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ropeimpl.h

// SGI's rope class implementation -*- C++ -*-

// Copyright (C) 2001-2018 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/*
 * Copyright (c) 1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file ropeimpl.h
 *  This is an internal header file, included by other library headers.
 *  Do not attempt to use it directly. @headername{ext/rope}
 */

#include <cstdio>
#include <ostream>
#include <bits/functexcept.h>

#include <ext/algorithm> // For copy_n and lexicographical_compare_3way
#include <ext/memory> // For uninitialized_copy_n
#include <ext/numeric> // For power

namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

using std::size_t;
  using std::printf;
  using std::basic_ostream;
  using std::__throw_length_error;
  using std::_Destroy;
  using std::__uninitialized_fill_n_a;

// Set buf_start, buf_end, and buf_ptr appropriately, filling tmp_buf
  // if necessary.  Assumes _M_path_end[leaf_index] and leaf_pos are correct.
  // Results in a valid buf_ptr if the iterator can be legitimately
  // dereferenced.
  template <class _CharT, class _Alloc>
    void
    _Rope_iterator_base<_CharT, _Alloc>::
    _S_setbuf(_Rope_iterator_base<_CharT, _Alloc>& __x)
    {
      const _RopeRep* __leaf = __x._M_path_end[__x._M_leaf_index];
      size_t __leaf_pos = __x._M_leaf_pos;
      size_t __pos = __x._M_current_pos;

switch(__leaf->_M_tag)
	{
	case __detail::_S_leaf:
	  __x._M_buf_start = ((_Rope_RopeLeaf<_CharT, _Alloc>*)__leaf)->_M_data;
	  __x._M_buf_ptr = __x._M_buf_start + (__pos - __leaf_pos);
	  __x._M_buf_end = __x._M_buf_start + __leaf->_M_size;
	  break;
	case __detail::_S_function:
	case __detail::_S_substringfn:
	  {
	    size_t __len = _S_iterator_buf_len;
	    size_t __buf_start_pos = __leaf_pos;
	    size_t __leaf_end = __leaf_pos + __leaf->_M_size;
	    char_producer<_CharT>* __fn = ((_Rope_RopeFunction<_CharT,
					    _Alloc>*)__leaf)->_M_fn;
	    if (__buf_start_pos + __len <= __pos)
	      {
		__buf_start_pos = __pos - __len / 4;
		if (__buf_start_pos + __len > __leaf_end)
		  __buf_start_pos = __leaf_end - __len;
	      }
	    if (__buf_start_pos + __len > __leaf_end)
	      __len = __leaf_end - __buf_start_pos;
	    (*__fn)(__buf_start_pos - __leaf_pos, __len, __x._M_tmp_buf);
	    __x._M_buf_ptr = __x._M_tmp_buf + (__pos - __buf_start_pos);
	    __x._M_buf_start = __x._M_tmp_buf;
	    __x._M_buf_end = __x._M_tmp_buf + __len;
	  }
	  break;
	default:
	  break;
	}
    }

// Set path and buffer inside a rope iterator.  We assume that
  // pos and root are already set.
  template <class _CharT, class _Alloc>
    void
    _Rope_iterator_base<_CharT, _Alloc>::
    _S_setcache(_Rope_iterator_base<_CharT, _Alloc>& __x)
    {
      const _RopeRep* __path[int(__detail::_S_max_rope_depth) + 1];
      const _RopeRep* __curr_rope;
      int __curr_depth = -1;  /* index into path    */
      size_t __curr_start_pos = 0;
      size_t __pos = __x._M_current_pos;
      unsigned char __dirns = 0; // Bit vector marking right turns in the path

if (__pos >= __x._M_root->_M_size)
	{
	  __x._M_buf_ptr = 0;
	  return;
	}
      __curr_rope = __x._M_root;
      if (0 != __curr_rope->_M_c_string)
	{
	  /* Treat the root as a leaf. */
	  __x._M_buf_start = __curr_rope->_M_c_string;
	  __x._M_buf_end = __curr_rope->_M_c_string + __curr_rope->_M_size;
	  __x._M_buf_ptr = __curr_rope->_M_c_string + __pos;
	  __x._M_path_end[0] = __curr_rope;
	  __x._M_leaf_index = 0;
	  __x._M_leaf_pos = 0;
	  return;
	}
      for(;;)
	{
	  ++__curr_depth;
	  __path[__curr_depth] = __curr_rope;
	  switch(__curr_rope->_M_tag)
	    {
	    case __detail::_S_leaf:
	    case __detail::_S_function:
	    case __detail::_S_substringfn:
	      __x._M_leaf_pos = __curr_start_pos;
	      goto done;
	    case __detail::_S_concat:
	      {
		_Rope_RopeConcatenation<_CharT, _Alloc>* __c =
		  (_Rope_RopeConcatenation<_CharT, _Alloc>*)__curr_rope;
		_RopeRep* __left = __c->_M_left;
		size_t __left_len = __left->_M_size;

__dirns <<= 1;
		if (__pos >= __curr_start_pos + __left_len)
		  {
		    __dirns |= 1;
		    __curr_rope = __c->_M_right;
		    __curr_start_pos += __left_len;
		  }
		else
		  __curr_rope = __left;
	      }
	      break;
	    }
	}
    done:
      // Copy last section of path into _M_path_end.
      {
	int __i = -1;
	int __j = __curr_depth + 1 - int(_S_path_cache_len);

if (__j < 0) __j = 0;
	while (__j <= __curr_depth)
	  __x._M_path_end[++__i] = __path[__j++];
	__x._M_leaf_index = __i;
      }
      __x._M_path_directions = __dirns;
      _S_setbuf(__x);
    }

// Specialized version of the above.  Assumes that
  // the path cache is valid for the previous position.
  template <class _CharT, class _Alloc>
    void
    _Rope_iterator_base<_CharT, _Alloc>::
    _S_setcache_for_incr(_Rope_iterator_base<_CharT, _Alloc>& __x)
    {
      int __current_index = __x._M_leaf_index;
      const _RopeRep* __current_node = __x._M_path_end[__current_index];
      size_t __len = __current_node->_M_size;
      size_t __node_start_pos = __x._M_leaf_pos;
      unsigned char __dirns = __x._M_path_directions;
      _Rope_RopeConcatenation<_CharT, _Alloc>* __c;

