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git-svn-id: https://tesseract-ocr.googlecode.com/svn/trunk@649 d0cd1f9f-072b-0410-8dd7-cf729c803f20
413 lines
18 KiB
C
413 lines
18 KiB
C
/* -*-C-*-
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********************************************************************************
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*
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* File: trie.h (Formerly trie.h)
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* Description: Functions to build a trie data structure.
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* Author: Mark Seaman, SW Productivity
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* Created: Fri Oct 16 14:37:00 1987
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* Modified: Fri Jul 26 11:26:34 1991 (Mark Seaman) marks@hpgrlt
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* Language: C
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* Package: N/A
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* Status: Reusable Software Component
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*
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* (c) Copyright 1987, Hewlett-Packard Company.
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** Licensed under the Apache License, Version 2.0 (the "License");
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** you may not use this file except in compliance with the License.
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** You may obtain a copy of the License at
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** http://www.apache.org/licenses/LICENSE-2.0
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** Unless required by applicable law or agreed to in writing, software
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** distributed under the License is distributed on an "AS IS" BASIS,
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** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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** See the License for the specific language governing permissions and
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** limitations under the License.
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*
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*********************************************************************************/
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#ifndef TRIE_H
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#define TRIE_H
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#include "dawg.h"
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#include "cutil.h"
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#include "genericvector.h"
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class UNICHARSET;
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// Note: if we consider either NODE_REF or EDGE_INDEX to ever exceed
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// max int32, we will need to change GenericVector to use int64 for size
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// and address indices. This does not seem to be needed immediately,
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// since currently the largest number of edges limit used by tesseract
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// (kMaxNumEdges in wordlist2dawg.cpp) is far less than max int32.
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// There are also int casts below to satisfy the WIN32 compiler that would
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// need to be changed.
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// It might be cleanest to change the types of most of the Trie/Dawg related
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// typedefs to int and restrict the casts to extracting these values from
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// the 64 bit EDGE_RECORD.
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typedef inT64 EDGE_INDEX; // index of an edge in a given node
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typedef bool *NODE_MARKER;
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typedef GenericVector<EDGE_RECORD> EDGE_VECTOR;
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struct TRIE_NODE_RECORD {
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EDGE_VECTOR forward_edges;
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EDGE_VECTOR backward_edges;
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};
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typedef GenericVector<TRIE_NODE_RECORD *> TRIE_NODES;
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namespace tesseract {
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/**
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* Concrete class for Trie data structure that allows to store a list of
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* words (extends Dawg base class) as well as dynamically add new words.
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* This class stores a vector of pointers to TRIE_NODE_RECORDs, each of
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* which has a vector of forward and backward edges.
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*/
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class Trie : public Dawg {
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public:
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enum RTLReversePolicy {
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RRP_DO_NO_REVERSE,
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RRP_REVERSE_IF_HAS_RTL,
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RRP_FORCE_REVERSE,
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};
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// Minimum number of concrete characters at the beginning of user patterns.
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static const int kSaneNumConcreteChars = 4;
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// Various unicode whitespace characters are used to denote unichar patterns,
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// (character classifier would never produce these whitespace characters as a
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// valid classification).
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static const char kAlphaPatternUnicode[];
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static const char kDigitPatternUnicode[];
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static const char kAlphanumPatternUnicode[];
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static const char kPuncPatternUnicode[];
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static const char kLowerPatternUnicode[];
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static const char kUpperPatternUnicode[];
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static const char *get_reverse_policy_name(
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RTLReversePolicy reverse_policy);
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// max_num_edges argument allows limiting the amount of memory this
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// Trie can consume (if a new word insert would cause the Trie to
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// contain more edges than max_num_edges, all the edges are cleared
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// so that new inserts can proceed).
