2002-11-21 Phil Edwards <pme@gcc.gnu.org>

[official-gcc.git] / libstdc++-v3 / include / ext / ropeimpl.h

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

// Copyright (C) 2001, 2002 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 2, 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.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/*
 * 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.
 *  You should not attempt to use it directly.
 */

#include <cstdio>     
#include <iostream>
#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
{
using std::size_t;
using std::printf;
using std::basic_ostream;  
using std::__throw_length_error;
using std::__alloc;
using std::_Destroy;
using std::uninitialized_fill_n;

// 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 _RopeRep::_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 _RopeRep::_S_function:
        case _RopeRep::_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[_RopeRep::_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 _RopeRep::_S_leaf:
          case _RopeRep::_S_function:
          case _RopeRep::_S_substringfn:
            __x._M_leaf_pos = __curr_start_pos;
            goto done;
          case _RopeRep::_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 - _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 (_RopeRep::_S_concat == __current_node->_M_tag) {
        ++__current_index;
        if (_S_path_cache_len == __current_index) {
            int __i;
            for (__i = 0; __i < _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 != _M_root) {
        // _Rope was modified.  Get things fixed up.
        _RopeRep::_S_unref(_M_root);
        _M_root = _M_root_rope->_M_tree_ptr;
        _RopeRep::_S_ref(_M_root);
        _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(_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 = _M_size + 1;
        _Destroy(__cstr, __cstr + __size);
        _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);
    }
//  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 _S_leaf:
            {
                _Rope_RopeLeaf<_CharT,_Alloc>* __l
                        = (_Rope_RopeLeaf<_CharT,_Alloc>*)this;
                __l->_Rope_RopeLeaf<_CharT,_Alloc>::~_Rope_RopeLeaf();
                _L_deallocate(__l, 1);
                break;
            }
        case _S_concat:
            {
                _Rope_RopeConcatenation<_CharT,_Alloc>* __c
                    = (_Rope_RopeConcatenation<_CharT,_Alloc>*)this;
                __c->_Rope_RopeConcatenation<_CharT,_Alloc>::
                       ~_Rope_RopeConcatenation();
                _C_deallocate(__c, 1);
                break;
            }
        case _S_function:
            {
                _Rope_RopeFunction<_CharT,_Alloc>* __f
                    = (_Rope_RopeFunction<_CharT,_Alloc>*)this;
                __f->_Rope_RopeFunction<_CharT,_Alloc>::~_Rope_RopeFunction();
                _F_deallocate(__f, 1);
                break;
            }
        case _S_substringfn:
            {
                _Rope_RopeSubstring<_CharT,_Alloc>* __ss =
                        (_Rope_RopeSubstring<_CharT,_Alloc>*)this;
                __ss->_Rope_RopeSubstring<_CharT,_Alloc>::
                        ~_Rope_RopeSubstring();
                _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*)
        _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->get_allocator());
    }
    catch(...)
      {
        _RopeRep::__STL_FREE_STRING(__new_data, __old_len + __len,
                                    __r->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->get_allocator());
  size_t __depth = __result->_M_depth;
    
  if (__depth > 20 && (__result->_M_size < 1000 ||
                       __depth > _RopeRep::_S_max_rope_depth)) 
    {
      _RopeRep* __balanced;
      