if (__x._M_current_pos - __node_start_pos < __len)
	{
	  /* More stuff in this leaf, we just didn't cache it. */
	  _S_setbuf(__x);
	  return;
	}
      //  node_start_pos is starting position of last_node.
      while (--__current_index >= 0)
	{
	  if (!(__dirns & 1) /* Path turned left */)
	    break;
	  __current_node = __x._M_path_end[__current_index];
	  __c = (_Rope_RopeConcatenation<_CharT, _Alloc>*)__current_node;
	  // Otherwise we were in the right child.  Thus we should pop
	  // the concatenation node.
	  __node_start_pos -= __c->_M_left->_M_size;
	  __dirns >>= 1;
	}
      if (__current_index < 0)
	{
	  // We underflowed the cache. Punt.
	  _S_setcache(__x);
	  return;
	}
      __current_node = __x._M_path_end[__current_index];
      __c = (_Rope_RopeConcatenation<_CharT, _Alloc>*)__current_node;
      // current_node is a concatenation node.  We are positioned on the first
      // character in its right child.
      // node_start_pos is starting position of current_node.
      __node_start_pos += __c->_M_left->_M_size;
      __current_node = __c->_M_right;
      __x._M_path_end[++__current_index] = __current_node;
      __dirns |= 1;
      while (__detail::_S_concat == __current_node->_M_tag)
	{
	  ++__current_index;
	  if (int(_S_path_cache_len) == __current_index)
	    {
	      int __i;
	      for (__i = 0; __i < int(_S_path_cache_len) - 1; __i++)
		__x._M_path_end[__i] = __x._M_path_end[__i+1];
	      --__current_index;
	    }
	  __current_node =
	    ((_Rope_RopeConcatenation<_CharT, _Alloc>*)__current_node)->_M_left;
	  __x._M_path_end[__current_index] = __current_node;
	  __dirns <<= 1;
	  // node_start_pos is unchanged.
	}
      __x._M_leaf_index = __current_index;
      __x._M_leaf_pos = __node_start_pos;
      __x._M_path_directions = __dirns;
      _S_setbuf(__x);
    }

template <class _CharT, class _Alloc>
    void
    _Rope_iterator_base<_CharT, _Alloc>::
    _M_incr(size_t __n)
    {
      _M_current_pos += __n;
      if (0 != _M_buf_ptr)
	{
	  size_t __chars_left = _M_buf_end - _M_buf_ptr;
	  if (__chars_left > __n)
	    _M_buf_ptr += __n;
	  else if (__chars_left == __n)
	    {
	      _M_buf_ptr += __n;
	      _S_setcache_for_incr(*this);
	    }
	  else
	    _M_buf_ptr = 0;
	}
    }

template <class _CharT, class _Alloc>
    void
    _Rope_iterator_base<_CharT, _Alloc>::
    _M_decr(size_t __n)
    {
      if (0 != _M_buf_ptr)
	{
	  size_t __chars_left = _M_buf_ptr - _M_buf_start;
	  if (__chars_left >= __n)
	    _M_buf_ptr -= __n;
	  else
	    _M_buf_ptr = 0;
	}
      _M_current_pos -= __n;
    }

template <class _CharT, class _Alloc>
    void
    _Rope_iterator<_CharT, _Alloc>::
    _M_check()
    {
      if (_M_root_rope->_M_tree_ptr != this->_M_root)
	{
	  // _Rope was modified.  Get things fixed up.
	  _RopeRep::_S_unref(this->_M_root);
	  this->_M_root = _M_root_rope->_M_tree_ptr;
	  _RopeRep::_S_ref(this->_M_root);
	  this->_M_buf_ptr = 0;
	}
    }

template <class _CharT, class _Alloc>
    inline
    _Rope_const_iterator<_CharT, _Alloc>::
    _Rope_const_iterator(const _Rope_iterator<_CharT, _Alloc>& __x)
    : _Rope_iterator_base<_CharT, _Alloc>(__x)
    { }

template <class _CharT, class _Alloc>
    inline
    _Rope_iterator<_CharT, _Alloc>::
    _Rope_iterator(rope<_CharT, _Alloc>& __r, size_t __pos)
    : _Rope_iterator_base<_CharT,_Alloc>(__r._M_tree_ptr, __pos),
      _M_root_rope(&__r)
    { _RopeRep::_S_ref(this->_M_root); }

template <class _CharT, class _Alloc>
    inline size_t
    rope<_CharT, _Alloc>::
    _S_char_ptr_len(const _CharT* __s)
    {
      const _CharT* __p = __s;
      
      while (!_S_is0(*__p))
	++__p;
      return (__p - __s);
    }

#ifndef __GC

template <class _CharT, class _Alloc>
    inline void
    _Rope_RopeRep<_CharT, _Alloc>::
    _M_free_c_string()
    {
      _CharT* __cstr = _M_c_string;
      if (0 != __cstr)
	{
	  size_t __size = this->_M_size + 1;
	  _Destroy(__cstr, __cstr + __size, _M_get_allocator());
	  this->_Data_deallocate(__cstr, __size);
	}
    }

template <class _CharT, class _Alloc>
    inline void
    _Rope_RopeRep<_CharT, _Alloc>::
    _S_free_string(_CharT* __s, size_t __n, allocator_type& __a)
    {
      if (!_S_is_basic_char_type((_CharT*)0))
	_Destroy(__s, __s + __n, __a);
      
      //  This has to be a static member, so this gets a bit messy
      __a.deallocate(__s,
		     _Rope_RopeLeaf<_CharT, _Alloc>::_S_rounded_up_size(__n));
    }

//  There are several reasons for not doing this with virtual destructors
  //  and a class specific delete operator:
  //  - A class specific delete operator can't easily get access to
  //    allocator instances if we need them.
  //  - Any virtual function would need a 4 or byte vtable pointer;
  //    this only requires a one byte tag per object.
  template <class _CharT, class _Alloc>
    void
    _Rope_RopeRep<_CharT, _Alloc>::
    _M_free_tree()
    {
      switch(_M_tag)
	{
	case __detail::_S_leaf:
	  {
	    _Rope_RopeLeaf<_CharT, _Alloc>* __l
	      = (_Rope_RopeLeaf<_CharT, _Alloc>*)this;
	    __l->_Rope_RopeLeaf<_CharT, _Alloc>::~_Rope_RopeLeaf();
	    this->_L_deallocate(__l, 1);
	    break;
	  }
	case __detail::_S_concat:
	  {
	    _Rope_RopeConcatenation<_CharT,_Alloc>* __c
	      = (_Rope_RopeConcatenation<_CharT, _Alloc>*)this;
	    __c->_Rope_RopeConcatenation<_CharT, _Alloc>::
	      ~_Rope_RopeConcatenation();
	    this->_C_deallocate(__c, 1);
	    break;
	  }
	case __detail::_S_function:
	  {
	    _Rope_RopeFunction<_CharT, _Alloc>* __f
	      = (_Rope_RopeFunction<_CharT, _Alloc>*)this;
	    __f->_Rope_RopeFunction<_CharT, _Alloc>::~_Rope_RopeFunction();
	    this->_F_deallocate(__f, 1);
	    break;
	  }
	case __detail::_S_substringfn:
	  {
	    _Rope_RopeSubstring<_CharT, _Alloc>* __ss =
	      (_Rope_RopeSubstring<_CharT, _Alloc>*)this;
	    __ss->_Rope_RopeSubstring<_CharT, _Alloc>::
	      ~_Rope_RopeSubstring();
	    this->_S_deallocate(__ss, 1);
	    break;
	  }
	}
    }
#else

template <class _CharT, class _Alloc>
    inline void
    _Rope_RopeRep<_CharT, _Alloc>::
    _S_free_string(const _CharT*, size_t, allocator_type)
    { }

