tesseract/dict/trie.cpp

/* -*-C-*-
 ********************************************************************************
 *
 * File:        trie.c  (Formerly trie.c)
 * Description:  Functions to build a trie data structure.
 * Author:       Mark Seaman, OCR Technology
 * Created:      Fri Oct 16 14:37:00 1987
 * Modified:     Fri Jul 26 12:18:10 1991 (Mark Seaman) marks@hpgrlt
 * Language:     C
 * Package:      N/A
 * Status:       Reusable Software Component
 *
 * (c) Copyright 1987, Hewlett-Packard Company.
 ** Licensed under the Apache License, Version 2.0 (the "License");
 ** you may not use this file except in compliance with the License.
 ** You may obtain a copy of the License at
 ** http://www.apache.org/licenses/LICENSE-2.0
 ** Unless required by applicable law or agreed to in writing, software
 ** distributed under the License is distributed on an "AS IS" BASIS,
 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 ** See the License for the specific language governing permissions and
 ** limitations under the License.
 *
 *********************************************************************************/
/*----------------------------------------------------------------------
              I n c l u d e s
----------------------------------------------------------------------*/
#include "trie.h"
#include "callcpp.h"

#ifdef __UNIX__
#include <assert.h>
#endif
#include <stdio.h>

/*----------------------------------------------------------------------
              V a r i a b l e s
----------------------------------------------------------------------*/
static INT32 move_counter = 0;
static INT32 new_counter  = 0;
static INT32 edge_counter = 0;

/*----------------------------------------------------------------------
              F u n c t i o n s
----------------------------------------------------------------------*/
/**********************************************************************
 * add_edge_linkage
 *
 * Add a single edge linkage to between the two nodes.  This function
 * can be used to add either forward or backward links.
 **********************************************************************/
void add_edge_linkage(EDGE_ARRAY dawg,
                      NODE_REF node1,
                      NODE_REF node2,
                      INT32 direction,
                      char character,
                      INT32 word_end) {
  EDGE_REF edge1 = node1;
  EDGE_REF edge2;
  INT32      num_edges = edges_in_node (dawg, node1);
  INT32      last_one;

  word_end  = (word_end ? WERD_END_FLAG : 0);

  if (num_edges == 0) {          /* No edges yet */
    direction = ((direction == FORWARD_EDGE) ? DIRECTION_FLAG : 0);
    link_edge  (dawg, edge1, node2,  character,
      LAST_FLAG | direction | word_end);
  }
  else {
                                 /* Forward links */
    if (direction == FORWARD_EDGE) {
      last_one = (forward_edge (dawg, edge1) ? 0 : LAST_FLAG);
      if (debug)
        cprintf ("moving edges (nodes = %ld, %dl, num = %ld)\n",
          edge1, edge1+1, num_edges);
      copy_edges (dawg, edge1, edge1+1, num_edges);
      link_edge  (dawg, edge1, node2,  character,
        last_one | DIRECTION_FLAG | word_end);
    }
    else {                       /* Backward links */

      if (forward_edge (dawg, edge1))
        edge_loop(dawg, edge1);

                                 /* Existing back edges */
      if (backward_edge (dawg,edge1)) {
        num_edges = 0;
        edge2 = edge1;
        do { num_edges++; }
        edge_loop(dawg, edge2);

        if (debug)
          cprintf ("moving edges (nodes = %ld, %ld, num = %ld)\n",
            edge1, edge1+1, num_edges);
        copy_edges (dawg, edge1, edge1+1, num_edges);
        link_edge(dawg, edge1, node2, character, word_end);
      }
      else {                     /* First back edge */
        link_edge  (dawg, edge1, node2,  character,
          LAST_FLAG | word_end);
      }
    }
  }
}


/**********************************************************************
 * add_new_edge
 *
 * Add an edge between two nodes in the DAWG.  Link the nodes both ways.
 **********************************************************************/
void add_new_edge(EDGE_ARRAY dawg,
                  NODE_REF *node1,
                  NODE_REF *node2,
                  char character,
                  INT32 word_end,
                  INT32 max_num_edges,
                  INT32 reserved_edges) {
  int direction;

  if (debug)
    cprintf ("add_new_edge (nodes = %ld, %ld, ch = '%c', end = %d)\n",
      *node1, *node2,  character, word_end);
  edge_counter++;

  move_node_if_needed(dawg, *node1, max_num_edges, reserved_edges);
  move_node_if_needed(dawg, *node2, max_num_edges, reserved_edges);

  direction = (int) FORWARD_EDGE;

  add_edge_linkage(dawg, *node1, *node2, direction, character, word_end);

  direction = (int) BACKWARD_EDGE;
  add_edge_linkage(dawg, *node2, *node1, direction, character, word_end);
}


