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/* Code for doing intervals.
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   Copyright (C) 1993 Free Software Foundation, Inc.
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This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.

GNU Emacs 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 GNU Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */


/* NOTES:

   Have to ensure that we can't put symbol nil on a plist, or some
   functions may work incorrectly.

   An idea:  Have the owner of the tree keep count of splits and/or
   insertion lengths (in intervals), and balance after every N.

   Need to call *_left_hook when buffer is killed.

   Scan for zero-length, or 0-length to see notes about handling
   zero length interval-markers.

   There are comments around about freeing intervals.  It might be
   faster to explicitly free them (put them on the free list) than
   to GC them.

*/


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#include <config.h>
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#include "lisp.h"
#include "intervals.h"
#include "buffer.h"
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#include "puresize.h"
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/* The rest of the file is within this conditional.  */
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#ifdef USE_TEXT_PROPERTIES

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/* Factor for weight-balancing interval trees.  */
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Lisp_Object interval_balance_threshold;
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Lisp_Object merge_properties_sticky ();
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54

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/* Utility functions for intervals.  */
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/* Create the root interval of some object, a buffer or string.  */
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INTERVAL
create_root_interval (parent)
     Lisp_Object parent;
{
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  INTERVAL new;

  CHECK_IMPURE (parent);

  new = make_interval ();
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  if (XTYPE (parent) == Lisp_Buffer)
    {
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      new->total_length = (BUF_Z (XBUFFER (parent))
			   - BUF_BEG (XBUFFER (parent)));
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      XBUFFER (parent)->intervals = new;
    }
  else if (XTYPE (parent) == Lisp_String)
    {
      new->total_length = XSTRING (parent)->size;
      XSTRING (parent)->intervals = new;
    }

  new->parent = (INTERVAL) parent;
  new->position = 1;

  return new;
}

/* Make the interval TARGET have exactly the properties of SOURCE */

void
copy_properties (source, target)
     register INTERVAL source, target;
{
  if (DEFAULT_INTERVAL_P (source) && DEFAULT_INTERVAL_P (target))
    return;

  COPY_INTERVAL_CACHE (source, target);
  target->plist = Fcopy_sequence (source->plist);
}

/* Merge the properties of interval SOURCE into the properties
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   of interval TARGET.  That is to say, each property in SOURCE
   is added to TARGET if TARGET has no such property as yet.  */
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static void
merge_properties (source, target)
     register INTERVAL source, target;
{
  register Lisp_Object o, sym, val;

  if (DEFAULT_INTERVAL_P (source) && DEFAULT_INTERVAL_P (target))
    return;

  MERGE_INTERVAL_CACHE (source, target);

  o = source->plist;
  while (! EQ (o, Qnil))
    {
      sym = Fcar (o);
      val = Fmemq (sym, target->plist);

      if (NILP (val))
	{
	  o = Fcdr (o);
	  val = Fcar (o);
	  target->plist = Fcons (sym, Fcons (val, target->plist));
	  o = Fcdr (o);
	}
      else
	o = Fcdr (Fcdr (o));
    }
}

/* Return 1 if the two intervals have the same properties,
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   0 otherwise.  */
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int
intervals_equal (i0, i1)
     INTERVAL i0, i1;
{
  register Lisp_Object i0_cdr, i0_sym, i1_val;
  register i1_len;

  if (DEFAULT_INTERVAL_P (i0) && DEFAULT_INTERVAL_P (i1))
    return 1;

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  if (DEFAULT_INTERVAL_P (i0) || DEFAULT_INTERVAL_P (i1))
    return 0;

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  i1_len = XFASTINT (Flength (i1->plist));
  if (i1_len & 0x1)		/* Paranoia -- plists are always even */
    abort ();
  i1_len /= 2;
  i0_cdr = i0->plist;
  while (!NILP (i0_cdr))
    {
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      /* Lengths of the two plists were unequal.  */
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      if (i1_len == 0)
	return 0;

      i0_sym = Fcar (i0_cdr);
      i1_val = Fmemq (i0_sym, i1->plist);

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      /* i0 has something i1 doesn't.  */
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      if (EQ (i1_val, Qnil))
	return 0;

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      /* i0 and i1 both have sym, but it has different values in each.  */
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      i0_cdr = Fcdr (i0_cdr);
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      if (! EQ (Fcar (Fcdr (i1_val)), Fcar (i0_cdr)))
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	return 0;

      i0_cdr = Fcdr (i0_cdr);
      i1_len--;
    }

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  /* Lengths of the two plists were unequal.  */
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  if (i1_len > 0)
    return 0;

  return 1;
}

static int icount;
static int idepth;
static int zero_length;