#endif

// Concatenate a C string onto a leaf rope by copying the rope data.
  // Used for short ropes.
  template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeLeaf*
    rope<_CharT, _Alloc>::
    _S_leaf_concat_char_iter(_RopeLeaf* __r, const _CharT* __iter, size_t __len)
    {
      size_t __old_len = __r->_M_size;
      _CharT* __new_data = (_CharT*)
	rope::_Data_allocate(_S_rounded_up_size(__old_len + __len));
      _RopeLeaf* __result;

uninitialized_copy_n(__r->_M_data, __old_len, __new_data);
      uninitialized_copy_n(__iter, __len, __new_data + __old_len);
      _S_cond_store_eos(__new_data[__old_len + __len]);
      __try
	{
	  __result = _S_new_RopeLeaf(__new_data, __old_len + __len,
				     __r->_M_get_allocator());
	}
      __catch(...)
	{
	  _RopeRep::__STL_FREE_STRING(__new_data, __old_len + __len,
				      __r->_M_get_allocator());
	  __throw_exception_again;
	}
      return __result;
    }

#ifndef __GC
  // As above, but it's OK to clobber original if refcount is 1
  template <class _CharT, class _Alloc>
    typename rope<_CharT,_Alloc>::_RopeLeaf*
    rope<_CharT, _Alloc>::
    _S_destr_leaf_concat_char_iter(_RopeLeaf* __r, const _CharT* __iter,
				   size_t __len)
    {
      if (__r->_M_ref_count > 1)
	return _S_leaf_concat_char_iter(__r, __iter, __len);
      size_t __old_len = __r->_M_size;
      if (_S_allocated_capacity(__old_len) >= __old_len + __len)
	{
	  // The space has been partially initialized for the standard
	  // character types.  But that doesn't matter for those types.
	  uninitialized_copy_n(__iter, __len, __r->_M_data + __old_len);
	  if (_S_is_basic_char_type((_CharT*)0))
	    _S_cond_store_eos(__r->_M_data[__old_len + __len]);
	  else if (__r->_M_c_string != __r->_M_data && 0 != __r->_M_c_string)
	    {
	      __r->_M_free_c_string();
	      __r->_M_c_string = 0;
	    }
	  __r->_M_size = __old_len + __len;
	  __r->_M_ref_count = 2;
	  return __r;
	}
      else
	{
	  _RopeLeaf* __result = _S_leaf_concat_char_iter(__r, __iter, __len);
	  return __result;
	}
    }
#endif

// Assumes left and right are not 0.
  // Does not increment (nor decrement on exception) child reference counts.
  // Result has ref count 1.
  template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeRep*
    rope<_CharT, _Alloc>::
    _S_tree_concat(_RopeRep* __left, _RopeRep* __right)
    {
      _RopeConcatenation* __result = _S_new_RopeConcatenation(__left, __right,
							      __left->
							      _M_get_allocator());
      size_t __depth = __result->_M_depth;
      
      if (__depth > 20
	  && (__result->_M_size < 1000
	      || __depth > size_t(__detail::_S_max_rope_depth)))
	{
	  _RopeRep* __balanced;

__try
	    {
	      __balanced = _S_balance(__result);
	      __result->_M_unref_nonnil();
	    }
	  __catch(...)
	    {
	      rope::_C_deallocate(__result,1);
	      __throw_exception_again;
	    }
	  // In case of exception, we need to deallocate
	  // otherwise dangling result node.  But caller
	  // still owns its children.  Thus unref is
	  // inappropriate.
	  return __balanced;
	}
      else
	return __result;
    }

template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeRep*
    rope<_CharT, _Alloc>::
    _S_concat_char_iter(_RopeRep* __r, const _CharT*__s, size_t __slen)
    {
      _RopeRep* __result;
      if (0 == __slen)
	{
	  _S_ref(__r);
	  return __r;
	}
      if (0 == __r)
	return __STL_ROPE_FROM_UNOWNED_CHAR_PTR(__s, __slen,
						__r->_M_get_allocator());
      if (__r->_M_tag == __detail::_S_leaf
	  && __r->_M_size + __slen <= size_t(_S_copy_max))
	{
	  __result = _S_leaf_concat_char_iter((_RopeLeaf*)__r, __s, __slen);
	  return __result;
	}
      if (__detail::_S_concat == __r->_M_tag
	  && __detail::_S_leaf == ((_RopeConcatenation*) __r)->_M_right->_M_tag)
	{
	  _RopeLeaf* __right =
	    (_RopeLeaf* )(((_RopeConcatenation* )__r)->_M_right);
	  if (__right->_M_size + __slen <= size_t(_S_copy_max))
	    {
	      _RopeRep* __left = ((_RopeConcatenation*)__r)->_M_left;
	      _RopeRep* __nright =
		_S_leaf_concat_char_iter((_RopeLeaf*)__right, __s, __slen);
	      __left->_M_ref_nonnil();
	      __try
		{ __result = _S_tree_concat(__left, __nright); }
	      __catch(...)
		{
		  _S_unref(__left);
		  _S_unref(__nright);
		  __throw_exception_again;
		}
	      return __result;
	    }
	}
      _RopeRep* __nright =
	__STL_ROPE_FROM_UNOWNED_CHAR_PTR(__s, __slen, __r->_M_get_allocator());
      __try
	{
	  __r->_M_ref_nonnil();
	  __result = _S_tree_concat(__r, __nright);
	}
      __catch(...)
	{
	  _S_unref(__r);
	  _S_unref(__nright);
	  __throw_exception_again;
	}
      return __result;
    }

#ifndef __GC
  template <class _CharT, class _Alloc>
    typename rope<_CharT,_Alloc>::_RopeRep*
    rope<_CharT,_Alloc>::
    _S_destr_concat_char_iter(_RopeRep* __r, const _CharT* __s, size_t __slen)
    {
      _RopeRep* __result;
      if (0 == __r)
	return __STL_ROPE_FROM_UNOWNED_CHAR_PTR(__s, __slen,
						__r->_M_get_allocator());
      size_t __count = __r->_M_ref_count;
      size_t __orig_size = __r->_M_size;
      if (__count > 1)
	return _S_concat_char_iter(__r, __s, __slen);
      if (0 == __slen)
	{
	  __r->_M_ref_count = 2;      // One more than before
	  return __r;
	}
      if (__orig_size + __slen <= size_t(_S_copy_max)
	  && __detail::_S_leaf == __r->_M_tag)
	{
	  __result = _S_destr_leaf_concat_char_iter((_RopeLeaf*)__r, __s, 
						    __slen);
	  return __result;
	}
      if (__detail::_S_concat == __r->_M_tag)
	{
	  _RopeLeaf* __right = (_RopeLeaf*)(((_RopeConcatenation*)
					     __r)->_M_right);
	  if (__detail::_S_leaf == __right->_M_tag
	      && __right->_M_size + __slen <= size_t(_S_copy_max))
	    {
	      _RopeRep* __new_right =
		_S_destr_leaf_concat_char_iter(__right, __s, __slen);
	      if (__right == __new_right)
		__new_right->_M_ref_count = 1;
	      else
		__right->_M_unref_nonnil();
	      __r->_M_ref_count = 2;    // One more than before.
	      ((_RopeConcatenation*)__r)->_M_right = __new_right;
	      __r->_M_size = __orig_size + __slen;
	      if (0 != __r->_M_c_string)
		{
		  __r->_M_free_c_string();
		  __r->_M_c_string = 0;
		}
	      return __r;
	    }
	}
      _RopeRep* __right =
	__STL_ROPE_FROM_UNOWNED_CHAR_PTR(__s, __slen, __r->_M_get_allocator());
      __r->_M_ref_nonnil();
      __try
	{ __result = _S_tree_concat(__r, __right); }
      __catch(...)
	{
	  _S_unref(__r);
	  _S_unref(__right);
	  __throw_exception_again;
	}
      return __result;
    }
#endif /* !__GC */
  