/**********************************************************************
 * add_word_to_dawg
 *
 * Add in a word by creating the necessary nodes and edges.
 **********************************************************************/
void add_word_to_dawg(EDGE_ARRAY dawg,
                      char *string,
                      INT32 max_num_edges,
                      INT32 reserved_edges) {
  EDGE_REF    edge;
  NODE_REF    last_node = 0;
  NODE_REF    the_next_node;
  INT32         i;
  INT32         still_finding_chars = TRUE;
  INT32         word_end = FALSE;

  for (i=0; i<strlen(string)-1; i++) {
    if (still_finding_chars) {
      edge = edge_char_of (dawg, last_node, string[i], word_end);
      if (debug) cprintf ("exploring edge = %d\n", edge);
      if (edge == NO_EDGE)
        still_finding_chars = FALSE;
      else
      if (next_node (dawg, edge) == 0) {
        word_end = TRUE;
        still_finding_chars = FALSE;
        if (! case_sensative) string[i] = tolower (string[i]);
        remove_edge (dawg, last_node, 0, string[i], word_end);
      }
      else {
        last_node = next_node (dawg, edge);
      }
    }

    if (! still_finding_chars) {
      the_next_node = new_dawg_node (dawg, DEFAULT_NODE_SIZE, max_num_edges, reserved_edges);
      if (edges_in_node (dawg, last_node) + last_node == the_next_node) {
        cprintf ("Node collision at %d\n", the_next_node);
        the_next_node = new_dawg_node (dawg, DEFAULT_NODE_SIZE, max_num_edges, reserved_edges);
      }
      if (! case_sensative) string[i] = tolower (string[i]);
      add_new_edge (dawg, &last_node, &the_next_node,
        string[i], word_end, max_num_edges, reserved_edges);
      word_end = FALSE;
      if (debug)
        cprintf ("adding node = %ld\n", the_next_node);
      last_node = the_next_node;
    }
  }

  the_next_node = 0;
  if (! case_sensative) string[i] = tolower (string[i]);
  add_new_edge (dawg, &last_node, &the_next_node,
    string[i], TRUE, max_num_edges, reserved_edges);

  if (edges_in_node (dawg, 0) > reserved_edges) {
    cprintf ("error: Not enough room in root node, %d\n",
      edges_in_node (dawg, 0));
    exit (1);
  }
}


/**********************************************************************
 * initialize_dawg
 *
 * Initialize the DAWG data structure for further used.  Reset each of
 * the edge cells to NO_EDGE.
 **********************************************************************/
void initialize_dawg(EDGE_ARRAY dawg, INT32 max_num_edges) {
  INT32 x;


   //changed by jetsoft
  // these values were not getting changes.

  move_counter = 0;
  new_counter  = 0;
  edge_counter = 0;
  // end jetsoft

  clear_all_edges(dawg, x, max_num_edges);
}


/**********************************************************************
 * move_node
 *
 * Move the location in the edge array of this node in the DAWG.
 **********************************************************************/
NODE_REF move_node(EDGE_ARRAY dawg,
                   NODE_REF node,
                   INT32 max_num_edges,
                   INT32 reserved_edges) {
  NODE_REF   this_new_node;
  EDGE_REF   edge;
  INT32        num_edges = edges_in_node (dawg, node);

  if (debug)
    print_dawg_node(dawg, node);

  this_new_node = new_dawg_node (dawg, num_edges + EDGE_NUM_MARGIN, max_num_edges, reserved_edges);

  if (debug)
    cprintf ("move_node  (from = %ld, to = %ld, num = %ld)\n",
      node, this_new_node, num_edges);

  move_edges(dawg, node, this_new_node, num_edges);

  if (debug)
    print_dawg_node(dawg, this_new_node);

  edge = this_new_node;
  if (forward_edge (dawg, edge)) {
    do {
      relocate_edge (dawg, next_node (dawg, edge), node, this_new_node);
    } edge_loop (dawg, edge);
  }
  if (backward_edge (dawg, edge)) {
    do {
      relocate_edge (dawg, next_node (dawg, edge), node, this_new_node);
    } edge_loop (dawg, edge);
  }

  move_counter++;
  return (this_new_node);
}


/**********************************************************************
 * new_dawg_node
 *
 * Create a space within the DAWG data structure to house a node that
 * consists of the requested number of edges.
 **********************************************************************/
NODE_REF new_dawg_node(EDGE_ARRAY dawg,
                       INT32 num_edges,
                       INT32 max_num_edges,
                       INT32 reserved_edges) {
  INT32        i;
  INT32        n;
  INT32        edge_index;
  INT32        edge_collision;
  /* Try several times */
  for (i=0; i<NUM_PLACEMENT_ATTEMPTS; i++) {

    edge_index = reserved_edges +
      long_rand (max_num_edges - MAX_WERD_LENGTH - reserved_edges);
    edge_collision = FALSE;
    /* Find N adjacent slots */
    for  (n=0; n<num_edges && !edge_collision; n++) {
      if (edge_occupied (dawg, edge_index + n))
        edge_collision = TRUE;
    }

    if (! edge_collision) {
      new_counter++;
      //?			max_new_attempts = max (max_new_attempts, i);
      return (edge_index);
    }
  }

  cprintf ("DAWG Table is too full, nodes = %ld, edges = %ld, moves %ld\n",
    new_counter, edge_counter, move_counter);
  exit (1);
  return 0;
}


