basic_string.tcc

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	  const size_type __len = __size + this->size();
	  if (__len > this->capacity() || _M_rep()->_M_is_shared())
	    this->reserve(__len);
	  _M_copy(_M_data() + this->size(), __str._M_data(), __size);
	  _M_rep()->_M_set_length_and_sharable(__len);
	}
      return *this;
    }    

  template<typename _CharT, typename _Traits, typename _Alloc>
    basic_string<_CharT, _Traits, _Alloc>&
    basic_string<_CharT, _Traits, _Alloc>::
    append(const basic_string& __str, size_type __pos, size_type __n)
    {
      __str._M_check(__pos, "basic_string::append");
      __n = __str._M_limit(__pos, __n);
      if (__n)
	{
	  const size_type __len = __n + this->size();
	  if (__len > this->capacity() || _M_rep()->_M_is_shared())
	    this->reserve(__len);
	  _M_copy(_M_data() + this->size(), __str._M_data() + __pos, __n);
	  _M_rep()->_M_set_length_and_sharable(__len);	  
	}
      return *this;
    }

   template<typename _CharT, typename _Traits, typename _Alloc>
     basic_string<_CharT, _Traits, _Alloc>&
     basic_string<_CharT, _Traits, _Alloc>::
     insert(size_type __pos, const _CharT* __s, size_type __n)
     {
       __glibcxx_requires_string_len(__s, __n);
       _M_check(__pos, "basic_string::insert");
       _M_check_length(size_type(0), __n, "basic_string::insert");
       if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
         return _M_replace_safe(__pos, size_type(0), __s, __n);
       else
         {
           // Work in-place.
           const size_type __off = __s - _M_data();
           _M_mutate(__pos, 0, __n);
           __s = _M_data() + __off;
           _CharT* __p = _M_data() + __pos;
           if (__s  + __n <= __p)
             _M_copy(__p, __s, __n);
           else if (__s >= __p)
             _M_copy(__p, __s + __n, __n);
           else
             {
	       const size_type __nleft = __p - __s;
               _M_copy(__p, __s, __nleft);
               _M_copy(__p + __nleft, __p + __n, __n - __nleft);
             }
           return *this;
         }
     }

   template<typename _CharT, typename _Traits, typename _Alloc>
     basic_string<_CharT, _Traits, _Alloc>&
     basic_string<_CharT, _Traits, _Alloc>::
     replace(size_type __pos, size_type __n1, const _CharT* __s,
	     size_type __n2)
     {
       __glibcxx_requires_string_len(__s, __n2);
       _M_check(__pos, "basic_string::replace");
       __n1 = _M_limit(__pos, __n1);
       _M_check_length(__n1, __n2, "basic_string::replace");
       bool __left;
       if (_M_disjunct(__s) || _M_rep()->_M_is_shared())
         return _M_replace_safe(__pos, __n1, __s, __n2);
       else if ((__left = __s + __n2 <= _M_data() + __pos)
		|| _M_data() + __pos + __n1 <= __s)
	 {
	   // Work in-place: non-overlapping case.
	   size_type __off = __s - _M_data();
	   __left ? __off : (__off += __n2 - __n1);
	   _M_mutate(__pos, __n1, __n2);
	   _M_copy(_M_data() + __pos, _M_data() + __off, __n2);
	   return *this;
	 }
       else
	 {
	   // Todo: overlapping case.
	   const basic_string __tmp(__s, __n2);
	   return _M_replace_safe(__pos, __n1, __tmp._M_data(), __n2);
	 }
     }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    basic_string<_CharT, _Traits, _Alloc>::_Rep::
    _M_destroy(const _Alloc& __a) throw ()
    {
      const size_type __size = sizeof(_Rep_base) +
	                       (this->_M_capacity + 1) * sizeof(_CharT);
      _Raw_bytes_alloc(__a).deallocate(reinterpret_cast<char*>(this), __size);
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    basic_string<_CharT, _Traits, _Alloc>::
    _M_leak_hard()
    {
#ifndef _GLIBCXX_FULLY_DYNAMIC_STRING
      if (_M_rep() == &_S_empty_rep())
	return;
#endif
      if (_M_rep()->_M_is_shared())
	_M_mutate(0, 0, 0);
      _M_rep()->_M_set_leaked();
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    basic_string<_CharT, _Traits, _Alloc>::
    _M_mutate(size_type __pos, size_type __len1, size_type __len2)
    {
      const size_type __old_size = this->size();
      const size_type __new_size = __old_size + __len2 - __len1;
      const size_type __how_much = __old_size - __pos - __len1;

