[pulseaudio-discuss] Threaded Main Loop data callbacks
Mitchell Fang
mitchell.fang at gmail.com
Wed Mar 20 13:51:22 PDT 2013
Hi,
I have a question about how to use the threaded main loop data callback
feature. I've been looking at the documentation and trying it out.
To try the data callback, I've taken the AsyncDeviceList example ,
changed the mainloop to a threaded mainloop and tried to make the callback
here use the pa_threaded_mainloop_signal(ml,1) and
pa_threaded_mainloop_accept(). I'm not sure if I'm putting the signal(ml,
1) in the wrong place but the programs hangs for me. What I've noticed is
after the call to signal(1) from the callback, when the wait() wakes up,
the return value of get_state() is still OPERATION_RUNNING.
From my understanding this makes sense because the accept() needs to be
called in order for the signal to progress. However, the documentation's
example of data callbacks is coded this way so I'm a bit lost as to how
properly go about this.
Some help and clarification would be helpful. Also, I will add this
example to the wiki page when resolved.
Thanks for your time,
Mitchell
p.s. I have copied the code below and also attached it.
gcc -Wall -o pulsedevicelist pulsedevicelist.c -lpulse
Resources:
http://freedesktop.org/software/pulseaudio/doxygen/threaded_mainloop.html
http://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/Developer/Clients/Samples/AsyncDeviceList
#include <stdio.h>
#include <string.h>
#include <pulse/pulseaudio.h>
#include <pulse/stream.h>
// Field list is here:
http://0pointer.de/lennart/projects/pulseaudio/doxygen/structpa__sink__info.html
typedef struct pa_devicelist {
uint8_t initialized;
char name[512];
uint32_t index;
char description[256];
} pa_devicelist_t;
void pa_state_cb(pa_context *c, void *userdata);
void pa_sinklist_cb(pa_context *c, const pa_sink_info *l, int eol, void
*userdata);
void pa_sourcelist_cb(pa_context *c, const pa_source_info *l, int eol, void
*userdata);
int pa_get_devicelist(pa_devicelist_t *input, pa_devicelist_t *output);
pa_threaded_mainloop *pa_ml;
int main(int argc, char *argv[]) {
int ctr;
// This is where we'll store the input device list
pa_devicelist_t pa_input_devicelist[16];
// This is where we'll store the output device list
pa_devicelist_t pa_output_devicelist[16];
if (pa_get_devicelist(pa_input_devicelist, pa_output_devicelist) < 0) {
fprintf(stderr, "failed to get device list\n");
return 1;
}
for (ctr = 0; ctr < 16; ctr++) {
if (! pa_output_devicelist[ctr].initialized) {
break;
}
printf("=======[ Output Device #%d ]=======\n", ctr+1);
printf("Description: %s\n", pa_output_devicelist[ctr].description);
printf("Name: %s\n", pa_output_devicelist[ctr].name);
printf("Index: %d\n", pa_output_devicelist[ctr].index);
printf("\n");
}
for (ctr = 0; ctr < 16; ctr++) {
if (! pa_input_devicelist[ctr].initialized) {
break;
}
printf("=======[ Input Device #%d ]=======\n", ctr+1);
printf("Description: %s\n", pa_input_devicelist[ctr].description);
printf("Name: %s\n", pa_input_devicelist[ctr].name);
printf("Index: %d\n", pa_input_devicelist[ctr].index);
printf("\n");
}
return 0;
}
int pa_get_devicelist(pa_devicelist_t *input, pa_devicelist_t *output) {
// Define our pulse audio loop and connection variables
//pa_threaded_mainloop *pa_ml;
pa_mainloop_api *pa_mlapi;
pa_operation *pa_op;
pa_context *pa_ctx;
pa_operation_state_t temp;
// We'll need these state variables to keep track of our requests
int state = 0;
int pa_ready = 0;
// Initialize our device lists
memset(input, 0, sizeof(pa_devicelist_t) * 16);
memset(output, 0, sizeof(pa_devicelist_t) * 16);
// Create a mainloop API and connection to the default server
pa_ml = pa_threaded_mainloop_new();
pa_mlapi = pa_threaded_mainloop_get_api(pa_ml);
pa_ctx = pa_context_new(pa_mlapi, "test");
//pa_stream *s = pa_stream_new(pa_ctx, "stream", &ss, &map);
// This function connects to the pulse server
pa_context_connect(pa_ctx, NULL, PA_CONTEXT_NOFLAGS, NULL);
// This function defines a callback so the server will tell us it's
state.
// Our callback will wait for the state to be ready. The callback will
// modify the variable to 1 so we know when we have a connection and
it's
// ready.