      try 
        {
          __balanced = _S_balance(__result);
          __result->_M_unref_nonnil();
        }
      catch(...)
        { 
          _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->get_allocator());
    if (_RopeRep::_S_leaf == __r->_M_tag && 
          __r->_M_size + __slen <= _S_copy_max) {
        __result = _S_leaf_concat_char_iter((_RopeLeaf*)__r, __s, __slen);
        return __result;
    }
    if (_RopeRep::_S_concat == __r->_M_tag
        && _RopeRep::_S_leaf == ((_RopeConcatenation*)__r)->_M_right->_M_tag) {
        _RopeLeaf* __right = 
          (_RopeLeaf* )(((_RopeConcatenation* )__r)->_M_right);
        if (__right->_M_size + __slen <= _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->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->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 <= _S_copy_max && 
          _RopeRep::_S_leaf == __r->_M_tag) {
        __result = _S_destr_leaf_concat_char_iter((_RopeLeaf*)__r, __s, __slen);
        return __result;
    }
    if (_RopeRep::_S_concat == __r->_M_tag) {
        _RopeLeaf* __right = (_RopeLeaf*)(((_RopeConcatenation*)__r)->_M_right);
        if (_RopeRep::_S_leaf == __right->_M_tag
            && __right->_M_size + __slen <= _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->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 (_RopeRep::_S_leaf == __right->_M_tag) {
        if (_RopeRep::_S_leaf == __left->_M_tag) {
          if (__right->_M_size + __left->_M_size <= _S_copy_max) {
            return _S_leaf_concat_char_iter((_RopeLeaf*)__left,
                                         ((_RopeLeaf*)__right)->_M_data,
                                         __right->_M_size);
          }
        } else if (_RopeRep::_S_concat == __left->_M_tag
                   && _RopeRep::_S_leaf ==
                      ((_RopeConcatenation*)__left)->_M_right->_M_tag) {
          _RopeLeaf* __leftright =
                    (_RopeLeaf*)(((_RopeConcatenation*)__left)->_M_right); 
          if (__leftright->_M_size + __right->_M_size <= _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 _RopeRep::_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 _RopeRep::_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->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->get_allocator());
#               endif
                return __result;
            }
        case _RopeRep::_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->get_allocator());
                    return __result;

                } // *** else fall through: ***
            }
        case _RopeRep::_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*)
                        _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->get_allocator());
                    __throw_exception_again;
                  }
                _S_cond_store_eos(__section[__result_len]);
                return _S_new_RopeLeaf(__section, __result_len,
                                       __base->get_allocator());
            }
    }
  lazy:
    {
        // Create substring node.
        return _S_new_RopeSubstring(__base, __start, __adj_endp1 - __start,
                               __base->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 _RopeRep::_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 _RopeRep::_S_leaf:
            {
                _RopeLeaf* __l = (_RopeLeaf*)__r;
                return __c(__l->_M_data + __begin, __end - __begin);
            }
        case _RopeRep::_S_function:
        case _RopeRep::_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, _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 _RopeRep::_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 _RopeRep::_S_leaf:
            {
                _RopeLeaf* __l = (_RopeLeaf*)__r;
                return copy_n(__l->_M_data, __l->_M_size, __buffer).second;
            }
        case _RopeRep::_S_function:
        case _RopeRep::_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 (_RopeRep::_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 {
        char* __kind;

        switch (__r->_M_tag) {
            case _RopeRep::_S_leaf:
                __kind = "Leaf";
                break;
            case _RopeRep::_S_function:
                __kind = "Function";
                break;
            case _RopeRep::_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[
  _Rope_RopeRep<_CharT,_Alloc>::_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[_RopeRep::_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 <= _RopeRep::_S_max_rope_depth; ++__i) 
      __forest[__i] = 0;
    try {
      _S_add_to_forest(__r, __forest);
      for (__i = 0; __i <= _RopeRep::_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) && defined(__EXCEPTIONS)
          __forest[__i] = 0;
#       endif
      }
    }
    catch(...)
      {
        for(__i = 0; __i <= _RopeRep::_S_max_rope_depth; __i++)
          _S_unref(__forest[__i]);
        __throw_exception_again;
      }

    if (__result->_M_depth > _RopeRep::_S_max_rope_depth)
      __throw_length_error("rope too long");
    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 == _RopeRep::_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 _RopeRep::_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 _RopeRep::_S_leaf:
            {
                _RopeLeaf* __l = (_RopeLeaf*)__r;
                return __l->_M_data[__i];
            }
        case _RopeRep::_S_function:
        case _RopeRep::_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[_RopeRep::_S_max_rope_depth];
    size_t __csptr = 0;

