racket-sound/libao/c/ao-play-async/ao_playasync.c

#include "ao_playasync.h"
#include <pthread.h>
#include <unistd.h>
#include <assert.h>
#include <malloc.h>
#include <string.h>
#include <dlfcn.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

typedef enum {
    PLAY = 1,
    STOP = 2
} Command_t;

typedef void * ao_device;

typedef struct _queue_ {
    Command_t command;
    void *buf;
    int buflen;
    double at_second;
    struct _queue_ *next;
    struct _queue_ *prev;
} Queue_t;

typedef struct {
    Queue_t     *play_queue;
    Queue_t     *last_frame;
    ao_device   *ao_device;
    pthread_mutex_t mutex;
    pthread_t    thread;
    double       at_second;
} AO_Handle;

static int(*ao_play)(void *device, char *samples, uint32_t n) = NULL;


static Queue_t *front(AO_Handle *h)
{
    assert(h->play_queue != NULL);
    return h->play_queue;
}

static Queue_t *get(AO_Handle *h)
{
    assert(h->play_queue != NULL);
    Queue_t *q = h->play_queue;
    h->play_queue = h->play_queue->next;
    if (h->play_queue == NULL) {
        h->last_frame = NULL;
    } else {
        h->play_queue->prev = NULL;
    }
    return q;
}

static void add(AO_Handle *h, Queue_t *elem)
{
    if (h->last_frame == NULL) {
        h->play_queue = elem;
        elem->next = NULL;
        elem->prev = NULL;
        h->last_frame = h->play_queue;
    } else {
        h->last_frame->next = elem;
        elem->prev = h->last_frame;
        elem->next = NULL;
        h->last_frame = elem;
    }
}

static Queue_t *new_elem(int command, double at_second, int buf_len, void *buf)
{
    Queue_t *q = (Queue_t *) malloc(sizeof(Queue_t));
    void *new_buf;

    if (buf_len != 0) {
        new_buf = (void *) malloc(buf_len);
        memcpy(new_buf, buf, buf_len);
    } else {
        new_buf = NULL;
    }
    q->at_second = at_second;
    q->buf = new_buf;
    q->buflen = buf_len;
    q->command = command;
    q->next = NULL;
    q->prev = NULL;
    return q;
}

static void del_elem(Queue_t *q)
{
    if (q->buflen != 0) {
        free(q->buf);
    }
    free(q);
}

static void clear(AO_Handle *h)
{
    while (h->play_queue != NULL) {
        Queue_t *q = get(h);
        del_elem(q);
    }
}

static void *run(void *arg)
{
    AO_Handle *handle = (AO_Handle *) arg;

    int go_on = (1 == 1);

    while(go_on) {
        pthread_mutex_lock(&handle->mutex);
        int has_frames = (handle->play_queue != NULL);

        if (has_frames) {
            Queue_t *q = get(handle);
            handle->at_second = q->at_second;
            pthread_mutex_unlock(&handle->mutex);

            if (q->command == STOP) {
                go_on = (1 == 0);
            } else {
                ao_play(handle->ao_device, q->buf, q->buflen);
            }

            del_elem(q);
        } else {
            pthread_mutex_unlock(&handle->mutex);
            usleep(5000);   // sleep for 5ms
        }
    }

    return NULL;
}

static void get_ao_play(void)
{
    char *lib = "libao.so";
    void *handle = dlopen(lib, RTLD_LAZY);
    if (!handle) {
        fprintf(stderr, "Cannot open library %s: %s\n", lib, dlerror());
        exit(EXIT_FAILURE);
    }

    ao_play = dlsym(handle, "ao_play");
    char *err;
    err = dlerror();
    if (err != NULL) {
        fprintf(stderr, "Cannot get function ao_play: %s\n", err);
        exit(EXIT_FAILURE);
    }
}


void *ao_create_async(void *ao_device_yeah)
{
    if (ao_play == NULL) { get_ao_play(); }

    AO_Handle *handle = (AO_Handle *) malloc(sizeof(AO_Handle));

    handle->ao_device = (ao_device *) ao_device_yeah;
    handle->play_queue = NULL;
    handle->last_frame = NULL;
    handle->at_second = -1;
    pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
    handle->mutex = m;

    pthread_create(&handle->thread, NULL, run, handle);

    return (void *) handle;
}

void ao_stop_async(void *ao_handle)
{
    AO_Handle *h = (AO_Handle *) ao_handle;

    pthread_mutex_lock(&h->mutex);
    clear(h);
    Queue_t *q = new_elem(STOP, 0.0, 0, NULL);
    add(h, q);
    pthread_mutex_unlock(&h->mutex);

    void *retval;
    pthread_join(h->thread, &retval);
    free(h);
}

void ao_play_async(void *ao_handle, double at_second, int buf_size, void *mem)
{
    AO_Handle *h = (AO_Handle *) ao_handle;
    Queue_t *q = new_elem(PLAY, at_second, buf_size, mem);
    pthread_mutex_lock(&h->mutex);
    add(h, q);
    pthread_mutex_unlock(&h->mutex);
}

double ao_is_at_second_async(void *ao_handle)
{
    AO_Handle *h = (AO_Handle *) ao_handle;
    return h->at_second;
}