Adds read_sw function to be able to read any size of frames.

src/alsaaudio.c

@@ -1448,6 +1448,114 @@ alsapcm_read(alsapcm_t *self, PyObject *args)
 	return tuple_obj;
 }
 
+static PyObject *
+alsapcm_read_sw(alsapcm_t *self, PyObject *args)
+{
+	snd_pcm_state_t state;
+	int res;
+	int max_frames_to_read;
+	int size;
+	int sizeout = 0;
+	PyObject *buffer_obj, *tuple_obj, *res_obj;
+	char *buffer;
+
+	if (!PyArg_ParseTuple(args,"i:read_sw", &max_frames_to_read))
+		return NULL;
+
+	if (!self->handle) {
+		PyErr_SetString(ALSAAudioError, "PCM device is closed");
+		return NULL;
+  }
+
+	if (self->pcmtype != SND_PCM_STREAM_CAPTURE)
+	{
+		PyErr_Format(ALSAAudioError, "Cannot read from playback PCM [%s]",
+					 self->cardname);
+		return NULL;
+	}
+
+	size = self->framesize * max_frames_to_read;
+
+#if PY_MAJOR_VERSION < 3
+	buffer_obj = PyString_FromStringAndSize(NULL, size);
+	if (!buffer_obj)
+		return NULL;
+	buffer = PyString_AS_STRING(buffer_obj);
+#else
+	buffer_obj = PyBytes_FromStringAndSize(NULL, size);
+	if (!buffer_obj)
+		return NULL;
+	buffer = PyBytes_AS_STRING(buffer_obj);
+#endif
+
+	// After drop() and drain(), we need to prepare the stream again.
+	// Note that fresh streams are already prepared by snd_pcm_hw_params().
+	state = snd_pcm_state(self->handle);
+	if ((state != SND_PCM_STATE_SETUP) ||
+		!(res = snd_pcm_prepare(self->handle))) {
+
+		Py_BEGIN_ALLOW_THREADS
+		res = snd_pcm_readi(self->handle, buffer, max_frames_to_read);
+		Py_END_ALLOW_THREADS
+
+		if (res == -EPIPE) {
+			// This means buffer overrun, which we need to report.
+			// However, we recover the stream, so the next PCM.read() will work
+			// again. If recovery fails (very unlikely), report that instead.
+			if (!(res = snd_pcm_prepare(self->handle)))
+				res = -EPIPE;
+		}
+	}
+
+	if (res != -EPIPE)
+	{
+		if (res == -EAGAIN)
+		{
+			res = 0;
+		}
+		else if (res < 0) {
+			PyErr_Format(ALSAAudioError, "%s [%s]", snd_strerror(res),
+						 self->cardname);
+
+			Py_DECREF(buffer_obj);
+			return NULL;
+		}
+		else
+		{
+			sizeout = res * self->framesize;
+		}
+	}
+
+	if (size != sizeout) {
+#if PY_MAJOR_VERSION < 3
+		/* If the following fails, it will free the object */
+		if (_PyString_Resize(&buffer_obj, sizeout))
+			return NULL;
+#else
+		/* If the following fails, it will free the object */
+		if (_PyBytes_Resize(&buffer_obj, sizeout))
+			return NULL;
+#endif
+	}
+
+	res_obj = PyLong_FromLong(res);
+	if (!res_obj) {
+		Py_DECREF(buffer_obj);
+		return NULL;
+	}
+	tuple_obj = PyTuple_New(2);
+	if (!tuple_obj) {
+		Py_DECREF(buffer_obj);
+		Py_DECREF(res_obj);
+		return NULL;
+	}
+	/* Steal reference counts */
+	PyTuple_SET_ITEM(tuple_obj, 0, res_obj);
+	PyTuple_SET_ITEM(tuple_obj, 1, buffer_obj);
+
+	return tuple_obj;
+}
+
 static PyObject *alsapcm_write(alsapcm_t *self, PyObject *args)
 {
 	int datalen;
@@ -1767,6 +1875,7 @@ static PyMethodDef alsapcm_methods[] = {
 	{"getratebounds", (PyCFunction)alsapcm_getratemaxmin, METH_VARARGS},
 	{"getrates", (PyCFunction)alsapcm_getrates, METH_VARARGS},
 	{"read", (PyCFunction)alsapcm_read, METH_VARARGS},
+	{"read_sw", (PyCFunction)alsapcm_read_sw, METH_VARARGS},
 	{"write", (PyCFunction)alsapcm_write, METH_VARARGS},
 	{"avail", (PyCFunction)alsapcm_avail, METH_VARARGS},
 	{"pause", (PyCFunction)alsapcm_pause, METH_VARARGS},