// If there's an error, the callback will set pa_ready to 2
pa_context_set_state_callback(pa_ctx, pa_state_cb, &pa_ready);
pa_threaded_mainloop_start(pa_ml);
// Now we'll enter into an infinite loop until we get the data we
receive
// or if there's an error
for (;;) {
// We can't do anything until PA is ready, so just iterate the
mainloop
// and continue
if (pa_ready == 0) {
//pa_mainloop_iterate(pa_ml, 1, NULL);
continue;
}
// We couldn't get a connection to the server, so exit out
if (pa_ready == 2) {
pa_context_disconnect(pa_ctx);
pa_context_unref(pa_ctx);
pa_threaded_mainloop_free(pa_ml);
return -1;
}
// At this point, we're connected to the server and ready to make
// requests
switch (state) {
// State 0: we haven't done anything yet
case 0:
// This sends an operation to the server. pa_sinklist_info
is
// our callback function and a pointer to our devicelist
will
// be passed to the callback The operation ID is stored in
the
// pa_op variable
pa_threaded_mainloop_lock(pa_ml);
pa_op = pa_context_get_sink_info_list(pa_ctx,
pa_sinklist_cb,
output
);
while (pa_operation_get_state(pa_op) ==
PA_OPERATION_RUNNING) { // MF
temp = pa_operation_get_state(pa_op); // MF
pa_threaded_mainloop_wait(pa_ml); // MF
} // MF
// Update state for next iteration through the loop
state++;
break;
case 1:
// Now we wait for our operation to complete. When it's
// complete our pa_output_devicelist is filled out, and we
move
// along to the next state
if (pa_operation_get_state(pa_op) == PA_OPERATION_DONE) {
pa_operation_unref(pa_op);
pa_threaded_mainloop_accept(pa_ml); // MF
pa_threaded_mainloop_unlock(pa_ml); // MF
// Now we perform another operation to get the source
// (input device) list just like before. This time we
pass
// a pointer to our input structure
pa_threaded_mainloop_lock(pa_ml);
pa_op = pa_context_get_source_info_list(pa_ctx,
pa_sourcelist_cb,
input
);
// Update the state so we know what to do next
state++;
}
break;
case 2:
if (pa_operation_get_state(pa_op) == PA_OPERATION_DONE) {
// Now we're done, clean up and disconnect and return
pa_operation_unref(pa_op);
pa_context_disconnect(pa_ctx);
pa_context_unref(pa_ctx);
pa_threaded_mainloop_free(pa_ml);
return 0;
}
break;
default:
// We should never see this state
fprintf(stderr, "in state %d\n", state);
return -1;
}
// Iterate the main loop and go again. The second argument is
whether
// or not the iteration should block until something is ready to be
// done. Set it to zero for non-blocking.
//pa_mainloop_iterate(pa_ml, 1, NULL);
}
}
// This callback gets called when our context changes state. We really only
// care about when it's ready or if it has failed
void pa_state_cb(pa_context *c, void *userdata) {
pa_context_state_t state;
int *pa_ready = (int *)userdata;
state = pa_context_get_state(c);
switch (state) {
// There are just here for reference
case PA_CONTEXT_UNCONNECTED:
case PA_CONTEXT_CONNECTING:
case PA_CONTEXT_AUTHORIZING:
case PA_CONTEXT_SETTING_NAME:
default:
break;
case PA_CONTEXT_FAILED:
case PA_CONTEXT_TERMINATED:
*pa_ready = 2;
break;
case PA_CONTEXT_READY:
*pa_ready = 1;
break;
}
}
// pa_mainloop will call this function when it's ready to tell us about a
sink.
// Since we're not threading, there's no need for mutexes on the devicelist
// structure
void pa_sinklist_cb(pa_context *c, const pa_sink_info *l, int eol, void
*userdata) {
pa_devicelist_t *pa_devicelist = (pa_devicelist_t *)userdata;
int ctr = 0;
// If eol is set to a positive number, you're at the end of the list
if (eol > 0) {
pa_threaded_mainloop_signal(pa_ml, 1); // MF
return;
}
// We know we've allocated 16 slots to hold devices. Loop through our
// structure and find the first one that's "uninitialized." Copy the
// contents into it and we're done. If we receive more than 16 devices,
// they're going to get dropped. You could make this dynamically
allocate
// space for the device list, but this is a simple example.
for (ctr = 0; ctr < 16; ctr++) {
if (! pa_devicelist[ctr].initialized) {
strncpy(pa_devicelist[ctr].name, l->name, 511);
strncpy(pa_devicelist[ctr].description, l->description, 255);
pa_devicelist[ctr].index = l->index;
pa_devicelist[ctr].initialized = 1;
break;
}
}
}
// See above. This callback is pretty much identical to the previous
void pa_sourcelist_cb(pa_context *c, const pa_source_info *l, int eol, void
*userdata) {
pa_devicelist_t *pa_devicelist = (pa_devicelist_t *)userdata;
int ctr = 0;
if (eol > 0) {
return;
}
for (ctr = 0; ctr < 16; ctr++) {
if (! pa_devicelist[ctr].initialized) {
strncpy(pa_devicelist[ctr].name, l->name, 511);
strncpy(pa_devicelist[ctr].description, l->description, 255);
pa_devicelist[ctr].index = l->index;
pa_devicelist[ctr].initialized = 1;
break;
}
}
}
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