/*
 * 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.
 */

#ifndef _ROPE_H
# define _ROPE_H

# include <iterator.h>
# include <algobase.h>
# include <algo.h>
# include <function.h>
# include <stddef.h>
# include <alloc.h>
# include <hashtable.h>
# ifdef __GC
#   define __GC_CONST const
# else
#   define __GC_CONST   // constant except for deallocation
# endif
# ifdef __STL_SGI_THREADS
#    include <mutex.h>
# endif

// The end-of-C-string character.
// This is what the draft standard says it should be.
template <class charT>
inline charT __eos(charT*) { return charT(); }

// Test for basic character types.
// For basic character types leaves having a trailing eos.
template <class charT>
inline bool __is_basic_char_type(charT* c) { return false; }
template <class charT>
inline bool __is_one_byte_char_type(charT* c) { return false; }

inline bool __is_basic_char_type(char* c) { return true; }
inline bool __is_one_byte_char_type(char* c) { return true; }
inline bool __is_basic_char_type(wchar_t* c) { return true; }

// Store an eos iff charT is a basic character type.
// Do not reference __eos if it isn't.
template <class charT>
inline void __cond_store_eos(charT& c) {}

inline void __cond_store_eos(char& c) { c = 0; }
inline void __cond_store_eos(wchar_t& c) { c = 0; }
	

// rope<charT,Alloc> is a sequence of charT.
// Ropes appear to be mutable, but update operations
// really copy enough of the data structure to leave the original
// valid.  Thus ropes can be logically copied by just copying
// a pointer value.
// The __eos function is used for those functions that
// convert to/from C-like strings to detect the end of the string.
// __compare is used as the character comparison function.
template <class charT>
class char_producer {
    public:
	virtual ~char_producer() {};
	virtual void operator()(size_t start_pos, size_t len, charT* buffer)
		= 0;
	// Buffer should really be an arbitrary output iterator.
	// That way we could flatten directly into an ostream, etc.
	// This is thoroughly impossible, since iterator types don't
	// have runtime descriptions.
};

// Sequence buffers:
//
// Sequence must provide an append operation that appends an
// array to the sequence.  Sequence buffers are useful only if
// appending an entire array is cheaper than appending element by element.
// This is true for many string representations.
// This should  perhaps inherit from ostream<sequence::value_type>
// and be implemented correspondingly, so that they can be used
// for formatted.  For the sake of portability, we don't do this yet.
//
// For now, sequence buffers behave as output iterators.  But they also
// behave a little like basic_ostringstream<sequence::value_type> and a
// little like containers.

template<class sequence, size_t buf_sz = 100
#   if defined(__sgi) && !defined(__GNUC__)
#	 define __TYPEDEF_WORKAROUND
         ,class v = typename sequence::value_type
#   endif
        >
// The 3rd parameter works around a common compiler bug.
class sequence_buffer : public output_iterator {
    public:
#       ifndef __TYPEDEF_WORKAROUND
	    typedef typename sequence::value_type value_type;
#	else
	    typedef v value_type;
#	endif
    protected:
	sequence *prefix;
	value_type buffer[buf_sz];
	size_t buf_count;
    public:
	void flush() {
	    prefix->append(buffer, buffer + buf_count);
	    buf_count = 0;
	}
	~sequence_buffer() { flush(); }
	sequence_buffer() : prefix(0), buf_count(0) {}
	sequence_buffer(const sequence_buffer & x) {
	    prefix = x.prefix;
            buf_count = x.buf_count;
            copy(x.buffer, x.buffer + x.buf_count, buffer);
	}
	sequence_buffer(sequence_buffer & x) {
	    x.flush();
	    prefix = x.prefix;
	    buf_count = 0;
	}
	sequence_buffer(sequence& s) : prefix(&s), buf_count(0) {}
	sequence_buffer& operator= (sequence_buffer& x) {
	    x.flush();
	    prefix = x.prefix;
	    buf_count = 0;
	    return *this;
	}
	sequence_buffer& operator= (const sequence_buffer& x) {
	    prefix = x.prefix;
	    buf_count = x.buf_count;
	    copy(x.buffer, x.buffer + x.buf_count, buffer);
	    return *this;
	}
	void push_back(value_type x)
	{
	    if (buf_count < buf_sz) {
		buffer[buf_count] = x;
		++buf_count;
	    } else {
		flush();
		buffer[0] = x;
		buf_count = 1;
	    }
	}
	void append(value_type *s, size_t len)
	{
	    if (len + buf_count <= buf_sz) {
		size_t i, j;
		for (i = buf_count, j = 0; j < len; i++, j++) {
		    buffer[i] = s[j];
		}
		buf_count += len;
	    } else if (0 == buf_count) {
		prefix->append(s, s + len);
	    } else {
		flush();
		append(s, len);
	    }
	}
	sequence_buffer& write(value_type *s, size_t len)
	{
	    append(s, len);
	    return *this;
	}
	sequence_buffer& put(value_type x)
	{
	    push_back(x);
	    return *this;
	}
	sequence_buffer& operator=(const value_type& rhs)
	{
	    push_back(rhs);
	    return *this;
	}
	sequence_buffer& operator*() { return *this; }
	sequence_buffer& operator++() { return *this; }
	sequence_buffer& operator++(int) { return *this; }
};

// The following should be treated as private, at least for now.
template<class charT>
class __rope_char_consumer {
    public:
	// If we had member templates, these should not be virtual.
	// For now we need to use run-time parametrization where
	// compile-time would do.  Hence this should all be private
	// for now.
	// The symmetry with char_producer is accidental and temporary.
	virtual ~__rope_char_consumer() {};
	virtual bool operator()(const charT* buffer, size_t len) = 0;
};

//
// What follows should really be local to rope.  Unfortunately,
// that doesn't work, since it makes it impossible to define generic
// equality on rope iterators.  According to the draft standard, the
// template parameters for such an equality operator cannot be inferred
// from the occurence of a member class as a parameter.
// (SGI compilers in fact allow this, but the result wouldn't be
// portable.)
// Similarly, some of the static member functions are member functions
// only to avoid polluting the global namespace, and to circumvent
// restrictions on type inference for template functions.
//

template<class CharT, class Alloc=__ALLOC> class rope;
template<class CharT, class Alloc> struct __rope_RopeConcatenation;
template<class CharT, class Alloc> struct __rope_RopeLeaf;
template<class CharT, class Alloc> struct __rope_RopeFunction;
template<class CharT, class Alloc> struct __rope_RopeSubstring;
template<class CharT, class Alloc> class __rope_iterator;
template<class CharT, class Alloc> class __rope_const_iterator;
template<class CharT, class Alloc> class __rope_charT_ref_proxy;
template<class CharT, class Alloc> class __rope_charT_ptr_proxy;

//
// The internal data structure for representing a rope.  This is
// private to the implementation.  A rope is really just a pointer
// to one of these.
//
// A few basic functions for manipulating this data structure
// are members of RopeBase.  Most of the more complex algorithms
// are implemented as rope members.
//
// Some of the static member functions of RopeBase have identically
// named functions in rope that simply invoke the RopeBase versions.
//