/* Traverse an interval tree TREE, performing FUNCTION on each node.
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   Pass FUNCTION two args: an interval, and ARG.  */
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void
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traverse_intervals (tree, position, depth, function, arg)
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     INTERVAL tree;
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     int position, depth;
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     void (* function) ();
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     Lisp_Object arg;
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{
  if (NULL_INTERVAL_P (tree))
    return;

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  traverse_intervals (tree->left, position, depth + 1, function, arg);
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  position += LEFT_TOTAL_LENGTH (tree);
  tree->position = position;
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  (*function) (tree, arg);
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  position += LENGTH (tree);
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  traverse_intervals (tree->right, position, depth + 1,  function, arg);
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}

#if 0
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/* These functions are temporary, for debugging purposes only.  */
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INTERVAL search_interval, found_interval;

void
check_for_interval (i)
     register INTERVAL i;
{
  if (i == search_interval)
    {
      found_interval = i;
      icount++;
    }
}

INTERVAL
search_for_interval (i, tree)
     register INTERVAL i, tree;
{
  icount = 0;
  search_interval = i;
  found_interval = NULL_INTERVAL;
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  traverse_intervals (tree, 1, 0, &check_for_interval, Qnil);
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  return found_interval;
}

static void
inc_interval_count (i)
     INTERVAL i;
{
  icount++;
  if (LENGTH (i) == 0)
    zero_length++;
  if (depth > idepth)
    idepth = depth;
}

int
count_intervals (i)
     register INTERVAL i;
{
  icount = 0;
  idepth = 0;
  zero_length = 0;
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  traverse_intervals (i, 1, 0, &inc_interval_count, Qnil);
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  return icount;
}

static INTERVAL
root_interval (interval)
     INTERVAL interval;
{
  register INTERVAL i = interval;

  while (! ROOT_INTERVAL_P (i))
    i = i->parent;

  return i;
}
#endif

/* Assuming that a left child exists, perform the following operation:

     A		  B
    / \		 / \
   B       =>       A
  / \		   / \
     c		  c
*/

static INTERVAL
rotate_right (interval)
     INTERVAL interval;
{
  INTERVAL i;
  INTERVAL B = interval->left;
  int len = LENGTH (interval);

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  /* Deal with any Parent of A;  make it point to B.  */
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  if (! ROOT_INTERVAL_P (interval))
    if (AM_LEFT_CHILD (interval))
      interval->parent->left = interval->left;
    else
      interval->parent->right = interval->left;
  interval->left->parent = interval->parent;

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  /* B gets the same length as A, since it get A's position in the tree.  */
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  interval->left->total_length = interval->total_length;

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  /* B becomes the parent of A.  */
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  i = interval->left->right;
  interval->left->right = interval;
  interval->parent = interval->left;

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  /* A gets c as left child.  */
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  interval->left = i;
  if (! NULL_INTERVAL_P (i))
    i->parent = interval;
  interval->total_length = (len + LEFT_TOTAL_LENGTH (interval)
			    + RIGHT_TOTAL_LENGTH (interval));

  return B;
}

/* Assuming that a right child exists, perform the following operation:

    A               B   
   / \	           / \  
      B	   =>     A
     / \         / \    
    c               c
*/

static INTERVAL
rotate_left (interval)
     INTERVAL interval;
{
  INTERVAL i;
  INTERVAL B = interval->right;
  int len = LENGTH (interval);

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  /* Deal with the parent of A.  */
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  if (! ROOT_INTERVAL_P (interval))
    if (AM_LEFT_CHILD (interval))
      interval->parent->left = interval->right;
    else
      interval->parent->right = interval->right;
  interval->right->parent = interval->parent;

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  /* B must have the same total length of A.  */
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  interval->right->total_length = interval->total_length;

  /* Make B the parent of A */
  i = interval->right->left;
  interval->right->left = interval;
  interval->parent = interval->right;

