Generate tone with alsa

ALSA_Sine.cc

#include <cmath>
#include <random>
#include <iostream>
#include "alsa/asoundlib.h"

unsigned const size   = 1024;
unsigned const rate   = 44100;
float    const circle = 6.28318530;

inline void do_audio(float* out)
{
    static float phase = 0.f;
    static const float frequency = 440.f;

    *out = std::sin(phase * circle);
    phase += frequency / rate;
    if (phase >= 1.f) phase -= 1.f;
}

int main()
{
        snd_pcm_t *ostream;
        snd_pcm_hw_params_t *oparams;
        snd_pcm_open(&ostream, "default", SND_PCM_STREAM_PLAYBACK, SND_PCM_ASYNC);

        snd_pcm_hw_params_alloca ( &oparams );
        snd_pcm_hw_params_any(ostream, oparams);
        snd_pcm_hw_params_set_format(ostream, oparams, SND_PCM_FORMAT_FLOAT_LE);
        snd_pcm_hw_params_set_rate(ostream, oparams, rate, 0);

        snd_pcm_hw_params(ostream, oparams);

        float odata[size] = {0};
        while (true)
        {
                for (unsigned n = 0; n < size; n++) do_audio(&odata[n]);
                snd_pcm_writei(ostream, odata, size);
        }
        snd_pcm_drain(ostream);
}