mxml/mxml-index.c

//
// Index support code for Mini-XML, a small XML file parsing library.
//
// https://www.msweet.org/mxml
//
// Copyright © 2003-2024 by Michael R Sweet.
//
// Licensed under Apache License v2.0.  See the file "LICENSE" for more
// information.
//

#include "mxml-private.h"


//
// Local functions...
//

static int	index_compare(mxml_index_t *ind, mxml_node_t *first, mxml_node_t *second);
static int	index_find(mxml_index_t *ind, const char *element, const char *value, mxml_node_t *node);
static void	index_sort(mxml_index_t *ind, int left, int right);


//
// 'mxmlIndexDelete()' - Delete an index.
//

void
mxmlIndexDelete(mxml_index_t *ind)	// I - Index to delete
{
  // Range check input..
  if (!ind)
    return;

  // Free memory...
  free(ind->attr);
  free(ind->nodes);
  free(ind);
}


//
// 'mxmlIndexEnum()' - Return the next node in the index.
//
// You should call @link mxmlIndexReset@ prior to using this function to get
// the first node in the index.  Nodes are returned in the sorted order of the
// index.
//

mxml_node_t *				// O - Next node or `NULL` if there is none
mxmlIndexEnum(mxml_index_t *ind)	// I - Index to enumerate
{
  // Range check input...
  if (!ind)
    return (NULL);

  // Return the next node...
  if (ind->cur_node < ind->num_nodes)
    return (ind->nodes[ind->cur_node ++]);
  else
    return (NULL);
}


//
// 'mxmlIndexFind()' - Find the next matching node.
//
// You should call @link mxmlIndexReset@ prior to using this function for
// the first time with a particular set of "element" and "value"
// strings. Passing `NULL` for both "element" and "value" is equivalent
// to calling @link mxmlIndexEnum@.
//

mxml_node_t *				// O - Node or `NULL` if none found
mxmlIndexFind(mxml_index_t *ind,	// I - Index to search
              const char   *element,	// I - Element name to find, if any
	      const char   *value)	// I - Attribute value, if any
{
  int		diff,			// Difference between names
		current,		// Current entity in search
		first,			// First entity in search
		last;			// Last entity in search


  MXML_DEBUG("mxmlIndexFind(ind=%p, element=\"%s\", value=\"%s\")\n", ind, element ? element : "(null)", value ? value : "(null)");

  // Range check input...
  if (!ind || (!ind->attr && value))
  {
    MXML_DEBUG("mxmlIndexFind: Returning NULL, ind->attr=\"%s\"...\n", ind && ind->attr ? ind->attr : "(null)");
    return (NULL);
  }

  // If both element and value are NULL, just enumerate the nodes in the index...
  if (!element && !value)
    return (mxmlIndexEnum(ind));

  // If there are no nodes in the index, return NULL...
  if (!ind->num_nodes)
  {
    MXML_DEBUG("mxmlIndexFind: Returning NULL, no nodes...\n");
    return (NULL);
  }

  // If cur_node == 0, then find the first matching node...
  if (ind->cur_node == 0)
  {
    // Find the first node using a modified binary search algorithm...
    first = 0;
    last  = ind->num_nodes - 1;

    MXML_DEBUG("mxmlIndexFind: Find first time, num_nodes=%d...\n", ind->num_nodes);

    while ((last - first) > 1)
    {
      current = (first + last) / 2;

      MXML_DEBUG("mxmlIndexFind: first=%d, last=%d, current=%d\n", first, last, current);

      if ((diff = index_find(ind, element, value, ind->nodes[current])) == 0)
      {
        // Found a match, move back to find the first...
        MXML_DEBUG("mxmlIndexFind: match.\n");

        while (current > 0 && !index_find(ind, element, value, ind->nodes[current - 1]))
	  current --;

        MXML_DEBUG("mxmlIndexFind: Returning first match=%d\n", current);

        // Return the first match and save the index to the next...
        ind->cur_node = current + 1;

	return (ind->nodes[current]);
      }
      else if (diff < 0)
      {
	last = current;
      }
      else
      {
	first = current;
      }

      MXML_DEBUG("mxmlIndexFind: diff=%d\n", diff);
    }

    // If we get this far, then we found exactly 0 or 1 matches...
    for (current = first; current <= last; current ++)
    {
      if (!index_find(ind, element, value, ind->nodes[current]))
      {
        // Found exactly one (or possibly two) match...
	MXML_DEBUG("mxmlIndexFind: Returning only match %d...\n", current);
	ind->cur_node = current + 1;

	return (ind->nodes[current]);
      }
    }

    // No matches...
    ind->cur_node = ind->num_nodes;
    MXML_DEBUG("mxmlIndexFind: Returning NULL...\n");
    return (NULL);
  }
  else if (ind->cur_node < ind->num_nodes && !index_find(ind, element, value, ind->nodes[ind->cur_node]))
  {
    // Return the next matching node...
    MXML_DEBUG("mxmlIndexFind: Returning next match %d...\n", ind->cur_node);
    return (ind->nodes[ind->cur_node ++]);
  }

  // If we get this far, then we have no matches...
  ind->cur_node = ind->num_nodes;

  MXML_DEBUG("mxmlIndexFind: Returning NULL...\n");
  return (NULL);
}


//
// 'mxmlIndexGetCount()' - Get the number of nodes in an index.
//

int					// I - Number of nodes in index
mxmlIndexGetCount(mxml_index_t *ind)	// I - Index of nodes
{
  // Range check input...
  if (!ind)
    return (0);

  // Return the number of nodes in the index...
  return (ind->num_nodes);
}


//
// 'mxmlIndexNew()' - Create a new index.
//
// The index will contain all nodes that contain the named element and/or
// attribute.  If both "element" and "attr" are `NULL`, then the index will
// contain a sorted list of the elements in the node tree.  Nodes are
// sorted by element name and optionally by attribute value if the "attr"
// argument is not NULL.
//

mxml_index_t *				// O - New index
mxmlIndexNew(mxml_node_t *node,		// I - XML node tree
             const char  *element,	// I - Element to index or `NULL` for all
             const char  *attr)		// I - Attribute to index or `NULL` for none
{
  mxml_index_t	*ind;			// New index
  mxml_node_t	*current,		// Current node in index
  		**temp;			// Temporary node pointer array


  // Range check input...
  MXML_DEBUG("mxmlIndexNew(node=%p, element=\"%s\", attr=\"%s\")\n", node, element ? element : "(null)", attr ? attr : "(null)");

  if (!node)
    return (NULL);

  // Create a new index...
  if ((ind = calloc(1, sizeof(mxml_index_t))) == NULL)
  {
    mxml_error("Unable to allocate memory for index.");
    return (NULL);
  }

  if (attr)
  {
    if ((ind->attr = strdup(attr)) == NULL)
    {
      mxml_error("Unable to allocate memory for index attribute.");
      free(ind);
      return (NULL);
    }
  }

  if (!element && !attr)
    current = node;
  else
    current = mxmlFindElement(node, node, element, attr, NULL, MXML_DESCEND);

  while (current)
  {
    if (ind->num_nodes >= ind->alloc_nodes)
    {
      if (!ind->alloc_nodes)
        temp = malloc(64 * sizeof(mxml_node_t *));
      else
        temp = realloc(ind->nodes, (ind->alloc_nodes + 64) * sizeof(mxml_node_t *));

      if (!temp)
      {
        // Unable to allocate memory for the index, so abort...
        mxml_error("Unable to allocate memory for index nodes.");
        mxmlIndexDelete(ind);
	return (NULL);
      }

      ind->nodes       = temp;
      ind->alloc_nodes += 64;
    }

    ind->nodes[ind->num_nodes ++] = current;

    current = mxmlFindElement(current, node, element, attr, NULL, MXML_DESCEND);
  }

  // Sort nodes based upon the search criteria...
  if (ind->num_nodes > 1)
    index_sort(ind, 0, ind->num_nodes - 1);

