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/* SPDX-License-Identifier: GPL-2.0 */
/** \file write.h Writer API
*
* Writers are part of para_audiod(1), para_write(1) and para_play(1). They
* represent data sinks which receive input via the buffer tree mechanism
* from their parent buffer tree node and consume input data without
* producing any output.
*
* An instance of a writer is described by struct \ref writer_node, whose
* buffer tree node \ref writer_node::btrn is set up as a leaf node of the
* buffer tree, see \ref buffer_tree.h.
*
* The alsa and the ao writer defined in \ref alsa_write.c and \ref ao_write.c
* consume the data received from higher level buffer tree nodes by writing
* data to an audio device, employing the alsa and ao low level libraries. The
* file writer (see \ref file_write.c) writes data to an output file instead.
*
* The functions declared here are defined in \ref write_common.c.
*/
/**
* Describes one running instance of a writer.
*
* A writer node corresponds to a buffer tree node and a task.
*/
struct writer_node {
/** The ID of this writer. */
int wid;
/** Writer-specific data. */
void *private_data;
/** The parsed command line, merged with options given in the config file. */
struct lls_parse_result *lpr;
/** The buffer tree node associated with this writer node. */
struct btr_node *btrn;
/** The task of this writer node. */
struct task *task;
/** The minimal input queue size (size of one audio sample). */
size_t min_iqs;
};
/**
* Describes a data sink for audio streams.
*
* This structure contains the methods which have to be implemented by each
* writer. Note that there is no open method. Writers generally need to defer
* initialization until data is available and the stream parameters are known
* (e.g., the sample rate and the number of channels). The writers obtain this
* information from the other buffer tree nodes by calling \ref btr_exec_up().
*
* \sa struct \ref writer_node, struct \ref receiver, struct \ref filter.
*/
struct writer {
/** Ask the scheduler to check whether data can be written. */
void (*pre_monitor)(struct sched *s, void *context);
/** Write audio data. */
int (*post_monitor)(struct sched *s, void *context);
/**
* Close one instance of the writer.
*
* This function should deallocate all resources, particularly the
* private data pointer. It is assumed to succeed.
*/
void (*close)(struct writer_node *);
};
/** \cond doxygen_ignore */
#define WRITE_CMD(_num) (lls_cmd(_num, write_cmd_suite))
#define WRITE_CMD_OPT_RESULT(_cmd, _opt, _lpr) \
(lls_opt_result(LSG_WRITE_CMD_ ## _cmd ## _OPT_ ## _opt, _lpr))
#define WRITE_CMD_OPT_GIVEN(_cmd, _opt, _lpr) \
(lls_opt_given(WRITE_CMD_OPT_RESULT(_cmd, _opt, _lpr)))
#define WRITE_CMD_OPT_UINT32_VAL(_cmd, _opt, _lpr) \
(lls_uint32_val(0, WRITE_CMD_OPT_RESULT(_cmd, _opt, (_lpr))))
#define WRITE_CMD_OPT_STRING_VAL(_cmd, _opt, _lpr) \
(lls_string_val(0, WRITE_CMD_OPT_RESULT(_cmd, _opt, (_lpr))))
/** \endcond */
int check_writer_arg_or_die(const char *wa, struct lls_parse_result **lprp);
const struct writer *writer_get(int wid);
const char *writer_name(int wid);
void register_writer_node(struct writer_node *wn, struct btr_node *parent,
struct sched *s);
int get_btr_sample_rate(struct btr_node *btrn, int32_t *result);
int get_btr_channels(struct btr_node *btrn, int32_t *result);
int get_btr_sample_format(struct btr_node *btrn, int32_t *result);
void print_writer_helps(bool detailed);
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