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439 lines
16 KiB
C++
439 lines
16 KiB
C++
///////////////////////////////////////////////////////////////////////
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// File: unicharcompress.cpp
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// Description: Unicode re-encoding using a sequence of smaller numbers in
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// place of a single large code for CJK, similarly for Indic,
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// and dissection of ligatures for other scripts.
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// Author: Ray Smith
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// Created: Wed Mar 04 14:45:01 PST 2015
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//
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// (C) Copyright 2015, Google Inc.
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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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#include "unicharcompress.h"
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#include "tprintf.h"
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namespace tesseract {
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// String used to represent the null_id in direct_set.
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const char* kNullChar = "<nul>";
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// Local struct used only for processing the radical-stroke table.
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struct RadicalStroke {
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RadicalStroke() : num_strokes(0) {}
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RadicalStroke(const STRING& r, int s) : radical(r), num_strokes(s) {}
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bool operator==(const RadicalStroke& other) const {
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return radical == other.radical && num_strokes == other.num_strokes;
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}
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// The radical is encoded as a string because its format is of an int with
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// an optional ' mark to indicate a simplified shape. To treat these as
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// distinct, we use a string and a UNICHARSET to do the integer mapping.
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STRING radical;
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// The number of strokes we treat as dense and just take the face value from
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// the table.
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int num_strokes;
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};
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// Hash functor for RadicalStroke.
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struct RadicalStrokedHash {
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size_t operator()(const RadicalStroke& rs) const {
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size_t result = rs.num_strokes;
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for (int i = 0; i < rs.radical.length(); ++i) {
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result ^= rs.radical[i] << (6 * i + 8);
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}
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return result;
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}
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};
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// A hash map to convert unicodes to radical,stroke pair.
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typedef std::unordered_map<int, RadicalStroke> RSMap;
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// A hash map to count occurrences of each radical,stroke pair.
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typedef std::unordered_map<RadicalStroke, int, RadicalStrokedHash> RSCounts;
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// Helper function builds the RSMap from the radical-stroke file, which has
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// already been read into a STRING. Returns false on error.
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// The radical_stroke_table is non-const because it gets split and the caller
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// is unlikely to want to use it again.
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static bool DecodeRadicalStrokeTable(STRING* radical_stroke_table,
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RSMap* radical_map) {
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GenericVector<STRING> lines;
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radical_stroke_table->split('\n', &lines);
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for (int i = 0; i < lines.size(); ++i) {
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if (lines[i].length() == 0 || lines[i][0] == '#') continue;
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int unicode, radical, strokes;
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STRING str_radical;
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if (sscanf(lines[i].string(), "%x\t%d.%d", &unicode, &radical, &strokes) ==
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3) {
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str_radical.add_str_int("", radical);
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} else if (sscanf(lines[i].string(), "%x\t%d'.%d", &unicode, &radical,
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&strokes) == 3) {
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str_radical.add_str_int("'", radical);
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} else {
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tprintf("Invalid format in radical stroke table at line %d: %s\n", i,
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lines[i].string());
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return false;
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}
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(*radical_map)[unicode] = RadicalStroke(str_radical, strokes);
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}
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return true;
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}
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UnicharCompress::UnicharCompress() : code_range_(0) {}
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UnicharCompress::UnicharCompress(const UnicharCompress& src) { *this = src; }
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UnicharCompress::~UnicharCompress() { Cleanup(); }
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UnicharCompress& UnicharCompress::operator=(const UnicharCompress& src) {
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Cleanup();
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encoder_ = src.encoder_;
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code_range_ = src.code_range_;
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SetupDecoder();
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return *this;
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}
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// Computes the encoding for the given unicharset. It is a requirement that
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// the file training/langdata/radical-stroke.txt have been read into the
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// input string radical_stroke_table.
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// Returns false if the encoding cannot be constructed.
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bool UnicharCompress::ComputeEncoding(const UNICHARSET& unicharset, int null_id,
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STRING* radical_stroke_table) {
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RSMap radical_map;
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if (!DecodeRadicalStrokeTable(radical_stroke_table, &radical_map))
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return false;
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encoder_.clear();
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UNICHARSET direct_set;
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UNICHARSET radicals;
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// To avoid unused codes, clear the special codes from the unicharsets.