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Trie(DawgType type, const STRING &lang, PermuterType perm,
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uinT64 max_num_edges, int unicharset_size, int debug_level) {
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init(type, lang, perm, unicharset_size, debug_level);
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num_edges_ = 0;
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max_num_edges_ = max_num_edges;
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deref_node_index_mask_ = ~letter_mask_;
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new_dawg_node(); // need to allocate node 0
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initialized_patterns_ = false;
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}
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virtual ~Trie() { nodes_.delete_data_pointers(); }
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// Reset the Trie to empty.
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void clear();
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/** Returns the edge that corresponds to the letter out of this node. */
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EDGE_REF edge_char_of(NODE_REF node_ref, UNICHAR_ID unichar_id,
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bool word_end) const {
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EDGE_RECORD *edge_ptr;
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EDGE_INDEX edge_index;
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if (!edge_char_of(node_ref, NO_EDGE, FORWARD_EDGE, word_end, unichar_id,
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&edge_ptr, &edge_index)) return NO_EDGE;
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return make_edge_ref(node_ref, edge_index);
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}
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/**
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* Fills the given NodeChildVector with all the unichar ids (and the
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* corresponding EDGE_REFs) for which there is an edge out of this node.
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*/
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void unichar_ids_of(NODE_REF node, NodeChildVector *vec) const {
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const EDGE_VECTOR &forward_edges =
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nodes_[static_cast<int>(node)]->forward_edges;
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for (int i = 0; i < forward_edges.size(); ++i) {
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vec->push_back(NodeChild(unichar_id_from_edge_rec(forward_edges[i]),
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make_edge_ref(node, i)));
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}
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}
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/**
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* Returns the next node visited by following the edge
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* indicated by the given EDGE_REF.
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*/
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NODE_REF next_node(EDGE_REF edge_ref) const {
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if (edge_ref == NO_EDGE || num_edges_ == 0) return NO_EDGE;
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return next_node_from_edge_rec(*deref_edge_ref(edge_ref));
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}
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/**
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* Returns true if the edge indicated by the given EDGE_REF
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* marks the end of a word.
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*/
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bool end_of_word(EDGE_REF edge_ref) const {
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if (edge_ref == NO_EDGE || num_edges_ == 0) return false;
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return end_of_word_from_edge_rec(*deref_edge_ref(edge_ref));
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}
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/** Returns UNICHAR_ID stored in the edge indicated by the given EDGE_REF. */
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UNICHAR_ID edge_letter(EDGE_REF edge_ref) const {
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if (edge_ref == NO_EDGE || num_edges_ == 0) return INVALID_UNICHAR_ID;
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return unichar_id_from_edge_rec(*deref_edge_ref(edge_ref));
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}
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// Prints the contents of the node indicated by the given NODE_REF.
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// At most max_num_edges will be printed.
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void print_node(NODE_REF node, int max_num_edges) const;
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// Writes edges from nodes_ to an EDGE_ARRAY and creates a SquishedDawg.
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// Eliminates redundant edges and returns the pointer to the SquishedDawg.
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// Note: the caller is responsible for deallocating memory associated
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// with the returned SquishedDawg pointer.
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SquishedDawg *trie_to_dawg();
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// Inserts the list of words from the given file into the Trie.
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// If reverse is true, calls WERD_CHOICE::reverse_unichar_ids_if_rtl()
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// on each word before inserting it into the Trie.
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bool read_word_list(const char *filename,
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const UNICHARSET &unicharset,
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Trie::RTLReversePolicy reverse);
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// Inserts the list of patterns from the given file into the Trie.
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// The pattern list file should contain one pattern per line in UTF-8 format.
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//
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// Each pattern can contain any non-whitespace characters, however only the
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// patterns that contain characters from the unicharset of the corresponding
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// language will be useful.
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// The only meta character is '\'. To be used in a pattern as an ordinary
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// string it should be escaped with '\' (e.g. string "C:\Documents" should
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// be written in the patterns file as "C:\\Documents").
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// This function supports a very limited regular expression syntax. One can
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// express a character, a certain character class and a number of times the
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// entity should be repeated in the pattern.
