C++ Boost Asio NCBI Fastq 文件下载器，支持断点续传

#include #include #include <boost/asio.hpp> #include <boost/bind.hpp> #include <boost/format.hpp>

using boost::asio::ip::tcp;

class NCBIFileDownloader { public: NCBIFileDownloader(boost::asio::io_service& io_service, const std::string& accession) : io_service_(io_service), socket_(io_service), accession_(accession), file_size_(0), bytes_transferred_(0) { std::string hostname = "ftp.ncbi.nlm.nih.gov"; std::string path = "/sra/sra-instant/reads/ByRun/sra/" + accession_.substr(0, 3) + "/" + accession_.substr(0, 6) + "/" + accession_ + "/" + accession_ + ".fastq.gz"; tcp::resolver resolver(io_service_); tcp::resolver::query query(hostname, "ftp"); tcp::resolver::iterator endpoint_iterator = resolver.resolve(query); tcp::resolver::iterator end; boost::system::error_code error = boost::asio::error::host_not_found; while (error && endpoint_iterator != end) { socket_.close(); socket_.connect(*endpoint_iterator++, error); } if (error) { throw boost::system::system_error(error); } request_ = boost::str(boost::format("GET %1% HTTP/1.1\r\nHost: %2%\r\nRange: bytes=%3%-\r\nConnection: close\r\n\r\n") % path % hostname % bytes_transferred_); }

void start() {
    boost::asio::async_write(socket_, boost::asio::buffer(request_), boost::bind(&NCBIFileDownloader::handle_write, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));
}

void handle_write(const boost::system::error_code& error, std::size_t /*bytes_transferred*/) {
    if (!error) {
        boost::asio::async_read_until(socket_, response_, "\r\n\r\n", boost::bind(&NCBIFileDownloader::handle_header, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));
    } else {
        std::cout << "Error: " << error.message() << std::endl;
        socket_.close();
    }
}

void handle_header(const boost::system::error_code& error, std::size_t /*bytes_transferred*/) {
    if (!error) {
        std::istream response_stream(&response_);
        std::string http_version;
        response_stream >> http_version;
        unsigned int status_code;
        response_stream >> status_code;
        std::string status_message;
        std::getline(response_stream, status_message);
        if (status_code == 200 || status_code == 206) {
            std::string header;
            while (std::getline(response_stream, header) && header != "\r") {
                if (header.find("Content-Length: ") == 0) {
                    file_size_ = std::stoull(header.substr(16));
                }
            }
            std::cout << "File size: " << file_size_ << " bytes" << std::endl;
            std::string output_filename = accession_ + ".fastq.gz";
            output_file_.open(output_filename, std::ios::app | std::ios::binary);
            if (!output_file_.is_open()) {
                throw std::runtime_error("Failed to open file for writing: " + output_filename);
            }
            boost::asio::async_read(socket_, response_, boost::asio::transfer_at_least(1), boost::bind(&NCBIFileDownloader::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));
        } else if (status_code == 206) {
            // Resume download from the last transferred byte
            std::cout << "Resuming download from byte: " << bytes_transferred_ << std::endl;
            boost::asio::async_read(socket_, response_, boost::asio::transfer_at_least(1), boost::bind(&NCBIFileDownloader::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));
        } else {
            std::cout << "Download failed with status code: " << status_code << std::endl;
            socket_.close();
        }
    } else {
        std::cout << "Error: " << error.message() << std::endl;
        socket_.close();
    }
}

void handle_read(const boost::system::error_code& error, std::size_t bytes_transferred) {
    if (!error) {
        bytes_transferred_ += bytes_transferred;
        output_file_.write(boost::asio::buffer_cast<const char*>(response_.data()), bytes_transferred);
        response_.consume(bytes_transferred);
        if (bytes_transferred_ < file_size_) {
            boost::asio::async_read(socket_, response_, boost::asio::transfer_at_least(1), boost::bind(&NCBIFileDownloader::handle_read, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));
        } else {
            std::cout << "Download completed" << std::endl;
            output_file_.close();
            socket_.close();
        }
    } else {
        std::cout << "Error: " << error.message() << std::endl;
        output_file_.close();
        socket_.close();
    }
}

private: boost::asio::io_service& io_service_; tcp::socket socket_; std::string accession_; std::string request_; boost::asio::streambuf response_; std::ofstream output_file_; std::size_t file_size_; std::size_t bytes_transferred_; };

int main() { std::string accession = "SRR000000"; boost::asio::io_service io_service; NCBIFileDownloader downloader(io_service, accession); downloader.start(); io_service.run(); return 0; }