template<class charT, class Alloc>
struct __rope_RopeBase {
    typedef rope<charT,Alloc> my_rope;
    typedef simple_alloc<__rope_RopeConcatenation<charT,Alloc>, Alloc> CAlloc;
    typedef simple_alloc<__rope_RopeLeaf<charT,Alloc>, Alloc> LAlloc;
    typedef simple_alloc<__rope_RopeFunction<charT,Alloc>, Alloc> FAlloc;
    typedef simple_alloc<__rope_RopeSubstring<charT,Alloc>, Alloc> SAlloc;
    public:
    enum { max_rope_depth = 45 };
    enum {leaf, concat, substringfn, function} tag:8;
    bool is_balanced:8;
    unsigned char depth;
    size_t size;
    __GC_CONST charT * c_string;
			/* Flattened version of string, if needed.  */
			/* typically 0.                             */
			/* If it's not 0, then the memory is owned  */
			/* by this node.                            */
			/* In the case of a leaf, this may point to */
			/* the same memory as the data field.	    */
#   ifndef __GC
#       if defined(__STL_WIN32THREADS)
	    long refcount;  	// InterlockedIncrement wants a long *
#	else
	    size_t refcount;
#	endif
	// We count references from rope instances
	// and references from other rope nodes.  We
	// do not count const_iterator references.
	// Iterator references are counted so that rope modifications
	// can be detected after the fact.
	// Generally function results are counted, i.e.
	// a pointer returned by a function is included at the
	// point at which the pointer is returned.
	// The recipient should decrement the count if the
	// result is not needed.
	// Generally function arguments are not reflected
	// in the reference count.  The callee should increment
	// the count before saving the argument someplace that
	// will outlive the call.
#   endif
#   ifndef __GC
#       ifdef __STL_SGI_THREADS
	    // Reference counting with multiple threads and no
	    // hardware or thread package support is pretty awful.
	    // Mutexes are normally too expensive.
	    // We'll assume a COMPARE_AND_SWAP(destp, old, new)
	    // operation, which might be cheaper.
#           if __mips < 3 || !(defined (_ABIN32) || defined(_ABI64))
#               define __add_and_fetch(l,v) add_then_test((unsigned long *)l,v)
#           endif
	    void init_refcount_lock() {}
	    void incr_refcount ()
	    {
		__add_and_fetch(&refcount, 1);
	    }
	    size_t decr_refcount ()
	    {
		return __add_and_fetch(&refcount, (size_t)(-1));
	    }
#       elif defined(__STL_WIN32THREADS)
	    void init_refcount_lock() {}
            void incr_refcount ()
            {
                InterlockedIncrement(&refcount);
            }
            size_t decr_refcount ()
            {
                return InterlockedDecrement(&refcount);
            }
#	elif defined(_PTHREADS)
	    // This should be portable, but performance is expected
	    // to be quite awful.  This really needs platform specific
	    // code.
	    pthread_mutex_t refcount_lock;
	    void init_refcount_lock() {
		pthread_mutex_init(&refcount_lock, 0);
	    }
	    void incr_refcount ()
            {   
		pthread_mutex_lock(&refcount_lock);
                ++refcount;
		pthread_mutex_unlock(&refcount_lock);
            }
            size_t decr_refcount ()
            {   
		size_t result;
		pthread_mutex_lock(&refcount_lock);
                result = --refcount;
		pthread_mutex_unlock(&refcount_lock);
                return result;
            }
#	else
	    void init_refcount_lock() {}
	    void incr_refcount ()
	    {
		++refcount;
	    }
	    size_t decr_refcount ()
	    {
		--refcount;
		return refcount;
	    }
#       endif
#   else
	void incr_refcount () {}
#   endif
	static void free_string(charT *, size_t len);
			// Deallocate data section of a leaf.
			// This shouldn't be a member function.
			// But its hard to do anything else at the
			// moment, because it's templatized w.r.t.
			// an allocator.
			// Does nothing if __GC is defined.
#   ifndef __GC
	  void free_c_string();
	  void free_tree();
			// Deallocate t. Assumes t is not 0.
	  void unref_nonnil()
	  {
	      if (0 == decr_refcount()) free_tree();
	  }
	  void ref_nonnil()
	  {
	      incr_refcount();
	  }
	  static void unref(__rope_RopeBase* t)
	  {
	      if (0 != t) {
		  t -> unref_nonnil();
	      }
	  }
	  static void ref(__rope_RopeBase* t)
	  {
	      if (0 != t) t -> incr_refcount();
	  }
#   else /* __GC */
	  void unref_nonnil() {}
	  void ref_nonnil() {}
	  static void unref(__rope_RopeBase* t) {}
	  static void ref(__rope_RopeBase* t) {}
	  static void fn_finalization_proc(void * tree, void *);
#   endif

    // The data fields of leaves are allocated with some
    // extra space, to accomodate future growth and for basic
    // character types, to hold a trailing eos character.
    enum { alloc_granularity = 8 };
    static size_t rounded_up_size(size_t n) {
        size_t size_with_eos;
	     
        if (__is_basic_char_type((charT *)0)) {
    	    size_with_eos = (n + 1) * sizeof(charT);
    	} else {
  	    size_with_eos = n * sizeof(charT);
	}
#       ifdef __GC
   	   return size_with_eos;
#	else
	   // Allow slop for in-place expansion.
	   return (size_with_eos + alloc_granularity-1)
			&~ (alloc_granularity-1);
#	endif
    }
};

template<class charT, class Alloc>
struct __rope_RopeLeaf : public __rope_RopeBase<charT,Alloc> {
  public:  // Apparently needed by VC++
    __GC_CONST charT* data;     /* Not necessarily 0 terminated. */
				/* The allocated size is	 */
				/* rounded_up_size(size), except */
				/* in the GC case, in which it	 */
				/* doesn't matter.		 */
};

template<class charT, class Alloc>
struct __rope_RopeConcatenation : public __rope_RopeBase<charT,Alloc> {
  public:
    __rope_RopeBase<charT,Alloc>* left;
    __rope_RopeBase<charT,Alloc>* right;
};

template<class charT, class Alloc>
struct __rope_RopeFunction : public __rope_RopeBase<charT,Alloc> {
  public:
    char_producer<charT>* fn;
#   ifndef __GC
      bool delete_when_done;	// Char_producer is owned by the
				// rope and should be explicitly
				// deleted when the rope becomes
				// inaccessible.
#   else
      // In the GC case, we either register the rope for
      // finalization, or not.  Thus the field is unnecessary;
      // the information is stored in the collector data structures.
#   endif
};
// Substring results are usually represented using just
// concatenation nodes.  But in the case of very long flat ropes
// or ropes with a functional representation that isn't practical.
// In that case, we represent the result as a special case of
// RopeFunction, whose char_producer points back to the rope itself.
// In all cases except repeated substring operations and
// deallocation, we treat the result as a RopeFunction.
template<class charT, class Alloc>
struct __rope_RopeSubstring: public __rope_RopeFunction<charT,Alloc>,
			     public char_producer<charT> {
  public:
    __rope_RopeBase<charT,Alloc> * base;	// not 0
    size_t start;
    virtual ~__rope_RopeSubstring() {}
    virtual void operator()(size_t start_pos, size_t req_len,
			    charT *buffer) {
	switch(base -> tag) {
	    case function:
	    case substringfn:
	      {
		char_producer<charT> *fn =
			((__rope_RopeFunction<charT,Alloc> *)base) -> fn;
		__stl_assert(start_pos + req_len <= size);
		__stl_assert(start + size <= base -> size);
		(*fn)(start_pos + start, req_len, buffer);
	      }
	      break;
	    case leaf:
	      {
		__GC_CONST charT * s =
			((__rope_RopeLeaf<charT,Alloc> *)base) -> data;
		uninitialized_copy_n(s + start_pos + start, req_len,
				     buffer);
	      }
	      break;
	    default:
	      __stl_assert(false);
	}
    }
    __rope_RopeSubstring(__rope_RopeBase<charT,Alloc> * b, size_t s, size_t l) :
	base(b), start(s) {
#       ifndef __GC
	    refcount = 1;
	    init_refcount_lock();
	    base -> ref_nonnil();
#       endif
	size = l;
	tag = substringfn;
	depth = 0;
	c_string = 0;
	fn = this;
    }
};


// Self-destructing pointers to RopeBase.
// These are not conventional smart pointers.  Their
// only purpose in life is to ensure that unref is called
// on the pointer either at normal exit or if an exception
// is raised.  It is the caller's responsibility to
// adjust reference counts when these pointers are initialized
// or assigned to.  (This convention significantly reduces
// the number of potentially expensive reference count
// updates.)
#ifndef __GC
  template<class charT, class Alloc>
  struct __rope_self_destruct_ptr {
    __rope_RopeBase<charT,Alloc> * ptr;
    ~__rope_self_destruct_ptr() { __rope_RopeBase<charT,Alloc>::unref(ptr); }
#   ifdef __STL_USE_EXCEPTIONS
	__rope_self_destruct_ptr() : ptr(0) {};
#   else
	__rope_self_destruct_ptr() {};
#   endif
    __rope_self_destruct_ptr(__rope_RopeBase<charT,Alloc> * p) : ptr(p) {}
    __rope_RopeBase<charT,Alloc> & operator*() { return *ptr; }
    __rope_RopeBase<charT,Alloc> * operator->() { return ptr; }
    operator __rope_RopeBase<charT,Alloc> *() { return ptr; }
    __rope_self_destruct_ptr & operator= (__rope_RopeBase<charT,Alloc> * x)
	{ ptr = x; return *this; }
  };
#endif