  template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeRep*
    rope<_CharT, _Alloc>::
    _S_concat(_RopeRep* __left, _RopeRep* __right)
    {
      if (0 == __left)
	{
	  _S_ref(__right);
	  return __right;
	}
      if (0 == __right)
	{
	  __left->_M_ref_nonnil();
	  return __left;
	}
      if (__detail::_S_leaf == __right->_M_tag)
	{
	  if (__detail::_S_leaf == __left->_M_tag)
	    {
	      if (__right->_M_size + __left->_M_size <= size_t(_S_copy_max))
		return _S_leaf_concat_char_iter((_RopeLeaf*)__left,
						((_RopeLeaf*)__right)->_M_data,
						__right->_M_size);
	    }
	  else if (__detail::_S_concat == __left->_M_tag
		   && __detail::_S_leaf == ((_RopeConcatenation*)
						   __left)->_M_right->_M_tag)
	    {
	      _RopeLeaf* __leftright =
		(_RopeLeaf*)(((_RopeConcatenation*)__left)->_M_right);
	      if (__leftright->_M_size
		  + __right->_M_size <= size_t(_S_copy_max))
		{
		  _RopeRep* __leftleft = ((_RopeConcatenation*)__left)->_M_left;
		  _RopeRep* __rest = _S_leaf_concat_char_iter(__leftright,
							      ((_RopeLeaf*)
							       __right)->
							      _M_data,
							      __right->_M_size);
		  __leftleft->_M_ref_nonnil();
		  __try
		    { return(_S_tree_concat(__leftleft, __rest)); }
		  __catch(...)
		    {
		      _S_unref(__leftleft);
		      _S_unref(__rest);
		      __throw_exception_again;
		    }
		}
	    }
	}
      __left->_M_ref_nonnil();
      __right->_M_ref_nonnil();
      __try
	{ return(_S_tree_concat(__left, __right)); }
      __catch(...)
	{
	  _S_unref(__left);
	  _S_unref(__right);
	  __throw_exception_again;
	}
    }

template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeRep*
    rope<_CharT, _Alloc>::
    _S_substring(_RopeRep* __base, size_t __start, size_t __endp1)
    {
      if (0 == __base)
	return 0;
      size_t __len = __base->_M_size;
      size_t __adj_endp1;
      const size_t __lazy_threshold = 128;
      
      if (__endp1 >= __len)
	{
	  if (0 == __start)
	    {
	      __base->_M_ref_nonnil();
	      return __base;
	    }
	  else
	    __adj_endp1 = __len;
	  
	}
      else
	__adj_endp1 = __endp1;

switch(__base->_M_tag)
	{
	case __detail::_S_concat:
	    {
	      _RopeConcatenation* __c = (_RopeConcatenation*)__base;
	      _RopeRep* __left = __c->_M_left;
	      _RopeRep* __right = __c->_M_right;
	      size_t __left_len = __left->_M_size;
	      _RopeRep* __result;
	      
	      if (__adj_endp1 <= __left_len)
		return _S_substring(__left, __start, __endp1);
	      else if (__start >= __left_len)
		return _S_substring(__right, __start - __left_len,
				    __adj_endp1 - __left_len);
	      _Self_destruct_ptr __left_result(_S_substring(__left,
							    __start,
							    __left_len));
	      _Self_destruct_ptr __right_result(_S_substring(__right, 0,
							     __endp1 
							     - __left_len));
	      __result = _S_concat(__left_result, __right_result);
	      return __result;
	    }
	case __detail::_S_leaf:
	  {
	    _RopeLeaf* __l = (_RopeLeaf*)__base;
	    _RopeLeaf* __result;
	    size_t __result_len;
	    if (__start >= __adj_endp1)
	      return 0;
	    __result_len = __adj_endp1 - __start;
	    if (__result_len > __lazy_threshold)
	      goto lazy;
#ifdef __GC
	    const _CharT* __section = __l->_M_data + __start;
	    __result = _S_new_RopeLeaf(__section, __result_len,
				       __base->_M_get_allocator());
	    __result->_M_c_string = 0;  // Not eos terminated.
#else
	    // We should sometimes create substring node instead.
	    __result = __STL_ROPE_FROM_UNOWNED_CHAR_PTR(__l->_M_data + __start,
							__result_len,
							__base->
							_M_get_allocator());
#endif
	    return __result;
	  }
	case __detail::_S_substringfn:
	  // Avoid introducing multiple layers of substring nodes.
	  {
	    _RopeSubstring* __old = (_RopeSubstring*)__base;
	    size_t __result_len;
	    if (__start >= __adj_endp1)
	      return 0;
	    __result_len = __adj_endp1 - __start;
	    if (__result_len > __lazy_threshold)
	      {
		_RopeSubstring* __result =
		  _S_new_RopeSubstring(__old->_M_base,
				       __start + __old->_M_start,
				       __adj_endp1 - __start,
				       __base->_M_get_allocator());
		return __result;
		
	      } // *** else fall through: ***
	  }
	case __detail::_S_function:
	  {
	    _RopeFunction* __f = (_RopeFunction*)__base;
	    _CharT* __section;
	    size_t __result_len;
	    if (__start >= __adj_endp1)
	      return 0;
	    __result_len = __adj_endp1 - __start;
	    
	    if (__result_len > __lazy_threshold)
	      goto lazy;
	    __section = (_CharT*)
	      rope::_Data_allocate(_S_rounded_up_size(__result_len));
	    __try
	      {	(*(__f->_M_fn))(__start, __result_len, __section); }
	    __catch(...)
	      {
		_RopeRep::__STL_FREE_STRING(__section, __result_len,
					    __base->_M_get_allocator());
		__throw_exception_again;
	      }
	    _S_cond_store_eos(__section[__result_len]);
	    return _S_new_RopeLeaf(__section, __result_len,
				   __base->_M_get_allocator());
	  }
	}
    lazy:
      {
	// Create substring node.
	return _S_new_RopeSubstring(__base, __start, __adj_endp1 - __start,
				    __base->_M_get_allocator());
      }
    }

template<class _CharT>
    class _Rope_flatten_char_consumer
    : public _Rope_char_consumer<_CharT>
    {
    private:
      _CharT* _M_buf_ptr;
    public:
      
      _Rope_flatten_char_consumer(_CharT* __buffer)
      { _M_buf_ptr = __buffer; }

~_Rope_flatten_char_consumer() {}
      
      bool
      operator()(const _CharT* __leaf, size_t __n)
      {
	uninitialized_copy_n(__leaf, __n, _M_buf_ptr);
	_M_buf_ptr += __n;
	return true;
      }
    };

template<class _CharT>
    class _Rope_find_char_char_consumer
    : public _Rope_char_consumer<_CharT>
    {
    private:
      _CharT _M_pattern;
    public:
      size_t _M_count;  // Number of nonmatching characters
      
