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