nncmpp/mpd.c

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// Copied from desktop-tools, should go to liberty if it proves useful
// --- MPD client interface ----------------------------------------------------
// This is a rather thin MPD client interface intended for basic tasks
#define MPD_SUBSYSTEM_TABLE(XX) \
XX (DATABASE, 0, "database") \
XX (UPDATE, 1, "update") \
XX (STORED_PLAYLIST, 2, "stored_playlist") \
XX (PLAYLIST, 3, "playlist") \
XX (PLAYER, 4, "player") \
XX (MIXER, 5, "mixer") \
XX (OUTPUT, 6, "output") \
XX (OPTIONS, 7, "options") \
XX (STICKER, 8, "sticker") \
XX (SUBSCRIPTION, 9, "subscription") \
XX (MESSAGE, 10, "message")
enum mpd_subsystem
{
#define XX(a, b, c) MPD_SUBSYSTEM_ ## a = (1 << b),
MPD_SUBSYSTEM_TABLE (XX)
#undef XX
MPD_SUBSYSTEM_MAX
};
static const char *mpd_subsystem_names[] =
{
#define XX(a, b, c) [b] = c,
MPD_SUBSYSTEM_TABLE (XX)
#undef XX
};
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
enum mpd_client_state
{
MPD_DISCONNECTED, ///< Not connected
MPD_CONNECTING, ///< Currently connecting
MPD_CONNECTED ///< Connected
};
struct mpd_response
{
bool success; ///< OK or ACK
// ACK-only fields:
int error; ///< Numeric error value (ack.h)
int list_offset; ///< Offset of command in list
char *current_command; ///< Name of the erroring command
char *message_text; ///< Error message
};
/// Task completion callback
typedef void (*mpd_client_task_cb) (const struct mpd_response *response,
const struct str_vector *data, void *user_data);
struct mpd_client_task
{
LIST_HEADER (struct mpd_client_task)
mpd_client_task_cb callback; ///< Callback on completion
void *user_data; ///< User data
};
struct mpd_client
{
struct poller *poller; ///< Poller
// Connection:
enum mpd_client_state state; ///< Connection state
struct connector *connector; ///< Connection establisher
int socket; ///< MPD socket
struct str read_buffer; ///< Input yet to be processed
struct str write_buffer; ///< Outut yet to be be sent out
struct poller_fd socket_event; ///< We can read from the socket
struct poller_timer timeout_timer; ///< Connection seems to be dead
// Protocol:
bool got_hello; ///< Got the OK MPD hello message
bool idling; ///< Sent idle as the last command
unsigned idling_subsystems; ///< Subsystems we're idling for
bool in_list; ///< We're inside a command list
struct mpd_client_task *tasks; ///< Task queue
struct mpd_client_task *tasks_tail; ///< Tail of task queue
struct str_vector data; ///< Data from last command
// User configuration:
void *user_data; ///< User data for callbacks
/// Callback after connection has been successfully established
void (*on_connected) (void *user_data);
/// Callback for general failures or even normal disconnection;
/// the interface is reinitialized
void (*on_failure) (void *user_data);
/// Callback to receive "idle" updates.
/// Remember to restart the idle if needed.