  /* Make A point to c */
  interval->right = i;
  if (! NULL_INTERVAL_P (i))
    i->parent = interval;
  interval->total_length = (len + LEFT_TOTAL_LENGTH (interval)
			    + RIGHT_TOTAL_LENGTH (interval));

  return B;
}

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/* Split INTERVAL into two pieces, starting the second piece at
   character position OFFSET (counting from 0), relative to INTERVAL.
   INTERVAL becomes the left-hand piece, and the right-hand piece
   (second, lexicographically) is returned.
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   The size and position fields of the two intervals are set based upon
   those of the original interval.  The property list of the new interval
   is reset, thus it is up to the caller to do the right thing with the
   result.
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   Note that this does not change the position of INTERVAL;  if it is a root,
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   it is still a root after this operation.  */
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INTERVAL
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split_interval_right (interval, offset)
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     INTERVAL interval;
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     int offset;
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{
  INTERVAL new = make_interval ();
  int position = interval->position;
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  int new_length = LENGTH (interval) - offset;
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  new->position = position + offset;
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  new->parent = interval;

  if (LEAF_INTERVAL_P (interval) || NULL_RIGHT_CHILD (interval))
    {
      interval->right = new;
      new->total_length = new_length;

      return new;
    }

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  /* Insert the new node between INTERVAL and its right child.  */
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  new->right = interval->right;
  interval->right->parent = new;
  interval->right = new;

  new->total_length = new_length + new->right->total_length;

  return new;
}

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/* Split INTERVAL into two pieces, starting the second piece at
   character position OFFSET (counting from 0), relative to INTERVAL.
   INTERVAL becomes the right-hand piece, and the left-hand piece
   (first, lexicographically) is returned.
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   The size and position fields of the two intervals are set based upon
   those of the original interval.  The property list of the new interval
   is reset, thus it is up to the caller to do the right thing with the
   result.

   Note that this does not change the position of INTERVAL;  if it is a root,
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   it is still a root after this operation.  */
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INTERVAL
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split_interval_left (interval, offset)
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     INTERVAL interval;
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     int offset;
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{
  INTERVAL new = make_interval ();
  int position = interval->position;
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  int new_length = offset;
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  new->position = interval->position;
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  interval->position = interval->position + offset;
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  new->parent = interval;

  if (NULL_LEFT_CHILD (interval))
    {
      interval->left = new;
      new->total_length = new_length;

      return new;
    }

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  /* Insert the new node between INTERVAL and its left child.  */
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  new->left = interval->left;
  new->left->parent = new;
  interval->left = new;
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  new->total_length = new_length + LEFT_TOTAL_LENGTH (new);
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  return new;
}

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/* Find the interval containing text position POSITION in the text
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   represented by the interval tree TREE.  POSITION is a buffer
   position; the earliest position is 1.  If POSITION is at the end of
   the buffer, return the interval containing the last character.
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   The `position' field, which is a cache of an interval's position,
   is updated in the interval found.  Other functions (e.g., next_interval)
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   will update this cache based on the result of find_interval.  */
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INLINE INTERVAL
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find_interval (tree, position)
     register INTERVAL tree;
     register int position;
{
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  /* The distance from the left edge of the subtree at TREE
                    to POSITION.  */
  register int relative_position = position - BEG;
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  if (NULL_INTERVAL_P (tree))
    return NULL_INTERVAL;

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  if (relative_position > TOTAL_LENGTH (tree))
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    abort ();			/* Paranoia */

  while (1)
    {
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      if (relative_position < LEFT_TOTAL_LENGTH (tree))
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	{
	  tree = tree->left;
	}
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      else if (! NULL_RIGHT_CHILD (tree)
	       && relative_position >= (TOTAL_LENGTH (tree)
					- RIGHT_TOTAL_LENGTH (tree)))
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	{
	  relative_position -= (TOTAL_LENGTH (tree)
				- RIGHT_TOTAL_LENGTH (tree));
	  tree = tree->right;
	}
      else
	{
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	  tree->position =
	    (position - relative_position /* the left edge of *tree */
	     + LEFT_TOTAL_LENGTH (tree)); /* the left edge of this interval */

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	  return tree;
	}
    }
}

/* Find the succeeding interval (lexicographically) to INTERVAL.
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   Sets the `position' field based on that of INTERVAL (see
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   find_interval).  */
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INTERVAL
next_interval (interval)
     register INTERVAL interval;
{
  register INTERVAL i = interval;
  register int next_position;

  if (NULL_INTERVAL_P (i))
    return NULL_INTERVAL;
  next_position = interval->position + LENGTH (interval);

  if (! NULL_RIGHT_CHILD (i))
    {
      i = i->right;
      while (! NULL_LEFT_CHILD (i))
	i = i->left;

      i->position = next_position;
      return i;
    }

  while (! NULL_PARENT (i))
    {
      if (AM_LEFT_CHILD (i))
	{
	  i = i->parent;
	  i->position = next_position;
	  return i;
	}

      i = i->parent;
    }

  return NULL_INTERVAL;
}

/* Find the preceding interval (lexicographically) to INTERVAL.
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   Sets the `position' field based on that of INTERVAL (see
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   find_interval).  */
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INTERVAL
previous_interval (interval)
     register INTERVAL interval;
{
  register INTERVAL i;
  register position_of_previous;

