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102 lines
3.9 KiB
102 lines
3.9 KiB
/* |
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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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