// unwind-protect
#	ifdef __STL_USE_EXCEPTIONS
#	    define __STL_TRY try {
#	    define __STL_UNWIND(action) } catch(...) { action; throw; }
#           define __STL_ALWAYS(action) action; } catch(...) { action; throw; }
#       else
#	    define __STL_TRY {
#	    define __STL_UNWIND(action) }
#           define __STL_ALWAYS(action) action; }
#	endif
// Dereferencing a nonconst iterator has to return something
// that behaves almost like a reference.  It's not possible to
// return an actual reference since assignment requires extra
// work.  And we would get into the same problems as with the
// CD2 version of basic_string.
template<class charT, class Alloc>
class __rope_charT_ref_proxy {
    friend class rope<charT,Alloc>;
    friend class __rope_iterator<charT,Alloc>;
    friend class __rope_charT_ptr_proxy<charT,Alloc>;
#   ifdef __GC
	typedef __rope_RopeBase<charT,Alloc> * self_destruct_ptr;
#   else
    	typedef __rope_self_destruct_ptr<charT,Alloc> self_destruct_ptr;
#   endif
    typedef __rope_RopeBase<charT,Alloc> RopeBase;
    typedef rope<charT,Alloc> my_rope;
    size_t pos;
    charT current;
    bool current_valid;
    my_rope * root;     // The whole rope.
  public:
    __rope_charT_ref_proxy(my_rope * r, size_t p) :
	pos(p), root(r), current_valid(false) {}
    __rope_charT_ref_proxy(my_rope * r, size_t p,
		    charT c) :
	pos(p), root(r), current(c), current_valid(true) {}
    operator charT () const;
    __rope_charT_ref_proxy& operator= (charT c);
    __rope_charT_ptr_proxy<charT,Alloc> operator& () const;
    __rope_charT_ref_proxy& operator= (const __rope_charT_ref_proxy& c) {
	return operator=((charT)c); 
    }
};

template<class charT, class Alloc>
class __rope_charT_ptr_proxy {
    friend class __rope_charT_ref_proxy<charT,Alloc>;
    size_t pos;
    charT current;
    bool current_valid;
    rope<charT,Alloc> * root;     // The whole rope.
  public:
    __rope_charT_ptr_proxy(const __rope_charT_ref_proxy<charT,Alloc> & x) :
	pos(x.pos), root(x.root), current_valid(x.current_valid),
	current(x.current) {}
    __rope_charT_ptr_proxy(const __rope_charT_ptr_proxy & x) :
	pos(x.pos), root(x.root), current_valid(x.current_valid),
	current(x.current) {}
    __rope_charT_ptr_proxy() {}
    __rope_charT_ptr_proxy(charT * x) : root(0), pos(0) {
	__stl_assert(0 == x);
    }
    __rope_charT_ptr_proxy& operator= (const __rope_charT_ptr_proxy& x) {
	pos = x.pos;
	current = x.current;
	current_valid = x.current_valid;
	root = x.root;
	return *this;
    }
    friend bool operator==
                (const __rope_charT_ptr_proxy<charT,Alloc> & x,
                 const __rope_charT_ptr_proxy<charT,Alloc> & y);
    __rope_charT_ref_proxy<charT,Alloc> operator *() const {
	if (current_valid) {
	    return __rope_charT_ref_proxy<charT,Alloc>(root, pos, current);
	} else {
	    return __rope_charT_ref_proxy<charT,Alloc>(root, pos);
	}
    }
};

// Rope iterators:
// Unlike in the C version, we cache only part of the stack
// for rope iterators, since they must be efficiently copyable.
// When we run out of cache, we have to reconstruct the iterator
// value.
// Pointers from iterators are not included in reference counts.
// Iterators are assumed to be thread private.  Ropes can
// be shared.

template<class charT, class Alloc>
class __rope_iterator_base:
  public random_access_iterator<charT, ptrdiff_t> {
  friend class rope<charT, Alloc>;
  public:
    typedef __rope_RopeBase<charT,Alloc> RopeBase;
	// Borland doesnt want this to be protected.
  protected:
    enum { path_cache_len = 4 }; // Must be <= 9.
    enum { iterator_buf_len = 15 };
    size_t current_pos;
    RopeBase * root;     // The whole rope.
    size_t leaf_pos;    // Starting position for current leaf
    __GC_CONST charT * buf_start;
			// Buffer possibly
			// containing current char.
    __GC_CONST charT * buf_ptr;
			// Pointer to current char in buffer.
			// != 0 ==> buffer valid.
    __GC_CONST charT * buf_end;
			// One past last valid char in buffer.
    // What follows is the path cache.  We go out of our
    // way to make this compact.
    // Path_end contains the bottom section of the path from
    // the root to the current leaf.
    const RopeBase * path_end[path_cache_len];
    int leaf_index;     // Last valid pos in path_end;
    			// path_end[0] ... path_end[leaf_index-1]
			// point to concatenation nodes.
    unsigned char path_directions;
			  // (path_directions >> i) & 1 is 1
			  // iff we got from path_end[leaf_index - i - 1]
			  // to path_end[leaf_index - i] by going to the
			  // right. Assumes path_cache_len <= 9.
    charT tmp_buf[iterator_buf_len];
			// Short buffer for surrounding chars.
			// This is useful primarily for 
			// RopeFunctions.  We put the buffer
			// here to avoid locking in the
			// multithreaded case.
    // The cached path is generally assumed to be valid
    // only if the buffer is valid.
    static void setbuf(__rope_iterator_base &x);
					// Set buffer contents given
					// path cache.
    static void setcache(__rope_iterator_base &x);
					// Set buffer contents and
					// path cache.
    static void setcache_for_incr(__rope_iterator_base &x);
					// As above, but assumes path
					// cache is valid for previous posn.
    __rope_iterator_base() {}
    __rope_iterator_base(RopeBase * root, size_t pos):
		   root(root), current_pos(pos), buf_ptr(0) {}
    __rope_iterator_base(const __rope_iterator_base& x) {
	if (0 != x.buf_ptr) {
	    *this = x;
	} else {
	    current_pos = x.current_pos;
	    root = x.root;
	    buf_ptr = 0;
	}
    }
    void incr(size_t n);
    void decr(size_t n);
  public:
    size_t index() const { return current_pos; }
};

template<class charT, class Alloc> class __rope_iterator;

template<class charT, class Alloc>
class __rope_const_iterator : public __rope_iterator_base<charT,Alloc> {
    friend class rope<charT,Alloc>;
  protected:
    __rope_const_iterator(const RopeBase * root, size_t pos):
		   __rope_iterator_base<charT,Alloc>(
		     const_cast<RopeBase *>(root), pos)
		   // Only nonconst iterators modify root ref count
    {}

  public:
    __rope_const_iterator() {};
    __rope_const_iterator(const __rope_const_iterator & x) :
				__rope_iterator_base<charT,Alloc>(x) { }
    __rope_const_iterator(const __rope_iterator<charT,Alloc> & x);
    __rope_const_iterator(const rope<charT,Alloc> &r, size_t pos) :
	__rope_iterator_base<charT,Alloc>(r.tree_ptr, pos) {}
    __rope_const_iterator& operator= (const __rope_const_iterator & x) {
	if (0 != x.buf_ptr) {
	    *this = x;
	} else {
	    current_pos = x.current_pos;
	    root = x.root;
	    buf_ptr = 0;
	}
	return(*this);
    }
    const charT& operator*() {
	if (0 == buf_ptr) setcache(*this);
	return *buf_ptr;
    }
    __rope_const_iterator& operator++() {
	__GC_CONST charT * next;
	if (0 != buf_ptr && (next = buf_ptr + 1) < buf_end) {
	    buf_ptr = next;
	    ++current_pos;
	} else {
	    incr(1);
	}
	return *this;
    }
    __rope_const_iterator& operator+=(ptrdiff_t n) {
	if (n >= 0) {
	    incr(n);
	} else {
	    decr(-n);
	}
	return *this;
    }
    __rope_const_iterator& operator--() {
	decr(1);
	return *this;
    }
    __rope_const_iterator& operator-=(ptrdiff_t n) {
	if (n >= 0) {
	    decr(n);
	} else {
	    incr(-n);
	}
	return *this;
    }
    __rope_const_iterator operator++(int) {
	size_t old_pos = current_pos;
	incr(1);
	return __rope_const_iterator<charT,Alloc>(root, old_pos);
	// This makes a subsequent dereference expensive.
	// Perhaps we should instead copy the iterator
	// if it has a valid cache?
    }
    __rope_const_iterator operator--(int) {
	size_t old_pos = current_pos;
	decr(1);
	return __rope_const_iterator<charT,Alloc>(root, old_pos);
    }
    friend __rope_const_iterator<charT,Alloc> operator-
	(const __rope_const_iterator<charT,Alloc> & x,
	 ptrdiff_t n);
    friend __rope_const_iterator<charT,Alloc> operator+
	(const __rope_const_iterator<charT,Alloc> & x,
	 ptrdiff_t n);
    friend __rope_const_iterator<charT,Alloc> operator+
	(ptrdiff_t n,
	 const __rope_const_iterator<charT,Alloc> & x);
    charT operator[](size_t n) {
	return rope<charT,Alloc>::fetch(root, current_pos + n);
    }
    friend bool operator==
	(const __rope_const_iterator<charT,Alloc> & x,
	 const __rope_const_iterator<charT,Alloc> & y);
    friend bool operator<
	(const __rope_const_iterator<charT,Alloc> & x,
	 const __rope_const_iterator<charT,Alloc> & y);
    friend ptrdiff_t operator-
	(const __rope_const_iterator<charT,Alloc> & x,
	 const __rope_const_iterator<charT,Alloc> & y);
};