  if (NULL_INTERVAL_P (interval))
    return NULL_INTERVAL;

  if (! NULL_LEFT_CHILD (interval))
    {
      i = interval->left;
      while (! NULL_RIGHT_CHILD (i))
	i = i->right;

      i->position = interval->position - LENGTH (i);
      return i;
    }

  i = interval;
  while (! NULL_PARENT (i))
    {
      if (AM_RIGHT_CHILD (i))
	{
	  i = i->parent;

	  i->position = interval->position - LENGTH (i);
	  return i;
	}
      i = i->parent;
    }

  return NULL_INTERVAL;
}

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#if 0
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/* Traverse a path down the interval tree TREE to the interval
   containing POSITION, adjusting all nodes on the path for
   an addition of LENGTH characters.  Insertion between two intervals
   (i.e., point == i->position, where i is second interval) means
   text goes into second interval.

   Modifications are needed to handle the hungry bits -- after simply
   finding the interval at position (don't add length going down),
   if it's the beginning of the interval, get the previous interval
   and check the hugry bits of both.  Then add the length going back up
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   to the root.  */
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static INTERVAL
adjust_intervals_for_insertion (tree, position, length)
     INTERVAL tree;
     int position, length;
{
  register int relative_position;
  register INTERVAL this;

  if (TOTAL_LENGTH (tree) == 0)	/* Paranoia */
    abort ();

  /* If inserting at point-max of a buffer, that position
     will be out of range */
  if (position > TOTAL_LENGTH (tree))
    position = TOTAL_LENGTH (tree);
  relative_position = position;
  this = tree;

  while (1)
    {
      if (relative_position <= LEFT_TOTAL_LENGTH (this))
	{
	  this->total_length += length;
	  this = this->left;
	}
      else if (relative_position > (TOTAL_LENGTH (this)
				    - RIGHT_TOTAL_LENGTH (this)))
	{
	  relative_position -= (TOTAL_LENGTH (this)
				- RIGHT_TOTAL_LENGTH (this));
	  this->total_length += length;
	  this = this->right;
	}
      else
	{
	  /* If we are to use zero-length intervals as buffer pointers,
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	     then this code will have to change.  */
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	  this->total_length += length;
	  this->position = LEFT_TOTAL_LENGTH (this)
	                   + position - relative_position + 1;
	  return tree;
	}
    }
}
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#endif

/* Effect an adjustment corresponding to the addition of LENGTH characters
   of text.  Do this by finding the interval containing POSITION in the
   interval tree TREE, and then adjusting all of it's ancestors by adding
   LENGTH to them.

   If POSITION is the first character of an interval, meaning that point
   is actually between the two intervals, make the new text belong to
   the interval which is "sticky".

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   If both intervals are "sticky", then make them belong to the left-most
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   interval.  Another possibility would be to create a new interval for
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   this text, and make it have the merged properties of both ends.  */
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static INTERVAL
adjust_intervals_for_insertion (tree, position, length)
     INTERVAL tree;
     int position, length;
{
  register INTERVAL i;
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  register INTERVAL temp;
  int eobp = 0;
  
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  if (TOTAL_LENGTH (tree) == 0)	/* Paranoia */
    abort ();

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  /* If inserting at point-max of a buffer, that position will be out
     of range.  Remember that buffer positions are 1-based.  */
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  if (position >= BEG + TOTAL_LENGTH (tree)){
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    position = BEG + TOTAL_LENGTH (tree);
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    eobp = 1;
  }
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  i = find_interval (tree, position);
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  /* If in middle of an interval which is not sticky either way,
     we must not just give its properties to the insertion.
     So split this interval at the insertion point.  */
  if (! (position == i->position || eobp)
      && END_NONSTICKY_P (i)
      && ! FRONT_STICKY_P (i))
    {
      temp = split_interval_right (i, position - i->position);
      copy_properties (i, temp);
      i = temp;
    }

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  /* If we are positioned between intervals, check the stickiness of
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     both of them.  We have to do this too, if we are at BEG or Z.  */
  if (position == i->position || eobp)
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    {
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      register INTERVAL prev;

      if (position == BEG)
	prev = 0;
      else if (eobp)
	{
	  prev = i;
	  i = 0;
	}
      else
	prev = previous_interval (i);
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      /* Even if we are positioned between intervals, we default
	 to the left one if it exists.  We extend it now and split
	 off a part later, if stickyness demands it.  */
      for (temp = prev ? prev : i; ! NULL_INTERVAL_P (temp); temp = temp->parent)
	temp->total_length += length;
      