      if (__new_size > this->capacity() || _M_rep()->_M_is_shared())
	{
	  // Must reallocate.
	  const allocator_type __a = get_allocator();
	  _Rep* __r = _Rep::_S_create(__new_size, this->capacity(), __a);

	  if (__pos)
	    _M_copy(__r->_M_refdata(), _M_data(), __pos);
	  if (__how_much)
	    _M_copy(__r->_M_refdata() + __pos + __len2,
		    _M_data() + __pos + __len1, __how_much);

	  _M_rep()->_M_dispose(__a);
	  _M_data(__r->_M_refdata());
	}
      else if (__how_much && __len1 != __len2)
	{
	  // Work in-place.
	  _M_move(_M_data() + __pos + __len2,
		  _M_data() + __pos + __len1, __how_much);
	}
      _M_rep()->_M_set_length_and_sharable(__new_size);
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    basic_string<_CharT, _Traits, _Alloc>::
    reserve(size_type __res)
    {
      if (__res != this->capacity() || _M_rep()->_M_is_shared())
        {
	  // Make sure we don't shrink below the current size
	  if (__res < this->size())
	    __res = this->size();
	  const allocator_type __a = get_allocator();
	  _CharT* __tmp = _M_rep()->_M_clone(__a, __res - this->size());
	  _M_rep()->_M_dispose(__a);
	  _M_data(__tmp);
        }
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    basic_string<_CharT, _Traits, _Alloc>::
    swap(basic_string& __s)
    {
      if (_M_rep()->_M_is_leaked())
	_M_rep()->_M_set_sharable();
      if (__s._M_rep()->_M_is_leaked())
	__s._M_rep()->_M_set_sharable();
      if (this->get_allocator() == __s.get_allocator())
	{
	  _CharT* __tmp = _M_data();
	  _M_data(__s._M_data());
	  __s._M_data(__tmp);
	}
      // The code below can usually be optimized away.
      else
	{
	  const basic_string __tmp1(_M_ibegin(), _M_iend(),
				    __s.get_allocator());
	  const basic_string __tmp2(__s._M_ibegin(), __s._M_iend(),
				    this->get_allocator());
	  *this = __tmp2;
	  __s = __tmp1;
	}
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    typename basic_string<_CharT, _Traits, _Alloc>::_Rep*
    basic_string<_CharT, _Traits, _Alloc>::_Rep::
    _S_create(size_type __capacity, size_type __old_capacity,
	      const _Alloc& __alloc)
    {
      // _GLIBCXX_RESOLVE_LIB_DEFECTS
      // 83.  String::npos vs. string::max_size()
      if (__capacity > _S_max_size)
	__throw_length_error(__N("basic_string::_S_create"));

      // The standard places no restriction on allocating more memory
      // than is strictly needed within this layer at the moment or as
      // requested by an explicit application call to reserve().

      // Many malloc implementations perform quite poorly when an
      // application attempts to allocate memory in a stepwise fashion
      // growing each allocation size by only 1 char.  Additionally,
      // it makes little sense to allocate less linear memory than the
      // natural blocking size of the malloc implementation.
      // Unfortunately, we would need a somewhat low-level calculation
      // with tuned parameters to get this perfect for any particular
      // malloc implementation.  Fortunately, generalizations about
      // common features seen among implementations seems to suffice.

      // __pagesize need not match the actual VM page size for good
      // results in practice, thus we pick a common value on the low
      // side.  __malloc_header_size is an estimate of the amount of
      // overhead per memory allocation (in practice seen N * sizeof
      // (void*) where N is 0, 2 or 4).  According to folklore,
      // picking this value on the high side is better than
      // low-balling it (especially when this algorithm is used with
      // malloc implementations that allocate memory blocks rounded up
      // to a size which is a power of 2).
      const size_type __pagesize = 4096;
      const size_type __malloc_header_size = 4 * sizeof(void*);