template<class charT, class Alloc>
class __rope_iterator : public __rope_iterator_base<charT,Alloc> {
    friend class rope<charT,Alloc>;
  protected:
    rope<charT,Alloc> * root_rope;
	// root is treated as a cached version of this,
	// and is used to detect changes to the underlying
	// rope.
	// Root is included in the reference count.
	// This is necessary so that we can detect changes reliably.
	// Unfortunately, it requires careful bookkeeping for the
	// nonGC case.
    __rope_iterator(rope<charT,Alloc> * r, size_t pos):
	     __rope_iterator_base<charT,Alloc>(r -> tree_ptr, pos),
	     root_rope(r) {
		RopeBase::ref(root);
	     }
    void check();
  public:
    rope<charT,Alloc>& container() { return *root_rope; }
    __rope_iterator() {
	root = 0;  // Needed for reference counting.
    };
    __rope_iterator(const __rope_iterator & x) :
	__rope_iterator_base<charT,Alloc>(x) {
	root_rope = x.root_rope;
	RopeBase::ref(root);
    }
    __rope_iterator(rope<charT,Alloc>& r, size_t pos);
    ~__rope_iterator() {
	RopeBase::unref(root);
    }
    __rope_iterator& operator= (const __rope_iterator & x) {
	RopeBase *old = root;

	RopeBase::ref(x.root);
	if (0 != x.buf_ptr) {
	    *this = x;
	} else {
	    current_pos = x.current_pos;
	    root = x.root;
	    root_rope = x.root_rope;
	    buf_ptr = 0;
	}
	RopeBase::unref(old);
	return(*this);
    }
    __rope_charT_ref_proxy<charT,Alloc> operator*() {
	check();
	if (0 == buf_ptr) {
	    return __rope_charT_ref_proxy<charT,Alloc>(root_rope, current_pos);
	} else {
	    return __rope_charT_ref_proxy<charT,Alloc>(root_rope,
						       current_pos, *buf_ptr);
	}
    }
    __rope_iterator& operator++() {
	incr(1);
	return *this;
    }
    __rope_iterator& operator+=(difference_type n) {
	if (n >= 0) {
	    incr(n);
	} else {
	    decr(-n);
	}
	return *this;
    }
    __rope_iterator& operator--() {
	decr(1);
	return *this;
    }
    __rope_iterator& operator-=(difference_type n) {
	if (n >= 0) {
	    decr(n);
	} else {
	    incr(-n);
	}
	return *this;
    }
    __rope_iterator operator++(int) {
	size_t old_pos = current_pos;
	incr(1);
	return __rope_iterator<charT,Alloc>(root_rope, old_pos);
    }
    __rope_iterator operator--(int) {
	size_t old_pos = current_pos;
	decr(1);
	return __rope_iterator<charT,Alloc>(root_rope, old_pos);
    }
    __rope_charT_ref_proxy<charT,Alloc> operator[](ptrdiff_t n) {
	return __rope_charT_ref_proxy<charT,Alloc>(root_rope, current_pos + n);
    }
    friend bool operator==
	(const __rope_iterator<charT,Alloc> & x,
	 const __rope_iterator<charT,Alloc> & y);
    friend bool operator<
	(const __rope_iterator<charT,Alloc> & x,
	 const __rope_iterator<charT,Alloc> & y);
    friend ptrdiff_t operator-
	(const __rope_iterator<charT,Alloc> & x,
	 const __rope_iterator<charT,Alloc> & y);
    friend __rope_iterator<charT,Alloc> operator-
	(const __rope_iterator<charT,Alloc> & x,
	 ptrdiff_t n);
    friend __rope_iterator<charT,Alloc> operator+
	(const __rope_iterator<charT,Alloc> & x,
	 ptrdiff_t n);
    friend __rope_iterator<charT,Alloc> operator+
	(ptrdiff_t n,
	 const __rope_iterator<charT,Alloc> & x);

};

template <class charT, class Alloc>
class rope {
    public:
	typedef charT value_type;
	typedef ptrdiff_t difference_type;
	typedef size_t size_type;
	typedef const charT& const_reference;
	typedef const charT* const_pointer;
	typedef __rope_iterator<charT,Alloc> iterator;
	typedef __rope_const_iterator<charT,Alloc> const_iterator;
	typedef __rope_charT_ref_proxy<charT,Alloc> reference;
	typedef __rope_charT_ptr_proxy<charT,Alloc> pointer;

	friend class __rope_iterator<charT,Alloc>;
	friend class __rope_const_iterator<charT,Alloc>;
	friend struct __rope_RopeBase<charT,Alloc>;
	friend class __rope_iterator_base<charT,Alloc>;
	friend class __rope_charT_ptr_proxy<charT,Alloc>;
	friend class __rope_charT_ref_proxy<charT,Alloc>;
	friend struct __rope_RopeSubstring<charT,Alloc>;

    protected:
	typedef __GC_CONST charT * cstrptr;
#       ifdef __STL_SGI_THREADS
	    static cstrptr atomic_swap(cstrptr *p, cstrptr q) {
#               if __mips < 3 || !(defined (_ABIN32) || defined(_ABI64))
                    return (cstrptr) test_and_set((unsigned long *)p,
			   		          (unsigned long)q);
#		else
                    return (cstrptr) __test_and_set((unsigned long *)p,
			   		            (unsigned long)q);
#		endif
            }
#       elif defined(__STL_WIN32THREADS)
	    static cstrptr atomic_swap(cstrptr *p, cstrptr q) {
		return (cstrptr) InterlockedExchange((LPLONG)p, (LONG)q);
	    }
#	elif defined(_PTHREADS)
	    // This should be portable, but performance is expected
	    // to be quite awful.  This really needs platform specific
	    // code.
	    static pthread_mutex_t swap_lock;
	    static cstrptr atomic_swap(cstrptr *p, cstrptr q) {
		pthread_mutex_lock(&swap_lock);
		cstrptr result = *p;
		*p = q;
		pthread_mutex_unlock(&swap_lock);
		return result;
            }
#	else
	    static cstrptr atomic_swap(cstrptr *p, cstrptr q) {
                cstrptr result = *p;
                *p = q;
		return result;
	    }
#       endif

	static charT empty_c_str[1];

    	typedef simple_alloc<__rope_RopeConcatenation<charT,Alloc>, Alloc> CAlloc;
    	typedef simple_alloc<__rope_RopeLeaf<charT,Alloc>, Alloc> LAlloc;
    	typedef simple_alloc<__rope_RopeFunction<charT,Alloc>, Alloc> FAlloc;
    	typedef simple_alloc<__rope_RopeSubstring<charT,Alloc>, Alloc> SAlloc;
	static bool is0(charT c) { return c == __eos((charT *)0); }
	enum { copy_max = 23 };
		// For strings shorter than copy_max, we copy to
		// concatenate.

	typedef __rope_RopeBase<charT,Alloc> RopeBase;
	typedef __rope_RopeConcatenation<charT,Alloc> RopeConcatenation;
	typedef __rope_RopeLeaf<charT,Alloc> RopeLeaf;
	typedef __rope_RopeFunction<charT,Alloc> RopeFunction;
	typedef __rope_RopeSubstring<charT,Alloc> RopeSubstring;

	// The only data member of a rope:
	RopeBase *tree_ptr;

	// Retrieve a character at the indicated position.
	static charT fetch(RopeBase * r, size_type pos);

#	ifndef __GC
	    // Obtain a pointer to the character at the indicated position.
	    // The pointer can be used to change the character.
	    // If such a pointer cannot be produced, as is frequently the
	    // case, 0 is returned instead.
	    // (Returns nonzero only if all nodes in the path have a refcount
	    // of 1.)
	    static charT * fetch_ptr(RopeBase * r, size_type pos);
#	endif

	static bool apply_to_pieces(
				// should be template parameter
				__rope_char_consumer<charT>& c,
				const RopeBase * r,
				size_t begin, size_t end);
				// begin and end are assumed to be in range.

