async_encoder.h

Go to the documentation of this file.

/* -*- c++ -*- */
/*
 * Copyright 2014 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 */
 
#ifndef INCLUDED_FEC_ASYNC_ENCODER_H
#define INCLUDED_FEC_ASYNC_ENCODER_H
 
#include <gnuradio/block.h>
#include <gnuradio/fec/api.h>
#include <gnuradio/fec/generic_encoder.h>
#include <memory>
 
namespace gr {
namespace fec {
 
/*!
 * \brief Creates the encoder block for use in GNU Radio
 * flowgraphs with async message from a given FEC API object
 * derived from the generic_encoder class.
 * \ingroup error_coding_blk
 *
 * \details
 *
 * Encodes frames received as async messages or as a PDU over a
 * message port. This encoder works off a full message as one
 * frame or block to encode. The message length is used as the
 * frame length. To support this, the encoder variable used will
 * have had its frame_size set. This block treats that initial
 * frame_size value as the maximum transmission unit (MTU) and
 * will not process frames larger than that.
 *
 * This deployment works off messages and expects them to either
 * be messages full of unpacked bits or PDU messages, which means
 * full bytes of a frame from the higher layers, including things
 * like headers, tails, CRC check bytes, etc. For handling PDUs,
 * set the \p packed option of this deployment block to True. The
 * block will then use the FEC API to properly unpack the bits
 * from the PDU, pass it through the encoder, and repack them to
 * output the PDUs for the next stage of processing.
 *
 * The packed PDU form of this deployment is designed to work well
 * with other PDU-based blocks to operate within the processing
 * flow of data packets or frames.
 *
 * Due to differences in how data is packed and processed, this
 * block also offers the ability to change the direction of how
 * bits are unpacked and packed, where reading or writing from the
 * LSB or MSB. By default, the \p rev_unpack and \p rev_pack modes
 * are set to True. Using this setup allows the async block to
 * behave with PDUs in the same operation and format as the tagged
 * stream encoders. That is, putting the same data into both the
 * tagged stream encoder deployment and this with these default
 * settings should produce the same data.
 */
class FEC_API async_encoder : virtual public block
{
public:
    typedef std::shared_ptr<async_encoder> sptr;
 
    /*!
     * Build the PDU-based FEC encoder block from an FECAPI encoder object.
     *
     * \param my_encoder An FECAPI encoder object child of the generic_encoder class.
     * \param packed True if working on packed bytes (like PDUs).
     * \param rev_unpack Reverse the unpacking order from input bytes to bits.
     * \param rev_pack Reverse the packing order from bits to output bytes.
     * \param mtu The Maximum Transmission Unit (MTU) of the input
     *            frame that the block will be able to
     *            process. Specified in bytes and defaults to 1500.
     */
    static sptr make(generic_encoder::sptr my_encoder,
                     bool packed = false,
                     bool rev_unpack = true,
                     bool rev_pack = true,
                     int mtu = 1500);
 
    int general_work(int noutput_items,
                     gr_vector_int& ninput_items,
                     gr_vector_const_void_star& input_items,
                     gr_vector_void_star& output_items) override = 0;
};
 
} /* namespace fec */
} /* namespace gr */
 
#endif /* INCLUDED_FEC_ASYNC_ENCODER_H */