c++ - 查找 zlib 压缩流的结尾

Question

我正在使用 Qt 开发 NMDC 客户端(p2p、DC++ 和 friend )。协议(protocol)本身非常简单:

$command parameters|

除了 compression :

"ZPipe works by sending a command $ZOn| to the client. After $ZOn a ZLib compressed stream containing commands will follow. This stream will end with an EOF that ZLib defines. (there is no $ZOff in the compressed stream!)"

相关代码如下:

QTcpSocket *conn;
bool compressed;
QByteArray zbuffer;
QByteArray buffer;

// ...

void NMDCConnection::on_conn_readyRead() {
    // this gets called whenever we get new data from the hub

    if(compressed) {            // gets set when we receive $ZOn
        zbuffer.append(conn->readAll());


        // Magic happens here


        if( stream_is_complete ) {
            buffer.append(uncompressed_stream);
            buffer.append(remainder_of_data);
            compressed = false;
        }
    } else { 
        buffer.append(conn->readAll());
    };
    parse(buffer);
}

那么，如何获取 stream_is_complete、uncompressed_stream 和 remainder_of_data 的值？我无法查找下一个“$”，因为流可以包含它。我试图在 zlib 文档中寻找类似 EOF 的东西，但没有这样的东西，事实上，每个流都以看似随机的字符结尾。

我也玩过 qUncompress()，但它需要一个完整的流，仅此而已。

Answer 1

你是直接使用 zlib 吗？

完全未经测试...

z_stream zstrm;
QByteArray zout;
// when you see a $ZOn|, initialize the z_stream struct
parse() {
    ...
    if (I see a $ZOn|) {
        zstrm.next_in = Z_NULL;
        zstrm.avail_in = 0;
        zstrm.zalloc = Z_NULL;
        zstrm.zfree = Z_NULL;
        zstrm.opaque = 0;
        inflateInit(&zstrm);
        compressed = true;
    }
}
void NMDCConnection::on_conn_readyRead() {
    if (compressed) {
        zbuffer.append(conn->readAll());
        int rc;
        do {
            zstrm.next_in = zbuffer.data();
            zstrm.avail_in = zbuffer.size();
            zout.resize(zstrm.total_out + BLOCK_SIZE);
            zstrm.next_out = zout.data() + zstrm.total_out;
            zstrm.avail_out = BLOCK_SIZE;
            rc = inflate(&zstrm, Z_SYNC_FLUSH);
            zbuffer.remove(0, zstrm.next_in - zbuffer.data());
        } while (rc == Z_OK && zstrm->avail_out == 0);
        if (rc == Z_STREAM_END) {
            zout.truncate(zstrm.total_out);
            buffer.append(zout);
            zout.clear();
            buffer.append(zbuffer);
            zbuffer.clear();
            compress = false;
            inflateEnd(&zstrm);
        }
        else if (rc != Z_OK) {
            // ERROR!  look at zstrm.msg
        }
    }
    else // whatever
}

这会逐渐从 qbuffer 解压缩(膨胀)到 qout，并在 inflate 说“不再”时停止。

或许向QuaZip借用会更好相反。