      _Rope_find_char_char_consumer(_CharT __p)
      : _M_pattern(__p), _M_count(0) {}
	
      ~_Rope_find_char_char_consumer() {}
      
      bool
      operator()(const _CharT* __leaf, size_t __n)
      {
	size_t __i;
	for (__i = 0; __i < __n; __i++)
	  {
	    if (__leaf[__i] == _M_pattern)
	      {
		_M_count += __i;
		return false;
	      }
	  }
	_M_count += __n; return true;
      }
    };

template<class _CharT, class _Traits>
  // Here _CharT is both the stream and rope character type.
    class _Rope_insert_char_consumer
    : public _Rope_char_consumer<_CharT>
    {
    private:
      typedef basic_ostream<_CharT,_Traits> _Insert_ostream;
      _Insert_ostream& _M_o;
    public:
      _Rope_insert_char_consumer(_Insert_ostream& __writer)
	: _M_o(__writer) {}
      ~_Rope_insert_char_consumer() { }
      // Caller is presumed to own the ostream
      bool operator() (const _CharT* __leaf, size_t __n);
      // Returns true to continue traversal.
    };

template<class _CharT, class _Traits>
    bool
    _Rope_insert_char_consumer<_CharT, _Traits>::
    operator()(const _CharT* __leaf, size_t __n)
    {
      size_t __i;
      //  We assume that formatting is set up correctly for each element.
      for (__i = 0; __i < __n; __i++)
	_M_o.put(__leaf[__i]);
      return true;
    }

template <class _CharT, class _Alloc>
    bool
    rope<_CharT, _Alloc>::
    _S_apply_to_pieces(_Rope_char_consumer<_CharT>& __c,
		       const _RopeRep* __r, size_t __begin, size_t __end)
    {
      if (0 == __r)
	return true;
      switch(__r->_M_tag)
	{
	case __detail::_S_concat:
	  {
	    _RopeConcatenation* __conc = (_RopeConcatenation*)__r;
	    _RopeRep* __left =  __conc->_M_left;
	    size_t __left_len = __left->_M_size;
	    if (__begin < __left_len)
	      {
		size_t __left_end = std::min(__left_len, __end);
		if (!_S_apply_to_pieces(__c, __left, __begin, __left_end))
		  return false;
	      }
	    if (__end > __left_len)
	      {
		_RopeRep* __right =  __conc->_M_right;
		size_t __right_start = std::max(__left_len, __begin);
		if (!_S_apply_to_pieces(__c, __right,
					__right_start - __left_len,
					__end - __left_len))
		  return false;
	      }
	  }
	  return true;
	case __detail::_S_leaf:
	  {
	    _RopeLeaf* __l = (_RopeLeaf*)__r;
	    return __c(__l->_M_data + __begin, __end - __begin);
	  }
	case __detail::_S_function:
	case __detail::_S_substringfn:
	    {
	      _RopeFunction* __f = (_RopeFunction*)__r;
	      size_t __len = __end - __begin;
	      bool __result;
	      _CharT* __buffer =
		(_CharT*)_Alloc().allocate(__len * sizeof(_CharT));
	      __try
		{
		  (*(__f->_M_fn))(__begin, __len, __buffer);
		  __result = __c(__buffer, __len);
                  _Alloc().deallocate(__buffer, __len * sizeof(_CharT));
                }
	      __catch(...)
		{
		  _Alloc().deallocate(__buffer, __len * sizeof(_CharT));
		  __throw_exception_again;
		}
	      return __result;
	    }
	default:
	  return false;
	}
    }

template<class _CharT, class _Traits>
    inline void
    _Rope_fill(basic_ostream<_CharT, _Traits>& __o, size_t __n)
    {
      char __f = __o.fill();
      size_t __i;
      
      for (__i = 0; __i < __n; __i++)
	__o.put(__f);
    }

template <class _CharT>
    inline bool
    _Rope_is_simple(_CharT*)
    { return false; }

inline bool
  _Rope_is_simple(char*)
  { return true; }

inline bool
  _Rope_is_simple(wchar_t*)
  { return true; }

template<class _CharT, class _Traits, class _Alloc>
    basic_ostream<_CharT, _Traits>&
    operator<<(basic_ostream<_CharT, _Traits>& __o,
	       const rope<_CharT, _Alloc>& __r)
    {
      size_t __w = __o.width();
      bool __left = bool(__o.flags() & std::ios::left);
      size_t __pad_len;
      size_t __rope_len = __r.size();
      _Rope_insert_char_consumer<_CharT, _Traits> __c(__o);
      bool __is_simple = _Rope_is_simple((_CharT*)0);
      
      if (__rope_len < __w)
	__pad_len = __w - __rope_len;
      else
	__pad_len = 0;

if (!__is_simple)
	__o.width(__w / __rope_len);
      __try
	{
	  if (__is_simple && !__left && __pad_len > 0)
	    _Rope_fill(__o, __pad_len);
	  __r.apply_to_pieces(0, __r.size(), __c);
	  if (__is_simple && __left && __pad_len > 0)
	    _Rope_fill(__o, __pad_len);
	  if (!__is_simple)
	    __o.width(__w);
	}
      __catch(...)
	{
	  if (!__is_simple)
	    __o.width(__w);
	  __throw_exception_again;
	}
      return __o;
    }

template <class _CharT, class _Alloc>
    _CharT*
    rope<_CharT, _Alloc>::
    _S_flatten(_RopeRep* __r, size_t __start, size_t __len,
	       _CharT* __buffer)
    {
      _Rope_flatten_char_consumer<_CharT> __c(__buffer);
      _S_apply_to_pieces(__c, __r, __start, __start + __len);
      return(__buffer + __len);
    }

template <class _CharT, class _Alloc>
    size_t
    rope<_CharT, _Alloc>::
    find(_CharT __pattern, size_t __start) const
    {
      _Rope_find_char_char_consumer<_CharT> __c(__pattern);
      _S_apply_to_pieces(__c, this->_M_tree_ptr, __start, size());
      size_type __result_pos = __start + __c._M_count;
#ifndef __STL_OLD_ROPE_SEMANTICS
      if (__result_pos == size())
	__result_pos = npos;
#endif
      return __result_pos;
    }

template <class _CharT, class _Alloc>
    _CharT*
    rope<_CharT, _Alloc>::
    _S_flatten(_RopeRep* __r, _CharT* __buffer)
    {
      if (0 == __r)
	return __buffer;
      switch(__r->_M_tag)
	{
	case __detail::_S_concat:
	  {
	    _RopeConcatenation* __c = (_RopeConcatenation*)__r;
	    _RopeRep* __left = __c->_M_left;
	    _RopeRep* __right = __c->_M_right;
	    _CharT* __rest = _S_flatten(__left, __buffer);
	    return _S_flatten(__right, __rest);
	  }
	case __detail::_S_leaf:
	  {
	    _RopeLeaf* __l = (_RopeLeaf*)__r;
	    return copy_n(__l->_M_data, __l->_M_size, __buffer).second;
	  }
	case __detail::_S_function:
	case __detail::_S_substringfn:
	  // We don't yet do anything with substring nodes.
	  // This needs to be fixed before ropefiles will work well.
	  {
	    _RopeFunction* __f = (_RopeFunction*)__r;
	    (*(__f->_M_fn))(0, __f->_M_size, __buffer);
	    return __buffer + __f->_M_size;
	  }
	default:
	  return 0;
	}
    }