#	ifndef __GC
	  static void unref(RopeBase* t)
	  {
	      RopeBase::unref(t);
	  }
	  static void ref(RopeBase* t)
	  {
	      RopeBase::ref(t);
	  }
#       else /* __GC */
	  static void unref(RopeBase* t) {}
	  static void ref(RopeBase* t) {}
#       endif


#       ifdef __GC
	    typedef __rope_RopeBase<charT,Alloc> * self_destruct_ptr;
#   	else
	    typedef __rope_self_destruct_ptr<charT,Alloc> self_destruct_ptr;
#	endif

	// Result is counted in refcount.
	static RopeBase * substring(RopeBase * base,
				    size_t start, size_t endp1);

	static RopeBase * concat_char_iter(RopeBase * r,
					  const charT *iter, size_t slen);
		// Concatenate rope and char ptr, copying s.
		// Should really take an arbitrary iterator.
		// Result is counted in refcount.
	static RopeBase * destr_concat_char_iter(RopeBase * r,
						 const charT *iter, size_t slen)
		// As above, but one reference to r is about to be
		// destroyed.  Thus the pieces may be recycled if all
		// relevent reference counts are 1.
#	    ifdef __GC
		// We can't really do anything since refcounts are unavailable.
		{ return concat_char_iter(r, iter, slen); }
#	    else
		;
#	    endif

	static RopeBase * concat(RopeBase *left, RopeBase *right);
		// General concatenation on RopeBase.  Result
		// has refcount of 1.  Adjusts argument refcounts.

   public:
	void apply_to_pieces( size_t begin, size_t end,
			      __rope_char_consumer<charT>& c) const {
	    apply_to_pieces(c, tree_ptr, begin, end);
	}


   protected:

	static size_t rounded_up_size(size_t n) {
	    return RopeBase::rounded_up_size(n);
	}

	static size_t allocated_capacity(size_t n) {
	    if (__is_basic_char_type((charT *)0)) {
		return rounded_up_size(n) - 1;
	    } else {
		return rounded_up_size(n);
	    }
	}
		
	// s should really be an arbitrary input iterator.
	// Adds a trailing NULL for basic char types.
	static charT * alloc_copy(const charT *s, size_t size)
	{
	    charT * result = (charT *)
				Alloc::allocate(rounded_up_size(size));

	    uninitialized_copy_n(s, size, result);
	    __cond_store_eos(result[size]);
	    return(result);
	}

	// Basic constructors for rope tree nodes.
	// These return tree nodes with a 0 reference count.
	static RopeLeaf * RopeLeaf_from_char_ptr(__GC_CONST charT *s,
						 size_t size);
		// Takes ownership of its argument.
		// Result has refcount 1.
		// In the nonGC, basic_char_type  case it assumes that s
		// is eos-terminated.
		// In the nonGC case, it was allocated from Alloc with
		// rounded_up_size(size).

	// Concatenation of nonempty strings.
	// Always builds a concatenation node.
	// Rebalances if the result is too deep.
	// Result has refcount 1.
	// Does not increment left and right ref counts even though
	// they are referenced.
	static RopeBase * tree_concat(RopeBase * left, RopeBase * right);

	// Result has refcount 1.
	// If delete_fn is true, then fn is deleted when the rope
	// becomes inaccessible.
	static RopeFunction * RopeFunction_from_fn
			(char_producer<charT> *fn, size_t size,
			 bool delete_fn);

	// Concatenation helper functions
	static RopeLeaf * leaf_concat_char_iter
			(RopeLeaf * r, const charT * iter, size_t slen);
		// Concatenate by copying leaf.
		// should take an arbitrary iterator
		// result has refcount 1.
#	ifndef __GC
	  static RopeLeaf * destr_leaf_concat_char_iter
			(RopeLeaf * r, const charT * iter, size_t slen);
	  // A version that potentially clobbers r if r -> refcount == 1.
#       endif

	// A helper function for exponentiating strings.
	// This uses a nonstandard refcount convention.
	// The result has refcount 0.
	struct concat_fn;
	friend struct rope<charT,Alloc>::concat_fn;

	struct concat_fn
		: binary_function<RopeBase *, RopeBase *, RopeBase *> {
		RopeBase * operator() (RopeBase * x, RopeBase *y) {
		    RopeBase * result;
		    x -> ref_nonnil();
		    y -> ref_nonnil();
		    __STL_TRY
		      result = tree_concat(x, y);
#		      ifndef __GC
			result -> refcount = 0;
#		      endif
		    __STL_UNWIND(unref(x); unref(y));
		    return result;
		    // In the nonGC case, x and y must remain accessible through
		    // the result.  Use of concat could result on a memory leak.
		}
	};

        friend RopeBase* identity_element(concat_fn) { return 0; }

	static size_t char_ptr_len(const charT * s);
			// slightly generalized strlen

	rope(RopeBase *t) : tree_ptr(t) { }


	// Copy r to the CharT buffer.
	// Returns buffer + r -> size.
	// Assumes that buffer is uninitialized.
	static charT * flatten(RopeBase * r, charT * buffer);

	// Again, with explicit starting position and length.
	// Assumes that buffer is uninitialized.
	static charT * flatten(RopeBase * r,
			       size_t start, size_t len,
			       charT * buffer);

	static const unsigned long min_len[RopeBase::max_rope_depth + 1];

	static bool is_balanced(RopeBase *r)
		{ return (r -> size >= min_len[r -> depth]); }

	static bool is_almost_balanced(RopeBase *r)
		{ return (r -> depth == 0 ||
			  r -> size >= min_len[r -> depth - 1]); }

	static bool is_roughly_balanced(RopeBase *r)
		{ return (r -> depth <= 1 ||
			  r -> size >= min_len[r -> depth - 2]); }

	// Assumes the result is not empty.
	static RopeBase * concat_and_set_balanced(RopeBase *left,
						  RopeBase *right)
	{
	    RopeBase * result = concat(left, right);
	    if (is_balanced(result)) result -> is_balanced = true;
	    return result;
	}

	// The basic rebalancing operation.  Logically copies the
	// rope.  The result has refcount of 1.  The client will
	// usually decrement the reference count of r.
	// The result isd within height 2 of balanced by the above
	// definition.
	static RopeBase * balance(RopeBase * r);

	// Add all unbalanced subtrees to the forest of balanceed trees.
	// Used only by balance.
	static void add_to_forest(RopeBase *r, RopeBase **forest);
	
	// Add r to forest, assuming r is already balanced.
	static void add_leaf_to_forest(RopeBase *r, RopeBase **forest);

	// Print to stdout, exposing structure
	static void dump(RopeBase * r, int indent = 0);

