Introduce and use generic_filter_pre_select().
[paraslash.git] / filter.h
1 /*
2 * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
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 /** The filter chain this filter node belongs to. */
19 struct filter_chain *fc;
20 /**
21 * Each filter may store any filter-specific information about the particular
22 * instance of the filter here.
23 */
24 void *private_data;
25 /** The output buffer. */
26 char *buf;
27 /** The size of the output buffer. */
28 size_t bufsize;
29 /** The number of bytes currently loaded in \a buf. */
30 size_t loaded;
31 /** The list of registered callbacks. */
32 struct list_head callbacks;
33 /** A pointer to the configuration of this instance. */
34 void *conf;
35 struct btr_node *btrn;
36 struct task task;
37 size_t min_iqs;
38 };
39
40 /** Describes one running instance of a chain of filters */
41 struct filter_chain {
42 /** The length of the filter chain. */
43 unsigned int num_filters;
44 /**
45 * The number of channels of the current stream.
46 *
47 * Set by the decoding filter.
48 */
49 unsigned int channels;
50 /**
51 * Current sample rate in Hz.
52 *
53 * Set by the decoding filter.
54 */
55 unsigned int samplerate;
56 /** The list containing all filter nodes in this filter chain. */
57 struct filter_node *filter_nodes;
58 /**
59 * The input buffer of the filter chain.
60 *
61 * This is set to point to the output buffer of the receiving application (the
62 * buffer used to read from stdin for para_filter; the output buffer of the
63 * current receiver for para_audiod).
64 */
65 char **inbufp;
66 /**
67 * The output buffer of the filter chain.
68 *
69 * Points to the output buffer of the last filter in the filter chain.
70 */
71 char **outbufp;
72 /** Contains the number of bytes loaded in the input buffer. */
73 size_t *in_loaded;
74 /** Contains the number of bytes loaded in the output buffer. */
75 size_t *out_loaded;
76 /** Pointer to the error variable of the receiving application. */
77 int *input_error;
78 /** Pointer to the error variable of the writing application. */
79 int *output_error;
80 /** The task associated with the filter chain. */
81 struct task task;
82 };
83
84 #define FOR_EACH_FILTER_NODE(fn, fc, i) for (i = 0; i < (fc)->num_filters \
85 && (fn = (fc)->filter_nodes + i); i++)
86
87
88 /**
89 * Used to manage grab clients.
90 *
91 * An application using paraslash's filter subsystem may register any number of
92 * callbacks for each filter_node. It is possible to attach a filter callback
93 * while the filter is running. This is used for stream grabbing in
94 * para_audiod: Whenever a client sends the 'grab' command, para_audiod adds a
95 * filter callback to the list of callbacks for the filter node specified in
96 * the grab command.
97 */
98 struct filter_callback {
99 /** All callbacks are organized in a doubly linked list. */
100 struct list_head node;
101 /**
102 * The input callback.
103 *
104 * If not \p NULL, the filter subsystem calls this function whenever the filter
105 * consumed some or all of its input buffer. A pointer to the buffer of consumed
106 * data, its length and a pointer to the own \a filter_callback structure are passed
107 * to \a input_cb. The input callback is expected to return a negative value on errors.
108 */
109 int (*input_cb)(char *buf, size_t len, struct filter_callback *fc);
110 /**
111 * The output callback.
112 *
113 * If not NULL, this is called whenever the filter produces output. A pointer
114 * to the output data, its length and a pointer to the own \a filter_callback
115 * structure are passed to \a output_cb. Like the input callback, the output
116 * callback is expected to return a negative value on errors.
117 */
118 int (*output_cb)(char *buf, size_t len, struct filter_callback *fc);
119 /**
120 * The callback close function.
121 *
122 * This gets called whenever the input/output callback returned an error, or if
123 * the filter chain is going to be destroyed, e.g. because the end of the
124 * stream was encountered. It is assumed to succeed.
