Function unicode_regex_split_stl

subprojects/llama.cpp/src/unicode.cpp:501–528

use std::wregex to split the text

// use std::wregex to split the text
static std::vector<size_t> unicode_regex_split_stl(const std::wstring & wtext, const std::wstring & regex_expr, const std::vector<size_t> & offsets) {
    std::wregex expr(regex_expr, std::regex_constants::optimize | std::regex_constants::nosubs);
    std::vector<size_t> bpe_offsets; // store the offset of each word
    bpe_offsets.reserve(offsets.size()); // Reserve memory for the approximate size
    size_t start = 0;
    for (auto offset : offsets) {
        std::wcregex_iterator it(wtext.data() + start, wtext.data() + start + offset, expr);
        std::wcregex_iterator end;

        int64_t start_idx = 0;
        while (it != end) {
            std::wcmatch match = *it;
            if (match.position() > start_idx) {
                bpe_offsets.emplace_back(match.position() - start_idx);
            }
            bpe_offsets.emplace_back(match.length());
            start_idx = match.position() + match.length();
            ++it;
        }

        if (start_idx < (int64_t) offset) {
            bpe_offsets.emplace_back(offset - start_idx);
        }
        start += offset;
    }

    return bpe_offsets;
}

// use std::regex to split the text
static std::vector<size_t> unicode_regex_split_stl(const std::string & text, const std::string & regex_expr, const std::vector<size_t> & offsets) {