	// Return -1, 0, or 1 if x < y, x == y, or x > y resp.
	static int compare(const RopeBase *x, const RopeBase *y);

   public:
	bool empty() const { return 0 == tree_ptr; }

	// Comparison member function.  This is public only for those
	// clients that need a ternary comparison.  Others
	// should use the comparison operators below.
	int compare(const rope &y) const {
	    return compare(tree_ptr, y.tree_ptr);
	}

	rope(const charT *s)
	{
	    size_t len = char_ptr_len(s);

	    if (0 == len) {
		tree_ptr = 0;
	    } else {
		tree_ptr = RopeLeaf_from_char_ptr(alloc_copy(s, len), len);
#		ifndef __GC
		  __stl_assert(1 == tree_ptr -> refcount);
#		endif
	    }
	}

	rope(const charT *s, size_t len)
	{
	    if (0 == len) {
		tree_ptr = 0;
	    } else {
		tree_ptr = RopeLeaf_from_char_ptr(alloc_copy(s, len), len);
	    }
	}

	rope(const charT *s, charT *e)
	{
	    size_t len = e - s;

	    if (0 == len) {
		tree_ptr = 0;
	    } else {
		tree_ptr = RopeLeaf_from_char_ptr(alloc_copy(s, len), len);
	    }
	}

	rope(const const_iterator& s, const const_iterator& e)
	{
	    tree_ptr = substring(s.root, s.current_pos, e.current_pos);
	}

	rope(const iterator& s, const iterator& e)
	{
	    tree_ptr = substring(s.root, s.current_pos, e.current_pos);
	}

	rope(charT c)
	{
	    charT * buf = (charT *)Alloc::allocate(rounded_up_size(1));

	    construct(buf, c);
	    tree_ptr = RopeLeaf_from_char_ptr(buf, 1);
	}

	rope(size_t n, charT c);

	// Should really be templatized with respect to the iterator type
	// and use sequence_buffer.  (It should perhaps use sequence_buffer
	// even now.)
	rope(const charT *i, const charT *j)
	{
	    if (i == j) {
		tree_ptr = 0;
	    } else {
		size_t len = j - i;
		tree_ptr = RopeLeaf_from_char_ptr(alloc_copy(i, len), len);
	    }
	}

	rope()
	{
	    tree_ptr = 0;
	}

	// Construct a rope from a function that can compute its members
	rope(char_producer<charT> *fn, size_t len, bool delete_fn)
	{
	    tree_ptr = RopeFunction_from_fn(fn, len, delete_fn);
	}

	rope(const rope &x)
	{
	    tree_ptr = x.tree_ptr;
	    ref(tree_ptr);
	}

	~rope()
	{
	    unref(tree_ptr);
	}

	rope& operator=(const rope& x)
	{
	    RopeBase *old = tree_ptr;
	    tree_ptr = x.tree_ptr;
	    ref(tree_ptr);
	    unref(old);
	    return(*this);
	}

	void push_back(charT x)
	{
	    RopeBase *old = tree_ptr;
	    tree_ptr = concat_char_iter(tree_ptr, &x, 1);
	    unref(old);
	}

	void pop_back()
	{
	    RopeBase *old = tree_ptr;
	    tree_ptr = substring(tree_ptr, 0, tree_ptr -> size - 1);
	    unref(old);
	}

	charT back() const
	{
	    return fetch(tree_ptr, tree_ptr -> size - 1);
	}

	void push_front(const charT& x)
	{
	    RopeBase *old = tree_ptr;
	    charT *buf = alloc_copy(&x, 1);
	    RopeBase *left;

	    __STL_TRY
	      left = RopeLeaf_from_char_ptr(buf, 1);
	    __STL_UNWIND(RopeBase::free_string(buf, 1))
	    __STL_TRY
	      tree_ptr = concat(left, tree_ptr);
	      unref(old);
	    __STL_ALWAYS(unref(left))
	}

	void pop_front()
	{
	    RopeBase *old = tree_ptr;
	    tree_ptr = substring(tree_ptr, 1, tree_ptr -> size);
	    unref(old);
	}

	charT front() const
	{
	    return fetch(tree_ptr, 0);
	}

	void balance()
	{
	    RopeBase *old = tree_ptr;
	    tree_ptr = balance(tree_ptr);
	    unref(old);
	}

	void copy(charT * buffer) const {
	    destroy(buffer, buffer + size());
	    flatten(tree_ptr, buffer);
	}

	// This is the copy function from the standard, but
	// with the arguments reordered to make it consistent with the
	// rest of the interface.
	// Note that this guaranteed not to compile if the draft standard
	// order is assumed.
	size_type copy(size_type pos, size_type n, charT *buffer) const {
	    size_t sz = size();
	    size_t len = (pos + n > sz? sz - pos : n);

	    destroy(buffer, buffer + len);
	    flatten(tree_ptr, pos, len, buffer);
	    return len;
	}

	// Print to stdout, exposing structure.  May be useful for
	// performance debugging.
	void dump() {
	    dump(tree_ptr);
	}

	// Convert to 0 terminated string in new allocated memory.
	// Embedded 0s in the input do not terminate the copy.
	const charT * c_str() const;

	// As above, but lso use the flattened representation as the
	// the new rope representation.
	const charT * replace_with_c_str();

	// Reclaim memory for the c_str generated flattened string.
	// Intentionally undocumented, since it's hard to say when this
	// is safe for multiple threads.
	void delete_c_str () {
	    if (0 == tree_ptr) return;
	    if (RopeBase::leaf == tree_ptr -> tag
		&& ((RopeLeaf *)tree_ptr) -> data == tree_ptr -> c_string) {
		// Representation shared
		return;
	    }
#	    ifndef __GC
	      tree_ptr -> free_c_string();
#	    endif
	    tree_ptr -> c_string = 0;
	}

	charT operator[] (size_type pos) const {
	    return fetch(tree_ptr, pos);
	}

	charT at(size_type pos) const {
	   // if (pos >= size()) throw out_of_range;
	   return (*this)[pos];
	}

	const_iterator begin() const {
	    return(const_iterator(tree_ptr, 0));
	}

	// An easy way to get a const iterator from a non-const container.
	const_iterator const_begin() const {
	    return(const_iterator(tree_ptr, 0));
	}

	const_iterator end() const {
	    return(const_iterator(tree_ptr, size()));
	}

	const_iterator const_end() const {
	    return(const_iterator(tree_ptr, size()));
	}

	size_type size() const { 
	    return(0 == tree_ptr? 0 : tree_ptr -> size);
	}

	size_type length() const {
	    return size();
	}

	size_type max_size() const {
	    return min_len[RopeBase::max_rope_depth-1] - 1;
	    //  Guarantees that the result can be sufficirntly
	    //  balanced.  Longer ropes will probably still work,
	    //  but it's harder to make guarantees.
	}

	typedef reverse_iterator<const_iterator, value_type, const_reference,
				 difference_type>  const_reverse_iterator;
 
	const_reverse_iterator rbegin() const {
	    return const_reverse_iterator(end());
	}

	const_reverse_iterator const_rbegin() const {
	    return const_reverse_iterator(end());
	}

	const_reverse_iterator rend() const {
	    return const_reverse_iterator(begin());
	}

	const_reverse_iterator const_rend() const {
	    return const_reverse_iterator(begin());
	}

	friend rope<charT,Alloc> operator+ (const rope<charT,Alloc> &left,
					    const rope<charT,Alloc> &right);
	
	friend rope<charT,Alloc> operator+ (const rope<charT,Alloc> &left,
					    const charT* right);
	
	friend rope<charT,Alloc> operator+ (const rope<charT,Alloc> &left,
					    charT right);
	
	// The symmetric cases are intentionally omitted, since they're presumed
	// to be less common, and we don't handle them as well.

	// The following should really be templatized.
	// The first argument should be an input iterator or
	// forward iterator with value_type charT.
	rope& append(const charT* iter, size_t n) {
	    RopeBase* result = destr_concat_char_iter(tree_ptr, iter, n);
	    unref(tree_ptr);
	    tree_ptr = result;
	    return *this;
	}

	rope& append(const charT* c_string) {
	    size_t len = char_ptr_len(c_string);
	    append(c_string, len);
	    return(*this);
	}

	rope& append(const charT* s, const charT* e) {
	    RopeBase* result =
			destr_concat_char_iter(tree_ptr, s, e - s);
	    unref(tree_ptr);
	    tree_ptr = result;
	    return *this;
	}

	rope& append(const_iterator s, const_iterator e) {
	    __stl_assert(s.root == e.root);
	    self_destruct_ptr appendee(substring(s.root, s.current_pos,
						 e.current_pos));
	    RopeBase* result = concat(tree_ptr, (RopeBase *)appendee);
	    unref(tree_ptr);
	    tree_ptr = result;
	    return *this;
	}

	rope& append(charT c) {
	    RopeBase* result = destr_concat_char_iter(tree_ptr, &c, 1);
	    unref(tree_ptr);
	    tree_ptr = result;
	    return *this;
	}