void (*on_event) (unsigned subsystems, void *user_data);
};
static void mpd_client_reset (struct mpd_client *self);
static void mpd_client_destroy_connector (struct mpd_client *self);
static void
mpd_client_init (struct mpd_client *self, struct poller *poller)
{
memset (self, 0, sizeof *self);
self->poller = poller;
self->socket = -1;
str_init (&self->read_buffer);
str_init (&self->write_buffer);
str_vector_init (&self->data);
poller_fd_init (&self->socket_event, poller, -1);
poller_timer_init (&self->timeout_timer, poller);
}
static void
mpd_client_free (struct mpd_client *self)
{
// So that we don't have to repeat most of the stuff
mpd_client_reset (self);
str_free (&self->read_buffer);
str_free (&self->write_buffer);
str_vector_free (&self->data);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
/// Reinitialize the interface so that you can reconnect anew
static void
mpd_client_reset (struct mpd_client *self)
{
if (self->state == MPD_CONNECTING)
mpd_client_destroy_connector (self);
if (self->socket != -1)
xclose (self->socket);
self->socket = -1;
self->socket_event.closed = true;
poller_fd_reset (&self->socket_event);
poller_timer_reset (&self->timeout_timer);
str_reset (&self->read_buffer);
str_reset (&self->write_buffer);
str_vector_reset (&self->data);
self->got_hello = false;
self->idling = false;
self->idling_subsystems = 0;
self->in_list = false;
LIST_FOR_EACH (struct mpd_client_task, iter, self->tasks)
free (iter);
self->tasks = self->tasks_tail = NULL;
self->state = MPD_DISCONNECTED;
}
static void
mpd_client_fail (struct mpd_client *self)
{
mpd_client_reset (self);
if (self->on_failure)
self->on_failure (self->user_data);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
mpd_client_parse_response (const char *p, struct mpd_response *response)
{
if (!strcmp (p, "OK"))
return response->success = true;
if (!strcmp (p, "list_OK"))
// TODO: either implement this or fail the connection properly
hard_assert (!"command_list_ok_begin not implemented");
char *end = NULL;
if (*p++ != 'A' || *p++ != 'C' || *p++ != 'K' || *p++ != ' ' || *p++ != '[')
return false;
errno = 0;
response->error = strtoul (p, &end, 10);
if (errno != 0 || end == p)
return false;
p = end;
if (*p++ != '@')
return false;
errno = 0;
response->list_offset = strtoul (p, &end, 10);
if (errno != 0 || end == p)
return false;
p = end;
if (*p++ != ']' || *p++ != ' ' || *p++ != '{' || !(end = strchr (p, '}')))
return false;
response->current_command = xstrndup (p, end - p);
p = end + 1;
if (*p++ != ' ')
return false;
response->message_text = xstrdup (p);
response->success = false;
return true;
}
static void
mpd_client_dispatch (struct mpd_client *self, struct mpd_response *response)
{
struct mpd_client_task *task;
if (!(task = self->tasks))
return;
if (task->callback)
task->callback (response, &self->data, task->user_data);
str_vector_reset (&self->data);
LIST_UNLINK_WITH_TAIL (self->tasks, self->tasks_tail, task);
free (task);
}
static bool
mpd_client_parse_hello (struct mpd_client *self, const char *line)
{
const char hello[] = "OK MPD ";
if (strncmp (line, hello, sizeof hello - 1))
{
print_debug ("invalid MPD hello message");
return false;
}
// TODO: call "on_connected" now. We should however also set up a timer
// so that we don't wait on this message forever.
return self->got_hello = true;
}
static bool
mpd_client_parse_line (struct mpd_client *self, const char *line)
{
print_debug ("MPD >> %s", line);
if (!self->got_hello)
return mpd_client_parse_hello (self, line);
struct mpd_response response;
memset (&response, 0, sizeof response);
if (mpd_client_parse_response (line, &response))
{
mpd_client_dispatch (self, &response);
free (response.current_command);
free (response.message_text);
}
else
str_vector_add (&self->data, line);
return true;
}
/// All output from MPD commands seems to be in a trivial "key: value" format
static char *
mpd_client_parse_kv (char *line, char **value)
{
char *sep;
if (!(sep = strstr (line, ": ")))
return NULL;
*sep = 0;
*value = sep + 2;
return line;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static void
mpd_client_update_poller (struct mpd_client *self)
{
poller_fd_set (&self->socket_event,
self->write_buffer.len ? (POLLIN | POLLOUT) : POLLIN);
}
static bool
mpd_client_process_input (struct mpd_client *self)
{
// Split socket input at newlines and process them separately
struct str *rb = &self->read_buffer;
char *start = rb->str, *end = start + rb->len;
for (char *p = start; p < end; p++)
{
if (*p != '\n')
continue;
*p = 0;
if (!mpd_client_parse_line (self, start))
return false;
start = p + 1;
}
str_remove_slice (rb, 0, start - rb->str);
return true;
}
static void
mpd_client_on_ready (const struct pollfd *pfd, void *user_data)
{
(void) pfd;
struct mpd_client *self = user_data;
if (socket_io_try_read (self->socket, &self->read_buffer) != SOCKET_IO_OK
|| !mpd_client_process_input (self)
|| socket_io_try_write (self->socket, &self->write_buffer) != SOCKET_IO_OK)
mpd_client_fail (self);
else
mpd_client_update_poller (self);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
mpd_client_must_quote_char (char c)
{
return (unsigned char) c <= ' ' || c == '"' || c == '\'';
}
static bool
mpd_client_must_quote (const char *s)
{
if (!*s)
return true;
for (; *s; s++)
if (mpd_client_must_quote_char (*s))
return true;
return false;
}
static void
mpd_client_quote (const char *s, struct str *output)
{
str_append_c (output, '"');
for (; *s; s++)
{
if (mpd_client_must_quote_char (*s))
str_append_c (output, '\\');
str_append_c (output, *s);
}
str_append_c (output, '"');
}
/// Beware that delivery of the event isn't deferred and you musn't make
/// changes to the interface while processing the event!
