/* -*- c++ -*- */
/*
 * Copyright 2005-2011 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * GNU Radio is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 *
 * GNU Radio is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <gr_throttle.h>
#include <gr_io_signature.h>
#include <cstring>
#include <boost/thread/thread.hpp>

class gr_throttle_impl : public gr_throttle{
public:
    gr_throttle_impl(size_t itemsize):
        gr_sync_block("throttle",
            gr_make_io_signature(1, 1, itemsize),
            gr_make_io_signature(1, 1, itemsize)),
        d_itemsize(itemsize)
    {
        /* NOP */
    }

    void set_sample_rate(double rate){
        //changing the sample rate performs a reset of state params
        d_start = boost::get_system_time();
        d_total_samples = 0;
        d_samps_per_tick = rate/boost::posix_time::time_duration::ticks_per_second();
        d_samps_per_us = rate/1e6;
    }

    int work (
        int noutput_items,
        gr_vector_const_void_star &input_items,
        gr_vector_void_star &output_items
    ){
        //calculate the expected number of samples to have passed through
        boost::system_time now = boost::get_system_time();
        boost::int64_t ticks = (now - d_start).ticks();
        uint64_t expected_samps = uint64_t(d_samps_per_tick*ticks);

        //if the expected samples was less, we need to throttle back
        if (d_total_samples > expected_samps){
            boost::this_thread::sleep(boost::posix_time::microseconds(
                long((d_total_samples - expected_samps)/d_samps_per_us)
            ));
        }

        //copy all samples output[i] <= input[i]
        const char *in = (const char *) input_items[0];
        char *out = (char *) output_items[0];
        std::memcpy(out, in, noutput_items * d_itemsize);
        d_total_samples += noutput_items;
        return noutput_items;
    }

private:
    boost::system_time d_start;
    size_t d_itemsize;
    uint64_t d_total_samples;
    double d_samps_per_tick, d_samps_per_us;
};

gr_throttle::sptr
gr_make_throttle(size_t itemsize, double samples_per_sec)
{
    gr_throttle::sptr throttle(new gr_throttle_impl(itemsize));
    throttle->set_sample_rate(samples_per_sec);
    return throttle;
}