server: Convert com_addatt() to lopsub.
[paraslash.git] / filter.h
1 /*
2 * Copyright (C) 2005 Andre Noll <maan@tuebingen.mpg.de>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6
7 /** \file filter.h Filter-related structures and exported symbols from filter_common.c. */
8
9 /** The list of supported filters. */
10 enum filter_enum {FILTER_ENUM};
11
12 /**
13 * Describes one running instance of a filter.
14 */
15 struct filter_node {
16 /** The number in the array of available filters. */
17 unsigned filter_num;
18 /**
19 * Each filter may store any filter-specific information about the particular
20 * instance of the filter here.
21 */
22 void *private_data;
23 /** The list of registered callbacks. */
24 struct list_head callbacks;
25 /** A pointer to the configuration of this instance. */
26 void *conf;
27 /** The buffer tree node. */
28 struct btr_node *btrn;
29 /** The task corresponding to this filter node. */
30 struct task *task;
31 /** The minimal input queue size, see \ref btr_node_status(). */
32 size_t min_iqs;
33 };
34
35 /**
36 * The structure associated with a paraslash filter.
37 *
38 * Paraslash filters are "modules" which are used to transform an audio stream.
39 * struct filter contains pointers to functions that must be supplied by the
40 * filter code in order to be used by the driving application (currently
41 * para_audiod and para_filter).
42 *
43 * Note: As several instances of the same filter may be running at the same
44 * time, all these filter functions must be reentrant; no static non-constant
45 * variables may be used.
46 * \sa mp3dec_filter.c, oggdec_filter.c, wav_filter.c, compress_filter.c, filter_node
47 */
48 struct filter {
49 /** The name of the filter. */
50 const char *name;
51 /**
52 * Pointer to the filter init routine.
53 *
54 * This function is only called once at startup. It must initialize the
55 * other non-optional function pointers of this structure.
56 */
57 void (*init)(struct filter *f);
58 /**
59 * Open one instance of this filter.
60 *
61 * This should allocate the output buffer of the given filter node and
62 * do any other filter-specific preparations like initializing the
63 * private_data member of \a fn suitably. The open function is
64 * optional, If it is provided, it is assumed to succeed.
65 */
66 void (*open)(struct filter_node *fn);
67 /**
68 * Close one instance of this filter.
69 *
70 * Free all resources associated with \a fn that were previously
71 * allocated by the open() function. It's OK to set this to NULL if the
72 * filter does not need to perform any cleanup operation.
73 */
74 void (*close)(struct filter_node *fn);
75 /**
76 * A pointer to the filter's command line parser.
77 *
78 * If this optional function pointer is not NULL, any filter options
79 * are passed from the main program to this command line parser once at
80 * application startup. The command line parser should check its
81 * command line options given by \a argc and \a argv and abort on
82 * errors. Success must be indicated by a non-negative return value. In
83 * this case the function should return a pointer to the
84 * filter-specific configuration data determined by \a argc and \a
85 * argv. On failure, a negative paraslash error code must be returned.
86 */
87 int (*parse_config)(int argc, char **argv, void **config);
88 /**
89 * Deallocate the memory for the configuration.
90 *
91 * This is called to free whatever ->parse_config() has allocated.
92 */
93 void (*free_config)(void *conf);
94
95 /** The help texts for this filter. */
96 struct ggo_help help;
97 /**
98 * Set scheduler timeout and add file descriptors to fd sets.
99 *
100 * This function controls the timeout value for the next call to
101 * select(2). It may decrease the current timeout but shall never
102 * increase it. The second purpose of this function is to add file
103 * descriptors to the two fd sets of the sched structure. The
104 * descriptors in these sets will be watched by the subsequent
105 * select(2) call.
106 */
107 void (*pre_select)(struct sched *s, void *context);
108 /**
109 * Convert (filter) the given data.
110 *
111 * Pointer to the converting function of the filter. On errors, the
112 * post_select function is supposed to return a negative error code.
113 */
114 int (*post_select)(struct sched *s, void *context);
115 /**
116 * Answer a buffer tree query.
117 *
118 * This optional function pointer is used for inter node communications
119 * of the buffer tree nodes. See \ref btr_command_handler for details.
120 */
121 btr_command_handler execute;
122 };
123
124 void filter_init(void);
125 int check_filter_arg(const char *fa, void **conf);
126 void print_filter_helps(unsigned flags);
127 void generic_filter_pre_select(struct sched *s, void *context);
128 int decoder_execute(const char *cmd, unsigned sample_rate, unsigned channels,
129 char **result);
130
131 static inline void write_int16_host_endian(char *buf, int val)
132 {
133 #ifdef WORDS_BIGENDIAN
134 *buf = val >> 8;
135 *(buf + 1) = val & 0xff;
136 #else
137 *buf = val & 0xff;
138 *(buf + 1) = val >> 8;
139 #endif
140 }
141
142 DECLARE_FILTER_INITS
143
144 const struct filter *filter_get(int filter_num);