// This needs work for _CharT != char
  template <class _CharT, class _Alloc>
    void
    rope<_CharT, _Alloc>::
    _S_dump(_RopeRep* __r, int __indent)
    {
      for (int __i = 0; __i < __indent; __i++)
	putchar(' ');
      if (0 == __r)
	{
	  printf("NULL\n");
	  return;
	}
      if (__detail::_S_concat == __r->_M_tag)
	{
	  _RopeConcatenation* __c = (_RopeConcatenation*)__r;
	  _RopeRep* __left = __c->_M_left;
	  _RopeRep* __right = __c->_M_right;
	  
#ifdef __GC
	  printf("Concatenation %p (depth = %d, len = %ld, %s balanced)\n",
		 __r, __r->_M_depth, __r->_M_size,
		 __r->_M_is_balanced? "" : "not");
#else
	  printf("Concatenation %p (rc = %ld, depth = %d, "
		 "len = %ld, %s balanced)\n",
		 __r, __r->_M_ref_count, __r->_M_depth, __r->_M_size,
		 __r->_M_is_balanced? "" : "not");
#endif
	  _S_dump(__left, __indent + 2);
	  _S_dump(__right, __indent + 2);
	  return;
	}
      else
	{
	  const char* __kind;
	  
	  switch (__r->_M_tag)
	    {
	    case __detail::_S_leaf:
	      __kind = "Leaf";
	      break;
	    case __detail::_S_function:
	      __kind = "Function";
	      break;
	    case __detail::_S_substringfn:
	      __kind = "Function representing substring";
	      break;
	    default:
	      __kind = "(corrupted kind field!)";
	    }
#ifdef __GC
	  printf("%s %p (depth = %d, len = %ld) ",
		 __kind, __r, __r->_M_depth, __r->_M_size);
#else
	  printf("%s %p (rc = %ld, depth = %d, len = %ld) ",
		 __kind, __r, __r->_M_ref_count, __r->_M_depth, __r->_M_size);
#endif
	  if (_S_is_one_byte_char_type((_CharT*)0))
	    {
	      const int __max_len = 40;
	      _Self_destruct_ptr __prefix(_S_substring(__r, 0, __max_len));
	      _CharT __buffer[__max_len + 1];
	      bool __too_big = __r->_M_size > __prefix->_M_size;
	      
	      _S_flatten(__prefix, __buffer);
	      __buffer[__prefix->_M_size] = _S_eos((_CharT*)0);
	      printf("%s%s\n", (char*)__buffer,
		     __too_big? "...\n" : "\n");
	    }
	  else
	    printf("\n");
	}
    }

template <class _CharT, class _Alloc>
    const unsigned long
    rope<_CharT, _Alloc>::
    _S_min_len[int(__detail::_S_max_rope_depth) + 1] = {
      /* 0 */1, /* 1 */2, /* 2 */3, /* 3 */5, /* 4 */8, /* 5 */13, /* 6 */21,
      /* 7 */34, /* 8 */55, /* 9 */89, /* 10 */144, /* 11 */233, /* 12 */377,
      /* 13 */610, /* 14 */987, /* 15 */1597, /* 16 */2584, /* 17 */4181,
      /* 18 */6765, /* 19 */10946, /* 20 */17711, /* 21 */28657, /* 22 */46368,
      /* 23 */75025, /* 24 */121393, /* 25 */196418, /* 26 */317811,
      /* 27 */514229, /* 28 */832040, /* 29 */1346269, /* 30 */2178309,
      /* 31 */3524578, /* 32 */5702887, /* 33 */9227465, /* 34 */14930352,
      /* 35 */24157817, /* 36 */39088169, /* 37 */63245986, /* 38 */102334155,
      /* 39 */165580141, /* 40 */267914296, /* 41 */433494437,
      /* 42 */701408733, /* 43 */1134903170, /* 44 */1836311903,
      /* 45 */2971215073u };
  // These are Fibonacci numbers < 2**32.

template <class _CharT, class _Alloc>
    typename rope<_CharT, _Alloc>::_RopeRep*
    rope<_CharT, _Alloc>::
    _S_balance(_RopeRep* __r)
    {
      _RopeRep* __forest[int(__detail::_S_max_rope_depth) + 1];
      _RopeRep* __result = 0;
      int __i;
      // Invariant:
      // The concatenation of forest in descending order is equal to __r.
      // __forest[__i]._M_size >= _S_min_len[__i]
      // __forest[__i]._M_depth = __i
      // References from forest are included in refcount.
      
      for (__i = 0; __i <= int(__detail::_S_max_rope_depth); ++__i)
	__forest[__i] = 0;
      __try
	{
	  _S_add_to_forest(__r, __forest);
	  for (__i = 0; __i <= int(__detail::_S_max_rope_depth); ++__i)
	    if (0 != __forest[__i])
	      {
#ifndef __GC
		_Self_destruct_ptr __old(__result);
#endif
		__result = _S_concat(__forest[__i], __result);
		__forest[__i]->_M_unref_nonnil();
#if !defined(__GC) && __cpp_exceptions
		__forest[__i] = 0;
#endif
	      }
	}
      __catch(...)
	{
	  for(__i = 0; __i <= int(__detail::_S_max_rope_depth); __i++)
	    _S_unref(__forest[__i]);
	  __throw_exception_again;
	}
      
      if (__result->_M_depth > int(__detail::_S_max_rope_depth))
	__throw_length_error(__N("rope::_S_balance"));
      return(__result);
    }

template <class _CharT, class _Alloc>
    void
    rope<_CharT, _Alloc>::
    _S_add_to_forest(_RopeRep* __r, _RopeRep** __forest)
    {
      if (__r->_M_is_balanced)
	{
	  _S_add_leaf_to_forest(__r, __forest);
	  return;
	}

{
	_RopeConcatenation* __c = (_RopeConcatenation*)__r;
	
	_S_add_to_forest(__c->_M_left, __forest);
	_S_add_to_forest(__c->_M_right, __forest);
      }
    }

template <class _CharT, class _Alloc>
    void
    rope<_CharT, _Alloc>::
    _S_add_leaf_to_forest(_RopeRep* __r, _RopeRep** __forest)
    {
      _RopeRep* __insertee;		// included in refcount
      _RopeRep* __too_tiny = 0;		// included in refcount
      int __i;				// forest[0..__i-1] is empty
      size_t __s = __r->_M_size;
      