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//
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// To denote a character class use one of:
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// \c - unichar for which UNICHARSET::get_isalpha() is true (character)
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// \d - unichar for which UNICHARSET::get_isdigit() is true
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// \n - unichar for which UNICHARSET::get_isdigit() and
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// UNICHARSET::isalpha() are true
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// \p - unichar for which UNICHARSET::get_ispunct() is true
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// \a - unichar for which UNICHARSET::get_islower() is true
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// \A - unichar for which UNICHARSET::get_isupper() is true
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//
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// \* could be specified after each character or pattern to indicate that
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// the character/pattern can be repeated any number of times before the next
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// character/pattern occurs.
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//
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// Examples:
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// 1-8\d\d-GOOG-411 will be expanded to strings:
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// 1-800-GOOG-411, 1-801-GOOG-411, ... 1-899-GOOG-411.
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//
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// http://www.\n\*.com will be expanded to strings like:
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// http://www.a.com http://www.a123.com ... http://www.ABCDefgHIJKLMNop.com
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//
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// Note: In choosing which patterns to include please be aware of the fact
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// providing very generic patterns will make tesseract run slower.
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// For example \n\* at the beginning of the pattern will make Tesseract
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// consider all the combinations of proposed character choices for each
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// of the segmentations, which will be unacceptably slow.
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// Because of potential problems with speed that could be difficult to
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// identify, each user pattern has to have at least kSaneNumConcreteChars
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// concrete characters from the unicharset at the beginning.
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bool read_pattern_list(const char *filename, const UNICHARSET &unicharset);
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// Initializes the values of *_pattern_ unichar ids.
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// This function should be called before calling read_pattern_list().
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void initialize_patterns(UNICHARSET *unicharset);
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// Fills in the given unichar id vector with the unichar ids that represent
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// the patterns of the character classes of the given unichar_id.
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void unichar_id_to_patterns(UNICHAR_ID unichar_id,
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const UNICHARSET &unicharset,
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GenericVector<UNICHAR_ID> *vec) const;
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// Returns the given EDGE_REF if the EDGE_RECORD that it points to has
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// a self loop and the given unichar_id matches the unichar_id stored in the
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// EDGE_RECORD, returns NO_EDGE otherwise.
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virtual EDGE_REF pattern_loop_edge(EDGE_REF edge_ref,
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UNICHAR_ID unichar_id,
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bool word_end) const {
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if (edge_ref == NO_EDGE) return NO_EDGE;
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EDGE_RECORD *edge_rec = deref_edge_ref(edge_ref);
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return (marker_flag_from_edge_rec(*edge_rec) &&
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unichar_id == unichar_id_from_edge_rec(*edge_rec) &&
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word_end == end_of_word_from_edge_rec(*edge_rec)) ?
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edge_ref : NO_EDGE;
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}
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// Adds a word to the Trie (creates the necessary nodes and edges).
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//
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// If repetitions vector is not NULL, each entry in the vector indicates
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// whether the unichar id with the corresponding index in the word is allowed
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// to repeat an unlimited number of times. For each entry that is true, MARKER
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// flag of the corresponding edge created for this unichar id is set to true).
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//
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// Return true if add succeeded, false otherwise (e.g. when a word contained
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// an invalid unichar id or the trie was getting too large and was cleared).
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bool add_word_to_dawg(const WERD_CHOICE &word,
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const GenericVector<bool> *repetitions);
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bool add_word_to_dawg(const WERD_CHOICE &word) {
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return add_word_to_dawg(word, NULL);
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}
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protected:
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// The structure of an EDGE_REF for Trie edges is as follows:
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// [LETTER_START_BIT, flag_start_bit_):
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// edge index in *_edges in a TRIE_NODE_RECORD
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// [flag_start_bit, 30th bit]: node index in nodes (TRIE_NODES vector)
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//
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// With this arrangement there are enough bits to represent edge indices
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// (each node can have at most unicharset_size_ forward edges and
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// the position of flag_start_bit is set to be log2(unicharset_size_)).
