throttle.h

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/* -*- c++ -*- */
/*
 * Copyright 2005-2011,2013 Free Software Foundation, Inc.
 * Copyright 2021,2022 Marcus Müller
 *
 * This file is part of GNU Radio
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 */
 
#ifndef INCLUDED_GR_THROTTLE_H
#define INCLUDED_GR_THROTTLE_H
 
#include <gnuradio/blocks/api.h>
#include <gnuradio/sync_block.h>
 
namespace gr {
namespace blocks {
 
/*!
 * \brief throttle flow of samples such that the average rate does
 * not exceed samples_per_sec.
 * \ingroup misc_blk
 *
 * \details
 * input: one stream of itemsize; output: one stream of itemsize
 *
 * N.B. this should only be used in GUI apps where there is no
 * other rate limiting block. It is not intended nor effective at
 * precisely controlling the rate of samples. That should be
 * controlled by a source or sink tied to sample clock. E.g., a
 * USRP or audio card.
 *
 * You can insert this block "in series" with your sample flow, in which case it  does a
 * throttled copy of input to output. Alternatively, you can not connect its output and
 * just connect this block's input in parallel to an existing block in your flow graph. In
 * that case, Throttle will limit the rate at which samples are consumed; especially at
 * higher rates, where the copying overhead might be significant, this is functionally not
 * different to copying at a limited rate.
 */
class BLOCKS_API throttle : virtual public sync_block
{
public:
    typedef std::shared_ptr<throttle> sptr;
 
    /*!
     * Make a sptr to a Throttle block
     *
     * \param itemsize Size of each item, e.g. 8 for gr_complex
     *
     * \param samples_per_sec Number of items to be passed per second. Waiting time is
     * calculated based on this.
     *
     * \param ignore_tags Whether or not to react to "rx_rate" tags with a double value
     * specifying a new rate.
     *
     * \param maximum_items_per_chunk Limit the amount of items that are produced/consumed
     * between waiting. Set to 0 (or leave at default) to always wait for the full
     * duration dictated by the current size of workload items, divided by the
     * samples_per_sec.
     */
    static sptr make(size_t itemsize,
                     double samples_per_sec,
                     bool ignore_tags = true,
                     unsigned int maximum_items_per_chunk = 0);
 
    //! Sets the sample rate in samples per second.
    virtual void set_sample_rate(double rate) = 0;
 
    //! Get the sample rate in samples per second.
    virtual double sample_rate() const = 0;
 
    //! Set the maximum items that will be produced per waiting period
    virtual void set_maximum_items_per_chunk(unsigned int maximum_items_per_chunk) = 0;
 
    //! Get the maximum items that will be produced per waiting period
    virtual unsigned int maximum_items_per_chunk() const = 0;
};
 
} /* namespace blocks */
} /* namespace gr */
 
#endif /* INCLUDED_GR_THROTTLE_H */