	rope& append() { return append(charT()); }

	rope& append(const rope& y) {
	    RopeBase* result = concat(tree_ptr, y.tree_ptr);
	    unref(tree_ptr);
	    tree_ptr = result;
	    return *this;
	}

	rope& append(size_t n, charT c) {
	    rope<charT,Alloc> last(n, c);
	    return append(last);
	}

	void swap(rope& b) {
	    RopeBase * tmp = tree_ptr;
	    tree_ptr = b.tree_ptr;
	    b.tree_ptr = tmp;
	}


    protected:
	// Result is included in refcount.
	static RopeBase * replace(RopeBase *old, size_t pos1,
				  size_t pos2, RopeBase *r) {
	    if (0 == old) { ref(r); return r; }
	    self_destruct_ptr left(substring(old, 0, pos1));
	    self_destruct_ptr right(substring(old, pos2, old -> size));
	    RopeBase * result;

	    if (0 == r) {
		result = concat(left, right);
	    } else {
		self_destruct_ptr left_result(concat(left, r));
		result = concat(left_result, right);
	    }
	    return result;
	}

    public:
	void insert(size_t p, const rope& r) {
	    RopeBase * result = replace(tree_ptr, p, p,
					       r.tree_ptr);
	    unref(tree_ptr);
	    tree_ptr = result;
	}

	void insert(size_t p, size_t n, charT c) {
	    rope<charT,Alloc> r(n,c);
	    insert(p, r);
	}

	void insert(size_t p, const charT * i, size_t n) {
	    self_destruct_ptr left(substring(tree_ptr, 0, p));
	    self_destruct_ptr right(substring(tree_ptr, p, size()));
	    self_destruct_ptr left_result(concat_char_iter(left, i, n));
	    RopeBase * result =
				concat(left_result, right);
	    unref(tree_ptr);
	    tree_ptr = result;
	}

	void insert(size_t p, const charT * c_string) {
	    insert(p, c_string, char_ptr_len(c_string));
	}

	void insert(size_t p, charT c) {
	    insert(p, &c, 1);
	}

	void insert(size_t p) {
	    charT c = charT();
	    insert(p, &c, 1);
	}

	void insert(size_t p, const charT *i, const charT *j) {
	    rope r(i, j);
	    insert(p, r);
	}

	void insert(size_t p, const const_iterator& i,
			      const const_iterator& j) {
	    rope r(i, j);
	    insert(p, r);
	}

	void insert(size_t p, const iterator& i,
			      const iterator& j) {
	    rope r(i, j);
	    insert(p, r);
	}

	// (position, length) versions of replace operations:

	void replace(size_t p, size_t n, const rope& r) {
	    RopeBase * result = replace(tree_ptr, p, p + n,
					       r.tree_ptr);
	    unref(tree_ptr);
	    tree_ptr = result;
	}

	void replace(size_t p, size_t n, const charT *i, size_t i_len) {
	    rope r(i, i_len);
	    replace(p, n, r);
	}

	void replace(size_t p, size_t n, charT c) {
	    rope r(c);
	    replace(p, n, r);
	}

	void replace(size_t p, size_t n, const charT *c_string) {
	    rope r(c_string);
	    replace(p, n, r);
	}

	void replace(size_t p, size_t n, const charT *i, const charT *j) {
	    rope r(i, j);
	    replace(p, n, r);
	}

	void replace(size_t p, size_t n,
		     const const_iterator& i, const const_iterator& j) {
	    rope r(i, j);
	    replace(p, n, r);
	}

	void replace(size_t p, size_t n,
		     const iterator& i, const iterator& j) {
	    rope r(i, j);
	    replace(p, n, r);
	}

	// Single character variants:
	void replace(size_t p, charT c) {
	    iterator i(this, p);
	    *i = c;
	}

	void replace(size_t p, const rope& r) {
	    replace(p, 1, r);
	}

	void replace(size_t p, const charT *i, size_t i_len) {
	    replace(p, 1, i, i_len);
	}

	void replace(size_t p, const charT *c_string) {
	    replace(p, 1, c_string);
	}

	void replace(size_t p, const charT *i, const charT *j) {
	    replace(p, 1, i, j);
	}

	void replace(size_t p, const const_iterator& i,
			       const const_iterator& j) {
	    replace(p, 1, i, j);
	}

	void replace(size_t p, const iterator& i,
			       const iterator& j) {
	    replace(p, 1, i, j);
	}

	// Erase, (position, size) variant.
	void erase(size_t p, size_t n) {
	    RopeBase * result = replace(tree_ptr, p, p + n, 0);
	    unref(tree_ptr);
	    tree_ptr = result;
	}

	// Erase, single character
	void erase(size_t p) {
	    erase(p, p + 1);
	}

	// Insert, iterator variants.  
	iterator insert(const iterator& p, const rope& r)
		{ insert(p.index(), r); return p; }
	iterator insert(const iterator& p, size_t n, charT c)
		{ insert(p.index(), n, c); return p; }
	iterator insert(const iterator& p, charT c) 
		{ insert(p.index(), c); return p; }
	iterator insert(const iterator& p ) 
		{ insert(p.index()); return p; }
	iterator insert(const iterator& p, const charT *c_string) 
		{ insert(p.index(), c_string); return p; }
	iterator insert(const iterator& p, const charT *i, size_t n)
		{ insert(p.index(), i, n); return p; }
	iterator insert(const iterator& p, const charT *i, const charT *j)
		{ insert(p.index(), i, j);  return p; }
	iterator insert(const iterator& p,
			const const_iterator& i, const const_iterator& j)
		{ insert(p.index(), i, j); return p; }
	iterator insert(const iterator& p,
			const iterator& i, const iterator& j)
		{ insert(p.index(), i, j); return p; }

	// Replace, range variants.
	void replace(const iterator& p, const iterator& q,
		     const rope& r)
		{ replace(p.index(), q.index() - p.index(), r); }
	void replace(const iterator& p, const iterator& q, charT c)
		{ replace(p.index(), q.index() - p.index(), c); }
	void replace(const iterator& p, const iterator& q,
		     const charT * c_string)
		{ replace(p.index(), q.index() - p.index(), c_string); }
	void replace(const iterator& p, const iterator& q,
		     const charT *i, size_t n)
		{ replace(p.index(), q.index() - p.index(), i, n); }
	void replace(const iterator& p, const iterator& q,
		     const charT *i, const charT *j)
		{ replace(p.index(), q.index() - p.index(), i, j); }
	void replace(const iterator& p, const iterator& q,
		     const const_iterator& i, const const_iterator& j)
		{ replace(p.index(), q.index() - p.index(), i, j); }
	void replace(const iterator& p, const iterator& q,
		     const iterator& i, const iterator& j)
		{ replace(p.index(), q.index() - p.index(), i, j); }

	// Replace, iterator variants.
	void replace(const iterator& p, const rope& r)
		{ replace(p.index(), r); }
	void replace(const iterator& p, charT c)
		{ replace(p.index(), c); }
	void replace(const iterator& p, const charT * c_string)
		{ replace(p.index(), c_string); }
	void replace(const iterator& p, const charT *i, size_t n)
		{ replace(p.index(), i, n); }
	void replace(const iterator& p, const charT *i, const charT *j)
		{ replace(p.index(), i, j); }
	void replace(const iterator& p, const_iterator i, const_iterator j)
		{ replace(p.index(), i, j); }
	void replace(const iterator& p, iterator i, iterator j)
		{ replace(p.index(), i, j); }

	// Iterator and range variants of erase
	void erase(const iterator &p, const iterator &q)
		{ erase(p.index(), q.index() - p.index()); }
	void erase(const iterator &p)
		{ erase(p.index(), 1); }

	rope substr(size_t start, size_t len = 1) const {
	    return rope<charT,Alloc>(
			substring(tree_ptr, start, start + len));
	}

	rope substr(iterator start, iterator end) const {
	    return rope<charT,Alloc>(
			substring(tree_ptr, start.index(), end.index()));
	}
	
	rope substr(iterator start) const {
	    size_t pos = start.index();
	    return rope<charT,Alloc>(
			substring(tree_ptr, pos, pos + 1));
	}
	
	rope substr(const_iterator start, const_iterator end) const {
	    // This might eventually take advantage of the cache in the
	    // iterator.
	    return rope<charT,Alloc>
		(substring(tree_ptr, start.index(), end.index()));
	}

	rope<charT,Alloc> substr(const_iterator start) {
	    size_t pos = start.index();
	    return rope<charT,Alloc>(substring(tree_ptr, pos, pos + 1));
	}

	size_type find(charT c, size_type pos = 0) const;
	size_type find(charT *s, size_type pos = 0) const {
	    const_iterator result = search(const_begin() + pos, const_end(),
					   s, s + char_ptr_len(s));
	    return result.index();
	}

	iterator mutable_begin() {
	    return(iterator(this, 0));
	}

	iterator mutable_end() {
	    return(iterator(this, size()));
	}

	typedef reverse_iterator<iterator, value_type, reference,
				 difference_type>  reverse_iterator;

	reverse_iterator mutable_rbegin() {
	    return reverse_iterator(mutable_end());
	}

	reverse_iterator mutable_rend() {
	    return reverse_iterator(mutable_begin());
	}

	reference mutable_reference_at(size_type pos) {
	    return reference(this, pos);
	}

