ysynth/pymod.c

#include <Python.h>
#include <SDL/SDL.h>
#include <numpy/arrayobject.h>
#include <mpg123.h>

/* SDL error handling */
PyObject *SDLError;

/* MPG123 error handling */
PyObject *MP3Error;

/* The synthesis context, used mainly
 * for storing audio settings and state.
 */
typedef struct {
    PyObject_HEAD
    int
        samplerate,
        channels;
    int active;
    PyObject *callback;
} PyYSynthContext;

void PyYSynthContext_Dealloc(PyYSynthContext *self)
{
    puts("_ysynth: Dealloc context");
    if (self->active) {
        /* Allow any running Python audio routines
         * to finish their current chunk, then lock out
         * the audio callback and shut the audio device
         * down.
         * It is important to first unlock the GIL otherwise
         * we're at risk of causing deadlock.
         */
        Py_BEGIN_ALLOW_THREADS
        SDL_LockAudio();
        SDL_CloseAudio();
        SDL_UnlockAudio();
        Py_END_ALLOW_THREADS
        self->active = 0;
    }

    Py_XDECREF(self->callback);
    return;
}

PyTypeObject PyYSynthContext_Type;

PyTypeObject PyYSynthContext_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "_ysynth.ysynth context",            /*tp_name*/
    sizeof(PyYSynthContext),       /*tp_basicsize*/
    0,                          /*tp_itemsize*/
    /* methods */
    (destructor)PyYSynthContext_Dealloc, /*tp_dealloc*/
    0,                          /*tp_print*/
    0,                          /*tp_getattr*/
    0,                          /*tp_setattr*/
    0,                          /*tp_compare*/
    0,                          /*tp_repr*/
    0,                          /*tp_as_number*/
    0,                          /*tp_as_sequence*/
    0,                          /*tp_as_mapping*/
    0,                          /*tp_hash*/
};

/* SDL Audio callback */
void _sdl_audio_callback(void *user, Uint8 *stream, int len)
{
    PyYSynthContext *ctx = (PyYSynthContext*)user;
    PyObject *r, *args;
    NPY_AO *channels;
    PyGILState_STATE gstate;
    int local_len = len / sizeof(Sint16) / 2;
    Sint16 *local_stream = (Sint16*)stream;;
    npy_int dims[2] = {local_len, 2};

    /* This function is called from SDL's own thread, so we need to
     * register it with the Python interpreter before calling any
     * Python functions.
     */
    gstate = PyGILState_Ensure();

    /* Setup NumPy array for use within the Python synthesizer */
    channels = PyArray_New(&PyArray_Type, 2, dims, NPY_INT16, NULL, NULL, 2, 0, NULL);

    if (channels)
        args = Py_BuildValue("(O)", channels);

    /* Finally execute the callback */
    if (args)
        r = PyObject_CallObject(ctx->callback, (PyObject*)args);

    /* Print stacktrace if necessary */
    if (!r) {
        if (PyErr_Occurred())
            PyErr_Print();
    } else {
        /* Copy array data to local_stream */
        memcpy(local_stream, channels->data, len);

        /* Free the call's return value, probably Py_None */
        Py_DECREF(r);
    }

    /* Free arguments */
    Py_XDECREF(args);

    /* Free the channels */
    Py_XDECREF(channels);

    /* And leave the GIL */
    PyGILState_Release(gstate);
    return;
}

PyDoc_STRVAR(hello_doc, "Print hello message from Python module");

/* Output hello message */
static PyObject *pymod_hello(PyObject *self, PyObject *args)
{
    PyObject *r = NULL;;

    if (PyArg_ParseTuple(args, "")) {
        printf("Hello from Python module\n");

        Py_INCREF(Py_None);
        r = Py_None;
    }

    return r;
}

PyDoc_STRVAR(_ysynth_init_doc, "Initialise SDL audio and return context");

