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kc3-lang/kc3/libc3/facts_cursor.c

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  • libc3/facts_cursor.c 
  • /* c3
 * Copyright 2022 kmx.io <contact@kmx.io>
 *
 * Permission is hereby granted to use this software excepted
 * on Apple computers granted the above copyright notice and
 * this permission paragraph are included in all copies and
 * substantial portions of this software.
 *
 * THIS SOFTWARE IS PROVIDED "AS-IS" WITHOUT ANY GUARANTEE OF
 * PURPOSE AND PERFORMANCE. IN NO EVENT WHATSOEVER SHALL THE
 * AUTHOR BE CONSIDERED LIABLE FOR THE USE AND PERFORMANCE OF
 * THIS SOFTWARE.
 */
#include <assert.h>
#include <err.h>
#include <stdlib.h>
#include "facts_cursor.h"
#include "skiplist__fact.h"
#include "skiplist_node__fact.h"
#include "tag.h"

s_facts_cursor * facts_cursor_init (s_facts_cursor *cursor,
                                    s_skiplist__fact *index,
                                    s_fact *start,
                                    s_fact *end)
{
  s_skiplist_node__fact *pred;
  assert(cursor);
  assert(index);
  pred = skiplist_pred__fact(index, start);
  assert(pred);
  cursor->index = index;
  cursor->node = SKIPLIST_NODE_NEXT__fact(pred, 0);
  skiplist_node_delete__fact(pred);
  if (start)
    cursor->start = *start;
  else {
    cursor->start.subject   = TAG_FIRST;
    cursor->start.predicate = TAG_FIRST;
    cursor->start.object    = TAG_FIRST;
  }
  if (end)
    cursor->end = *end;
  else {
    cursor->end.subject   = TAG_LAST;
    cursor->end.predicate = TAG_LAST;
    cursor->end.object    = TAG_LAST;
  }
  cursor->var_subject   = NULL;
  cursor->var_predicate = NULL;
  cursor->var_object    = NULL;
  return cursor;
}

s_fact * facts_cursor_next (s_facts_cursor *cursor)
{
  assert(cursor);
  if (cursor->node) {
    cursor->node = SKIPLIST_NODE_NEXT__fact(cursor->node, 0);
    if (cursor->node &&
        cursor->index->compare(&cursor->end, cursor->node->fact) < 0)
      cursor->node = NULL;
  }
  if (cursor->node) {
    s_fact *fact = cursor->node->fact;
    if (cursor->var_subject)
      cursor->var_subject->data.var = fact->subject;
    if (cursor->var_predicate)
      cursor->var_predicate->data.var = fact->predicate;
    if (cursor->var_object)
      cursor->var_object->data.var = fact->object;
    return fact;
  }
  if (cursor->var_subject)
    tag_init_var(cursor->var_subject);
  if (cursor->var_predicate)
    tag_init_var(cursor->var_predicate);
  if (cursor->var_object)
    tag_init_var(cursor->var_object);
  return NULL;
}