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// It is also possible to accommodate a maximum number of nodes that is at
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// least as large as that of the SquishedDawg representation (in SquishedDawg
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// each EDGE_RECORD has 32-(flag_start_bit+NUM_FLAG_BITS) bits to represent
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// the next node index).
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//
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// Returns the pointer to EDGE_RECORD after decoding the location
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// of the edge from the information in the given EDGE_REF.
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// This function assumes that EDGE_REF holds valid node/edge indices.
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inline EDGE_RECORD *deref_edge_ref(EDGE_REF edge_ref) const {
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int edge_index = static_cast<int>(
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(edge_ref & letter_mask_) >> LETTER_START_BIT);
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int node_index = static_cast<int>(
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(edge_ref & deref_node_index_mask_) >> flag_start_bit_);
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TRIE_NODE_RECORD *node_rec = nodes_[node_index];
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return &(node_rec->forward_edges[edge_index]);
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}
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/** Constructs EDGE_REF from the given node_index and edge_index. */
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inline EDGE_REF make_edge_ref(NODE_REF node_index,
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EDGE_INDEX edge_index) const {
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return ((node_index << flag_start_bit_) |
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(edge_index << LETTER_START_BIT));
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}
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/** Sets up this edge record to the requested values. */
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inline void link_edge(EDGE_RECORD *edge, NODE_REF nxt, bool repeats,
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int direction, bool word_end, UNICHAR_ID unichar_id) {
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EDGE_RECORD flags = 0;
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if (repeats) flags |= MARKER_FLAG;
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if (word_end) flags |= WERD_END_FLAG;
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if (direction == BACKWARD_EDGE) flags |= DIRECTION_FLAG;
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*edge = ((nxt << next_node_start_bit_) |
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(static_cast<EDGE_RECORD>(flags) << flag_start_bit_) |
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(static_cast<EDGE_RECORD>(unichar_id) << LETTER_START_BIT));
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}
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/** Prints the given EDGE_RECORD. */
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inline void print_edge_rec(const EDGE_RECORD &edge_rec) const {
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tprintf("|" REFFORMAT "|%s%s%s|%d|", next_node_from_edge_rec(edge_rec),
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marker_flag_from_edge_rec(edge_rec) ? "R," : "",
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(direction_from_edge_rec(edge_rec) == FORWARD_EDGE) ? "F" : "B",
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end_of_word_from_edge_rec(edge_rec) ? ",E" : "",
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unichar_id_from_edge_rec(edge_rec));
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}
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// Returns true if the next node in recorded the given EDGE_RECORD
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// has exactly one forward edge.
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inline bool can_be_eliminated(const EDGE_RECORD &edge_rec) {
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NODE_REF node_ref = next_node_from_edge_rec(edge_rec);
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return (node_ref != NO_EDGE &&
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nodes_[static_cast<int>(node_ref)]->forward_edges.size() == 1);
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}
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// Prints the contents of the Trie.
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// At most max_num_edges will be printed for each node.
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void print_all(const char* msg, int max_num_edges) {
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tprintf("\n__________________________\n%s\n", msg);
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for (int i = 0; i < nodes_.size(); ++i) print_node(i, max_num_edges);
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tprintf("__________________________\n");
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}
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// Finds the edge with the given direction, word_end and unichar_id
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// in the node indicated by node_ref. Fills in the pointer to the
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// EDGE_RECORD and the index of the edge with the the values
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// corresponding to the edge found. Returns true if an edge was found.
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bool edge_char_of(NODE_REF node_ref, NODE_REF next_node,
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int direction, bool word_end, UNICHAR_ID unichar_id,
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EDGE_RECORD **edge_ptr, EDGE_INDEX *edge_index) const;
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// Adds an single edge linkage between node1 and node2 in the direction
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// indicated by direction argument.