125 */
126 void (*close)(struct filter_callback *fc);
127 };
128
129
130 /**
131 * The structure associated with a paraslash filter.
132 *
133 * Paraslash filters are "modules" which are used to transform an audio stream.
134 * struct filter contains pointers to functions that must be supplied by the
135 * filter code in order to be used by the driving application (currently
136 * para_audiod and para_filter).
137 *
138 * Note: As several instances of the same filter may be running at the same
139 * time, all these filter functions must be reentrant; no static non-constant
140 * variables may be used.
141 * \sa mp3dec_filter.c, oggdec_filter.c, wav_filter.c, compress_filter.c, filter_node
142 */
143 struct filter {
144 /** The name of the filter. */
145 const char *name;
146 /**
147 * Pointer to the filter init routine.
148 *
149 * This function is only called once at startup. It must initialize the
150 * other non-optional function pointers of this structure.
151 */
152 void (*init)(struct filter *f);
153 /**
154 * Open one instance of this filter.
155 *
156 * This should allocate the output buffer of the given filter node and do any
157 * other filter-specific preparations like initializing the private_data member
158 * of \a fn suitably. The open function is assumed to succeed.
159 */
160 void (*open)(struct filter_node *fn);
161 /**
162 * Convert (filter) the given data.
163 *
164 * Pointer to the converting function of the filter. It should convert the
165 * given input buffer \a inbuf which is of length \a len to the previously
166 * reserved output buffer of \a fn. On success, it must return the number of
167 * bytes it consumed from \a inbuf. On errors, a negative number indicating the
168 * kind of the error must be returned.
169 *
170 * A zero return value just means that nothing was converted (probably because
171 * the input buffer was too small). This is not interpreted as an error.
172 */
173 ssize_t (*convert)(char *inbuf, size_t len, struct filter_node *fn);
174 /**
175 * Close one instance of this filter.
176 *
177 * Free all resources of associated with \a fn that were previously allocated
178 * by the open() function.
179 */
180 void (*close)(struct filter_node *fn);
181 /**
182 * A pointer to the filter's command line parser.
183 *
184 * If this optional function pointer is not NULL, any filter options
185 * are passed from the main program to this command line parser once at
186 * application startup. The command line parser should check its
187 * command line options given by \a argc and \a argv and abort on
188 * errors. Success must be indicated by a non-negative return value. In
189 * this case the function should return a pointer to the
190 * filter-specific configuration data determined by \a argc and \a
191 * argv. On failure, a negative paraslash error code must be returned.
192 */
193 int (*parse_config)(int argc, char **argv, void **config);
194
195 /** The help texts for this filter. */
196 struct ggo_help help;
197
198 void (*pre_select)(struct sched *s, struct task *t);
199 void (*post_select)(struct sched *s, struct task *t);
200 btr_command_handler execute;
201 };
202
203 void close_filters(struct filter_chain *fc);
204 void filter_init(void);
205 int check_filter_arg(char *filter_arg, void **conf);
206 void filter_post_select(__a_unused struct sched *s, struct task *t);
207 void print_filter_helps(int detailed);
208 int prepare_filter_node(struct filter_node *fn);
209 void generic_filter_pre_select(struct sched *s, struct task *t);
210
211 static inline void write_int16_host_endian(char *buf, int val)
212 {
213 #ifdef WORDS_BIGENDIAN
214 *buf = val >> 8;
215 *(buf + 1) = val & 0xff;
216 #else
217 *buf = val & 0xff;
218 *(buf + 1) = val >> 8;
219 #endif
220 }
221
222 DECLARE_FILTER_INITS
223
224 #define FOR_EACH_SUPPORTED_FILTER(j) for (j = 0; j < NUM_SUPPORTED_FILTERS; j++)
225
226 /** The filter array, one structure for each supported filter. */
227 extern struct filter filters[NUM_SUPPORTED_FILTERS];