/* Initialise synthesizer */
static PyObject *_ysynth_init(PyObject *self, PyObject *args)
{
    PyObject *r = NULL;
    PyYSynthContext *ctx;
    int
        samplerate,
        channels;
    SDL_AudioSpec fmt, fmt_obtained;

    if (PyArg_ParseTuple(args, "ii;samplerate, channels", &samplerate, &channels)) {
        ctx = PyObject_NEW(PyYSynthContext, &PyYSynthContext_Type);
        r = (PyObject*)ctx;

        ctx->callback = NULL;

        /* Setup SDL Audio device */
        fmt.freq = samplerate;
        fmt.format = AUDIO_S16;
        fmt.channels = channels;
        fmt.samples = 512;
        fmt.callback = _sdl_audio_callback;
        fmt.userdata = r;

        /* Handle SDL error */
        if (SDL_OpenAudio(&fmt, &fmt_obtained) < 0) {
            PyErr_SetString(SDLError, SDL_GetError());
            Py_DECREF(r);
            return NULL;
        }
        SDL_PauseAudio(0);

        ctx->samplerate = fmt_obtained.freq;
        ctx->channels = fmt_obtained.channels;
        ctx->active = 1;

    }

    return r;
}

PyDoc_STRVAR(_ysynth_shutdown_doc, "Shutdown SDL audio device");

/* Shutdown SDL audio */
static PyObject *_ysynth_shutdown(PyObject *self, PyObject *args)
{
    PyObject *r = NULL;
    PyYSynthContext *ctx;

    if (!PyArg_ParseTuple(args, "O!", &PyYSynthContext_Type, (PyObject**)&ctx))
            {
        ctx->active = 0;
        SDL_CloseAudio();
        Py_XDECREF(ctx->callback);
        r = Py_None;
        Py_INCREF(r);
    }

    return r;
}

PyDoc_STRVAR(_ysynth_set_callback_doc, "Set audio callback");

/* Set Python audio callback */
static PyObject *_ysynth_set_callback(PyObject *self, PyObject *args)
{
    PyObject *r = NULL;
    PyYSynthContext *ctx;
    PyObject *callback;

    if (PyArg_ParseTuple(args, "O!O", &PyYSynthContext_Type, (PyObject**)&ctx,
            &callback)) {
        /* We don't have to lock SDL audio because Python's GIL will
         * have locked out the C callback for us, only this Python thread
         * can be executing at this time.
         */
        Py_XDECREF(ctx->callback);
        ctx->callback = callback;
        Py_INCREF(callback);

        r = Py_None;
        Py_INCREF(r);
    }

    return r;
}

PyDoc_STRVAR(_ysynth_get_callback_doc, "Get audio callback");

/* Get Python audio callback */
static PyObject *_ysynth_get_callback(PyObject *self, PyObject *args)
{
    PyObject *r = NULL;
    PyYSynthContext *ctx;

    if (PyArg_ParseTuple(args, "O!", PyYSynthContext_Type, (PyObject**)&ctx)) {
        if (ctx->callback) {
            Py_INCREF(ctx->callback);
            r = ctx->callback;
        } else {
            r = Py_None;
            Py_INCREF(r);
        }
    }

    return r;
}

/* MP3 Support */
typedef struct {
    PyObject_HEAD
    mpg123_handle *mh;
    int open, eof;
    long rate;
    int
        channels,
        encoding;
} PyYMP3Context;

void PyYMP3Context_Dealloc(PyYMP3Context *ctx)
{
    puts("_ysynth: Dealloc mp3 context");

    /* Close if necessary */
    if (ctx->open)
        mpg123_close(ctx->mh);

    /* Finally free the MP3 decoder handle */
    if (ctx->mh) {
        mpg123_delete(ctx->mh);
        ctx->mh = NULL;
    }

    return;
}

PyTypeObject PyYMP3Context_Type;

