Generate tone using OpenAL

gentone.c

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include <AL/al.h>
#include <AL/alc.h>

#define SAMPLE_RATE 48000

ALCdevice* openal_output_device;
ALCcontext* openal_output_context;

ALuint internal_buffer[2];
ALuint streaming_source[2];

void init_al() {
    const char * defname = alcGetString(NULL, ALC_DEFAULT_ALL_DEVICES_SPECIFIER);
    openal_output_device = alcOpenDevice(defname);
    openal_output_context = alcCreateContext(openal_output_device, NULL);
    alcMakeContextCurrent(openal_output_context);
}

void gen_buffers(int num) {
    alGenBuffers(num, internal_buffer);
}

short* make_sine(int freq, int seconds) {
    double pi = M_PI;
    size_t buf_size = seconds * SAMPLE_RATE;

    short* samples = (short *)malloc(sizeof(short) * buf_size);

    for(int i = 0; i < buf_size; i++) {
        samples[i] = 32760 * sin((2.f * pi * freq) / SAMPLE_RATE * i);
    }

    return samples;
}

short* make_triangular(int freq, int seconds) {
    size_t buf_size = seconds * SAMPLE_RATE;
    short now = 0;

    short* samples = (short *)malloc(sizeof(short) * buf_size);

    for(int i = 1; i <= buf_size; i++) {
        samples[i] = 4 / freq * ((float)(i / SAMPLE_RATE) - freq / 2 * floor(2 * (i / SAMPLE_RATE) / freq + 0.5f)) * powf(-1, floor(2 * (i / SAMPLE_RATE) / freq + 0.5f)); //from wikipedia
    }
    return samples;
}

short* make_sawtooth(int freq, int seconds) {
    size_t buf_size = seconds * SAMPLE_RATE;

    short* samples = (short *)malloc(sizeof(short) * buf_size);
    for(int i = 0; i < buf_size; i++) {
        samples[i] = (i % (SAMPLE_RATE / freq)) / (float)freq * 32760 * 2 - 32760;
    }
    return samples;
}

void load_buffer(short* samples, int seconds, int index) {
    alBufferData(internal_buffer[index], AL_FORMAT_MONO16, samples, SAMPLE_RATE * seconds, SAMPLE_RATE);
    free(samples);

    alGenSources(1, &streaming_source[index]);
    alSourcei(streaming_source[index], AL_BUFFER, internal_buffer[index]);
}

void play_buffer(int index) {
    ALenum currentState;

    alSourcePlay(streaming_source[index]);
    alGetSourcei(streaming_source[index], AL_SOURCE_STATE, &currentState);

    while(AL_PLAYING == currentState) {
        alGetSourcei(streaming_source[index], AL_SOURCE_STATE, &currentState);
    }
}

void delete_source_buffer(int index) {
    alSourcei(streaming_source[index], AL_BUFFER, 0);
    alDeleteSources(1, &streaming_source[index]);
    alDeleteBuffers(1, &streaming_source[index]);
}

void close_device() {
    alcMakeContextCurrent(NULL);
    alcDestroyContext(openal_output_context);
    alcCloseDevice(openal_output_device);
}

int al_check_error(const char * given_label) {

    ALenum al_error;
    al_error = alGetError();

    if(AL_NO_ERROR != al_error) {
        
        printf("ERROR %s %s\n", alGetString(al_error), given_label);
        return al_error;
    }
    return 0;
}

int main() {
    init_al();
    gen_buffers(2);
    short **waves = (short **)malloc(sizeof(short *) * 2);
    waves[0] = make_sine(880, 2);
    waves[1] = make_sawtooth(440, 2);
    for(int i = 0; i < 2; i++) {
        load_buffer(waves[i], 2, i);
        al_check_error("loadbuffer error");
    }
    play_buffer(0);
    play_buffer(1);
    al_check_error("playbuffer error");
    delete_source_buffer(0);
    delete_source_buffer(1);
    close_device();
}

// Compile with flag -lopenal -lm