      /* If at least one interval has sticky properties,
	 we check the stickyness property by property.  */
      if (END_NONSTICKY_P (prev) || FRONT_STICKY_P (i))
	{
	  Lisp_Object pleft = NULL_INTERVAL_P (prev) ? Qnil : prev->plist;
	  Lisp_Object pright = NULL_INTERVAL_P (i) ? Qnil : i->plist;
	  struct interval newi;

	  newi.plist = merge_properties_sticky (pleft, pright);

	  if(! prev) /* i.e. position == BEG */
	    {
	      if (! intervals_equal (i, &newi))
		{
		  i = split_interval_left (i, length);
		  i->plist = newi.plist;
		}
	    }
	  else if (! intervals_equal (prev, &newi))
	    {
	      prev = split_interval_right (prev,
					   position - prev->position);
	      prev->plist = newi.plist;
	      if (! NULL_INTERVAL_P (i)
		  && intervals_equal (prev, i))
		merge_interval_right (prev);
	    }

	  /* We will need to update the cache here later.  */
	}
      else if (! prev && ! NILP (i->plist))
        {
	  /* Just split off a new interval at the left.
	     Since I wasn't front-sticky, the empty plist is ok.  */
	  i = split_interval_left (i, length);
        }
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    }

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  /* Otherwise just extend the interval.  */
  else
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    {
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      for (temp = i; ! NULL_INTERVAL_P (temp); temp = temp->parent)
	temp->total_length += length;
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    }
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  return tree;
}
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Lisp_Object
merge_properties_sticky (pleft, pright)
     Lisp_Object pleft, pright;
{
  register Lisp_Object props = Qnil, front = Qnil, rear = Qnil;
  
  Lisp_Object lfront = textget (pleft, Qfront_sticky);
  Lisp_Object lrear = textget (pleft, Qrear_nonsticky);
  Lisp_Object rfront = textget (pright, Qfront_sticky);
  Lisp_Object rrear = textget (pright, Qrear_nonsticky);

  register Lisp_Object tail1, tail2, sym;

  /* Go through each element of PLEFT.  */
  for (tail1 = pleft; ! NILP (tail1); tail1 = Fcdr (Fcdr (tail1)))
    {
      sym = Fcar (tail1);

      /* Sticky properties get special treatment.  */
      if (EQ (sym, Qrear_nonsticky) || EQ (sym, Qfront_sticky))
	continue;
      
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      if (CONSP (lrear) ? NILP (Fmemq (sym, lrear)) : NILP (lrear))
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	{
	  /* rear-sticky is dominant, we needn't search in PRIGHT.  */
	  
	  props = Fcons (sym, Fcons (Fcar (Fcdr (tail1)), props));
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	  if ((CONSP (lfront) || NILP (lfront))
	      && ! NILP (Fmemq (sym, lfront)))
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	    front = Fcons (sym, front);
	}
      else
	{
	  /* Go through PRIGHT, looking for sym.  */
	  for (tail2 = pright; ! NILP (tail2); tail2 = Fcdr (Fcdr (tail2)))
	    if (EQ (sym, Fcar (tail2)))
	      {
		
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		if (CONSP (rfront)
		    ? ! NILP (Fmemq (sym, rfront)) : ! NILP (rfront))
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		  {
		    /* Nonsticky at the left and sticky at the right,
		       so take the right one.  */
		    props = Fcons (sym, Fcons (Fcar (Fcdr (tail2)), props));
		    front = Fcons (sym, front);
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		    if ((CONSP (rrear) || NILP (rrear))
			&& ! NILP (Fmemq (sym, rrear)))
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		      rear = Fcons (sym, rear);
		  }
		break;
	      }
	}
    }
  /* Now let's see what to keep from PRIGHT.  */
  for (tail2 = pright; ! NILP (tail2); tail2 = Fcdr (Fcdr (tail2)))
    {
      sym = Fcar (tail2);

      /* Sticky properties get special treatment.  */
      if (EQ (sym, Qrear_nonsticky) || EQ (sym, Qfront_sticky))
	continue;

      /* If it ain't sticky, we don't take it.  */
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      if (CONSP (rfront)
	  ? NILP (Fmemq (sym, rfront)) : NILP (rfront))
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	continue;
      