static void
mpd_client_add_task
(struct mpd_client *self, mpd_client_task_cb cb, void *user_data)
{
// This only has meaning with command_list_ok_begin, and then it requires
// special handling (all in-list tasks need to be specially marked and
// later flushed if an early ACK or OK arrives).
hard_assert (!self->in_list);
struct mpd_client_task *task = xcalloc (1, sizeof *self);
task->callback = cb;
task->user_data = user_data;
LIST_APPEND_WITH_TAIL (self->tasks, self->tasks_tail, task);
}
/// Send a command. Remember to call mpd_client_add_task() to handle responses,
/// unless the command is being sent in a list.
static void mpd_client_send_command
(struct mpd_client *self, const char *command, ...) ATTRIBUTE_SENTINEL;
static void
mpd_client_send_commandv (struct mpd_client *self, char **commands)
{
// Automatically interrupt idle mode
if (self->idling)
{
poller_timer_reset (&self->timeout_timer);
self->idling = false;
self->idling_subsystems = 0;
mpd_client_send_command (self, "noidle", NULL);
}
struct str line;
str_init (&line);
for (; *commands; commands++)
{
if (line.len)
str_append_c (&line, ' ');
if (mpd_client_must_quote (*commands))
mpd_client_quote (*commands, &line);
else
str_append (&line, *commands);
}
print_debug ("MPD << %s", line.str);
str_append_c (&line, '\n');
str_append_str (&self->write_buffer, &line);
str_free (&line);
mpd_client_update_poller (self);
}
static void
mpd_client_send_command (struct mpd_client *self, const char *command, ...)
{
struct str_vector v;
str_vector_init (&v);
va_list ap;
va_start (ap, command);
for (; command; command = va_arg (ap, const char *))
str_vector_add (&v, command);
va_end (ap);
mpd_client_send_commandv (self, v.vector);
str_vector_free (&v);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static void
mpd_client_list_begin (struct mpd_client *self)
{
hard_assert (!self->in_list);
mpd_client_send_command (self, "command_list_begin", NULL);
self->in_list = true;
}
/// End a list of commands. Remember to call mpd_client_add_task()
/// to handle the summary response.
static void
mpd_client_list_end (struct mpd_client *self)
{
hard_assert (self->in_list);
mpd_client_send_command (self, "command_list_end", NULL);
self->in_list = false;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static bool
mpd_resolve_subsystem (const char *name, unsigned *output)
{
for (size_t i = 0; i < N_ELEMENTS (mpd_subsystem_names); i++)
if (!strcasecmp_ascii (name, mpd_subsystem_names[i]))
{
*output |= 1 << i;
return true;
}
return false;
}
static void
mpd_client_on_idle_return (const struct mpd_response *response,
const struct str_vector *data, void *user_data)
{
(void) response;
struct mpd_client *self = user_data;
unsigned subsystems = 0;
for (size_t i = 0; i < data->len; i++)
{
char *value, *key;
if (!(key = mpd_client_parse_kv (data->vector[i], &value)))
print_debug ("%s: %s", "erroneous MPD output", data->vector[i]);
else if (strcasecmp_ascii (key, "changed"))
print_debug ("%s: %s", "unexpected idle key", key);
else if (!mpd_resolve_subsystem (value, &subsystems))
print_debug ("%s: %s", "unknown subsystem", value);
}
// Not resetting "idling" here, we may send an extra "noidle" no problem
if (self->on_event && subsystems)
self->on_event (subsystems, self->user_data);
}
static void mpd_client_idle (struct mpd_client *self, unsigned subsystems);
static void
mpd_client_on_timeout (void *user_data)
{
struct mpd_client *self = user_data;
unsigned subsystems = self->idling_subsystems;
// Just sending this out should bring a dead connection down over TCP
// TODO: set another timer to make sure the ping reply arrives
mpd_client_send_command (self, "ping", NULL);
mpd_client_add_task (self, NULL, NULL);
// Restore the incriminating idle immediately
mpd_client_idle (self, subsystems);
}
/// When not expecting to send any further commands, you should call this
/// in order to keep the connection alive. Or to receive updates.