/**********************************************************************
 * read_word_list
 *
 * Read the requested file (containing a list of words) and add all
 * the words to the DAWG.
 **********************************************************************/
void read_word_list(const char *filename,
                    EDGE_ARRAY dawg,
                    INT32 max_num_edges,
                    INT32 reserved_edges) {
  FILE       *word_file;
  char       string [CHARS_PER_LINE];

  word_file = open_file (filename, "r");

  initialize_dawg(dawg, max_num_edges);

  while (fgets (string, CHARS_PER_LINE, word_file) != NULL) {
    string [strlen (string) - 1] = (char) 0;
    if (strlen (string)) {
      add_word_to_dawg(dawg, string, max_num_edges, reserved_edges);

      if (! word_in_dawg (dawg, string)) {
        cprintf ("error: word not in DAWG after adding it '%s'\n", string);
        return;
      }
    }
  }
  fclose(word_file);
}


/**********************************************************************
 * relocate_edge
 *
 * The location of a node has moved, so an edge entry in another node
 * must be changed.  Change the value of this edge entry to match the
 * new location of the node.
 **********************************************************************/
void relocate_edge(EDGE_ARRAY dawg,
                   NODE_REF node,
                   NODE_REF old_node,
                   NODE_REF new_node) {
  EDGE_REF   edge;

  if (debug) cprintf ("relocate (%ld, %ld ==> %ld)\n", node, old_node, new_node);

  edge = node;
  if (forward_edge (dawg, edge)) {
    do {
      if (next_node (dawg, edge) == old_node) {
        if (debug)
          cprintf ("forward assign (%ld, %ld ==> %ld)\n", edge, old_node, new_node);

        set_next_edge(dawg, edge, new_node);
      }
    } edge_loop (dawg, edge);
  }

  if (backward_edge (dawg, edge)) {
    do {
      if (next_node (dawg, edge) == old_node) {
        if (debug)
          cprintf ("backward assign (%ld, %ld ==> %ld)\n", edge, old_node, new_node);

        set_next_edge(dawg, edge, new_node);
      }
    }
    edge_loop(dawg, edge);
  }
}


/**********************************************************************
 * remove_edge
 *
 * Add a single edge linkage to between the two nodes.  This function
 * can be used to add either forward or backward links.
 **********************************************************************/
void remove_edge(EDGE_ARRAY dawg,
                 NODE_REF node1,
                 NODE_REF node2,
                 char character,
                 INT32 word_end) {
  remove_edge_linkage(dawg, node1, node2, FORWARD_EDGE, character, word_end);

  remove_edge_linkage(dawg, node2, node1, BACKWARD_EDGE, character, word_end);
}


/**********************************************************************
 * remove_edge_linkage
 *
 * Remove this edge reference from this node.  Move the edge entries in
 * this node to fill the gap.
 **********************************************************************/
void remove_edge_linkage(EDGE_ARRAY dawg,
                         NODE_REF node,
                         NODE_REF next,
                         INT32 direction,
                         char character,
                         INT32 word_end) {
  INT32      forward_edges;
  INT32      num_edges;
  INT32      e = node;
  INT32      last_flag;

  forward_edges = num_forward_edges (dawg, node);
  num_edges = edges_in_node (dawg, node);

  for (e=node; e<node+num_edges; e++) {
    /* Is this the edge*/
    if ((edge_letter (dawg, e) == character) &&
      ((direction == FORWARD_EDGE) ?
      forward_edge(dawg,e) : backward_edge(dawg,e)) &&
      (next_node (dawg, e) == next) &&
    (word_end ? end_of_word(dawg,e) : (! end_of_word(dawg,e)))) {

      if (debug)
        cprintf ("remove (edge = %ld, character is '%c')\n",
          e, edge_letter (dawg, e));

      /* Delete the slot */
      last_flag = last_edge (dawg, e);
      set_empty_edge(dawg, e);
      move_edges (dawg, e+1, e, num_edges+node-e-1);
      /* Restore 'last' flag */
      if (direction == FORWARD_EDGE) {
        if ((forward_edges - 1) &&
        (forward_edges - 1 == e - node)) {
          set_last_flag (dawg, e - 1);
        }
      }
      else {
        if ((num_edges - forward_edges - 1) &&
        (num_edges - 1 == e - node)) {
          set_last_flag (dawg, e - 1);
        }
      }
      if (debug)
        print_dawg_node(dawg, node);
      return;
    }
  }
  cprintf ("error: Could not find the edge to remove, %d\n", next);
  print_dawg_node(dawg, node);
  exit (1);
}


/**********************************************************************
 * room_in_node
 *
 * Check to see if there is enough room left in this node for one more
 * edge link.  This may be a forward or backward link.
 **********************************************************************/
INT32 room_in_node(EDGE_ARRAY dawg, NODE_REF node) {
  EDGE_REF   edge = node;

  if (edge_occupied (dawg, edge + edges_in_node (dawg, node))) {
    return (FALSE);
  }
  else {
    return (TRUE);
  }
}