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direct_set.clear();
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radicals.clear();
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// Always keep space as 0;
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direct_set.unichar_insert(" ");
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// Null char is next if we have one.
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if (null_id >= 0) {
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direct_set.unichar_insert(kNullChar);
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}
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RSCounts radical_counts;
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// In the initial map, codes [0, unicharset.size()) are
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// reserved for non-han/hangul sequences of 1 or more unicodes.
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int hangul_offset = unicharset.size();
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// Hangul takes the next range [hangul_offset, hangul_offset + kTotalJamos).
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const int kTotalJamos = kLCount + kVCount + kTCount;
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// Han takes the codes beyond hangul_offset + kTotalJamos. Since it is hard
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// to measure the number of radicals and strokes, initially we use the same
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// code range for all 3 Han code positions, and fix them after.
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int han_offset = hangul_offset + kTotalJamos;
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int max_num_strokes = -1;
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for (int u = 0; u <= unicharset.size(); ++u) {
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bool self_normalized = false;
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// We special-case allow null_id to be equal to unicharset.size() in case
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// there is no space in unicharset for it.
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if (u == unicharset.size()) {
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if (u == null_id) {
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self_normalized = true;
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} else {
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break; // Finished.
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}
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} else {
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self_normalized = strcmp(unicharset.id_to_unichar(u),
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unicharset.get_normed_unichar(u)) == 0;
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}
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RecodedCharID code;
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// Convert to unicodes.
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GenericVector<int> unicodes;
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if (u < unicharset.size() &&
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UNICHAR::UTF8ToUnicode(unicharset.get_normed_unichar(u), &unicodes) &&
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unicodes.size() == 1) {
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// Check single unicodes for Hangul/Han and encode if so.
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int unicode = unicodes[0];
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int leading, vowel, trailing;
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auto it = radical_map.find(unicode);
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if (it != radical_map.end()) {
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// This is Han. Convert to radical, stroke, index.
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if (!radicals.contains_unichar(it->second.radical.string())) {
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radicals.unichar_insert(it->second.radical.string());
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}
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int radical = radicals.unichar_to_id(it->second.radical.string());
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int num_strokes = it->second.num_strokes;
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int num_samples = radical_counts[it->second]++;
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if (num_strokes > max_num_strokes) max_num_strokes = num_strokes;
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code.Set3(radical + han_offset, num_strokes + han_offset,
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num_samples + han_offset);
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} else if (DecomposeHangul(unicode, &leading, &vowel, &trailing)) {
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// This is Hangul. Since we know the exact size of each part at compile
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// time, it gets the bottom set of codes.
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code.Set3(leading + hangul_offset, vowel + kLCount + hangul_offset,
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trailing + kLCount + kVCount + hangul_offset);
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}
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}
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// If the code is still empty, it wasn't Han or Hangul.
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if (code.length() == 0) {
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// Special cases.
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if (u == UNICHAR_SPACE) {
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code.Set(0, 0); // Space.
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} else if (u == null_id || (unicharset.has_special_codes() &&
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u < SPECIAL_UNICHAR_CODES_COUNT)) {
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code.Set(0, direct_set.unichar_to_id(kNullChar));
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} else {
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// Add the direct_set unichar-ids of the unicodes in sequence to the
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// code.
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for (int i = 0; i < unicodes.size(); ++i) {
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int position = code.length();
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if (position >= RecodedCharID::kMaxCodeLen) {
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tprintf("Unichar %d=%s->%s is too long to encode!!\n", u,
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unicharset.id_to_unichar(u),
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unicharset.get_normed_unichar(u));
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return false;
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}
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int uni = unicodes[i];
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UNICHAR unichar(uni);
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char* utf8 = unichar.utf8_str();
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if (!direct_set.contains_unichar(utf8))
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direct_set.unichar_insert(utf8);
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code.Set(position, direct_set.unichar_to_id(utf8));
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delete[] utf8;
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if (direct_set.size() > unicharset.size()) {
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// Code space got bigger!
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tprintf("Code space expanded from original unicharset!!\n");
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return false;
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}
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}
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}
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}
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code.set_self_normalized(self_normalized);
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encoder_.push_back(code);
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}
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// Now renumber Han to make all codes unique. We already added han_offset to
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// all Han. Now separate out the radical, stroke, and count codes for Han.