      /* If sym is in PLEFT we already got it.  */
      for (tail1 = pleft; ! NILP (tail1); tail1 = Fcdr (Fcdr (tail1)))
	if (EQ (sym, Fcar (tail1)))
	  break;
      
      if (NILP (tail1))
	{
	  props = Fcons (sym, Fcons (Fcar (Fcdr (tail2)), props));
	  front = Fcons (sym, front);
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	  if ((CONSP (rrear) || NILP (rrear))
	      && ! NILP (Fmemq (sym, rrear)))
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	    rear = Fcons (sym, rear);
	}
    }
  if (! NILP (front))
    props = Fcons (Qfront_sticky, Fcons (front, props));
  if (! NILP (rear))
    props = Fcons (Qrear_nonsticky, Fcons (rear, props));
  return props;
  
}

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/* Delete an node I from its interval tree by merging its subtrees
   into one subtree which is then returned.  Caller is responsible for
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   storing the resulting subtree into its parent.  */
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static INTERVAL
delete_node (i)
     register INTERVAL i;
{
  register INTERVAL migrate, this;
  register int migrate_amt;

  if (NULL_INTERVAL_P (i->left))
    return i->right;
  if (NULL_INTERVAL_P (i->right))
    return i->left;

  migrate = i->left;
  migrate_amt = i->left->total_length;
  this = i->right;
  this->total_length += migrate_amt;
  while (! NULL_INTERVAL_P (this->left))
    {
      this = this->left;
      this->total_length += migrate_amt;
    }
  this->left = migrate;
  migrate->parent = this;

  return i->right;
}

/* Delete interval I from its tree by calling `delete_node'
   and properly connecting the resultant subtree.

   I is presumed to be empty; that is, no adjustments are made
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   for the length of I.  */
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void
delete_interval (i)
     register INTERVAL i;
{
  register INTERVAL parent;
  int amt = LENGTH (i);

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  if (amt > 0)			/* Only used on zero-length intervals now.  */
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    abort ();

  if (ROOT_INTERVAL_P (i))
    {
      Lisp_Object owner = (Lisp_Object) i->parent;
      parent = delete_node (i);
      if (! NULL_INTERVAL_P (parent))
	parent->parent = (INTERVAL) owner;

      if (XTYPE (owner) == Lisp_Buffer)
	XBUFFER (owner)->intervals = parent;
      else if (XTYPE (owner) == Lisp_String)
	XSTRING (owner)->intervals = parent;
      else
	abort ();

      return;
    }

  parent = i->parent;
  if (AM_LEFT_CHILD (i))
    {
      parent->left = delete_node (i);
      if (! NULL_INTERVAL_P (parent->left))
	parent->left->parent = parent;
    }
  else
    {
      parent->right = delete_node (i);
      if (! NULL_INTERVAL_P (parent->right))
	parent->right->parent = parent;
    }
}

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/* Find the interval in TREE corresponding to the relative position
   FROM and delete as much as possible of AMOUNT from that interval.
   Return the amount actually deleted, and if the interval was
   zeroed-out, delete that interval node from the tree.

   Note that FROM is actually origin zero, aka relative to the
   leftmost edge of tree.  This is appropriate since we call ourselves
   recursively on subtrees.
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   Do this by recursing down TREE to the interval in question, and
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   deleting the appropriate amount of text.  */
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static int
interval_deletion_adjustment (tree, from, amount)
     register INTERVAL tree;
     register int from, amount;
{
  register int relative_position = from;

  if (NULL_INTERVAL_P (tree))
    return 0;

  /* Left branch */
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  if (relative_position < LEFT_TOTAL_LENGTH (tree))
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    {
      int subtract = interval_deletion_adjustment (tree->left,
						   relative_position,
						   amount);
      tree->total_length -= subtract;
      return subtract;
    }
  /* Right branch */
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  else if (relative_position >= (TOTAL_LENGTH (tree)
				 - RIGHT_TOTAL_LENGTH (tree)))
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    {
      int subtract;

      relative_position -= (tree->total_length
			    - RIGHT_TOTAL_LENGTH (tree));
      subtract = interval_deletion_adjustment (tree->right,
					       relative_position,
					       amount);
      tree->total_length -= subtract;
      return subtract;
    }
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  /* Here -- this node.  */
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  else
    {
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      /* How much can we delete from this interval?  */
      int my_amount = ((tree->total_length 
			- RIGHT_TOTAL_LENGTH (tree))
		       - relative_position);

      if (amount > my_amount)
	amount = my_amount;

      tree->total_length -= amount;
      if (LENGTH (tree) == 0)
	delete_interval (tree);
      
      return amount;
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    }

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  /* Never reach here.  */
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}

