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// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40285824): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include "components/language_detection/core/ngram_hash_ops_utils.h"
#include <cstring>
#include "third_party/utf/src/include/utf.h"
namespace language_detection {
constexpr char kPrefix[] = "^";
constexpr char kSuffix[] = "$";
constexpr char kReplacementToken[] = " ";
TokenizedOutput::TokenizedOutput() = default;
TokenizedOutput::~TokenizedOutput() = default;
TokenizedOutput::TokenizedOutput(const TokenizedOutput& rhs) = default;
TokenizedOutput Tokenize(const char* input_str,
size_t len,
size_t max_tokens,
bool exclude_nonalphaspace_tokens) {
TokenizedOutput output;
size_t token_start = 0;
output.str.reserve(len + 2);
output.tokens.reserve(len + 2);
output.str.append(kPrefix);
output.tokens.emplace_back(std::make_pair(token_start, strlen(kPrefix)));
token_start += strlen(kPrefix);
Rune token;
for (size_t i = 0; i < len && output.tokens.size() + 1 < max_tokens;) {
if (input_str == nullptr)
break;
if (strlen(input_str) == 0)
break;
// Use the standard UTF-8 library to find the next token.
size_t bytes_read = charntorune(&token, input_str + i, len - i);
// Stop processing, if we can't read any more tokens, or we have reached
// maximum allowed tokens, allocating one token for the suffix.
if (bytes_read == 0) {
break;
}
// If `exclude_nonalphaspace_tokens` is set to true, and the token is not
// alphanumeric, replace it with a replacement token.
if (exclude_nonalphaspace_tokens && !isalpharune(token)) {
output.str.append(kReplacementToken);
output.tokens.emplace_back(
std::make_pair(token_start, strlen(kReplacementToken)));
token_start += strlen(kReplacementToken);
i += bytes_read;
continue;
}
// Append the token in the output string, and note its position and the
// number of bytes that token consumed.
output.str.append(input_str + i, bytes_read);
output.tokens.emplace_back(std::make_pair(token_start, bytes_read));
token_start += bytes_read;
i += bytes_read;
}
output.str.append(kSuffix);
output.tokens.emplace_back(std::make_pair(token_start, strlen(kSuffix)));
token_start += strlen(kSuffix);
return output;
}
void LowercaseUnicodeStr(const char* input_str,
int len,
std::string* output_str) {
for (int i = 0; i < len;) {
Rune token;
// Tokenize the given string, and get the appropriate lowercase token.
size_t bytes_read = charntorune(&token, input_str + i, len - i);
token = isalpharune(token) ? tolowerrune(token) : token;
// Write back the token to the output string.
char token_buf[UTFmax];
size_t bytes_to_write = runetochar(token_buf, &token);
output_str->append(token_buf, bytes_to_write);
i += bytes_read;
}
}
} // namespace language_detection
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