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// In the uniqued Han encoding, the 1st code uses the next radical_map.size()
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// values, the 2nd code uses the next max_num_strokes+1 values, and the 3rd
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// code uses the rest for the max number of duplicated radical/stroke combos.
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int num_radicals = radicals.size();
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for (int u = 0; u < unicharset.size(); ++u) {
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RecodedCharID* code = &encoder_[u];
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if ((*code)(0) >= han_offset) {
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code->Set(1, (*code)(1) + num_radicals);
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code->Set(2, (*code)(2) + num_radicals + max_num_strokes + 1);
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}
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}
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DefragmentCodeValues(null_id >= 0 ? 1 : -1);
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SetupDecoder();
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return true;
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}
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// Sets up an encoder that doesn't change the unichars at all, so it just
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// passes them through unchanged.
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void UnicharCompress::SetupPassThrough(const UNICHARSET& unicharset) {
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GenericVector<RecodedCharID> codes;
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for (int u = 0; u < unicharset.size(); ++u) {
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RecodedCharID code;
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code.Set(0, u);
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codes.push_back(code);
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}
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SetupDirect(codes);
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}
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// Sets up an encoder directly using the given encoding vector, which maps
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// unichar_ids to the given codes.
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void UnicharCompress::SetupDirect(const GenericVector<RecodedCharID>& codes) {
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encoder_ = codes;
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ComputeCodeRange();
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SetupDecoder();
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}
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// Renumbers codes to eliminate unused values.
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void UnicharCompress::DefragmentCodeValues(int encoded_null) {
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// There may not be any Hangul, but even if there is, it is possible that not
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// all codes are used. Likewise with the Han encoding, it is possible that not
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// all numbers of strokes are used.
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ComputeCodeRange();
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GenericVector<int> offsets;
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offsets.init_to_size(code_range_, 0);
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// Find which codes are used
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for (int c = 0; c < encoder_.size(); ++c) {
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const RecodedCharID& code = encoder_[c];
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for (int i = 0; i < code.length(); ++i) {
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offsets[code(i)] = 1;
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}
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}
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// Compute offsets based on code use.
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int offset = 0;
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for (int i = 0; i < offsets.size(); ++i) {
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// If not used, decrement everything above here.
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// We are moving encoded_null to the end, so it is not "used".
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if (offsets[i] == 0 || i == encoded_null) {
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--offset;
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} else {
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offsets[i] = offset;
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}
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}
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if (encoded_null >= 0) {
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// The encoded_null is moving to the end, for the benefit of TensorFlow,
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// which is offsets.size() + offsets.back().
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offsets[encoded_null] = offsets.size() + offsets.back() - encoded_null;
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}
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// Now apply the offsets.
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for (int c = 0; c < encoder_.size(); ++c) {
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RecodedCharID* code = &encoder_[c];
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for (int i = 0; i < code->length(); ++i) {
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int value = (*code)(i);
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code->Set(i, value + offsets[value]);
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}
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}
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ComputeCodeRange();
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}
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// Encodes a single unichar_id. Returns the length of the code, or zero if
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// invalid input, and the encoding itself
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int UnicharCompress::EncodeUnichar(int unichar_id, RecodedCharID* code) const {
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if (unichar_id < 0 || unichar_id >= encoder_.size()) return 0;
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*code = encoder_[unichar_id];
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return code->length();
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}
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// Decodes code, returning the original unichar-id, or
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// INVALID_UNICHAR_ID if the input is invalid.
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int UnicharCompress::DecodeUnichar(const RecodedCharID& code) const {
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int len = code.length();
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if (len <= 0 || len > RecodedCharID::kMaxCodeLen) return INVALID_UNICHAR_ID;
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auto it = decoder_.find(code);
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if (it == decoder_.end()) return INVALID_UNICHAR_ID;
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return it->second;
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}
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// Writes to the given file. Returns false in case of error.
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bool UnicharCompress::Serialize(TFile* fp) const {
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return encoder_.SerializeClasses(fp);
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}
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// Reads from the given file. Returns false in case of error.
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bool UnicharCompress::DeSerialize(TFile* fp) {
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if (!encoder_.DeSerializeClasses(fp)) return false;
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ComputeCodeRange();
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SetupDecoder();
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return true;
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}
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// Returns a STRING containing a text file that describes the encoding thus:
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// <index>[,<index>]*<tab><UTF8-str><newline>
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// In words, a comma-separated list of one or more indices, followed by a tab
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// and the UTF-8 string that the code represents per line. Most simple scripts
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// will encode a single index to a UTF8-string, but Chinese, Japanese, Korean
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// and the Indic scripts will contain a many-to-many mapping.
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// See the class comment above for details.
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STRING UnicharCompress::GetEncodingAsString(
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const UNICHARSET& unicharset) const {
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STRING encoding;
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for (int c = 0; c < encoder_.size(); ++c) {
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const RecodedCharID& code = encoder_[c];
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if (0 < c && c < SPECIAL_UNICHAR_CODES_COUNT && code == encoder_[c - 1]) {
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// Don't show the duplicate entry.
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continue;
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}
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encoding.add_str_int("", code(0));
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for (int i = 1; i < code.length(); ++i) {
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encoding.add_str_int(",", code(i));
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}
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encoding += "\t";
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if (c >= unicharset.size() || (0 < c && c < SPECIAL_UNICHAR_CODES_COUNT &&
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unicharset.has_special_codes())) {
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encoding += kNullChar;
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} else {
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encoding += unicharset.id_to_unichar(c);
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}
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encoding += "\n";
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}
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return encoding;
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}
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// Helper decomposes a Hangul unicode to 3 parts, leading, vowel, trailing.
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// Note that the returned values are 0-based indices, NOT unicode Jamo.
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// Returns false if the input is not in the Hangul unicode range.
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/* static */
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bool UnicharCompress::DecomposeHangul(int unicode, int* leading, int* vowel,
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int* trailing) {
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if (unicode < kFirstHangul) return false;
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int offset = unicode - kFirstHangul;
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if (offset >= kNumHangul) return false;
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const int kNCount = kVCount * kTCount;
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*leading = offset / kNCount;
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*vowel = (offset % kNCount) / kTCount;
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*trailing = offset % kTCount;
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return true;
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}
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// Computes the value of code_range_ from the encoder_.
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void UnicharCompress::ComputeCodeRange() {
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code_range_ = -1;
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for (int c = 0; c < encoder_.size(); ++c) {
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const RecodedCharID& code = encoder_[c];
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for (int i = 0; i < code.length(); ++i) {
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if (code(i) > code_range_) code_range_ = code(i);
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}
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}
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++code_range_;
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}
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// Initializes the decoding hash_map from the encoding array.
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void UnicharCompress::SetupDecoder() {
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Cleanup();
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is_valid_start_.init_to_size(code_range_, false);
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for (int c = 0; c < encoder_.size(); ++c) {
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const RecodedCharID& code = encoder_[c];
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if (code.self_normalized() || decoder_.find(code) == decoder_.end())
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decoder_[code] = c;
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is_valid_start_[code(0)] = true;
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RecodedCharID prefix = code;
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int len = code.length() - 1;
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prefix.Truncate(len);
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auto final_it = final_codes_.find(prefix);
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if (final_it == final_codes_.end()) {
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GenericVectorEqEq<int>* code_list = new GenericVectorEqEq<int>;
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code_list->push_back(code(len));
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final_codes_[prefix] = code_list;
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while (--len >= 0) {
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prefix.Truncate(len);
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auto next_it = next_codes_.find(prefix);
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if (next_it == next_codes_.end()) {
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GenericVectorEqEq<int>* code_list = new GenericVectorEqEq<int>;
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code_list->push_back(code(len));
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next_codes_[prefix] = code_list;
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} else {
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// We still have to search the list as we may get here via multiple
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// lengths of code.
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if (!next_it->second->contains(code(len)))
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next_it->second->push_back(code(len));
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break; // This prefix has been processed.
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}
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}
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} else {
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if (!final_it->second->contains(code(len)))
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final_it->second->push_back(code(len));
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}
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}
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}
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// Frees allocated memory.
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void UnicharCompress::Cleanup() {
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decoder_.clear();
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is_valid_start_.clear();
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for (auto it = next_codes_.begin(); it != next_codes_.end(); ++it) {
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delete it->second;
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}
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for (auto it = final_codes_.begin(); it != final_codes_.end(); ++it) {
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delete it->second;
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}
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next_codes_.clear();
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final_codes_.clear();
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}
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} // namespace tesseract.
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