Question

我有一台接收客户端文件的服务器，但外部网络中的传输速度太慢，读了一下我发现文件压缩的解决方案。我决定使用zlib进行压缩，我在文档中的一些示例中进行了搜索，下面是我想在项目中使用的两个示例。我的问题是，如何使用以下示例压缩文件而不保存到磁盘并通过套接字（客户端）发送。并接收和解压缩文件（服务器端）。

客户端应用程序在Windows上运行，服务器应用程序在Linux上运行。

客户端：

int def(FILE *source, FILE *dest, int level) 
{
        int ret, flush;
        unsigned have;
        z_stream strm;
        unsigned char in[CHUNK];
        unsigned char out[CHUNK];

        /* allocate deflate state */
        strm.zalloc = Z_NULL;
        strm.zfree = Z_NULL;
        strm.opaque = Z_NULL;
        ret = deflateInit(&strm, level);
        if (ret != Z_OK)
            return ret;

        /* compress until end of file */
        do {
            strm.avail_in = fread(in, 1, CHUNK, source);
            if (ferror(source)) {
                (void)deflateEnd(&strm);
                return Z_ERRNO;
            }
            flush = feof(source) ? Z_FINISH : Z_NO_FLUSH;
            strm.next_in = in;

            /* run deflate() on input until output buffer not full, finish
               compression if all of source has been read in */
            do {
                strm.avail_out = CHUNK;
                strm.next_out = out;
                ret = deflate(&strm, flush);    /* no bad return value */
                assert(ret != Z_STREAM_ERROR);  /* state not clobbered */
                have = CHUNK - strm.avail_out;
                if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
                    (void)deflateEnd(&strm);
                    return Z_ERRNO;
                }
            } while (strm.avail_out == 0);
            assert(strm.avail_in == 0);     /* all input will be used */

            /* done when last data in file processed */
        } while (flush != Z_FINISH);
        assert(ret == Z_STREAM_END);        /* stream will be complete */

        /* clean up and return */
        (void)deflateEnd(&strm);
        return Z_OK;
}

服务器端：

int inf(FILE *source, FILE *dest)
{
    int ret;
    unsigned have;
    z_stream strm;
    unsigned char in[CHUNK];
    unsigned char out[CHUNK];

    /* allocate inflate state */
    strm.zalloc = Z_NULL;
    strm.zfree = Z_NULL;
    strm.opaque = Z_NULL;
    strm.avail_in = 0;
    strm.next_in = Z_NULL;
    ret = inflateInit(&strm);
    if (ret != Z_OK)
        return ret;

    /* decompress until deflate stream ends or end of file */
    do {
        strm.avail_in = fread(in, 1, CHUNK, source);
        if (ferror(source)) {
            (void)inflateEnd(&strm);
            return Z_ERRNO;
        }
        if (strm.avail_in == 0)
            break;
        strm.next_in = in;

        /* run inflate() on input until output buffer not full */
        do {
            strm.avail_out = CHUNK;
            strm.next_out = out;
            ret = inflate(&strm, Z_NO_FLUSH);
            assert(ret != Z_STREAM_ERROR);  /* state not clobbered */
            switch (ret) {
            case Z_NEED_DICT:
                ret = Z_DATA_ERROR;     /* and fall through */
            case Z_DATA_ERROR:
            case Z_MEM_ERROR:
                (void)inflateEnd(&strm);
                return ret;
            }
            have = CHUNK - strm.avail_out;
            if (fwrite(out, 1, have, dest) != have || ferror(dest)) {
                (void)inflateEnd(&strm);
                return Z_ERRNO;
            }
        } while (strm.avail_out == 0);

        /* done when inflate() says it's done */
    } while (ret != Z_STREAM_END);

    /* clean up and return */
    (void)inflateEnd(&strm);
    return ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR;
}

Answer 1

一种方法是使用Boost Iostream compressor（它们支持开箱即用的zlib，gzip，bzip2）和来自Boost Asio的ip::tcp::iostream套接字。类似的东西：

#include <boost/iostreams/filtering_stream.hpp>
#include <boost/iostreams/filter/zlib.hpp>
#include <boost/asio/ip/tcp.hpp>

int main() {
    boost::asio::ip::tcp::iostream connection;

    boost::iostreams::filtering_stream<boost::iostreams::input> connection_reader;
    connection_reader.push(boost::iostreams::zlib_decompressor());
    connection_reader.push(connection);

    boost::iostreams::filtering_stream<boost::iostreams::output> connection_writer;
    connection_writer.push(boost::iostreams::zlib_compressor());
    connection_writer.push(connection);

    auto const url = "127.0.0.1";
    connection.connect(url, "http");

    // Send.
    connection_writer << "hello there\n";

    // Receive.
    for(std::string line; getline(connection_reader, line);) {
        // Process line.
    }
}

使用zlib进行文件压缩而不保存到磁盘并通过套接字发送

1 个答案: