741  	      if (__pos < __size)
742  		{
743  		  const _CharT* __data = _M_data();
744  		  const size_type __n = __size - __pos;
745  		  const _CharT* __p = traits_type::find(__data + __pos, __n, __c);
746  		  if (__p)
747  		    __ret = __p - __data;
748  		}
749  	      return __ret;
750  	    }
751  	
752  	  template<typename _CharT, typename _Traits, typename _Alloc>
753  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
754  	    basic_string<_CharT, _Traits, _Alloc>::
755  	    rfind(const _CharT* __s, size_type __pos, size_type __n) const
756  	    {
757  	      __glibcxx_requires_string_len(__s, __n);
758  	      const size_type __size = this->size();
759  	      if (__n <= __size)
760  		{
761  		  __pos = std::min(size_type(__size - __n), __pos);
762  		  const _CharT* __data = _M_data();
763  		  do
764  		    {
765  		      if (traits_type::compare(__data + __pos, __s, __n) == 0)
766  			return __pos;
767  		    }
768  		  while (__pos-- > 0);
769  		}
770  	      return npos;
771  	    }
772  	
773  	  template<typename _CharT, typename _Traits, typename _Alloc>
774  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
775  	    basic_string<_CharT, _Traits, _Alloc>::
776  	    rfind(_CharT __c, size_type __pos) const
777  	    {
778  	      size_type __size = this->size();
779  	      if (__size)
780  		{
781  		  if (--__size > __pos)
782  		    __size = __pos;
783  		  for (++__size; __size-- > 0; )
784  		    if (traits_type::eq(_M_data()[__size], __c))
785  		      return __size;
786  		}
787  	      return npos;
788  	    }
789  	
790  	  template<typename _CharT, typename _Traits, typename _Alloc>
791  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
792  	    basic_string<_CharT, _Traits, _Alloc>::
793  	    find_first_of(const _CharT* __s, size_type __pos, size_type __n) const
794  	    {
795  	      __glibcxx_requires_string_len(__s, __n);
796  	      for (; __n && __pos < this->size(); ++__pos)
797  		{
798  		  const _CharT* __p = traits_type::find(__s, __n, _M_data()[__pos]);
799  		  if (__p)
800  		    return __pos;
801  		}
802  	      return npos;
803  	    }
804  	
805  	  template<typename _CharT, typename _Traits, typename _Alloc>
806  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
807  	    basic_string<_CharT, _Traits, _Alloc>::
808  	    find_last_of(const _CharT* __s, size_type __pos, size_type __n) const
809  	    {
810  	      __glibcxx_requires_string_len(__s, __n);
811  	      size_type __size = this->size();
812  	      if (__size && __n)
813  		{
814  		  if (--__size > __pos)
815  		    __size = __pos;
816  		  do
817  		    {
818  		      if (traits_type::find(__s, __n, _M_data()[__size]))
819  			return __size;
820  		    }
821  		  while (__size-- != 0);
822  		}
823  	      return npos;
824  	    }
825  	
826  	  template<typename _CharT, typename _Traits, typename _Alloc>
827  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
828  	    basic_string<_CharT, _Traits, _Alloc>::
829  	    find_first_not_of(const _CharT* __s, size_type __pos, size_type __n) const
830  	    {
831  	      __glibcxx_requires_string_len(__s, __n);
832  	      for (; __pos < this->size(); ++__pos)
833  		if (!traits_type::find(__s, __n, _M_data()[__pos]))
834  		  return __pos;
835  	      return npos;
836  	    }
837  	
838  	  template<typename _CharT, typename _Traits, typename _Alloc>
839  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
840  	    basic_string<_CharT, _Traits, _Alloc>::
841  	    find_first_not_of(_CharT __c, size_type __pos) const
842  	    {
843  	      for (; __pos < this->size(); ++__pos)
844  		if (!traits_type::eq(_M_data()[__pos], __c))
845  		  return __pos;
846  	      return npos;
847  	    }
848  	
849  	  template<typename _CharT, typename _Traits, typename _Alloc>
850  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
851  	    basic_string<_CharT, _Traits, _Alloc>::
852  	    find_last_not_of(const _CharT* __s, size_type __pos, size_type __n) const
853  	    {
854  	      __glibcxx_requires_string_len(__s, __n);
855  	      size_type __size = this->size();
856  	      if (__size)
857  		{
858  		  if (--__size > __pos)
859  		    __size = __pos;
860  		  do
861  		    {
862  		      if (!traits_type::find(__s, __n, _M_data()[__size]))
863  			return __size;
864  		    }
865  		  while (__size--);
866  		}
867  	      return npos;
868  	    }
869  	
870  	  template<typename _CharT, typename _Traits, typename _Alloc>
871  	    typename basic_string<_CharT, _Traits, _Alloc>::size_type
872  	    basic_string<_CharT, _Traits, _Alloc>::
873  	    find_last_not_of(_CharT __c, size_type __pos) const
874  	    {
875  	      size_type __size = this->size();
876  	      if (__size)
877  		{
878  		  if (--__size > __pos)