      for (__i = 0; __s >= _S_min_len[__i+1]/* not this bucket */; ++__i)
	{
	  if (0 != __forest[__i])
	    {
#ifndef __GC
	      _Self_destruct_ptr __old(__too_tiny);
#endif
	      __too_tiny = _S_concat_and_set_balanced(__forest[__i],
						      __too_tiny);
	      __forest[__i]->_M_unref_nonnil();
	      __forest[__i] = 0;
	    }
	}
      {
#ifndef __GC
	_Self_destruct_ptr __old(__too_tiny);
#endif
	__insertee = _S_concat_and_set_balanced(__too_tiny, __r);
      }
      // Too_tiny dead, and no longer included in refcount.
      // Insertee is live and included.
      for (;; ++__i)
	{
	  if (0 != __forest[__i])
	    {
#ifndef __GC
	      _Self_destruct_ptr __old(__insertee);
#endif
	      __insertee = _S_concat_and_set_balanced(__forest[__i],
						      __insertee);
	      __forest[__i]->_M_unref_nonnil();
	      __forest[__i] = 0;
	    }
	  if (__i == int(__detail::_S_max_rope_depth)
	      || __insertee->_M_size < _S_min_len[__i+1])
	    {
	      __forest[__i] = __insertee;
	      // refcount is OK since __insertee is now dead.
	      return;
	    }
	}
    }

template <class _CharT, class _Alloc>
    _CharT
    rope<_CharT, _Alloc>::
    _S_fetch(_RopeRep* __r, size_type __i)
    {
      __GC_CONST _CharT* __cstr = __r->_M_c_string;
      
      if (0 != __cstr)
	return __cstr[__i];
      for(;;)
	{
	  switch(__r->_M_tag)
	    {
	    case __detail::_S_concat:
	      {
		_RopeConcatenation* __c = (_RopeConcatenation*)__r;
		_RopeRep* __left = __c->_M_left;
		size_t __left_len = __left->_M_size;
		
		if (__i >= __left_len)
		  {
		    __i -= __left_len;
		    __r = __c->_M_right;
		  } 
		else
		  __r = __left;
	      }
	      break;
	    case __detail::_S_leaf:
	      {
		_RopeLeaf* __l = (_RopeLeaf*)__r;
		return __l->_M_data[__i];
	      }
	    case __detail::_S_function:
	    case __detail::_S_substringfn:
	      {
		_RopeFunction* __f = (_RopeFunction*)__r;
		_CharT __result;
		
		(*(__f->_M_fn))(__i, 1, &__result);
		return __result;
	      }
	    }
	}
    }
  
#ifndef __GC
  // Return a uniquely referenced character slot for the given
  // position, or 0 if that's not possible.
  template <class _CharT, class _Alloc>
    _CharT*
    rope<_CharT, _Alloc>::
    _S_fetch_ptr(_RopeRep* __r, size_type __i)
    {
      _RopeRep* __clrstack[__detail::_S_max_rope_depth];
      size_t __csptr = 0;
      
      for(;;)
	{
	  if (__r->_M_ref_count > 1)
	    return 0;
	  switch(__r->_M_tag)
	    {
	    case __detail::_S_concat:
	      {
		_RopeConcatenation* __c = (_RopeConcatenation*)__r;
		_RopeRep* __left = __c->_M_left;
		size_t __left_len = __left->_M_size;
		
		if (__c->_M_c_string != 0)
		  __clrstack[__csptr++] = __c;
		if (__i >= __left_len)
		  {
		    __i -= __left_len;
		    __r = __c->_M_right;
		  } 
		else
		  __r = __left;
	      }
	      break;
	    case __detail::_S_leaf:
	      {
		_RopeLeaf* __l = (_RopeLeaf*)__r;
		if (__l->_M_c_string != __l->_M_data && __l->_M_c_string != 0)
		  __clrstack[__csptr++] = __l;
		while (__csptr > 0)
		  {
		    -- __csptr;
		    _RopeRep* __d = __clrstack[__csptr];
		    __d->_M_free_c_string();
		    __d->_M_c_string = 0;
		  }
		return __l->_M_data + __i;
	      }
	    case __detail::_S_function:
	    case __detail::_S_substringfn:
	      return 0;
	    }
	}
    }
#endif /* __GC */

// The following could be implemented trivially using
  // lexicographical_compare_3way.
  // We do a little more work to avoid dealing with rope iterators for
  // flat strings.
  template <class _CharT, class _Alloc>
    int
    rope<_CharT, _Alloc>::
    _S_compare (const _RopeRep* __left, const _RopeRep* __right)
    {
      size_t __left_len;
      size_t __right_len;
      
      if (0 == __right)
	return 0 != __left;
      if (0 == __left)
	return -1;
      __left_len = __left->_M_size;
      __right_len = __right->_M_size;
      if (__detail::_S_leaf == __left->_M_tag)
	{
	  _RopeLeaf* __l = (_RopeLeaf*) __left;
	  if (__detail::_S_leaf == __right->_M_tag)
	    {
	      _RopeLeaf* __r = (_RopeLeaf*) __right;
	      return lexicographical_compare_3way(__l->_M_data,
						  __l->_M_data + __left_len,
						  __r->_M_data, __r->_M_data
						  + __right_len);
	    }
	  else
	    {
	      const_iterator __rstart(__right, 0);
	      const_iterator __rend(__right, __right_len);
	      return lexicographical_compare_3way(__l->_M_data, __l->_M_data
						  + __left_len,
						  __rstart, __rend);
	    }
	}
      else
	{
	  const_iterator __lstart(__left, 0);
	  const_iterator __lend(__left, __left_len);
	  if (__detail::_S_leaf == __right->_M_tag)
	    {
	      _RopeLeaf* __r = (_RopeLeaf*) __right;
	      return lexicographical_compare_3way(__lstart, __lend,
						  __r->_M_data, __r->_M_data
						  + __right_len);
	    }
	  else
	    {
	      const_iterator __rstart(__right, 0);
	      const_iterator __rend(__right, __right_len);
	      return lexicographical_compare_3way(__lstart, __lend,
						  __rstart, __rend);
	    }
	}
    }

// Assignment to reference proxies.
  template <class _CharT, class _Alloc>
    _Rope_char_ref_proxy<_CharT, _Alloc>&
    _Rope_char_ref_proxy<_CharT, _Alloc>::
    operator=(_CharT __c)
    {
      _RopeRep* __old = _M_root->_M_tree_ptr;
#ifndef __GC
      // First check for the case in which everything is uniquely
      // referenced.  In that case we can do this destructively.
      _CharT* __ptr = _My_rope::_S_fetch_ptr(__old, _M_pos);
      if (0 != __ptr)
	{
	  *__ptr = __c;
	  return *this;
	}
#endif
      _Self_destruct_ptr __left(_My_rope::_S_substring(__old, 0, _M_pos));
      _Self_destruct_ptr __right(_My_rope::_S_substring(__old, _M_pos + 1,
							__old->_M_size));
      _Self_destruct_ptr __result_left(_My_rope::
				       _S_destr_concat_char_iter(__left,
								 &__c, 1));

