kc3-lang/kc3/libc3/facts_cursor.c

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• Hash : f990b98e
  Author : Thomas de Grivel
  Date : 2022-12-06T13:37:43
  

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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;
  }
  

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