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106 lines
4.0 KiB
106 lines
4.0 KiB
7 months ago
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/*
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* Copyright (C) 2018 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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// Utilities for tests.
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#ifndef LIBTEXTCLASSIFIER_UTILS_TOKENIZER_UTILS_H_
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#define LIBTEXTCLASSIFIER_UTILS_TOKENIZER_UTILS_H_
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#include <string>
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#include "annotator/types.h"
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#include "utils/codepoint-range.h"
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#include "utils/strings/utf8.h"
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#include "utils/utf8/unicodetext.h"
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#include "absl/container/flat_hash_set.h"
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#include "absl/strings/string_view.h"
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namespace libtextclassifier3 {
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struct FilterResult {
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// Whether split on this codepoint.
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bool to_split;
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// If the codepoint is used to split the text, whether to output it as a
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// token.
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bool to_keep;
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};
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// Returns a list of Tokens for a given input string, by tokenizing on space.
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std::vector<Token> TokenizeOnSpace(const std::string& text);
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// Returns a list of Tokens for a given input string, by tokenizing on the
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// given set of delimiter codepoints.
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// If create_tokens_for_non_space_delimiters is true, create tokens for
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// delimiters which are not white spaces. For example "This, is" -> {"This",
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// ",", "is"}.
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std::vector<Token> TokenizeOnDelimiters(
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const std::string& text, const absl::flat_hash_set<char32>& delimiters,
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bool create_tokens_for_non_space_delimiters = false);
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// This replicates how the original bert_tokenizer from the tflite-support
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// library pretokenize text by using regex_split with these default regexes.
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// It splits the text on spaces, punctuations and chinese characters and
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// output all the tokens except spaces.
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// So far, the only difference between this and the original implementation
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// we are aware of is that the original regexes has 8 ranges of chinese
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// unicodes. We have all these 8 ranges plus two extra ranges.
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std::vector<Token> TokenizeOnWhiteSpacePunctuationAndChineseLetter(
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const absl::string_view text);
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// Returns a list of Tokens for a given input string, by tokenizing on the
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// given filter function. Caller can control which codepoint to split and
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// whether a delimiter should be output as a token.
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template <typename FilterFn>
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std::vector<Token> TokenizeWithFilter(const absl::string_view input,
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FilterFn filter) {
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const UnicodeText input_unicode = UTF8ToUnicodeText(input, /*do_copy=*/false);
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std::vector<Token> tokens;
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UnicodeText::const_iterator start_it = input_unicode.begin();
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int token_start_codepoint = 0;
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int codepoint_idx = 0;
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for (auto it = input_unicode.begin(); it != input_unicode.end(); ++it) {
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const char32 code_point = *it;
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FilterResult filter_result = filter(code_point);
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if (filter_result.to_split) {
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const std::string token_text = UnicodeText::UTF8Substring(start_it, it);
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if (!token_text.empty()) {
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tokens.push_back(
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Token{token_text, token_start_codepoint, codepoint_idx});
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}
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if (filter_result.to_keep) {
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const std::string delimiter =
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UnicodeText::UTF8Substring(it, std::next(it));
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tokens.push_back(Token{delimiter, codepoint_idx, codepoint_idx + 1});
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}
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start_it = std::next(it);
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token_start_codepoint = codepoint_idx + 1;
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}
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codepoint_idx++;
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}
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// Flush the last token if any.
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if (start_it != input_unicode.end()) {
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const std::string token_text =
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UnicodeText::UTF8Substring(start_it, input_unicode.end());
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tokens.push_back(Token{token_text, token_start_codepoint, codepoint_idx});
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}
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return tokens;
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}
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} // namespace libtextclassifier3
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#endif // LIBTEXTCLASSIFIER_UTILS_TOKENIZER_UTILS_H_
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