static void
mpd_client_idle (struct mpd_client *self, unsigned subsystems)
{
hard_assert (!self->in_list);
struct str_vector v;
str_vector_init (&v);
str_vector_add (&v, "idle");
for (size_t i = 0; i < N_ELEMENTS (mpd_subsystem_names); i++)
if (subsystems & (1 << i))
str_vector_add (&v, mpd_subsystem_names[i]);
mpd_client_send_commandv (self, v.vector);
str_vector_free (&v);
self->timeout_timer.dispatcher = mpd_client_on_timeout;
self->timeout_timer.user_data = self;
poller_timer_set (&self->timeout_timer, 5 * 60 * 1000);
mpd_client_add_task (self, mpd_client_on_idle_return, self);
self->idling = true;
self->idling_subsystems = subsystems;
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
static void
mpd_client_finish_connection (struct mpd_client *self, int socket)
{
set_blocking (socket, false);
self->socket = socket;
self->state = MPD_CONNECTED;
poller_fd_init (&self->socket_event, self->poller, self->socket);
self->socket_event.dispatcher = mpd_client_on_ready;
self->socket_event.user_data = self;
mpd_client_update_poller (self);
if (self->on_connected)
self->on_connected (self->user_data);
}
static void
mpd_client_destroy_connector (struct mpd_client *self)
{
if (self->connector)
connector_free (self->connector);
free (self->connector);
self->connector = NULL;
// Not connecting anymore
self->state = MPD_DISCONNECTED;
}
static void
mpd_client_on_connector_failure (void *user_data)
{
struct mpd_client *self = user_data;
mpd_client_destroy_connector (self);
mpd_client_fail (self);
}
static void
mpd_client_on_connector_connected
(void *user_data, int socket, const char *host)
{
(void) host;
struct mpd_client *self = user_data;
mpd_client_destroy_connector (self);
mpd_client_finish_connection (self, socket);
}
static bool
mpd_client_connect_unix (struct mpd_client *self, const char *address,
struct error **e)
{
int fd = socket (AF_UNIX, SOCK_STREAM, 0);
if (fd == -1)
{
error_set (e, "%s: %s", "socket", strerror (errno));
return false;
}
// Expand tilde if needed
char *expanded = resolve_filename (address, xstrdup);
struct sockaddr_un sun;
sun.sun_family = AF_UNIX;
strncpy (sun.sun_path, expanded, sizeof sun.sun_path);
sun.sun_path[sizeof sun.sun_path - 1] = 0;
free (expanded);
if (connect (fd, (struct sockaddr *) &sun, sizeof sun))
{
error_set (e, "%s: %s", "connect", strerror (errno));
return false;
}
mpd_client_finish_connection (self, fd);
return true;
}
static bool
mpd_client_connect (struct mpd_client *self, const char *address,
const char *service, struct error **e)
{
hard_assert (self->state == MPD_DISCONNECTED);
// If it looks like a path, assume it's a UNIX socket
if (strchr (address, '/'))
return mpd_client_connect_unix (self, address, e);
struct connector *connector = xmalloc (sizeof *connector);
connector_init (connector, self->poller);
self->connector = connector;
connector->user_data = self;
connector->on_connected = mpd_client_on_connector_connected;
connector->on_failure = mpd_client_on_connector_failure;
connector_add_target (connector, address, service);
self->state = MPD_CONNECTING;
return true;
}