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/* Effect the adjustments necessary to the interval tree of BUFFER to
   correspond to the deletion of LENGTH characters from that buffer
   text.  The deletion is effected at position START (which is a
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   buffer position, i.e. origin 1).  */
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static void
adjust_intervals_for_deletion (buffer, start, length)
     struct buffer *buffer;
     int start, length;
{
  register int left_to_delete = length;
  register INTERVAL tree = buffer->intervals;
  register int deleted;

  if (NULL_INTERVAL_P (tree))
    return;

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  if (start > BEG + TOTAL_LENGTH (tree)
      || start + length > BEG + TOTAL_LENGTH (tree))
    abort ();

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  if (length == TOTAL_LENGTH (tree))
    {
      buffer->intervals = NULL_INTERVAL;
      return;
    }

  if (ONLY_INTERVAL_P (tree))
    {
      tree->total_length -= length;
      return;
    }

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  if (start > BEG + TOTAL_LENGTH (tree))
    start = BEG + TOTAL_LENGTH (tree);
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  while (left_to_delete > 0)
    {
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      left_to_delete -= interval_deletion_adjustment (tree, start - 1,
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						      left_to_delete);
      tree = buffer->intervals;
      if (left_to_delete == tree->total_length)
	{
	  buffer->intervals = NULL_INTERVAL;
	  return;
	}
    }
}

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/* Make the adjustments necessary to the interval tree of BUFFER to
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   represent an addition or deletion of LENGTH characters starting
   at position START.  Addition or deletion is indicated by the sign
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   of LENGTH.  */
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INLINE void
offset_intervals (buffer, start, length)
     struct buffer *buffer;
     int start, length;
{
  if (NULL_INTERVAL_P (buffer->intervals) || length == 0)
    return;

  if (length > 0)
    adjust_intervals_for_insertion (buffer->intervals, start, length);
  else
    adjust_intervals_for_deletion (buffer, start, -length);
}
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/* Merge interval I with its lexicographic successor. The resulting
   interval is returned, and has the properties of the original
   successor.  The properties of I are lost.  I is removed from the
   interval tree.

   IMPORTANT:
   The caller must verify that this is not the last (rightmost)
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   interval.  */
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INTERVAL
merge_interval_right (i)
     register INTERVAL i;
{
  register int absorb = LENGTH (i);
  register INTERVAL successor;

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  /* Zero out this interval.  */
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  i->total_length -= absorb;

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  /* Find the succeeding interval.  */
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  if (! NULL_RIGHT_CHILD (i))      /* It's below us.  Add absorb
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				      as we descend.  */
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    {
      successor = i->right;
      while (! NULL_LEFT_CHILD (successor))
	{
	  successor->total_length += absorb;
	  successor = successor->left;
	}

      successor->total_length += absorb;
      delete_interval (i);
      return successor;
    }

  successor = i;
  while (! NULL_PARENT (successor))	   /* It's above us.  Subtract as
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					      we ascend.  */
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    {
      if (AM_LEFT_CHILD (successor))
	{
	  successor = successor->parent;
	  delete_interval (i);
	  return successor;
	}

      successor = successor->parent;
      successor->total_length -= absorb;
    }

  /* This must be the rightmost or last interval and cannot
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     be merged right.  The caller should have known.  */
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  abort ();
}

/* Merge interval I with its lexicographic predecessor. The resulting
   interval is returned, and has the properties of the original predecessor.
   The properties of I are lost.  Interval node I is removed from the tree.

   IMPORTANT:
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   The caller must verify that this is not the first (leftmost) interval.  */
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INTERVAL
merge_interval_left (i)
     register INTERVAL i;
{
  register int absorb = LENGTH (i);
  register INTERVAL predecessor;

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  /* Zero out this interval.  */
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  i->total_length -= absorb;

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  /* Find the preceding interval.  */
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  if (! NULL_LEFT_CHILD (i))	/* It's below us. Go down,
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				   adding ABSORB as we go.  */
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    {
      predecessor = i->left;
      while (! NULL_RIGHT_CHILD (predecessor))
	{
	  predecessor->total_length += absorb;
	  predecessor = predecessor->right;
	}

      predecessor->total_length += absorb;
      delete_interval (i);
      return predecessor;
    }

  predecessor = i;
  while (! NULL_PARENT (predecessor))	/* It's above us.  Go up,
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				   subtracting ABSORB.  */
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    {
      if (AM_RIGHT_CHILD (predecessor))
	{
	  predecessor = predecessor->parent;
	  delete_interval (i);
	  return predecessor;
	}

      predecessor = predecessor->parent;
      predecessor->total_length -= absorb;
    }
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  /* This must be the leftmost or first interval and cannot
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     be merged left.  The caller should have known.  */
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  abort ();
}

