async.h File Reference

Asynchronous MPD connections. More...

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## Enumerations

enum | mpd_async_event { MPD_ASYNC_EVENT_READ = 1, MPD_ASYNC_EVENT_WRITE = 2, MPD_ASYNC_EVENT_HUP = 4, MPD_ASYNC_EVENT_ERROR = 8 }

## Functions

mpd_malloc struct mpd_async * | mpd_async_new (int fd)
void | mpd_async_free (struct mpd_async *async)
mpd_pure enum mpd_error | mpd_async_get_error (const struct mpd_async *async)
mpd_pure const char * | mpd_async_get_error_message (const struct mpd_async *async)
mpd_pure int | mpd_async_get_system_error (const struct mpd_async *async)
mpd_pure int | mpd_async_get_fd (const struct mpd_async *async)
void | mpd_async_set_keepalive (struct mpd_async *async, bool keepalive)
mpd_pure enum mpd_async_event | mpd_async_events (const struct mpd_async *async)
bool | mpd_async_io (struct mpd_async *async, enum mpd_async_event events)
bool | mpd_async_send_command_v (struct mpd_async *async, const char *command, va_list args)
mpd_sentinel bool | mpd_async_send_command (struct mpd_async *async, const char *command,...)
mpd_malloc char * | mpd_async_recv_line (struct mpd_async *async)

## Detailed Description

Asynchronous MPD connections.

This class provides a very basic interface to MPD connections. It does not know much about the MPD protocol, it does not know any specific MPD command.

The constructor expects a socket descriptor which is already connected to MPD. The first thing it does is read the server's handshake code ("OK MPD 0.15.0").

Definition in file async.h.

## Enumeration Type Documentation

enum mpd_async_event

Event bit mask for polling.

Enumerator
MPD_ASYNC_EVENT_READ | ready to read from the file descriptor
MPD_ASYNC_EVENT_WRITE | ready to write to the file descriptor
MPD_ASYNC_EVENT_HUP | hangup detected
MPD_ASYNC_EVENT_ERROR | I/O error

Definition at line 53 of file async.h.

## Function Documentation

mpd_malloc struct mpd_async* mpd_async_new | ( | int | fd | ) |

Creates a new asynchronous MPD connection, based on a stream socket connected with MPD.

Parameters

  fd | the socket file descriptor of the stream connection to MPD

Returns
  a mpd_async object, or NULL on out of memory

void mpd_async_free | ( | struct mpd_async * | async | ) |

Closes the socket and frees memory.

mpd_pure enum mpd_error mpd_async_get_error | ( | const struct mpd_async * | async | ) |

After an error has occurred, this function returns the error code. If no error has occurred, it returns MPD_ERROR_SUCCESS.

mpd_pure const char* mpd_async_get_error_message | ( | const struct mpd_async * | async | ) |

If mpd_async_is_alive() returns false, this function returns the human readable error message which caused this. This message is optional, and may be NULL. The pointer is invalidated by mpd_async_free().

For MPD_ERROR_SERVER, the error message is encoded in UTF-8. MPD_ERROR_SYSTEM obtains its error message from the operating system, and thus the locale's character set (and probably language) is used. Keep that in mind when you print error messages.

mpd_pure int mpd_async_get_system_error | ( | const struct mpd_async * | async | ) |

Returns the error code from the operating system; on most operating systems, this is the errno value. Calling this function is only valid if mpd_async_get_error() returned MPD_ERROR_SYSTEM.

May be 0 if the operating system did not specify an error code.

mpd_pure int mpd_async_get_fd | ( | const struct mpd_async * | async | ) |

Returns the file descriptor which should be polled by the caller. Do not use the file descriptor for anything except polling! The file descriptor never changes during the lifetime of this mpd_async object.

void mpd_async_set_keepalive | ( | struct mpd_async * | async,
|  | bool | keepalive
| ) |  |

Enables (or disables) TCP keepalives.

Keepalives are enabled using the SO_KEEPALIVE socket option. They may be required for long-idled connections to persist on some networks that would otherwise terminate inactive TCP sessions.

The default value is false.

Parameters

  async | the mpd_async object
  keepalive | whether TCP keepalives should be enabled

mpd_pure enum mpd_async_event mpd_async_events | ( | const struct mpd_async * | async | ) |

Returns a bit mask of events which should be polled for.

bool mpd_async_io | ( | struct mpd_async * | async,
|  | enum mpd_async_event | events
| ) |  |

Call this function when poll() has returned events for this object's file descriptor. libmpdclient will attempt to perform I/O operations.

Returns
  false if the connection was closed due to an error

bool mpd_async_send_command_v | ( | struct mpd_async * | async,
|  | const char * | command,
|  | va_list | args
| ) |  |

Appends a command to the output buffer.

Parameters

  async | the connection
  command | the command name, followed by arguments, terminated by NULL
  args | the argument list

Returns
  true on success, false if the buffer is full

mpd_sentinel bool mpd_async_send_command | ( | struct mpd_async * | async,
|  | const char * | command,
|  |  | ...
| ) |  |

Appends a command to the output buffer.

Parameters

  async | the connection
  command | the command name, followed by arguments, terminated by NULL

Returns
  true on success, false if the buffer is full

mpd_malloc char* mpd_async_recv_line | ( | struct mpd_async * | async | ) |

Receives a line from the input buffer. The result will be null-terminated, without the newline character. The pointer is only valid until the next async function is called.

Parameters

  async | the connection

Returns
  a line on success, NULL otherwise