PyTypeObject PyYMP3Context_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "_ysynth.ymp3 context",   /*tp_name*/
    sizeof(PyYMP3Context),      /*tp_basicsize*/
    0,                          /*tp_itemsize*/
    /* methods */
    (destructor)PyYMP3Context_Dealloc, /*tp_dealloc*/
    0,                          /*tp_print*/
    0,                          /*tp_getattr*/
    0,                          /*tp_setattr*/
    0,                          /*tp_compare*/
    0,                          /*tp_repr*/
    0,                          /*tp_as_number*/
    0,                          /*tp_as_sequence*/
    0,                          /*tp_as_mapping*/
    0,                          /*tp_hash*/
};

PyDoc_STRVAR(_ysynth_mp3_open_doc, "Open MP3 file and return context,"
    " raises exception if file does not exists\n"
    "Args:\n"
    "    filename: Path string to file\n"
    "Returns:\n"
    "    MP3 context");

/* Open MP3 file */
static PyObject *_ysynth_mp3_open(PyObject *self, PyObject *args)
{
    PyObject *r = NULL;
    char *filename;
    PyYMP3Context *ctx;
    mpg123_handle *mh;
    int err;

    if (PyArg_ParseTuple(args, "s;filename", &filename)) {
        /* Try to open MP3 */
        mh = mpg123_new(NULL, &err);
        if (!mh) {
            PyErr_SetString(MP3Error, mpg123_plain_strerror(err));
            return NULL;
        }

        /* Setup float samples */
        mpg123_param(mh, MPG123_ADD_FLAGS, MPG123_FORCE_FLOAT, 0.);

        /* Open the actual MP3 file */
        if (mpg123_open(mh, filename) != MPG123_OK) {
            PyErr_SetString(MP3Error, mpg123_strerror(mh));
            mpg123_delete(mh);
            return NULL;
        }

        /* Create object */
        ctx = PyObject_NEW(PyYMP3Context, &PyYMP3Context_Type);
        ctx->open = 1;
        ctx->eof = 0;
        ctx->mh = mh;
        r = (PyObject*)ctx;

        if (!ctx) {
            mpg123_close(mh);
            mpg123_delete(mh);
            return NULL;
        }

        /* Check-out file stream format */
        mpg123_getformat(mh, &ctx->rate, &ctx->channels, &ctx->encoding);

        if (ctx->encoding != MPG123_ENC_FLOAT_32) {
            PyErr_SetString(MP3Error,
                "Got non-float encoder while forcing float");
            Py_DECREF(ctx);
            return NULL;
        }

        /* Now don't allow the format to change.
         *
         * FIXME: Later on we probably do want to change this, as to
         * allow YSynth to handle any changes in samplerate instead of
         * allowing MPG123's crude resampler to do the job.
         */
        mpg123_format_none(mh);
        mpg123_format(mh, ctx->rate, ctx->channels, ctx->encoding);
    }

    return r;
}

PyDoc_STRVAR(_ysynth_mp3_close_doc, "Close MP3 file context\n"
    "Args:\n"
    "    context: MP3 context\n"
    "Returns:\n"
    "    None, but raises an MP3Error if the file has already been closed");

/* Close MP3 file */
static PyObject *_ysynth_mp3_close(PyObject *self, PyObject *args)
{
    PyObject *r = NULL;
    PyYMP3Context *ctx;

    if (PyArg_ParseTuple(args, "O!", &PyYMP3Context_Type, (PyObject**)&ctx)) {
        if (ctx->open) {
            ctx->open = 0;
            mpg123_close(ctx->mh);
            r = Py_None;
            Py_INCREF(r);

        } else {
            PyErr_SetString(MP3Error, "File already closed");
            r = NULL;
        }
    }

    return r;
}

PyDoc_STRVAR(_ysynth_mp3_get_format_doc, "Get MP3 format configuration\n"
    "Args: None\n"
    "Returns:\n"
    "    Tuple containing: (samplerate, channels)");