879  		    __size = __pos;
880  		  do
881  		    {
882  		      if (!traits_type::eq(_M_data()[__size], __c))
883  			return __size;
884  		    }
885  		  while (__size--);
886  		}
887  	      return npos;
888  	    }
889  	
890  	  template<typename _CharT, typename _Traits, typename _Alloc>
891  	    int
892  	    basic_string<_CharT, _Traits, _Alloc>::
893  	    compare(size_type __pos, size_type __n, const basic_string& __str) const
894  	    {
895  	      _M_check(__pos, "basic_string::compare");
896  	      __n = _M_limit(__pos, __n);
897  	      const size_type __osize = __str.size();
898  	      const size_type __len = std::min(__n, __osize);
899  	      int __r = traits_type::compare(_M_data() + __pos, __str.data(), __len);
900  	      if (!__r)
901  		__r = __n - __osize;
902  	      return __r;
903  	    }
904  	
905  	  template<typename _CharT, typename _Traits, typename _Alloc>
906  	    int
907  	    basic_string<_CharT, _Traits, _Alloc>::
908  	    compare(size_type __pos1, size_type __n1, const basic_string& __str,
909  		    size_type __pos2, size_type __n2) const
910  	    {
911  	      _M_check(__pos1, "basic_string::compare");
912  	      __str._M_check(__pos2, "basic_string::compare");
913  	      __n1 = _M_limit(__pos1, __n1);
914  	      __n2 = __str._M_limit(__pos2, __n2);
915  	      const size_type __len = std::min(__n1, __n2);
916  	      int __r = traits_type::compare(_M_data() + __pos1,
917  					     __str.data() + __pos2, __len);
918  	      if (!__r)
919  		__r = __n1 - __n2;
920  	      return __r;
921  	    }
922  	
923  	  template<typename _CharT, typename _Traits, typename _Alloc>
924  	    int
925  	    basic_string<_CharT, _Traits, _Alloc>::
926  	    compare(const _CharT* __s) const
927  	    {
928  	      __glibcxx_requires_string(__s);
929  	      const size_type __size = this->size();
930  	      const size_type __osize = traits_type::length(__s);
931  	      const size_type __len = std::min(__size, __osize);
932  	      int __r = traits_type::compare(_M_data(), __s, __len);
933  	      if (!__r)
934  		__r = __size - __osize;
935  	      return __r;
936  	    }
937  	
938  	  template<typename _CharT, typename _Traits, typename _Alloc>
939  	    int
940  	    basic_string <_CharT, _Traits, _Alloc>::
941  	    compare(size_type __pos, size_type __n1, const _CharT* __s) const
942  	    {
943  	      __glibcxx_requires_string(__s);
944  	      _M_check(__pos, "basic_string::compare");
945  	      __n1 = _M_limit(__pos, __n1);
946  	      const size_type __osize = traits_type::length(__s);
947  	      const size_type __len = std::min(__n1, __osize);
948  	      int __r = traits_type::compare(_M_data() + __pos, __s, __len);
949  	      if (!__r)
950  		__r = __n1 - __osize;
951  	      return __r;
952  	    }
953  	
954  	  template<typename _CharT, typename _Traits, typename _Alloc>
955  	    int
956  	    basic_string <_CharT, _Traits, _Alloc>::
957  	    compare(size_type __pos, size_type __n1, const _CharT* __s,
958  		    size_type __n2) const
959  	    {
960  	      __glibcxx_requires_string_len(__s, __n2);
961  	      _M_check(__pos, "basic_string::compare");
962  	      __n1 = _M_limit(__pos, __n1);
963  	      const size_type __len = std::min(__n1, __n2);
964  	      int __r = traits_type::compare(_M_data() + __pos, __s, __len);
965  	      if (!__r)
966  		__r = __n1 - __n2;
967  	      return __r;
968  	    }
969  	
970  	  // Inhibit implicit instantiations for required instantiations,
971  	  // which are defined via explicit instantiations elsewhere.
972  	  // NB: This syntax is a GNU extension.
973  	#if _GLIBCXX_EXTERN_TEMPLATE
974  	  extern template class basic_string<char>;
975  	  extern template
976  	    basic_istream<char>&
977  	    operator>>(basic_istream<char>&, string&);
978  	  extern template
979  	    basic_ostream<char>&
980  	    operator<<(basic_ostream<char>&, const string&);
981  	  extern template
982  	    basic_istream<char>&
983  	    getline(basic_istream<char>&, string&, char);
984  	  extern template
985  	    basic_istream<char>&
986  	    getline(basic_istream<char>&, string&);
987  	
988  	#ifdef _GLIBCXX_USE_WCHAR_T
989  	  extern template class basic_string<wchar_t>;
990  	  extern template
991  	    basic_istream<wchar_t>&
992  	    operator>>(basic_istream<wchar_t>&, wstring&);
993  	  extern template
994  	    basic_ostream<wchar_t>&
995  	    operator<<(basic_ostream<wchar_t>&, const wstring&);
996  	  extern template
997  	    basic_istream<wchar_t>&
998  	    getline(basic_istream<wchar_t>&, wstring&, wchar_t);
999  	  extern template
1000 	    basic_istream<wchar_t>&
1001 	    getline(basic_istream<wchar_t>&, wstring&);
1002 	#endif
1003 	#endif
1004 	} // namespace std
1005 	
1006 	#endif