#	ifdef __STD_STUFF
	    reference operator[] (size_type pos) {
		return charT_ref_proxy(this, pos);
	    }

	    reference at(size_type pos) {
		// if (pos >= size()) throw out_of_range;
		return (*this)[pos];
	    }

	    void resize(size_type n, charT c) {}
	    void resize(size_type n) {}
	    void reserve(size_type res_arg = 0) {}
	    size_type capacity() const {
		return max_size();
	    }

	  // Stuff below this line is dangerous because it's error prone.
	  // I would really like to get rid of it.
	    // copy function with funny arg ordering.
	      size_type copy(charT *buffer, size_type n, size_type pos = 0)
								const {
		return copy(pos, n, buffer);
	      }

	    iterator end() { return mutable_end(); }

	    iterator begin() { return mutable_begin(); }

	    reverse_iterator rend() { return mutable_rend(); }

	    reverse_iterator rbegin() { return mutable_rbegin(); }

#	else

	    const_iterator end() { return const_end(); }

	    const_iterator begin() { return const_begin(); }

	    const_reverse_iterator rend() { return const_rend(); }
  
	    const_reverse_iterator rbegin() { return const_rbegin(); }

#	endif
	
};

template <class charT, class Alloc>
inline bool operator== (const __rope_const_iterator<charT,Alloc> & x,
			const __rope_const_iterator<charT,Alloc> & y) {
	return (x.current_pos == y.current_pos && x.root == y.root);
}

template <class charT, class Alloc>
inline bool operator< (const __rope_const_iterator<charT,Alloc> & x,
		       const __rope_const_iterator<charT,Alloc> & y) {
	return (x.current_pos < y.current_pos);
}

template <class charT, class Alloc>
inline ptrdiff_t operator-(const __rope_const_iterator<charT,Alloc> & x,
			   const __rope_const_iterator<charT,Alloc> & y) {
	return x.current_pos - y.current_pos;
}

template <class charT, class Alloc>
inline __rope_const_iterator<charT,Alloc>
operator-(const __rope_const_iterator<charT,Alloc> & x,
	  ptrdiff_t n) {
	return __rope_const_iterator<charT,Alloc>(x.root, x.current_pos - n);
}

template <class charT, class Alloc>
inline __rope_const_iterator<charT,Alloc>
operator+(const __rope_const_iterator<charT,Alloc> & x,
	  ptrdiff_t n) {
	return __rope_const_iterator<charT,Alloc>(x.root, x.current_pos + n);
}

template <class charT, class Alloc>
inline __rope_const_iterator<charT,Alloc>
operator+(ptrdiff_t n,
	  const __rope_const_iterator<charT,Alloc> & x) {
	return __rope_const_iterator<charT,Alloc>(x.root, x.current_pos + n);
}

template <class charT, class Alloc>
inline bool operator== (const __rope_iterator<charT,Alloc> & x,
			const __rope_iterator<charT,Alloc> & y) {
	return (x.current_pos == y.current_pos && x.root_rope == y.root_rope);
}

template <class charT, class Alloc>
inline bool operator< (const __rope_iterator<charT,Alloc> & x,
			const __rope_iterator<charT,Alloc> & y) {
	return (x.current_pos < y.current_pos);
}

template <class charT, class Alloc>
inline ptrdiff_t operator-(const __rope_iterator<charT,Alloc> & x,
			   const __rope_iterator<charT,Alloc> & y) {
	return x.current_pos - y.current_pos;
}

template <class charT, class Alloc>
inline __rope_iterator<charT,Alloc>
operator-(const __rope_iterator<charT,Alloc> & x,
	  ptrdiff_t n) {
	return __rope_iterator<charT,Alloc>(x.root_rope, x.current_pos - n);
}

template <class charT, class Alloc>
inline __rope_iterator<charT,Alloc>
operator+(const __rope_iterator<charT,Alloc> & x,
	  ptrdiff_t n) {
	return __rope_iterator<charT,Alloc>(x.root_rope, x.current_pos + n);
}

template <class charT, class Alloc>
inline __rope_iterator<charT,Alloc>
operator+(ptrdiff_t n,
	  const __rope_iterator<charT,Alloc> & x) {
	return __rope_iterator<charT,Alloc>(x.root_rope, x.current_pos + n);
}

template <class charT, class Alloc>
inline
rope<charT,Alloc>
operator+ (const rope<charT,Alloc> &left,
	   const rope<charT,Alloc> &right)
{
    return rope<charT,Alloc>
		(rope<charT,Alloc>::concat(left.tree_ptr, right.tree_ptr));
    // Inlining this should make it possible to keep left and
    // right in registers.
}

template <class charT, class Alloc>
inline
rope<charT,Alloc>&
operator+= (rope<charT,Alloc> &left,
	    const rope<charT,Alloc> &right)
{
    left.append(right);
    return left;
}

template <class charT, class Alloc>
inline
rope<charT,Alloc>
operator+ (const rope<charT,Alloc> &left,
	   const charT* right) {
    size_t rlen = rope<charT,Alloc>::char_ptr_len(right);
    return rope<charT,Alloc>
	   (rope<charT,Alloc>::concat_char_iter(left.tree_ptr, right, rlen)); 
}

template <class charT, class Alloc>
inline
rope<charT,Alloc>&
operator+= (rope<charT,Alloc> &left,
	    const charT* right) {
    left.append(right);
    return left;
}

template <class charT, class Alloc>
inline
rope<charT,Alloc>
operator+ (const rope<charT,Alloc> &left, charT right) {
    return rope<charT,Alloc>
		(rope<charT,Alloc>::concat_char_iter(left.tree_ptr, &right, 1));
}

template <class charT, class Alloc>
inline
rope<charT,Alloc>&
operator+= (rope<charT,Alloc> &left, charT right) {
    left.append(right);
    return left;
}

template <class charT, class Alloc>
bool
operator< (const rope<charT,Alloc> &left, const rope<charT,Alloc> &right) {
    return left.compare(right) < 0;
}
	
template <class charT, class Alloc>
bool
operator== (const rope<charT,Alloc> &left, const rope<charT,Alloc> &right) {
    return left.compare(right) == 0;
}

template <class charT, class Alloc>
inline bool operator== (const __rope_charT_ptr_proxy<charT,Alloc> & x,
			const __rope_charT_ptr_proxy<charT,Alloc> & y) {
	return (x.pos == y.pos && x.root == y.root);
}

template<class charT, class Alloc>
ostream& operator<< (ostream& o, const rope<charT, Alloc>& r);        
	
typedef rope<char, __ALLOC> crope;
typedef rope<wchar_t, __ALLOC> wrope;

inline crope::reference __mutable_reference_at(crope& c, size_t i)
{
    return c.mutable_reference_at(i);
}

inline wrope::reference __mutable_reference_at(wrope& c, size_t i)
{
    return c.mutable_reference_at(i);
}

inline void swap(crope x, crope y) { x.swap(y); }
inline void swap(wrope x, wrope y) { x.swap(y); }

// Hash functions should probably be revisited later:
struct hash<crope>
{
  size_t operator()(const crope& str) const
  {
    size_t sz = str.size();

    if (0 == sz) return 0;
    return 13*str[0] + 5*str[sz - 1] + sz;
  }
};

struct hash<wrope>
{
  size_t operator()(const wrope& str) const
  {
    size_t sz = str.size();

    if (0 == sz) return 0;
    return 13*str[0] + 5*str[sz - 1] + sz;
  }
};

# include <ropeimpl.h>
# endif /* _ROPE_H */