/* Read MP3 data */
static PyObject *_ysynth_mp3_get_format(PyObject *self, PyObject *args)
{
    PyObject *r = NULL;
    PyYMP3Context *ctx;

    if (PyArg_ParseTuple(args, "O!", &PyYMP3Context_Type, (PyObject**)&ctx)) {
        if (ctx->open) {
            r = Py_BuildValue("(ii)", ctx->rate, ctx->channels);
        } else {
            PyErr_SetString(MP3Error, "File has been closed");
        }
    }

    return r;
}

PyDoc_STRVAR(_ysynth_mp3_read_doc, "Read MP3 data\n"
    "Args:\n"
    "    context: Open MP3 context\n"
    "    samples: Number of samples to decode\n"
    "Returns:\n"
    "    A NumPy array of shape (samples, channels)\n"
    "    This function raises an MP3Error on decode failure.\n"
    "    It shall output silence on EOF");

/* Read MP3 data */
static PyObject *_ysynth_mp3_read(PyObject *self, PyObject *args)
{
    PyObject *r = NULL;
    PyYMP3Context *ctx;
    int samples, bytes_read;
    int err;
    npy_int dims[2];
    NPY_AO *stream;

    if (PyArg_ParseTuple(args, "O!i", &PyYMP3Context_Type, (PyObject**)&ctx, &samples)) {
        if (ctx->open) {
            /* Allocate output array */
            dims[0] = samples;
            dims[1] = ctx->channels;
            stream = PyArray_New(&PyArray_Type, 2, dims, NPY_FLOAT32, NULL, NULL, 4, 0, NULL);

            if (!stream)
                return NULL;
            r = (PyObject*)stream;

            /* EOF Generates a silence stream */
            if (ctx->eof) {

                memset(PyArray_DATA(stream), 0x0, PyArray_NBYTES(stream));
            } else {

                /* Read the next set of MP3 samples */
                err = mpg123_read(ctx->mh, PyArray_DATA(stream),
                    PyArray_NBYTES(stream), &bytes_read);

                /* Handle any weird errors */
                if (err != MPG123_OK) {
                    if (err == MPG123_DONE) {
                        ctx->eof = 1;
                    } else {
                        Py_DECREF(stream);
                        PyErr_SetString(MP3Error, mpg123_strerror(ctx->mh));
                        return NULL;
                    }
                }

                /* Fill any missing data with silence, and of course complain
                 * whenever necessary
                 */
                if (bytes_read != PyArray_NBYTES(stream)) {
                    if (!ctx->eof)
                        fprintf(stderr, "warning: MPG123 did not return"
                            " enough data but did not set MPG123_DONE"
                            " either..\n");
                    memset(PyArray_BYTES(stream) + bytes_read, 0x0,
                        PyArray_NBYTES(stream) - bytes_read);
                }
            }
        } else {
            PyErr_SetString(MP3Error, "File has been closed");
        }
    }

    return r;
}

/* TODO: Let's use the same strategy NumPy uses for its built-ins, provide
 * the function signature in the docstrings
 */

PyDoc_STRVAR(_ysynth_mp3_seek_doc, "Seek to position in MP3\n"
    "Args:\n"
    "    context: Open MP3 context, providing somehting else\n"
    "             will result in an exception\n"
    "    position:  Integer position in samples to seek to\n"
    "Returns:\n"
    "    None, this functions raises an MP3Error when errors are encountered");