_RopeRep* __result = _My_rope::_S_concat(__result_left, __right);
#ifndef __GC
      _RopeRep::_S_unref(__old);
#endif
      _M_root->_M_tree_ptr = __result;
      return *this;
    }

template <class _CharT, class _Alloc>
    inline _Rope_char_ref_proxy<_CharT, _Alloc>::
    operator _CharT() const
    {
      if (_M_current_valid)
	return _M_current;
      else
	return _My_rope::_S_fetch(_M_root->_M_tree_ptr, _M_pos);
    }

template <class _CharT, class _Alloc>
    _Rope_char_ptr_proxy<_CharT, _Alloc>
    _Rope_char_ref_proxy<_CharT, _Alloc>::
    operator&() const
    { return _Rope_char_ptr_proxy<_CharT, _Alloc>(*this); }

template <class _CharT, class _Alloc>
    rope<_CharT, _Alloc>::
    rope(size_t __n, _CharT __c, const allocator_type& __a)
    : _Base(__a)
    {
      rope<_CharT,_Alloc> __result;
      const size_t __exponentiate_threshold = 32;
      size_t __exponent;
      size_t __rest;
      _CharT* __rest_buffer;
      _RopeRep* __remainder;
      rope<_CharT, _Alloc> __remainder_rope;

if (0 == __n)
	return;

__exponent = __n / __exponentiate_threshold;
      __rest = __n % __exponentiate_threshold;
      if (0 == __rest)
	__remainder = 0;
      else
	{
	  __rest_buffer = this->_Data_allocate(_S_rounded_up_size(__rest));
	  __uninitialized_fill_n_a(__rest_buffer, __rest, __c,
				   _M_get_allocator());
	  _S_cond_store_eos(__rest_buffer[__rest]);
	  __try
	    { __remainder = _S_new_RopeLeaf(__rest_buffer, __rest,
					    _M_get_allocator()); }
	  __catch(...)
	    {
	      _RopeRep::__STL_FREE_STRING(__rest_buffer, __rest,
					  _M_get_allocator());
	      __throw_exception_again;
	    }
	}
      __remainder_rope._M_tree_ptr = __remainder;
      if (__exponent != 0)
	{
	  _CharT* __base_buffer =
	    this->_Data_allocate(_S_rounded_up_size(__exponentiate_threshold));
	  _RopeLeaf* __base_leaf;
	  rope __base_rope;
	  __uninitialized_fill_n_a(__base_buffer, __exponentiate_threshold, __c,
				   _M_get_allocator());
	  _S_cond_store_eos(__base_buffer[__exponentiate_threshold]);
	  __try
	    {
	      __base_leaf = _S_new_RopeLeaf(__base_buffer,
					    __exponentiate_threshold,
					    _M_get_allocator());
	    }
	  __catch(...)
	    {
	      _RopeRep::__STL_FREE_STRING(__base_buffer,
					  __exponentiate_threshold,
					  _M_get_allocator());
	      __throw_exception_again;
	    }
	  __base_rope._M_tree_ptr = __base_leaf;
	  if (1 == __exponent)
	    __result = __base_rope;
	  else
	    __result = power(__base_rope, __exponent,
			     _Rope_Concat_fn<_CharT, _Alloc>());
	    
	  if (0 != __remainder)
	    __result += __remainder_rope;
	}
      else
	__result = __remainder_rope;
	  
      this->_M_tree_ptr = __result._M_tree_ptr;
      this->_M_tree_ptr->_M_ref_nonnil();
    }
      
  template<class _CharT, class _Alloc>
    _CharT
    rope<_CharT, _Alloc>::_S_empty_c_str[1];
      
  template<class _CharT, class _Alloc>
    const _CharT*
    rope<_CharT, _Alloc>::
    c_str() const
    {
      if (0 == this->_M_tree_ptr)
	{
	  _S_empty_c_str[0] = _S_eos((_CharT*)0);  // Possibly redundant,
	                                           // but probably fast.
	  return _S_empty_c_str;
	}
      __gthread_mutex_lock (&this->_M_tree_ptr->_M_c_string_lock);
      __GC_CONST _CharT* __result = this->_M_tree_ptr->_M_c_string;
      if (0 == __result)
	{
	  size_t __s = size();
	  __result = this->_Data_allocate(__s + 1);
	  _S_flatten(this->_M_tree_ptr, __result);
	  __result[__s] = _S_eos((_CharT*)0);
	  this->_M_tree_ptr->_M_c_string = __result;
	}
      __gthread_mutex_unlock (&this->_M_tree_ptr->_M_c_string_lock);
      return(__result);
    }
  
  template<class _CharT, class _Alloc>
    const _CharT* rope<_CharT, _Alloc>::
    replace_with_c_str()
    {
      if (0 == this->_M_tree_ptr)
	{
	  _S_empty_c_str[0] = _S_eos((_CharT*)0);
	  return _S_empty_c_str;
	}
      __GC_CONST _CharT* __old_c_string = this->_M_tree_ptr->_M_c_string;
      if (__detail::_S_leaf == this->_M_tree_ptr->_M_tag
	  && 0 != __old_c_string)
	return(__old_c_string);
      size_t __s = size();
      _CharT* __result = this->_Data_allocate(_S_rounded_up_size(__s));
      _S_flatten(this->_M_tree_ptr, __result);
      __result[__s] = _S_eos((_CharT*)0);
      this->_M_tree_ptr->_M_unref_nonnil();
      this->_M_tree_ptr = _S_new_RopeLeaf(__result, __s,
					  this->_M_get_allocator());
      return(__result);
    }

// Algorithm specializations.  More should be added.
  
  template<class _Rope_iterator>  // was templated on CharT and Alloc
    void		          // VC++ workaround
    _Rope_rotate(_Rope_iterator __first,
		 _Rope_iterator __middle,
		 _Rope_iterator __last)
    {
      typedef typename _Rope_iterator::value_type _CharT;
      typedef typename _Rope_iterator::_allocator_type _Alloc;
      
      rope<_CharT, _Alloc>& __r(__first.container());
      rope<_CharT, _Alloc> __prefix = __r.substr(0, __first.index());
      rope<_CharT, _Alloc> __suffix =
	__r.substr(__last.index(), __r.size() - __last.index());
      rope<_CharT, _Alloc> __part1 =
	__r.substr(__middle.index(), __last.index() - __middle.index());
      rope<_CharT, _Alloc> __part2 =
	__r.substr(__first.index(), __middle.index() - __first.index());
      __r = __prefix;
      __r += __part1;
      __r += __part2;
      __r += __suffix;
    }

#if !defined(__GNUC__)
  // Appears to confuse g++
  inline void
  rotate(_Rope_iterator<char, __STL_DEFAULT_ALLOCATOR(char)> __first,
	 _Rope_iterator<char, __STL_DEFAULT_ALLOCATOR(char)> __middle,
	 _Rope_iterator<char, __STL_DEFAULT_ALLOCATOR(char)> __last)
  { _Rope_rotate(__first, __middle, __last); }
#endif

# if 0
  // Probably not useful for several reasons:
  // - for SGIs 7.1 compiler and probably some others,
  //   this forces lots of rope<wchar_t, ...> instantiations, creating a
  //   code bloat and compile time problem.  (Fixed in 7.2.)
  // - wchar_t is 4 bytes wide on most UNIX platforms, making it
  //   unattractive for unicode strings.  Unsigned short may be a better
  //   character type.
  inline void
  rotate(_Rope_iterator<wchar_t, __STL_DEFAULT_ALLOCATOR(char)> __first,
	 _Rope_iterator<wchar_t, __STL_DEFAULT_ALLOCATOR(char)> __middle,
	 _Rope_iterator<wchar_t, __STL_DEFAULT_ALLOCATOR(char)> __last)
  { _Rope_rotate(__first, __middle, __last); }
# endif

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace

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