  // Return the new index...
  return (ind);
}


//
// 'mxmlIndexReset()' - Reset the enumeration/find pointer in the index and
//                      return the first node in the index.
//
// This function should be called prior to using @link mxmlIndexEnum@ or
// @link mxmlIndexFind@ for the first time.
//

mxml_node_t *				// O - First node or `NULL` if there is none
mxmlIndexReset(mxml_index_t *ind)	// I - Index to reset
{
  MXML_DEBUG("mxmlIndexReset(ind=%p)\n", ind);

  // Range check input...
  if (!ind)
    return (NULL);

  // Set the index to the first element...
  ind->cur_node = 0;

  // Return the first node...
  if (ind->num_nodes)
    return (ind->nodes[0]);
  else
    return (NULL);
}


//
// 'index_compare()' - Compare two nodes.
//

static int				// O - Result of comparison
index_compare(mxml_index_t *ind,	// I - Index
              mxml_node_t  *first,	// I - First node
              mxml_node_t  *second)	// I - Second node
{
  int	diff;				// Difference


  // Check the element name...
  if ((diff = strcmp(first->value.element.name, second->value.element.name)) != 0)
    return (diff);

  // Check the attribute value...
  if (ind->attr)
  {
    if ((diff = strcmp(mxmlElementGetAttr(first, ind->attr), mxmlElementGetAttr(second, ind->attr))) != 0)
      return (diff);
  }

  // No difference, return 0...
  return (0);
}


//
// 'index_find()' - Compare a node with index values.
//

static int				// O - Result of comparison
index_find(mxml_index_t *ind,		// I - Index
           const char   *element,	// I - Element name or `NULL`
	   const char   *value,		// I - Attribute value or `NULL`
           mxml_node_t  *node)		// I - Node
{
  int	diff;				// Difference


  // Check the element name...
  if (element)
  {
    if ((diff = strcmp(element, node->value.element.name)) != 0)
      return (diff);
  }

  // Check the attribute value...
  if (value)
  {
    if ((diff = strcmp(value, mxmlElementGetAttr(node, ind->attr))) != 0)
      return (diff);
  }

  // No difference, return 0...
  return (0);
}


//
// 'index_sort()' - Sort the nodes in the index...
//
// This function implements the classic quicksort algorithm...
//

static void
index_sort(mxml_index_t *ind,		// I - Index to sort
           int          left,		// I - Left node in partition
	   int          right)		// I - Right node in partition
{
  mxml_node_t	*pivot,			// Pivot node
		*temp;			// Swap node
  int		templ,			// Temporary left node
		tempr;			// Temporary right node


  // Loop until we have sorted all the way to the right...
  do
  {
    // Sort the pivot in the current partition...
    pivot = ind->nodes[left];

    for (templ = left, tempr = right; templ < tempr;)
    {
      // Move left while left node <= pivot node...
      while ((templ < right) && index_compare(ind, ind->nodes[templ], pivot) <= 0)
	templ ++;

      // Move right while right node > pivot node...
      while ((tempr > left) && index_compare(ind, ind->nodes[tempr], pivot) > 0)
	tempr --;

      // Swap nodes if needed...
      if (templ < tempr)
      {
	temp              = ind->nodes[templ];
	ind->nodes[templ] = ind->nodes[tempr];
	ind->nodes[tempr] = temp;
      }
    }

    // When we get here, the right (tempr) node is the new position for the pivot node...
    if (index_compare(ind, pivot, ind->nodes[tempr]) > 0)
    {
      ind->nodes[left]  = ind->nodes[tempr];
      ind->nodes[tempr] = pivot;
    }

    // Recursively sort the left partition as needed...
    if (left < (tempr - 1))
      index_sort(ind, left, tempr - 1);
  }
  while (right > (left = tempr + 1));
}