/* Seek MP3 data */
static PyObject *_ysynth_mp3_seek(PyObject *self, PyObject *args)
{
    PyObject *r = NULL;
    PyYMP3Context *ctx;
    int sample;
    int err;

    if (PyArg_ParseTuple(args, "O!i;context, position", &PyYMP3Context_Type,
            (PyObject**)&ctx, &sample)) {
        if (ctx->open) {
            err = mpg123_seek(ctx->mh, sample, SEEK_SET);
            if (err < 0) {
                PyErr_SetString(MP3Error, mpg123_strerror(ctx->mh));
            } else {
                r = Py_None;
                Py_INCREF(r);
            }
        } else {
            PyErr_SetString(MP3Error, "File has been closed");
        }
    }

    return r;
}

/* Exported methods */
static PyMethodDef pymod_methods[] = {
    {"_ysynth_init",            (PyCFunction)_ysynth_init,
        METH_VARARGS,           _ysynth_init_doc},
    {"_ysynth_shutdown",        (PyCFunction)_ysynth_shutdown,
        METH_VARARGS,           _ysynth_shutdown_doc},
    {"_ysynth_set_callback",    (PyCFunction)_ysynth_set_callback,
        METH_VARARGS,           _ysynth_set_callback_doc},
    {"_ysynth_get_callback",    (PyCFunction)_ysynth_get_callback,
        METH_VARARGS,           _ysynth_get_callback_doc},
    {"_ysynth_mp3_open",    (PyCFunction)_ysynth_mp3_open,
        METH_VARARGS,           _ysynth_mp3_open_doc},
    {"_ysynth_mp3_close",    (PyCFunction)_ysynth_mp3_close,
        METH_VARARGS,           _ysynth_mp3_close_doc},
    {"_ysynth_mp3_get_format",    (PyCFunction)_ysynth_mp3_get_format,
        METH_VARARGS,           _ysynth_mp3_get_format_doc},
    {"_ysynth_mp3_read",    (PyCFunction)_ysynth_mp3_read,
        METH_VARARGS,           _ysynth_mp3_read_doc},
    {"_ysynth_mp3_seek",    (PyCFunction)_ysynth_mp3_seek,
        METH_VARARGS,           _ysynth_mp3_seek_doc},
    {"hello",        (PyCFunction)pymod_hello,
        METH_VARARGS,           hello_doc},
    {NULL,              NULL}           /* sentinel */
};

/* Shutdown SDL/MPG123 */
void exitpymod(void)
{
    mpg123_exit();
    /* XXX: Should we check for successful initialisation of SDL? */
    SDL_Quit();
}


PyDoc_STRVAR(module_doc, "Simple test module");

/* Module initialisation, called by Python on import */
PyMODINIT_FUNC
initpymod(void)
{
    PyObject *m;
    int err;

    /* Setup SDL audio without signal handlers */
    if (SDL_Init(SDL_INIT_AUDIO | SDL_INIT_NOPARACHUTE) < 0)
        return;

#if 1
    /* Setup MPG123 */
    if ((err = mpg123_init()) != MPG123_OK) {
        fprintf(stderr, "Failure while initialising mgp123: %s\n",
            mpg123_plain_strerror(err));
        return;
    }
#endif

    /* Register exit handler
     * XXX: Later on try to use Python's atexit module?
     */
    atexit(exitpymod);

    puts("Hoi, module pymod loaded.");
    m = Py_InitModule3("pymod", pymod_methods, module_doc);
    if (m == NULL)
        return;

    /* Setup exceptions */
    SDLError = PyErr_NewException("_ysynth.SDLError", NULL, NULL);
    Py_INCREF(SDLError);
    PyModule_AddObject(m, "SDLError", SDLError);

    MP3Error = PyErr_NewException("_ysynth.MP3Error", NULL, NULL);
    Py_INCREF(MP3Error);
    PyModule_AddObject(m, "MP3Error", MP3Error);

    /* Setup types */
    if (PyType_Ready(&PyYSynthContext_Type) < 0)
        return;

    if (PyType_Ready(&PyYMP3Context_Type) < 0)
        return;

    /* Our module requires the GIL to be available */
    if (!PyEval_ThreadsInitialized()) {
        puts("Initialising multithreading for Python");
        PyEval_InitThreads();
    }

    import_array();

    return;
}