[C++] 318 BBS閲覧アプリの製作 その４ スレッドタイトルの取得 HTMLパーサーを使わず文字列処理

#include <iostream>
#include <string>
#include <vector>
#include <regex>
#include <curl/curl.h>
#include <iconv.h>

// コールバック関数
size_t WriteCallback(void* contents, size_t size, size_t nmemb, std::string* buffer) {
    size_t totalSize = size * nmemb;
    buffer->append((char*)contents, totalSize);
    return totalSize;
}

std::string ConvertShiftJISToUTF8(const std::string& input) {
    std::string output;

    iconv_t cd = iconv_open("UTF-8", "CP932");
    if (cd == (iconv_t)-1) {
        std::cerr << "Error: Failed to open iconv" << std::endl;
        return output;
    }

    size_t inBytes = input.size();
    size_t outBytes = inBytes * 4; // 変換後の最大バイト数を予測して確保する

    char* inBuf = const_cast<char*>(input.c_str());
    char* outBuf = new char[outBytes];
    char* outPtr = outBuf;

    if (iconv(cd, &inBuf, &inBytes, &outPtr, &outBytes) == (size_t)-1) {
        std::cerr << "Error: Failed to convert encoding: " << strerror(errno) << std::endl;
        delete[] outBuf;
        iconv_close(cd);
        return output;
    }

    output.assign(outBuf, outPtr - outBuf);

    delete[] outBuf;
    iconv_close(cd);

    return output;
}

int main() {
    // URLからHTMLファイルを取り込む
    std::string url = "HTMLファイルのURL";
    std::string htmlBuffer;
    CURL* curl = curl_easy_init();
    if (curl) {
        curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &htmlBuffer);
        CURLcode res = curl_easy_perform(curl);
        curl_easy_cleanup(curl);
        if (res != CURLE_OK) {
            std::cerr << "Error: Failed to download HTML" << std::endl;
            return 1;
        }
    } else {
        std::cerr << "Error: Failed to initialize CURL" << std::endl;
        return 1;
    }

    // 文字コードをCP932(Microsoftの拡張Shift-JIS)からUTF-8へ変換
    htmlBuffer = ConvertShiftJISToUTF8(htmlBuffer);

    // htmlBufferの確認
    // cout << "htmlBuffer: \n" << htmlBuffer << endl;

    // smallタグ部分を抽出
    std::string delimiter = "<small id=\"trad\">";
    htmlBuffer = htmlBuffer.substr(htmlBuffer.find(delimiter) + delimiter.length());
    delimiter = "</small>";
    htmlBuffer = htmlBuffer.substr(0, htmlBuffer.find(delimiter));

    // std::cout << "抽出内容:\n" << htmlBuffer << std::endl;

    // 正規表現を使ってaタグ内のhrefとaタグの内容を抽出 (.*?)部分
    std::regex pattern("<a.*?href=\"(.*?)/l50\".*?>(.*?)</a>");
    std::smatch matches;

    std::string::const_iterator searchStart(htmlBuffer.cbegin());
    std::vector<std::pair<std::string, std::string>> idTitlePairs;
    while (std::regex_search(searchStart, htmlBuffer.cend(), matches, pattern)) {
        std::string id = matches[1];
        std::string title = matches[2];
        idTitlePairs.push_back(std::make_pair(id, title));
        searchStart = matches.suffix().first;
    }

    for (const auto& pair : idTitlePairs) {
        std::cout << "id: " << pair.first << std::endl;
        std::cout << "title: " << pair.second << std::endl;
    }

    return 0;
}