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/* Make an exact copy of interval tree SOURCE which descends from
   PARENT.  This is done by recursing through SOURCE, copying
   the current interval and its properties, and then adjusting
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   the pointers of the copy.  */
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static INTERVAL
reproduce_tree (source, parent)
     INTERVAL source, parent;
{
  register INTERVAL t = make_interval ();

  bcopy (source, t, INTERVAL_SIZE);
  copy_properties (source, t);
  t->parent = parent;
  if (! NULL_LEFT_CHILD (source))
    t->left = reproduce_tree (source->left, t);
  if (! NULL_RIGHT_CHILD (source))
    t->right = reproduce_tree (source->right, t);

  return t;
}

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#if 0
/* Nobody calls this.  Perhaps it's a vestige of an earlier design.  */

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/* Make a new interval of length LENGTH starting at START in the
   group of intervals INTERVALS, which is actually an interval tree.
   Returns the new interval.

   Generate an error if the new positions would overlap an existing
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   interval.  */
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static INTERVAL
make_new_interval (intervals, start, length)
     INTERVAL intervals;
     int start, length;
{
  INTERVAL slot;

  slot = find_interval (intervals, start);
  if (start + length > slot->position + LENGTH (slot))
    error ("Interval would overlap");

  if (start == slot->position && length == LENGTH (slot))
    return slot;

  if (slot->position == start)
    {
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      /* New right node.  */
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      split_interval_right (slot, length);
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      return slot;
    }

  if (slot->position + LENGTH (slot) == start + length)
    {
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      /* New left node.  */
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      split_interval_left (slot, LENGTH (slot) - length);
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      return slot;
    }

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  /* Convert interval SLOT into three intervals.  */
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  split_interval_left (slot, start - slot->position);
  split_interval_right (slot, length);
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  return slot;
}
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#endif
1224

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/* Insert the intervals of SOURCE into BUFFER at POSITION.
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   LENGTH is the length of the text in SOURCE.
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   This is used in insdel.c when inserting Lisp_Strings into the
   buffer.  The text corresponding to SOURCE is already in the buffer
   when this is called.  The intervals of new tree are a copy of those
   belonging to the string being inserted; intervals are never
   shared.
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   If the inserted text had no intervals associated, and we don't
   want to inherit the surrounding text's properties, this function
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   simply returns -- offset_intervals should handle placing the
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   text in the correct interval, depending on the sticky bits.
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   If the inserted text had properties (intervals), then there are two
   cases -- either insertion happened in the middle of some interval,
   or between two intervals.

   If the text goes into the middle of an interval, then new
   intervals are created in the middle with only the properties of
   the new text, *unless* the macro MERGE_INSERTIONS is true, in
   which case the new text has the union of its properties and those
   of the text into which it was inserted.

   If the text goes between two intervals, then if neither interval
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   had its appropriate sticky property set (front_sticky, rear_sticky),
   the new text has only its properties.  If one of the sticky properties
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   is set, then the new text "sticks" to that region and its properties
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   depend on merging as above.  If both the preceding and succeeding
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   intervals to the new text are "sticky", then the new text retains
   only its properties, as if neither sticky property were set.  Perhaps
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   we should consider merging all three sets of properties onto the new
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   text...  */
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void
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graft_intervals_into_buffer (source, position, length, buffer, inherit)
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     INTERVAL source;
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     int position, length;
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     struct buffer *buffer;
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     int inherit;
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{
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  register INTERVAL under, over, this, prev;
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  register INTERVAL tree = buffer->intervals;
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  int middle;
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  /* If the new text has no properties, it becomes part of whatever
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     interval it was inserted into.  */
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  if (NULL_INTERVAL_P (source))
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    {
      Lisp_Object buf;
      if (!inherit)
	{
	  XSET (buf, Lisp_Buffer, buffer);
	  Fset_text_properties (make_number (position),
				make_number (position + length),
				Qnil, buf);
	}
      return;
    }
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  if (NULL_INTERVAL_P (tree))
    {
      /* The inserted text constitutes the whole buffer, so
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	 simply copy over the interval structure.  */
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      if ((BUF_Z (buffer) - BUF_BEG (buffer)) == TOTAL_LENGTH (source))
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	{
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	  Lisp_Object buf;
	  XSET (buf, Lisp_Buffer, buffer);
	  buffer->intervals = reproduce_tree (source, buf);
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	  /* Explicitly free the old tree here.  */
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	  return;
	}

      /* Create an interval tree in which to place a copy
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