      // The below implements an exponential growth policy, necessary to
      // meet amortized linear time requirements of the library: see
      // http://gcc.gnu.org/ml/libstdc++/2001-07/msg00085.html.
      // It's active for allocations requiring an amount of memory above
      // system pagesize. This is consistent with the requirements of the
      // standard: http://gcc.gnu.org/ml/libstdc++/2001-07/msg00130.html
      if (__capacity > __old_capacity && __capacity < 2 * __old_capacity)
	__capacity = 2 * __old_capacity;

      // NB: Need an array of char_type[__capacity], plus a terminating
      // null char_type() element, plus enough for the _Rep data structure.
      // Whew. Seemingly so needy, yet so elemental.
      size_type __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep);

      const size_type __adj_size = __size + __malloc_header_size;
      if (__adj_size > __pagesize && __capacity > __old_capacity)
	{
	  const size_type __extra = __pagesize - __adj_size % __pagesize;
	  __capacity += __extra / sizeof(_CharT);
	  // Never allocate a string bigger than _S_max_size.
	  if (__capacity > _S_max_size)
	    __capacity = _S_max_size;
	  __size = (__capacity + 1) * sizeof(_CharT) + sizeof(_Rep);
	}

      // NB: Might throw, but no worries about a leak, mate: _Rep()
      // does not throw.
      void* __place = _Raw_bytes_alloc(__alloc).allocate(__size);
      _Rep *__p = new (__place) _Rep;
      __p->_M_capacity = __capacity;
      return __p;
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    _CharT*
    basic_string<_CharT, _Traits, _Alloc>::_Rep::
    _M_clone(const _Alloc& __alloc, size_type __res)
    {
      // Requested capacity of the clone.
      const size_type __requested_cap = this->_M_length + __res;
      _Rep* __r = _Rep::_S_create(__requested_cap, this->_M_capacity,
				  __alloc);
      if (this->_M_length)
	_M_copy(__r->_M_refdata(), _M_refdata(), this->_M_length);

      __r->_M_set_length_and_sharable(this->_M_length);
      return __r->_M_refdata();
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    void
    basic_string<_CharT, _Traits, _Alloc>::
    resize(size_type __n, _CharT __c)
    {
      const size_type __size = this->size();
      _M_check_length(__size, __n, "basic_string::resize");
      if (__size < __n)
	this->append(__n - __size, __c);
      else if (__n < __size)
	this->erase(__n);
      // else nothing (in particular, avoid calling _M_mutate() unnecessarily.)
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    template<typename _InputIterator>
      basic_string<_CharT, _Traits, _Alloc>&
      basic_string<_CharT, _Traits, _Alloc>::
      _M_replace_dispatch(iterator __i1, iterator __i2, _InputIterator __k1,
			  _InputIterator __k2, __false_type)
      {
	const basic_string __s(__k1, __k2);
	const size_type __n1 = __i2 - __i1;
	_M_check_length(__n1, __s.size(), "basic_string::_M_replace_dispatch");
	return _M_replace_safe(__i1 - _M_ibegin(), __n1, __s._M_data(),
			       __s.size());
      }

  template<typename _CharT, typename _Traits, typename _Alloc>
    basic_string<_CharT, _Traits, _Alloc>&
    basic_string<_CharT, _Traits, _Alloc>::
    _M_replace_aux(size_type __pos1, size_type __n1, size_type __n2,
		   _CharT __c)
    {
      _M_check_length(__n1, __n2, "basic_string::_M_replace_aux");
      _M_mutate(__pos1, __n1, __n2);
      if (__n2)
	_M_assign(_M_data() + __pos1, __n2, __c);
      return *this;
    }

  template<typename _CharT, typename _Traits, typename _Alloc>
    basic_string<_CharT, _Traits, _Alloc>&
    basic_string<_CharT, _Traits, _Alloc>::
    _M_replace_safe(size_type __pos1, size_type __n1, const _CharT* __s,
		    size_type __n2)
    {
      _M_mutate(__pos1, __n1, __n2);
      if (__n2)
	_M_copy(_M_data() + __pos1, __s, __n2);
      return *this;
    }
   
  template<typename _CharT, typename _Traits, typename _Alloc>
    basic_string<_CharT, _Traits, _Alloc>
    operator+(const _CharT* __lhs,
	      const basic_string<_CharT, _Traits, _Alloc>& __rhs)