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[paraslash.git] / filter.h
1 /*
2 * Copyright (C) 2005-2014 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 do any
62 * other filter-specific preparations like initializing the private_data member
63 * of \a fn suitably. The open function is assumed to succeed.
64 */
65 void (*open)(struct filter_node *fn);
66 /**
67 * Close one instance of this filter.
68 *
69 * Free all resources of associated with \a fn that were previously allocated
70 * by the open() function. It's OK to leave this alone if the filter does not
71 * need any cleanups.
72 */
73 void (*close)(struct filter_node *fn);
74 /**
75 * A pointer to the filter's command line parser.
76 *
77 * If this optional function pointer is not NULL, any filter options
78 * are passed from the main program to this command line parser once at
79 * application startup. The command line parser should check its
80 * command line options given by \a argc and \a argv and abort on
81 * errors. Success must be indicated by a non-negative return value. In
82 * this case the function should return a pointer to the
83 * filter-specific configuration data determined by \a argc and \a
84 * argv. On failure, a negative paraslash error code must be returned.
85 */
86 int (*parse_config)(int argc, char **argv, void **config);
87 /**
88 * Deallocate the memory for the configuration.
89 *
90 * This is called to free whatever ->parse_config() has allocated.
91 */
92 void (*free_config)(void *conf);
93
94 /** The help texts for this filter. */
95 struct ggo_help help;
96 /**
97 * Set scheduler timeout and add file descriptors to fd sets.
98 *
99 * This function is used to control the timeout value for select. It
100 * only allowed to decrease the current value. The second purpose of
101 * this function is to set file descriptors to be watched by the
102 * subsequent select call to the two fd sets.
103 */
104 void (*pre_select)(struct sched *s, void *context);
105 /**
106 * Convert (filter) the given data.
107 *
108 * Pointer to the converting function of the filter. On errors, the
109 * post_select function is supposed to return a negative error code.
110 */
111 int (*post_select)(struct sched *s, void *context);
112 /**
113 * Answer a buffer tree query.
114 *
115 * This optional function pointer is used for inter node communications
116 * of the buffer tree nodes. See \ref btr_command_handler for details.
117 */
118 btr_command_handler execute;
119 };
120
121 void filter_init(void);
122 int check_filter_arg(char *filter_arg, void **conf);
123 void print_filter_helps(unsigned flags);
124 void generic_filter_pre_select(struct sched *s, void *context);
125 int decoder_execute(const char *cmd, unsigned sample_rate, unsigned channels,
126 char **result);
127
128 static inline void write_int16_host_endian(char *buf, int val)
129 {
130 #ifdef WORDS_BIGENDIAN
131 *buf = val >> 8;
132 *(buf + 1) = val & 0xff;
133 #else
134 *buf = val & 0xff;
135 *(buf + 1) = val >> 8;
136 #endif
137 }
138
139 DECLARE_FILTER_INITS
140
141 /** Iterate over the array of supported filters. */
142 #define FOR_EACH_SUPPORTED_FILTER(j) for (j = 0; j < NUM_SUPPORTED_FILTERS; j++)
143
144 /** The filter array, one structure for each supported filter. */
145 extern struct filter filters[NUM_SUPPORTED_FILTERS];