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bool add_edge_linkage(NODE_REF node1, NODE_REF node2, bool repeats,
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int direction, bool word_end,
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UNICHAR_ID unichar_id);
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// Adds forward edge linkage from node1 to node2 and the corresponding
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// backward edge linkage in the other direction.
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bool add_new_edge(NODE_REF node1, NODE_REF node2,
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bool repeats, bool word_end, UNICHAR_ID unichar_id) {
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return (add_edge_linkage(node1, node2, repeats, FORWARD_EDGE,
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word_end, unichar_id) &&
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add_edge_linkage(node2, node1, repeats, BACKWARD_EDGE,
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word_end, unichar_id));
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}
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// Sets the word ending flags in an already existing edge pair.
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// Returns true on success.
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void add_word_ending(EDGE_RECORD *edge,
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NODE_REF the_next_node,
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bool repeats,
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UNICHAR_ID unichar_id);
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// Allocates space for a new node in the Trie.
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NODE_REF new_dawg_node();
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// Removes a single edge linkage to between node1 and node2 in the
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// direction indicated by direction argument.
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void remove_edge_linkage(NODE_REF node1, NODE_REF node2, int direction,
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bool word_end, UNICHAR_ID unichar_id);
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// Removes forward edge linkage from node1 to node2 and the corresponding
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// backward edge linkage in the other direction.
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void remove_edge(NODE_REF node1, NODE_REF node2,
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bool word_end, UNICHAR_ID unichar_id) {
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remove_edge_linkage(node1, node2, FORWARD_EDGE, word_end, unichar_id);
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remove_edge_linkage(node2, node1, BACKWARD_EDGE, word_end, unichar_id);
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}
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// Compares edge1 and edge2 in the given node to see if they point to two
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// next nodes that could be collapsed. If they do, performs the reduction
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// and returns true.
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bool eliminate_redundant_edges(NODE_REF node, const EDGE_RECORD &edge1,
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const EDGE_RECORD &edge2);
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// Assuming that edge_index indicates the first edge in a group of edges
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// in this node with a particular letter value, looks through these edges
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// to see if any of them can be collapsed. If so does it. Returns to the
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// caller when all edges with this letter have been reduced.
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// Returns true if further reduction is possible with this same letter.
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bool reduce_lettered_edges(EDGE_INDEX edge_index,
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UNICHAR_ID unichar_id,
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NODE_REF node,
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const EDGE_VECTOR &backward_edges,
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NODE_MARKER reduced_nodes);
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/**
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* Order num_edges of consequtive EDGE_RECORDS in the given EDGE_VECTOR in
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* increasing order of unichar ids. This function is normally called
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* for all edges in a single node, and since number of edges in each node
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* is usually quite small, selection sort is used.
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*/
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void sort_edges(EDGE_VECTOR *edges);
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/** Eliminates any redundant edges from this node in the Trie. */
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void reduce_node_input(NODE_REF node, NODE_MARKER reduced_nodes);
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// Returns the pattern unichar id for the given character class code.
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UNICHAR_ID character_class_to_pattern(char ch);
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// Member variables
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TRIE_NODES nodes_; // vector of nodes in the Trie
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uinT64 num_edges_; // sum of all edges (forward and backward)
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uinT64 max_num_edges_; // maximum number of edges allowed
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uinT64 deref_direction_mask_; // mask for EDGE_REF to extract direction
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uinT64 deref_node_index_mask_; // mask for EDGE_REF to extract node index
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// Variables for translating character class codes denoted in user patterns
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// file to the unichar ids used to represent them in a Trie.
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bool initialized_patterns_;
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UNICHAR_ID alpha_pattern_;
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UNICHAR_ID digit_pattern_;
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UNICHAR_ID alphanum_pattern_;
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UNICHAR_ID punc_pattern_;
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UNICHAR_ID lower_pattern_;
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UNICHAR_ID upper_pattern_;
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};
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} // namespace tesseract
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#endif
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