    for(;;) {
      if (__r->_M_ref_count > 1) return 0;
      switch(__r->_M_tag) {
        case _RopeRep::_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 _RopeRep::_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 _RopeRep::_S_function:
        case _RopeRep::_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 (_RopeRep::_S_leaf == __left->_M_tag) {
        _RopeLeaf* __l = (_RopeLeaf*) __left;
        if (_RopeRep::_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 (_RopeRep::_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 = _Data_allocate(_S_rounded_up_size(__rest));
        uninitialized_fill_n(__rest_buffer, __rest, __c);
        _S_cond_store_eos(__rest_buffer[__rest]);
        try {
            __remainder = _S_new_RopeLeaf(__rest_buffer, __rest, __a);
        }
        catch(...)
          {
            _RopeRep::__STL_FREE_STRING(__rest_buffer, __rest, __a);
            __throw_exception_again;
          }
    }
    __remainder_rope._M_tree_ptr = __remainder;
    if (__exponent != 0) {
        _CharT* __base_buffer =
          _Data_allocate(_S_rounded_up_size(__exponentiate_threshold));
        _RopeLeaf* __base_leaf;
        rope __base_rope;
        uninitialized_fill_n(__base_buffer, __exponentiate_threshold, __c);
        _S_cond_store_eos(__base_buffer[__exponentiate_threshold]);
        try {
          __base_leaf = _S_new_RopeLeaf(__base_buffer,
                                        __exponentiate_threshold, __a);
        }
        catch(...)
          {
            _RopeRep::__STL_FREE_STRING(__base_buffer, 
                                        __exponentiate_threshold, __a);
            __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;
    }
    _M_tree_ptr = __result._M_tree_ptr;
    _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 == _M_tree_ptr) {
        _S_empty_c_str[0] = _S_eos((_CharT*)0);  // Possibly redundant,
                                             // but probably fast.
        return _S_empty_c_str;
    }
    __GC_CONST _CharT* __old_c_string = _M_tree_ptr->_M_c_string;
    if (0 != __old_c_string) return(__old_c_string);
    size_t __s = size();
    _CharT* __result = _Data_allocate(__s + 1);
    _S_flatten(_M_tree_ptr, __result);
    __result[__s] = _S_eos((_CharT*)0);
#   ifdef __GC
        _M_tree_ptr->_M_c_string = __result;
#   else
      if ((__old_c_string = (__GC_CONST _CharT*)
             std::_Atomic_swap((unsigned long *)(&(_M_tree_ptr->_M_c_string)),
                          (unsigned long)__result)) != 0) {
        // It must have been added in the interim.  Hence it had to have been
        // separately allocated.  Deallocate the old copy, since we just
        // replaced it.
        _Destroy(__old_c_string, __old_c_string + __s + 1);
        _Data_deallocate(__old_c_string, __s + 1);
      }
#   endif
    return(__result);
}

template<class _CharT, class _Alloc>
const _CharT* rope<_CharT,_Alloc>::replace_with_c_str() {
    if (0 == _M_tree_ptr) {
        _S_empty_c_str[0] = _S_eos((_CharT*)0);
        return _S_empty_c_str;
    }
    __GC_CONST _CharT* __old_c_string = _M_tree_ptr->_M_c_string;
    if (_RopeRep::_S_leaf == _M_tree_ptr->_M_tag && 0 != __old_c_string) {
        return(__old_c_string);
    }
    size_t __s = size();
    _CharT* __result = _Data_allocate(_S_rounded_up_size(__s));
    _S_flatten(_M_tree_ptr, __result);
    __result[__s] = _S_eos((_CharT*)0);
    _M_tree_ptr->_M_unref_nonnil();
    _M_tree_ptr = _S_new_RopeLeaf(__result, __s, 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

} // namespace __gnu_cxx

// Local Variables:
// mode:C++
// End: