102 lines
3.9 KiB
C++
102 lines
3.9 KiB
C++
/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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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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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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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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#include "smartselect/tokenizer.h"
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#include "util/strings/utf8.h"
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#include "util/utf8/unicodetext.h"
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namespace libtextclassifier {
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void Tokenizer::PrepareTokenizationCodepointRanges(
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const std::vector<TokenizationCodepointRange>& codepoint_range_configs) {
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codepoint_ranges_.clear();
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codepoint_ranges_.reserve(codepoint_range_configs.size());
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for (const TokenizationCodepointRange& range : codepoint_range_configs) {
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codepoint_ranges_.push_back(
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CodepointRange(range.start(), range.end(), range.role()));
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}
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std::sort(codepoint_ranges_.begin(), codepoint_ranges_.end(),
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[](const CodepointRange& a, const CodepointRange& b) {
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return a.start < b.start;
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});
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}
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TokenizationCodepointRange::Role Tokenizer::FindTokenizationRole(
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int codepoint) const {
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auto it = std::lower_bound(codepoint_ranges_.begin(), codepoint_ranges_.end(),
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codepoint,
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[](const CodepointRange& range, int codepoint) {
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// This function compares range with the
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// codepoint for the purpose of finding the first
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// greater or equal range. Because of the use of
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// std::lower_bound it needs to return true when
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// range < codepoint; the first time it will
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// return false the lower bound is found and
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// returned.
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//
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// It might seem weird that the condition is
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// range.end <= codepoint here but when codepoint
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// == range.end it means it's actually just
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// outside of the range, thus the range is less
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// than the codepoint.
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return range.end <= codepoint;
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});
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if (it != codepoint_ranges_.end() && it->start <= codepoint &&
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it->end > codepoint) {
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return it->role;
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} else {
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return TokenizationCodepointRange::DEFAULT_ROLE;
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}
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}
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std::vector<Token> Tokenizer::Tokenize(const std::string& utf8_text) const {
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UnicodeText context_unicode = UTF8ToUnicodeText(utf8_text, /*do_copy=*/false);
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std::vector<Token> result;
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Token new_token("", 0, 0);
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int codepoint_index = 0;
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for (auto it = context_unicode.begin(); it != context_unicode.end();
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++it, ++codepoint_index) {
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TokenizationCodepointRange::Role role = FindTokenizationRole(*it);
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if (role & TokenizationCodepointRange::SPLIT_BEFORE) {
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if (!new_token.value.empty()) {
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result.push_back(new_token);
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}
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new_token = Token("", codepoint_index, codepoint_index);
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}
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if (!(role & TokenizationCodepointRange::DISCARD_CODEPOINT)) {
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new_token.value += std::string(
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it.utf8_data(),
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it.utf8_data() + GetNumBytesForNonZeroUTF8Char(it.utf8_data()));
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++new_token.end;
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}
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if (role & TokenizationCodepointRange::SPLIT_AFTER) {
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if (!new_token.value.empty()) {
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result.push_back(new_token);
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}
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new_token = Token("", codepoint_index + 1, codepoint_index + 1);
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}
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}
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if (!new_token.value.empty()) {
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result.push_back(new_token);
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}
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return result;
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}
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} // namespace libtextclassifier
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